The microstructures and mechanical properties of a series of sand-cast Mg-Sm-Zn-Zr alloys under as-cast, solution-treated and peak-aged states were thoroughly investigated. The OM, XRD, SEM and HRTEM were employed to characterize the microstructural evolution. The results indicate that substitution Nd in the conventional Mg-2.5Nd-0.6Zn-0.5Zr alloy with different contents of Sm has comparative grain refinement effect and will fully change the dominant intermetallic phase. In addition, the substituted alloys perform clearly higher strength with comparative ductility at both as-cast and peak-aged conditions and much greater aging hardening response than the referential alloy. It is obvious that the strength increments of this alloy are attributed to the changes of the eutectic intermetallic particles on grain boundaries.

•The yield strength of Mg–Al–Sm alloy was improved by aging treatment.•A number of nano-scale precipitates formed in matrix after aging treatments.•The nanoscale precipitate was confirmed as Al3Sm based on the data of HAADF-STEM study.•The strengthening mechanisms of the nano-scale precipitate were quantitatively formulated.•The operative mechanism of precipitate strengthening is Orowan dislocation bypassing.In this paper we report a quantitative study of the age-hardening in the high-pressure die-cast Mg–4Al−5.6Sm−0.3Mn alloy. The results indicate that a number of nano-scale spherical precipitates identified as Al3Sm using high-angle annular dark-field scanning transmission electron microscopy, precipitated in Mg matrix after aging at 150–225 °C, with no obvious changes on grain sizes, intermetallic phases formed during solidification, and dislocation densities. From the existing strengthening theory equations in which some lacking parameters were taken from the first-principles density functional theory (DFT) calculations, a quantitative insight into the strengthening mechanisms of the nano-scale precipitate was formulated. The results are in reasonable agreement with the experimental values, and the operative mechanism of precipitation strengthening was revealed as Orowan dislocation bypassing.

The phase stability and the elastic properties of Al–La binary system intermetallic compounds were thoroughly investigated using first-principles calculations. Firstly, the 0 K phase diagram for this system was calculated using the formation enthalpy convex hull construction, which indicates three metastable phases, namely Al4La (I4/mmm), Al4La (Imm2), and AlLa3 (Pm-3m). Then, the stability of Al11La3 was examined at temperatures lower than 1000 K compared with the two Al4La allotropes and the Al + Al2La two-phase equilibrium. The results demonstrate that the needlelike phase in Mg–Al–La based alloys should be indexed as Al11La3, which is thermodynamically stable, with no decomposition under aging. Thirdly, AlLa3 (Pm-3m) is more stable than AlLa3 (P63/mmc) at temperatures higher than approximately 590 K, which well agrees with the experimental results. Finally, the elastic properties and vibrational properties for the stable Al–La intermetallic phases were calculated in this work.

Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd1−xZnxS is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd1−xZnxS can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln3+–Yb3+ couple. In this work, we designed a clean route to a broadband down-converter based on a core–shell-like Y2O3:[(Tb3+–Yb3+), Li+]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb3+–Yb3+), Li+]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb3+–Yb3+), Li+] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb3+–Yb3+ quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb3+–Yb3+), Li+]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb3+. Broadband down-conversion to the Yb3+ NIR emission was obtained in a wide range of 250–650 nm.

•A two-step synthetic method is adopted to obtain SFMTO series compounds.•The oxygen vacancy concentration increases with the increase of Ta.•SFMTO TECs match the electrolyte materials better than those of Co-based compounds.•High performance of SFMTO cathode is demonstrated by low polarization resistance.To date great efforts have been devoted to the development of solid oxide fuel cell (SOFC) devices that is able to run at intermediate temperature (IT) and to retain good electrochemical performance as in the high temperature regime. To this end, Tantalum (Ta) is doped into Sr2Fe1.5Mo0.5−xTaxO6−δ (0.0 ≤ x ≤ 0.15) to further improve the electrochemical performance as the cathode materials for IT-SOFC. Pure orthorhombic Sr2Fe1.5Mo0.5−xTaxO6−δ (0.0 ≤ x ≤ 0.15) samples, with space group Pnma (no. 62), are synthesized by a two-step method and identified via the powder X-ray Rietveld refinements. X-ray photoelectron spectroscopy and thermogravimetry results consistently show that the number of oxygen vacancy increases with the increasing of Ta content. The thermal expansion compatibility of the samples is found to match the electrolyte of La0.9Sr0.4Ga0.1Mg0.2O3−δ (LSGM) better than that of cobalt-containing electrode compounds. Finally, the higher oxygen vacancy concentration leads to the enhanced ionic conductivity although electrical conductivity is slightly decreased due to the oxygen vacancy blocking. Therefore, Ta-doped Sr2Fe1.5Mo0.5O6−δ is proved to be a promising candidate for future cathode materials of IT-SOFC.

•The trace boron can refine the dendrite arm spacing of HPDC Mg–Al–La-based alloy.•The dispersion of Al11La3 particles becomes irregular after adding trace boron.•The eutectic volume fraction is reduced by adding 0.01–0.02 wt.% boron.•Mechanical properties could be further improved by 0.03 wt.% boron addition.The influences of trace boron on microstructures and tensile properties of Mg–4Al–4La-based alloys prepared by cold-chamber high-pressure die-casting method were thoroughly investigated. The results indicated that adding trace boron to Mg–4Al–4La-based alloy can refine the dendrite arm spacing of primary α-Mg phases, which are mainly due to the little inoculating AlB2 particles. In addition, we found that adding 0.01–0.02 wt.% boron can drastically changes the eutectic morphology, with secondary particle dispersion becoming irregular and eutectic volume fraction being reduced. These phenomena can be attributed to the competitive nucleation between α-Mg and AlB2 particles for Al11La3 phases, and to the fact that more Al and La atoms saturate into the α-Mg matrix. Considering the tensile properties, although adding 0.01–0.02 wt.% boron decreased the strength of Mg–4Al–4La-based alloy, adding 0.03 wt.% boron significantly improved the tensile properties due to dispersion strengthening and, to a certain extent, solid-solution strengthening.

