Two new biaxial, diamond-like semiconductors, Li2CdGeSe4 and Li2CdSnSe4, were prepared via high-temperature, solid-state synthesis. Single crystal X-ray diffraction and X-ray powder diffraction coupled with Rietveld refinement were used to refine the crystal structures and assess the phase purity, respectively. Both compounds adopt the lithium cobalt(II) silicate structure type. Strong second-order nonlinear optical (NLO) susceptibility, phase matchability, relatively high thermal stability, and excellent transparency deem both materials potential infrared (IR) NLO candidates. Li2CdGeSe4 and Li2CdSnSe4 display optical bandgaps of approximately 2.5 and 2.2 eV, respectively. Li2CdSnSe4 exhibits a strong, red-light emission under 1064 nm excitation, allowing the compound to release energy that accumulates by two-photon absorption under Nd:YAG laser radiation. Therefore, Li2CdSnSe4 shows a high laser-induced damage threshold (LIDT) of 0.7 GW cm−2. This special phenomenon is remarkable and may open a new avenue in searching for promising IR NLO materials with large LIDTs.

Correction for ‘Infrared nonlinear optical properties of lithium-containing diamond-like semiconductors Li2ZnGeSe4 and Li2ZnSnSe4’ by Jian-Han Zhang et al., Dalton Trans., 2015, 44, 11212–11222.

Li2SnS3 is a fast Li+ ion conductor that exhibits high thermal stability (mp ∼750 °C) as well as environmental stability under ambient conditions. Polycrystalline Li2SnS3 was synthesized using high-temperature, solid-state synthesis. According to single-crystal X-ray diffraction, Li2SnS3 has a sodium chloride-like structure (space group C2/c), a result supported by synchrotron X-ray powder diffraction and 119Sn Mössbauer spectroscopy. According to impedance spectroscopy, Li2SnS3 exhibits Li+ ion conductivity up to 1.6 × 10–3 S/cm at 100 °C, which is among the highest for ternary chalcogenides. First-principles simulations of Li2SnS3 and the oxide analogue, Li2SnO3, provide insight into the basic properties and mechanisms of the ionic conduction. The high thermal stability, significant lithium ion conductivity, and environmental stability make Li2SnS3 a promising new solid-state electrolyte for lithium ion batteries.

The new Li2MnGeS4 and Li2CoSnS4 compounds result from employing a rational and simple design strategy that guides the discovery of diamond-like semiconductors (DLSs) with wide regions of optical transparency, high laser damage threshold, and efficient second-order optical nonlinearity. Single-crystal X-ray diffraction was used to solve and refine the crystal structures of Li2MnGeS4 and Li2CoSnS4, which crystallize in the noncentrosymmetric space groups Pna21 and Pn, respectively. Synchrotron X-ray powder diffraction (SXRPD) was used to assess the phase purity, and diffuse reflectance UV–vis–NIR spectroscopy was used to estimate the bandgaps of Li2MnGeS4 (Eg = 3.069(3) eV) and Li2CoSnS4 (Eg = 2.421(3) eV). In comparison with Li2FeGeS4, Li2FeSnS4, and Li2CoSnS4 DLSs, Li2MnGeS4 exhibits the widest region of optical transparency (0.60–25 μm) and phase matchability (≥1.6 μm). All four of the DLSs exhibit second-harmonic generation and are compared with the benchmark NLO material, AgGaSe2. Most remarkably, Li2MnGeS4 does not undergo two- or three-photon absorption upon exposure to a fundamental Nd:YAG beam (λ = 1.064 μm) and exhibits a laser damage threshold > 16 GW/cm2.

Two new lithium-containing diamond-like semiconductors, Li2ZnGeSe4 and Li2ZnSnSe4, have been prepared by high-temperature, solid-state synthesis. Single crystal X-ray diffraction reveals that both compounds adopt the wurtz–kesterite structure type, crystallizing in the noncentrosymmetric space group Pn. X-ray powder diffraction coupled with Rietveld refinement indicates the high degree of phase purity in which the materials are prepared. Both compounds display optical bandgaps around 1.8 eV, wide optical transparency windows from 0.7 to 25 μm and type-I phase matched second harmonic generation starting at 2500 nm and persisting deeper into the infrared. Using the Kurtz powder method, the second-order nonlinear optical coefficient, χ(2), was estimated to be 19 and 23 pm V−1 for Li2ZnGeSe4 and Li2ZnSnSe4, respectively. Using a 1064 nm incident laser beam with a pulse width (τ) of 30 ps both compounds exhibit a laser damage threshold of 0.3 GW cm−2, which is higher than that of the AgGaSe2 reference material measured under identical conditions. Differential thermal analysis shows that the title compounds are stable up to 684 and 736 °C, respectively. These properties collectively demonstrate that Li2ZnGeSe4 and Li2ZnSnSe4 have great potential for applications in tunable laser systems, especially in the infrared and even up to the terahertz regime. Electronic structure calculations using a plane-wave pseudopotential method within density functional theory provide insight regarding the nature of the bandgap and bonding.