•Most Ni atoms occupied the cubic voids while the remaining a few replaced Mo atoms.•Inserted Ni atoms enhanced both the electrical conductivity and thermopower.•The substitution reduced the thermal conductivity.•The thermoelectric properties of Mo3Sb7 were optimized by the addition of Ni.Thermoelectric properties of nickel-heavily-doped Mo3Sb7 compounds (NixMo3−yNiySb7, x + y = 0.00, 0.15, 0.20, 0.25 and 0.30), obtained via a metallurgical route, are reported. Structural analysis by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) suggest that most Ni atoms are inserted into the cubic voids while the remaining a few substitute Mo atoms. Ni in the cubic voids increases the densities and the slope of electronic states near Fermi level, resulting in the increase of electrical conductivity (σ) and thermopower (α). Meanwhile, Ni at the substituted sites induces phonon-scattering disorder in the crystal, leading to the decrease of the thermal conductivity (κ). These results indicate that the simple heavy-Ni-doping could provide a unique way to optimize all the thermoelectric parameters in this Mo3Sb7 compound.

•One-pot synthesis of aqueous ZnSe:Cu nanocrystals with tunable emission and high QY%.•ZnSe:Cu NCs exhibit high QY% at neutral pH suitable for biological application.•The microscopic mechanism underlying Cu-related emission has been provided.An one-pot synthesis of aqueous ZnSe:Cu nanocrystals (NCs) is realized in aqueous solution by a facile yet efficient hydrothermal technique. The dopant emission spectrum of the NCs is tunable, spanning a wide range from 438 to 543 nm. Room-temperature quantum yield for the NCs prepared at the optimal conditions reaches as high as 20% without any post-treatment. The ZnSe:Cu NCs prepared in a neutral aqueous solution (pH=8) are remarkably stable and exhibit comparatively high photoluminescent quantum yield (PL QY) as high as 17%. First-principles pseudopotential calculations using plane-wave basis functions have been performed. The formation energies of copper ions occupied in the interstitial octahedron and substitutional tetrahedral Zn2+ sites have been calculated. The occupation of copper ions in the interstitial octahedral site is found to be more thermodynamics-facilitated by −0.98 eV. The density of state analysis indicates that the Cu-related emission is primary dominated by the substitutional tetrahedral Cu ions, and the large dopant related emission width of ZnSe:Cu NCs originated from the corresponding Cu 3d impurity band.

A-site ordered double perovskites hold promise for potential device applications, where how their magnetic objects actually interact is known to influence functionality. Here, we investigate, by first-principles calculations, electronic and magnetic properties of YMn3Al4O12, and demonstrate that it is an antiferromagnetic insulator. Our calculations reveal the extended (Mn–O)–(O–Mn) superexchange as a primary magnetic coupling mechanism in YMn3Al4O12, and further identify the O–O bonds as a key factor to dominate coupling strength. We suggest that this superexchange mode is the origin of antiferromagnetic behavior, opening an additional avenue to understand magnetic coupling in A-site ordered double perovskites.Graphical abstractHighlights► YMn3Al4O12 is an antiferromagnetic insulator. ► Extended (Mn–O)–(O–Mn) superexchange is the primary magnetic coupling mechanism. ► O––O bonds are the key factor to dominate coupling strength.

A Mg–11Gd–4.5Y–1.5Zn–1Nd–0.5Zr alloy with high-strength and heat-resistance has successfully been prepared by hot extrusion and subsequent ageing. It exhibits an ultimate tensile strength of 473 MPa, 0.2% proof stress of 373 MPa and elongation to failure of 4.1% at room temperature. At 250 °C, this alloy shows an ultimate tensile strength of 369 MPa, 0.2% proof stress of 316 MPa and elongation to failure of 6.3%. Its good mechanical properties and thermal stability are attributed to the dispersion of large volume fraction of 14H-LPSO phase, small α-Mg grains, basal-fiber texture and dense distribution of precipitates at the grain boundaries and inside the grains.

Mg–1.5Y–1.2Zn–0.44Zr alloys were newly developed as degradable metallic biomaterials. A comprehensive investigation of the microstructure, mechanical properties, in vitro degradation assessments and in vitro cytotoxicity evaluations of the as-cast state, as-heat treated state and as-extruded state alloys was done. The microstructure observations show that the Mg–1.5Y–1.2Zn–0.44Zr alloys are mainly composed of the matrix α-Mg phases and the Mg12ZnY secondary phases (LPS structure). The hot extrusion method significantly refined the grains and eliminated the defects of both as-cast and heat treated alloys and thereby contributed to the better mechanical properties and biodegradation resistance. The values of tensile strength and tensile yield strength of the alloy in the as-extruded condition are about 236 and 178 MPa respectively, with an excellent elongation of 28%. Meanwhile, the value of compressive strength is about 471 MPa and the value of bending strength is about 501 MPa. The superior bending strength further demonstrates the excellent ductility of the hot extruded alloys. The results of immersion tests and electrochemical measurements in the SBF indicate that a protective film precipitated on the alloy's surface with the extension of degradation. The protective film contains Mg(OH)2 and hydroxyapatite (HA) which can reinforce osteoblast activity and promote good biocompatibility. No significant cytotoxicity towards L-929 cells was detected and the immersion extracts of alloy samples could enhance the cell proliferation with time in the cytotoxicity evaluations, implying that the Mg–1.5Y–1.2Zn–0.44Zr alloys have the potential to be used for biomedical applications.Highlights► Mg-1.5Y-1.2Zn-0.44Zr alloys were newly developed as degradable metallic implants. ► The alloys are mainly composed of the matrix α-Mg and Mg12ZnY secondary phases. ► The mechanical properties and biodegradation resistance were improved by extrusion. ► No significant cytotoxicity to L-929 cells was detected. ► The immersion extracts of alloy samples could enhance cell proliferation with time.

The n = 1 Ruddlesden–Popper (RP) phases LaSrM0.5Ru0.5O4±δ (M = Co, Ni and Zn) have been prepared by solid state reactions and structurally characterized by powder X-ray and electron diffraction. All the samples adopt the tetragonal I4/mmm space group with random M and Ru cation occupation on the B-sites. The potential causes of no cation ordering are discussed. A combined analysis of the tolerance factors, the distortion of the octahedral coordination of M and Ru cations and the magnetic interactions between M and Ru cations provide a better understanding for forming a phase with 3D cation ordering on the B-sites in the n = 1 RP phases. The investigation of XPS spectra suggests that the transition element species exist as mixed ion pairs, Ru(4−δ)+–Ru4+ ↔ Co2+–Co3+ in LaSrCo0.5Ru0.5O4, and Ru4+–Ru(4+δ)+ ↔ Ni+–Ni2+ in LaSrNi0.5Ru0.5O4, which is consistent with cation disorder over the B sites. LaSrCo0.5Ru0.5O4 shows a weakly ferromagnetic behaviour below 50 K; LaSrNi0.5Ru0.5O4 is evidenced by the presence of long-range magnetic ordering at a Néel temperature of 125 K, and LaSrZn0.5Ru0.5O4 exhibits a paramagnetic behaviour down to 5 K. Due to atomic disorder, Ru4d, O2p covalent coupling is weakened, strengthening the intraatomic spin–spin coupling among the π* electrons. Charge transfer between Ru and Co or Ru and Ni, as well as the increasing overlap of both nearest-neighbour and next-nearest-neighbour Ru 4d electrons due to atomic disorder, favour the formation of ferromagnetic interactions. Although antiferromagnetism is dominant, particularly in LaSrNi0.5Ru0.5O4, ferromagnetic interactions are stronger in the title compounds than in the related La2MRuO6 (M = Co, Ni) double perovskites where the B-site cations are ordered.

In order to optimize the electrical properties of co-doped ceria electrolytes, Ce0.8Ca0.15Sm0.05O2−δ (CCS) sintered at different temperatures (1150 °C, 1200 °C, 1250 °C, 1300 °C and 1350 °C for 8 h) have been prepared and systematically investigated. It is found that among these samples sintered at different conditions, the electrical conductivity (σ) measured at 800 °C can be ranked as: CCS1250 °C: σCCS1250°C800°C = 2.38 × 10−2 S cm−1 > CCS1200 °C: σCCS1200°C800°C = 1.81 × 10−2 S cm−1 > CCS1150 °C: σCCS1150°C800°C = 1.50 × 10−2 S cm−1 > CCS1300 °C: σCCS1300°C800°C = 1.26 × 10−2 S cm−1 > CCS1350 °C: σCCS1350°C800°C = 0.68 × 10−2 S cm−1. The electrical conductivity of CCS increases with the increase of sintering temperatures, and the 1250 °C-sintered sample presents the highest conductivity because of the best microstructures. However, the electrical conductivity of CCS decreases when the sintering temperatures goes beyond 1250 °C. We attribute this to the phase instability. It reveals that microstructures and the phase stability have important effects on the optimization of electrical properties for the co-doped ceria electrolytes.Highlights► Microstructures could be tailored by controlling sintering temperature. ► Optimal electricity is obtained in co-doped ceria due to the best microstructures. ► Phase stability should be considered during the selection of sintering condition.

Single-component electrolyte-free fuel cells possess a similar function to the traditional fuel cells with a complex three-component structure. However, how to enhance their electrical properties for practical industrial applications remains a timely and important issue. Here, we report the manipulation of concentration ratios of ionic to electronic conductors in an electrolyte-free Ce0.8Sm0.2O2-δ–Li0.15Ni0.45Zn0.4 by adjusting the relative weight between its two inside compositions. Our systematic investigations reveal that the fuel cell with 30% in weight of Li0.15Ni0.45Zn0.4 exhibits an almost uniform distribution of the two compositions and has a total conductivity as high as 10 × 10−2 S cm−1 at 600 °C. Such an enhancement is found to be attributed to the established balance between the numbers of its inside ionic and electronic conductors. These findings are relevant for the technological improvement of this new species of electrolyte-free fuel cell and represent an important step toward commercialization of this single-component fuel cell.

The effect of small addition of different sintering aids (MoO3 and WO3) on the electrical properties of Ce0.9Nd0.1O2−δ has been investigated. The (Ce0.9Nd0.1)1−xMxO2−δ (x = 0.0; M = Mo, W, x = 0.01; Ce0.9Nd0.1O2−δ: NDC, (Ce0.9Nd0.1)0.99Mo0.01O2−δ: NDCMo; (Ce0.9Nd0.1)0.99W0.01O2−δ: NDCW) solid solutions were prepared and characterized. The X-ray diffraction patterns indicate that all the samples are single phases with a cubic fluorite structure. Moreover, from the field-emission scanning electron microscopy results, it is found (Ce0.9Nd0.1)0.99M0.01O2−δ (M = Mo, W) sintered at 1300 °C for 15 h have better sinterability than Ce0.9Nd0.1O2−δ. The total conductivity (σt)(σt) by electrochemical impedance spectroscopy are ranked as: NDCW (σt-NDCW700°C=0.039Scm−1) > NDCMo (σt-NDCMo700°C=0.029Scm−1) > NDC (σt-NDC700°C=0.018Scm−1) measured at 700 °C, which is attributed to microstructures. It can be concluded that MoO3 and WO3 are both effective and WO3 seems to be more potential as sintering aids on the optimization of electrical properties for ceria-based electrolytes.Highlights► MoO3 as sintering aids improves electrical properties of ceria-based electrolytes. ► WO3 as sintering aids improves electrical properties of ceria-based electrolytes. ► WO3 would be more potential than MoO3 as sintering aids.

We have investigated the electronic and magnetic properties of A-site-ordered perovskite CaFe3Ti4O12 using first-principles calculations. Our calculated results indicate that CaFe3Ti4O12 is mechanically stable and it is an antiferromagnetic insulator. Similar to its isostructural perovskite CaCu3Ti4O12, the primary magnetic coupling mechanism in CaFe3Ti4O12 is ascribed to the Fe–O–Ti–O–Fe superexchange interaction. From this fact we can clearly see that the empty 3d orbitals play an important role to realize the superexchange interaction. Moreover, comparing CaFe3Ti4O12 and CaCu3Ti4O12 in some details, we find that Fe (Cu)–O bond distance is one of the important parameters to determine the antiferromagnetic strength within this superexchange interaction.Graphical abstractBy comparison to the electronic transport and magnetic properties of its isostructural perovskite CaCu3Ti4O12, we have predicted that A-site-ordered double perovskite CaFe3Ti4O12 is an antiferromagnetic insulator. More importantly, we attribute it to the fact that the primary magnetic coupling mechanism is the Fe–O–Ti–O–Fe superexchange interaction.Highlights► CaFe3Ti4O12 is predicted to be an antiferromagnetic insulator. ► CaFe3Ti4O12 is found to be mechanically stable. ► The primary magnetic coupling mechanism is Fe–O–Ti–O–Fe superexchange. ► Cu–O bond distance is a main parameter to determine the antiferromagnetic strength.

A series of Bi-doped La2–xBixCoMnO6 double perovskite oxides are synthesized, and the impact of doping on crystal structures and magnetic properties is investigated comprehensively. X-ray photoelectron spectroscopy and Raman spectrum analyses reveal that ordering of Co and Mn ions at B-site is gradually improved with the rise of Bi concentration. Meanwhile, magnetic disordering is suppressed greatly by showing larger magnetic moments. Structurally, the Rietveld refinement shows that the bonds are elongated, while the bond angles are shrunken after doping, giving rise to lowered Curie temperature. We also observe a large negative zero-field-cooling magnetization, which is attributed to the formation of spin antiparallel or canted ferromagnetic domains and clusters that are separated by the antiphase boundaries. First-principles calculations confirm the enhanced Co–Mn ordering upon Bi doping by taking into account both the ordering and disordering configurations of La2CoMnO6, LaBiCoMnO6, and Bi2CoMnO6. Moreover, we find a spin-state transition in the antisite Co ions from high-spin (Co2+-t2g5eg2) to low-spin state (Co3+-t2g6eg0), which is consistent with the increased total magnetic moments by the Bi doping.

An easy co-gelation route has been developed to synthesize porous graphitic carbons with high surface areas by using teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates as precursors. Using a one-pot co-gelation process, a polyfurfuryl alcohol–silica interpenetrating framework with metal ions uniformly dispersed was formed during the polymerization of FA and the hydrolysis of TEOS within an ethanol solution of the three precursors. This synthesis process is simple and time-saving in comparison with the conventional preparation methods. During the heat treatment, Fe7Co3 alloy nanoparticles were produced by carbothermal reduction and they then catalyzed the graphitization of the amorphous carbon. The graphitic carbons obtained have a high crystallinity as shown by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy analysis. The degree of graphitization can be controlled by the varying the loading amount of catalyst. The porous texture of the carbons combines miropores and bimodal mesopores, mainly originating from the silica template formed with different sizes and the loose packing of the graphite sheets. The carbons have large surface areas (up to 909 m2/g) and exhibit excellent electrochemical performance.Graphical abstractResearch highlights► An easy co-gelation route has been developed to synthesize porous graphitic carbons. ► This methods is simple and time-saving in comparison with the conventional ones. ► Fe7Co3 were produced by carbothermal reduction and then catalyzed the graphitization. ► The degree of graphitization can be controlled by varying the amount of catalyst. ► The carbons have large surface areas and exhibit excellent electrochemical performance.

In order to identify competitive ion-conducting materials in ceria-carbonates composite electrolytes, M-NLCO (M = Ce0.8Sm0.2O2-δ (SDC), Ce0.8Gd0.2O2-δ (GDC), Ce0.8Y0.2O2-δ (YDC); NLCO = 0.53Li2CO3–0.47Na2CO3) sintered at different temperatures (600° C, 625° C, 650° C, 675° C and 700° C) have been prepared and characterized. It is found that independent of systems, the 675° C-sintered composites in M-NLCO always present the highest conductivities because of the best NLCO distribution and interfacial microstructures. Moreover, among three composites (sintered at 675° C), the total (σtσt) and grain boundary (σgbσgb) conductivities measured at 600° C are ranked as: SDC-NLCO (σt−SDC-NLCO600°C=9.1×10−2Scm−1, σgb−SDC-NLCO600°C=28.1×10−2Scm−1) ﹥ GDC-NLCO (σt−GDC-NLCO600°C=5.8×10−2Scm−1, σgb−GDC-NLCO600°C=18.9×10−2Scm−1) ﹥ YDC-NLCO (σt−YDC-NLCO600°C=3.1×10−2Scm−1, σgb−YDC-NLCO600°C=12.6×10−2Scm−1), which is attributed to ionic-radius compatibility between the dopant and the host as well as the NLCO distribution and interfacial microstructures. It can be concluded that ionic-radius compatibility between the dopant and the host, NLCO distribution and interfacial microstructures have important effects on improving ionic conductivities for ceria-carbonates composite electrolytes.

A new kind of magnetic porous FeCo/carbon nanocomposites was successfully synthesized by using a facile co-gelation sol–gel route. The sol–gel process of this route started from an ethanol solution containing teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates. With the evaporation of solvent, the weak acidity produced from hydrolysis of metal nitrates simultaneously catalyzed the polymerization of FA and the hydrolysis of TEOS, which led to the inorganic/organic hybrid xerogel, accompanying metal salts spontaneously captured in the xerogel. The composites obtained have high surface areas, pore volumes and strong magnetic strengths, which make them exhibit excellent performance of adsorption for bulk dyes and easily separated from solution by external field after adsorption. Compared to the previous methods, this route is very simple and operable for the preparation of magnetic porous carbon composites. Such facile co-gelation route also provides a common path to the synthesis of nanoscale metal or alloy embedded in the porous carbon materials.Graphical abstractThe sol–gel co-gelation process of this route simultaneously involves hydrolysis of teraethylorthosilicate (TEOS), and polymerization of furfuryl alcohol (FA) within an ethanol solution containing TEOS, FA, and metal nitrates.Research highlights▶ A facile co-gelation route was developed to synthesize magnetic porous FeCo/carbon composites. ▶Compared to the previous methods, this route is very simple and operable for magnetic composites. ▶Such facile route also provides a common path to the synthesis of metal or alloy/carbon materials.

A novel organic–inorganic hybrid compound (C9H14N)2PbCl4 was grown via a solution-cooling process by employing the organic cation-2,4,6-trimethylaniline to control the hybrid compound and the structure was determined by single-crystal X-ray diffraction to be monoclinic, P2(1)/c with a = 24.350(0) Å, b = 25.167(0) Å, c = 7.694(0) Å, β = 95.77(9)°, and Z = 8. The compound adopted an unprecedented structure, which was built with the staircase-like 1-D chains of PbCl4 octahedra sandwiched with the square pyramids of PbCl5. Raman and infrared spectra were used to gain more information of the title compound. The hybrid compound showed the photoluminescence emission at 424 nm.

The structure stability and physical properties of CaCu3Ni4O12 have been studied by first-principles calculations. It shows that CaCu3Ni4O12 is stable both thermodynamically and mechanically. The electronic structure analysis reveals that the Cu covalence is formally +3 and that the Cu ions have the d9L configuration (L: an O 2p hole) that corresponds to the Zhang−Rice singlet state. It is predicted to be a ferromagnetic half-metal, comparable to the metallic character of its isostructural compound of CaCu3Co4O12. Electron correlation plays a vital role in stabilizing the half-metallic property of CaCu3Ni4O12. The Fermi level shifts toward the middle of the minority-spin gap with the increase of U, demonstrating its stability of the half metallicity against structural distortion. Moreover, it is found that O atoms carry unusual large magnetic moments due to the enhanced exchange splitting with the increase of U. All the predicted properties for CaCu3Ni4O12 are comparable with the corresponding existing compound CaCu3Co4O12. Therefore, interesting physical properties are also expected from CaCu3Ni4O12.

LaMnO3+δ nanofibers have been prepared by electrospinning. The nearly 70% of Mn atoms is Mn4+, which is much higher than that in the nanoparticles. The average grain size of our fibers is approximately 20 nm, which is the critical size producing the nanoscale effect. The nanofibers exhibit a very broad magnetic transition with Tc ≈ 255 K, and the Tc onset is around 310 K. The blocking temperature TB is 180 K. The sample shows weak ferromagnetic property above the TB and below Tc and superparamagnetic property near the Tc onset. The resistivity measurements show a metal−insulator transition near 210 K and an upturn at about 45 K.Keywords: electrical propery; LaMnO3+δ; magnetic property; Mn valence; nanofibers

An easy co-impregnation method has been developed to synthesize magnetic mesoporous FeNi alloy/carbon composites with an ordered hexagonal structure. Furfuryl alcohol and metal nitrates were used as the carbon and magnetic particle precursors and were impregnated into the silica template in one step using a simple ethanol solution of furfuryl alcohol and metal nitrates. Compared to the co-casting route with two-step impregnation, the co-impregnation makes the synthesis simpler and eliminates the difficult second impregnation step. The mesoporous FeNi/carbon composites obtained have large surface areas, large pore volumes and a bimodal pore size distribution. The FeNi alloy nanoparticles were well dispersed in the mesoporous carbon walls. The composites exhibit excellent superparamagnetic behavior and the saturation magnetization strength can be adjusted from 3.4 to 5.7 emu/g by increasing the content of alloy. Such bimodal mesoporous composites show a large immobilization capacity for the biomolecules of cytochrome c (up to 732 mg/g) and lysozyme (up to 790 mg/g).

Microstructures and mechanical properties of the Mg–8Gd–xZn–0.4Zr (x = 0, 1 and 3 wt.%) alloys, in the as-cast condition and the as-extruded condition, have been investigated. The results show that both the 14H long periodic stacking structure and the W-phase coexist together in the cast Zn-containing alloys. The volume fraction of the W-phase increases with increasing the addition of Zn. This phase is the crack source of the fracture. The 6H long periodic stacking structure is observed in the extruded Zn-containing alloys. The Mg–8Gd–1Zn–0.4Zr alloy exhibits the highest elongation, and the value of its elongation is 130% at 300 °C due to the refined microstructure. The W-phase plays an important role in improving the mechanical properties via pinning the movement of the grains at elevated temperature.

The structural and magnetic properties of Ta-doped Ca4Mn3−xTaxO10 (0≤x≤0.3) compounds have been investigated. Structural refinement indicates that the Ta doping maintains the orthorhombic layered perovskite structure with space group Pbca as Ca4Mn3O10 but induces an increase in both unit cell volume and octahedral distortion. The magnetization measurements reveal that the magnetization first increases and reaches to maximum for the x=0.1 sample and then gradually decreases with the increase of Ta content. There appear short-range ferromagnetic (FM) clusters in all the doped samples, which are caused by the double-exchange interaction between Mn4+ and Mn3+ that is induced by the charge compensation effect. As x is higher than 0.1, the overall results show evidence for the gradual appearance of a cluster glass behavior. When x increases to 0.3, the long-range antiferromagnetic (AFM) ground state is melted into the short-range magnetically ordered regions due to the increase of Ta5+ and Mn3+ at the expense of Mn4+. The competition between AFM regions and FM clusters makes the short-range magnetic components frustrate when the temperature falls to a frustrating point, and thus cluster glass transition occurs.The magnetic structures of Ca4Mn3−xTaxO10 transit from G-type AFM to cluster glass state with the intermediate state of FM clusters exhibited in AFM matrix as Ta increasing.

The crystal structure and magnetism of Ca2−xLaxFeReO6 (0≤x≤0.8) double perovskites have been investigated. The samples with low doping (x≤0.4) are found to crystallize with the monoclinic P21/n superstructure, while those in the high doping ones (x≥0.6) have orthorhombic Pbnm superstructure. With the increase of an La doping, the anti-site defects increases, giving rise to highly disordered samples at the Fe and Re positions. At the low doping region (x≤0.4), the compounds undergo a simultaneous structural and magnetic transition accompanying a slight increase of the Curie temperature. The increase of Curie temperature is discussed in terms of the structural change with doping.Graphical abstractThe crystal structures of Ca2−xLaxFeReO6 transform from monoclinic to orthorhombic; meanwhile, high degree of anti-site disorder was present at B/B′ position, which promotes AFM correlations as an La increases.

A new kind of magnetic mesoporous Fe7Co3/carbon nanocomposite has been successfully synthesized for the first time via a simple cocasting method. By introducing Fe7Co3 alloy nanoparticles into mesoporous carbon, the magnetic property of the nanocomposite is greatly improved compared to using a single metal Fe or Co nanoparticles, which makes the porous carbon easily separated from solution by an external magnetic field. The nanocomposite is successfully applied to magnetically separable adsorber and exhibits excellent performance of adsorption for bulk dyes due to its high surface area (up to 1429 m2/g) and pore volume (up to 1.93 cm3/g).

The magnetic and electronic properties of Ba2MnMoO6 are investigated by using the full-potential linearized augmented plane-wave method, with both generalized gradient approximations (GGA) and GGA + U approaches. The calculated results indicate that parameter U plays a vital role in the electronic structure characterization. The ground state is found to be antiferromagnetic and insulating. In terms of the Heisenberg model, the nearest-neighbor and the next-nearest-neighbor magnetic interaction parameters are determined to be J1 = −1.17 meV and J2 = −0.87 meV. The valence states of Mn and Mo are suggested to be divalent and hexavalent respectively, in agreement with the experimental data.

Electronic structure calculations based on density functional theory in both optimized monoclinic (No. 14 P21/n) and rhombohedral (No. 148 R3̅) phases of La2NiFeO6 have been performed using full-potential linearized augmented plane wave method. The result indicates that La2NiFeO6 is a half-metallic ferromagnet within both crystal structures, and electronic correlation (U) plays a vital role in stabilizing the ferromagnetic ground state. Substitution of Mn4+ with Fe3+ induces a hole on Ni, making the transition of semiconducting La2Ni2+Mn4+O6 to half-metallic La2Ni3+Fe3+O6. Moreover, the half-metallicity is found to be robust under the compressive and tensile strains for both phases. The magnetic interaction constant is calculated according to the Heisenberg model, from which the Curie temperature is estimated within the mean field approximation. The Curie temperature is predicted to be as large as 495 and 474 K in P21/n and R3̅, respectively, making this system interesting candidates in spintronic devices.

A facile co-gelation route has been developed to synthesize novel porous Fe7Co3/carbon composites with Fe7Co3 nanoparticles embedded in the porous carbon matrix. The sol−gel process of this route simultaneously involves the hydrolysis of tetraethylorthosilicate (TEOS) and the polymerization of furfuryl alcohol (FA) within an ethanol solution containing TEOS, FA, and metal nitrates, which led to the inorganic/organic hybrid xerogel, accompanying metal salts spontaneously captured in the xerogel, mostly in the framework of poly(furfuryl alcohol) (PFA). Compared to the nanocasting route, the advantage of this method is that the formation of silica template and the impregnation of carbon precursor and metal salts were simultaneously carried out in one co-gelation process, which makes the synthesis very simple and eliminates the time-consuming synthesis of the silica template and multistep impregnation process. Different amounts of Fe7Co3 can be introduced into the composites, which led to different pore structures and magnetic properties. The composites have large surface areas (as high as 651.4 m2/g) and high saturation magnetizations (as high as 31.2 emu/g). The Fe7Co3/carbon composites prepared were successfully applied to the removal of dyes from water and catalysis of hydrogenation as efficient magnetically separable adsober and catalyst support. The facile co-gelation route makes the scalable synthesis of magnetic porous carbon possible for application, and it also provides a promising path to the synthesis of nanoscale metal or alloy embedded in the porous carbon materials.

Die-cast Mg–4Al–4RE–0.4Mn (RE = Ce-rich mischmetal) and Mg–4Al–4La–0.4Mn magnesium alloys were prepared successfully and their microstructure, tensile and creep properties have been investigated. The results show that two binary Al–RE phases, Al11RE3 and Al2RE, are formed along grain boundaries in Mg–4Al–4RE–0.4Mn alloy, while the phase compositions of Mg–4Al–4La–0.4Mn alloy mainly consist of α-Mg phase and Al11La3 phase. And in Mg–4Al–4La–0.4Mn alloy the Al11La3 phase occupies a large grain boundary area and grows with complicated morphologies, which is characterized by scanning electron microscopy in detail. Changing the rare earth content of the alloy from Ce-rich mischmetal to lanthanum gives a further improvement in the tensile and creep properties, and the later could be attributed to the better thermal stability of Al11La3 phase in Mg–4Al–4La–0.4Mn alloy than that of Al11RE3 phase in Mg–4Al–4RE–0.4Mn alloy.

Die cast AZ91–xYmm (x = 0–0.8 wt.%) magnesium alloys with excellent tensile properties and corrosion resistance behavior were successfully prepared by a simple addition of yttrium-rich misch metal (Ymm) to AZ91. Influences of Ymm on the microstructure, mechanical properties and corrosion behavior of AZ91 were investigated. The results showed that addition of Ymm to die cast AZ91 alloy could refine the microstructure including primary α-Mg and eutectic β-Mg17Al12. When the content of Ymm reached 0.8 wt.% a small quantity of Al2Y phase would form. The tensile properties were improved greatly with addition of Ymm to AZ91. The creep rate of the AZ91–Ymm alloys, tested at 150 °C/50 MPa, was one order of magnitude lower than that of AZ91. When addition of Ymm was more than 0.3 wt.%, the salt-spray corrosion resistance of AZ91–Ymm alloys could be 30–40 times of that of AZ91. The improvement of corrosion resistance with addition of Ymm was confirmed by the results of electrochemical polarization experiments. Mechanism of the improvement of mechanical properties and corrosion behavior caused by Ymm was also discussed.

The ageing behavior of an extruded Mg–7Y–4Gd–0.5Zn–0.4Zr alloy during ageing at 250 °C has been investigated. Two types of phases have been observed during the ageing process. One is a lamellar phase with a 14H long periodic stacking structure, the other is the β′ phase with an ellipsoidal morphology. The increased mechanical properties of the peak-aged alloy are mainly ascribed to the presence of both of these phases at peak hardness.

High-pressure die-cast (HPDC) Mg–4Al–4RE–0.4Mn (RE = La, Ce) magnesium alloys were prepared and their microstructures, tensile properties, and creep behavior have been investigated in detail. The results show that two binary Al–Ce phases, Al11Ce3 and Al2Ce, are formed mainly along grain boundaries in Mg–4Al–4Ce–0.4Mn alloy, while the phase composition of Mg–4Al–4La–0.4Mn alloy contains only α-Mg and Al11La3. The Al11La3 phase comprises large coverage of the grain boundary region and complicated morphologies. Compared with Al11Ce3 phase, the higher volume fraction and better thermal stability of Al11La3 have resulted in better-fortified grain boundaries of the Mg–4Al–4La–0.4Mn alloy. Thus higher tensile strength and creep resistance could be obtained in Mg–4Al–4La–0.4Mn alloy in comparison with that of Mg–4Al–4Ce–0.4Mn. Results of the theoretical calculation that the stability of Al11La3 is the highest among four Al–RE intermetallic compounds supports the experimental results further.

A series of Pr0.55Ca0.45MnO3 compounds with average particle size ranging from 2000 to 30 nm have been synthesized by the sol−gel method and their charge ordering (CO) and magnetic properties are investigated. It is observed that with particle size decreasing, the CO transition is gradually suppressed and finally disappears upon particle size down to 35 nm, while the ferromagnetism (FM) emerges and exhibits a nonmonotonous variation with a maximum at 45 nm samples. The FM components in all samples never reach long-range ordering but rather only show short-range clusters. A new explanation considering the coupling between lattice, charge, and spin in the system is raised to understand the suppression of the CO state. Both the competition between the CO/AFM and FM states and the core−shell model are employed to explain the variation of the FM phase. These results may provide a deeper insight into the physics of particle size effect on the charge ordering manganite.

Microstructures and mechanical properties of the Mg–8Gd–xZn–0.4Zr (x = 0, 1 and 3 wt.%) alloys in the as-cast, as-extruded and extruded-T5 conditions, have been investigated. The peak-aged Mg–8Gd–1Zn–0.4Zr alloy during isothermal ageing at 423 K acquires highest mechanical properties, with the highest ultimate tensile strength and yield tensile strength of 314 and 217 MPa, respectively. Addition of Zn has obvious effect on age hardening responses, especially for 1 wt.% Zn addition. It is due to a uniform distribution of β′ phase which can impede the movement of dislocations. However, addition of 3 wt.% Zn to the Mg–8Gd–0.4Zr alloy leads to a precipitation of Mg3Zn3Gd2 phase (W-phase). This phase is incoherent with interface of the matrix and becomes cores of the fracture in tensile test at room or elevated temperature.

Microstructures and mechanical properties of the Mg–7Y–4Gd–xZn–0.4Zr (x = 0.5, 1.5, 3, and 5 wt.%) alloys in the as-cast, as-extruded, and peak-aged conditions have been investigated by using optical microscopy, scanning electron microscope, X-ray diffraction, and transmission electron microscopy. It is found that the peak-aged Mg–7Y–4Gd–1.5Zn–0.4Zr alloys have the highest strength after aging at 220 °C. The highest ultimate tensile strength and yield tensile strength are 418 and 320 MPa, respectively. The addition of 1.5 wt.% Zn to the based alloys results in a greater aging effect and better mechanical properties at both room and elevated temperatures. The improved mechanical properties are mainly ascribed to both a fine β′ phase and a long periodic stacking-ordered structure, which coexist together in the peak-aged alloys.

The Ruddlesden–Popper series of compounds Ca4Mn3−xNbxO10 (x = 0–0.2) have been prepared by solid-state methods. Structural, magnetic, electrical, and magnetoresistive studies were performed on the compounds. Nb doping caused increases in both unit cell volume and octahedral distortion. The magnetization measurements indicated that the doped samples displayed ferromagnetism-like behavior, which could be explained by the double-exchange interaction between Mn4+ and Mn3+ induced by the charge-compensation effect. A phase-separation picture with the appearance of ferromagnetic clusters embedded in an antiferromagnetic matrix described the magnetic ground state of the doped samples well. All of the samples exhibited semiconducting behavior over the whole measured temperature range, with the high-temperature behavior better described by the small polaron conduction model and the low-temperature behavior by the two-dimensional version of Mott’s variable range hopping model. A large magnetoresistance effect was observed for all of the doped samples, and its value rose with decreasing temperature and increasing Nb content, attaining 51% at 40 K under a magnetic field of 5 T for the x = 0.2 sample. Calculated results for Ca4Mn3O10 and Ca4Mn2.8Nb0.2O10 samples further verified the corresponding experimental determinations.

First principles calculations using the augmented plane wave plus local orbitals method, as implemented in the WIEN2k code, have been used to investigate the electronic and magnetic properties of YBaFe2O5, especially as regards the charge-orbital ordering. Although the total 3d charge disproportion is rather small, an orbital order parameter defined as the difference between t2g orbital occupations of Fe2+ and Fe3+ cations is large (0.73) and gives unambiguous evidence for charge and orbital ordering. Strong hybridization between O 2p and Fe eg states results in the nearly complete loss of the separation between the total charges at the Fe2+ and Fe3+ atoms. Furthermore, the relationship between the orbital ordering and charge ordering is also discussed. The dxz orbital ordering is responsible for the stability of the G-type antiferromagnetic spin ordering and the charge ordering pattern.

In this study, compositional dependence of age hardening characteristics and tensile properties were investigated for Mg–4Ho–xY–0.6Zr alloys (x = 0, 3, 5, and 7 wt%). The result showed that with increasing Y content, the hardness of the alloys increased in the as-quenched and aged-peak conditions. Considerable age hardening response was recognized for the alloys. When the alloy containing 7% Y showed the most remarkable age hardening response at aging temperature of 250 °C. The tensile strength of the alloys increased monotonously with increasing Y content, and Mg–4Ho–7Y–0.6Zr exhibited the maximum ultimate tensile strength and yield strength at peak hardness, and the values were 240 and 165 MPa at room temperature, and 204 and 131 MPa at 250 °C, respectively. The improvement in strength appeared to be associated with β′ and/or equilibrium Mg24Y(Ho)5 precipitates and high dense dislocation.

The elastic anisotropy of the potential low compressible and hard materials OsB2 and RuB2 were studied by first-principles investigation within density functional theory. The structure, elastic constants, bulk modulus, shear modulus, Poisson's ratio and Debye temperature have been calculated within both local density approximation (LDA) and generalized gradient approximation (GGA). The results indicated that the calculated bulk modulus and shear modulus were in good agreement with the experimental and previous theoretical studies. The calculated elastic constants anisotropic factors and directional bulk modulus showed that OsB2 and RuB2 possess high elastic anisotropic.

The electronic and magnetic properties of Y Ba2Fe3O8 have been systematically investigated within the framework of density-functional theory using the standard generalized gradient approximation (GGA) as well as the GGA plus Hubbard U(GGA+U) method. The GGA results show that the G-type antiferromagnetic (AFM) state is preferred among the considered magnetic configurations. The striking ionic character is shown for Y and Ba atoms while very strong hybridization is found between Fe 3d and O 2p orbitals. Furthermore, the Fe–O–Fe superexchange interaction should be responsible for the stability of the AFM magnetic structure in this case. In addition, our theoretical calculations reveal that the ground state of Y Ba2Fe3O8 is a strongly correlated charge-transfer insulator with a finite band gap above the Fermi level obtained by the GGA+U scheme, which is in agreement with the experimental observations.

Cobalt ferrite one-dimensional nanostructures (nanoribbons and nanofibers) were prepared by electrospinning combined with sol−gel technology. The nanoribbons and nanofibers were formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) (PVP) as the structure-directing template. Nanoribbons and nanofibers were obtained after calcining the precursor nanoribbons at different temperatures. Successive Ostwald ripening processes occur during the formation of CoFe2O4 nanoribbons and nanofibers. The sizes of nanoparticles varied with calcination temperatures, which leads to different one-dimensional structures and variable magnetic properties. These novel magnetic one-dimensional structures can potentially be used in nanoelectronic devices, magnetic sensors, and flexible magnets.

Spinel ferrite, MFe2O4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol−gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts. The ribbons exhibited weak saturation magnetizations and low coercivities at room temperature, but at low temperature, saturation magnetizations and coercivities increased a lot, especially for CoFe2O4 ribbons, reaching 72 emu/g and 1.45 T at 2 k, respectively. These novel magnetic ribbons can potentially be used in micro/nano electronic devices, gas-sensors, and catalysts.

Solid solutions of Ce1−xNdxO2−x/2 (0.05 ≤ x ≤ 0.2) and (Ce1−xNdx)0.95Mo0.05O2−δ (0.05 ≤ x ≤ 0.2) have been synthesized by a modified sol–gel method. Both materials have very low content of SiO2 (∼27 ppm). Their structures and ionic conductivities were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (EIS). The XRD patterns indicate that these materials are single phases with a cubic fluorite structure. The powders calcined at 300 °C with a crystal size of 5.7 nm have good sinterability, and the relative density could reach above 96% after being sintered at 1450 °C. With the addition of MoO3, the sintering temperature could be decreased to 1250 °C. Impedance spectroscopy measurement in the temperature range of 250–800 °C indicates that a sharp increase of conductivity is observed when a small amount of Nd2O3 is added into ceria, of which Ce0.85Nd0.15O1.925 (15NDC) shows the highest conductivity. With the addition of a small amount of MoO3, the grain boundary conductivity of 15NDC at 600 °C increases from 2.56 S m−1 to 5.62 S m−1.

La0.5Ba0.5MnO3 products with novel flowerlike, microcube, and nanocube structures were successfully synthesized by a simple hydrothermal route by controlling the alkalinity of the reaction solutions. The synthesized products were systematically studied by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results showed that the formation of the flowerlike structures with a layer assembly experienced a nucleation−aggregation−crystallization growth process, while the cubic structures experienced a nucleation−crystallization growth process due to the effect of different alkalinity in the reaction solutions. The higher alkalinity also led to a decrease in the size in the cubic structures. Suitable temperature and pressure were demonstrated to be crucial to the formation of the flowerlike structures by carrying out further control experiments. The measurement of the magnetic properties of three samples obtained at different alkaline conditions indicated that the size of the La0.5Ba0.5MnO3 products had an obvious influence on their properties; however, the dependence of the properties upon the morphology of the La0.5Ba0.5MnO3 products was minor.

We have investigated the structure, magnetization and magnetoresistance (MR) of the double perovskite compounds Sr2Fe1−xGaxMoO6 (0 ≤ x ≤ 0.25). Rietveld refinement results show that the anti-site defects (ASDs) concentration increases with x, giving rise to highly disordered samples at the B/B′ positions, for the highest doping levels. The evolution of bond lengths and ions oxidation states could be understood by the distribution of trivalent Ga ions at the B/B′ positions, which leads to the formation of more disorder structure. The saturation magnetization and Curie temperature decreased with the Ga content increases in the samples, and their origin was found that the cations disorder for the Ga-doped compounds is annihilating double exchange mechanism due to the presence of significant amounts of Fe and Ga cations on the B′ site. The low-field magnetoresistance of Sr2FeMoO6 (SFMO) can be greatly enhanced by replacing the Fe by the nonmagnetic Ga ion up to a temperature of 300 K, since Ga ions may act as a barrier for electron transport along the chain in the ferromagnetic segregation and weaken the ferromagnetic exchange.

Accurate ab initio density-functional calculations are performed to investigate the relationship of the ground-state crystal structures and electronic properties of Ag2BiO3 compound. The results indicate that Ag2BiO3 in Pnna phase, in which the bismuth atoms occupy the same Wyckoff positions, exhibits metallic conductivity, while in Pnn2 and Pn phases, Ag2BiO3 exhibits semiconducting character, which is in agreement with the experimental results. Charge ordering is indeed induced by the crystal inversion twin in the Pnn2 phase compared with the Pnna phase. In the low temperature phase Pn, the charge ordering is similar to that of Pnn2 phase although it is more distorted in Pn phase. In addition, the calculation indicates that the charge ordering is caused in the 6s electron rearrangement.GGA calculating results indicate that Ag2BiO3 in Pnna phase, in which the bismuth atoms occupy the same Wykoff positions, exhibits metallic conductivity, while in Pnn2 and Pn phases, Ag2BiO3 exhibits semiconducting character, which is in agreement with the experimental results. Charge ordering is indeed induced by the crystal inversion twin in the Pnn2 phase compared with the Pnna phase.

The electronic structure of CaCu3Mn4O12 and LaCu3Mn4O12 was investigated using a full-potential linearized augmented plane wave method within the Generalized Gradient Approximation (GGA). The ferrimagnetic and ferromagnetic states in these two compounds were investigated and the calculated spin magnetic moments were found to be close to the available experimental values. Calculations of spin polarization for these two oxides show that the ferrimagnetic configurations are the energetically favored ground state, which is consistent with experimental observation. The calculations predict that CaCu3Mn4O12 is a semiconductor and that LaCu3Mn4O12 is a half-metallic material. Furthermore, the relevance of these different electronic structures to the magnetoresistance is discussed.

The n = 1 Ruddlesden–Popper (RP) phases LaSrM0.5Ru0.5O4±δ (M = Co, Ni and Zn) have been prepared by solid state reactions and structurally characterized by powder X-ray and electron diffraction. All the samples adopt the tetragonal I4/mmm space group with random M and Ru cation occupation on the B-sites. The potential causes of no cation ordering are discussed. A combined analysis of the tolerance factors, the distortion of the octahedral coordination of M and Ru cations and the magnetic interactions between M and Ru cations provide a better understanding for forming a phase with 3D cation ordering on the B-sites in the n = 1 RP phases. The investigation of XPS spectra suggests that the transition element species exist as mixed ion pairs, Ru(4−δ)+–Ru4+ ↔ Co2+–Co3+ in LaSrCo0.5Ru0.5O4, and Ru4+–Ru(4+δ)+ ↔ Ni+–Ni2+ in LaSrNi0.5Ru0.5O4, which is consistent with cation disorder over the B sites. LaSrCo0.5Ru0.5O4 shows a weakly ferromagnetic behaviour below 50 K; LaSrNi0.5Ru0.5O4 is evidenced by the presence of long-range magnetic ordering at a Néel temperature of 125 K, and LaSrZn0.5Ru0.5O4 exhibits a paramagnetic behaviour down to 5 K. Due to atomic disorder, Ru4d, O2p covalent coupling is weakened, strengthening the intraatomic spin–spin coupling among the π* electrons. Charge transfer between Ru and Co or Ru and Ni, as well as the increasing overlap of both nearest-neighbour and next-nearest-neighbour Ru 4d electrons due to atomic disorder, favour the formation of ferromagnetic interactions. Although antiferromagnetism is dominant, particularly in LaSrNi0.5Ru0.5O4, ferromagnetic interactions are stronger in the title compounds than in the related La2MRuO6 (M = Co, Ni) double perovskites where the B-site cations are ordered.