While X-ray powder diffraction (XRPD) is a fundamental analytical technique used by solid-state laboratories across a breadth of disciplines, it is still underrepresented in most undergraduate curricula. In this work, we incorporate XRPD analysis into an inquiry-based project that requires students to identify the crystalline component(s) of familiar household products. Centering the project on materials which students encounter in their everyday lives helps to demystify the technique, making it accessible to everyone with a basic understanding of crystallinity and unit cells. In an XRPD study, each crystalline component generates a unique set of peaks in the diffractogram. Comparing the collected diffractogram to a library of diffractograms for known crystalline materials allows students to identify the crystalline components in their unknown. Students must determine for themselves the chemical compositions of the possible unknowns, and link their findings back to the analysis of the collected data. Initially challenging, this is the part of the work they respond to most strongly. This lab includes a data collection component, but its inquiry-based objectives can still be achieved by providing the students with simulated diffractograms when the appropriate instrumentation is unavailable.

•Varying the II ion in the Li2–II–GeS4 formula yields three different structure types.•Li2CoGeS4 crystallizes in the Pn space group with the wurtz-kesterite structure.•Li2MnGeS4 possesses a zeolite ABW-like [MnGeS4]2 − anionic framework.•Li2FeGeS4 exhibits a Li+ ion conductivity of 1.8(3) × 10− 4 S/cm at 100 °C.•Li2CdGeS4 shows the lowest activation energy for Li+ ion conduction, EA = 0.74(2) eV.The new Li2CoGeS4 compound crystallizes in the Pn space group with the wurtz-kesterite structure, according to single crystal X-ray diffraction. The structure of Li2CoGeS4 and the high degree of phase-purity in which it is prepared are supported by high-resolution synchrotron X-ray powder diffraction. Varying the divalent ion in Li2-II-GeS4 materials yields three different structure types, all of which are derived from hexagonal diamond. These structural variations give rise to Li+-encompassing [II–GeS4]2 − nets with different topologies that offer diversity in lithium ion diffusion pathways. In the first systematic study of the lithium ion conductivity in quaternary diamond-like materials, wurtz-kesterite-type Li2CoGeS4 and Li2FeGeS4 (Pn), lithium cobalt(II) silicate-type Li2MnGeS4 (Pna21), and wurtz-stannite-type Li2CdGeS4 (Pmn21) are presented as environmentally stable lithium ion conductors. These materials are comprised of cubic diamond-like [CoGeS4]2 − and [FeGeS4]2 − anionic frameworks, ABW-like [MnGeS4]2 −, and square lattice-like [CdGeS4]2 −. As assessed using impedance spectroscopy, Li2FeGeS4 exhibits the most promising Li+ ion conductivity of 1.8(3) × 10− 4 S/cm at 100 °C, while Li2CdGeS4 shows the lowest activation energy for lithium ion conduction, EA = 0.74(2) eV.

Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS), which are among the first magnetic semiconductors with the wurtz-kesterite structure, exhibit antiferromagnetism with TN ≈ 6 and 4 K, respectively. Both compounds undergo a conventional metamagnetic transition that is accompanied by a hysteresis; a reversible spin-flop transition is dominant. On the basis of constant-wavelength neutron powder diffraction data, we propose that LIGS and LITS exhibit collinear magnetic structures that are commensurate and incommensurate with propagation vectors km = [1/2, 1/2, 1/2] and [0, 0, 0.546(1)], respectively. The two compounds exhibit similar magnetic phase diagrams, as the critical fields are temperature-dependent. The nuclear structures of the bulk powder samples were verified using time-of-flight neutron powder diffraction along with synchrotron X-ray powder diffraction. 57Fe and 119Sn Mössbauer spectroscopy confirmed the presence of Fe2+ and Sn4+ as well as the number of crystallographically unique positions. LIGS and LITS are semiconductors with indirect and direct bandgaps of 1.42 and 1.86 eV, respectively, according to optical diffuse-reflectance UV–vis–NIR spectroscopy.

Cu2CdSnS4 and α/β-Cu2ZnSiS4 meet several criteria for promising nonlinear optical materials for use in the infrared (IR) region. Both are air-stable, crystallize in noncentrosymmetric space groups, and possess high thermal stabilities. Cu2CdSnS4 and α/β-Cu2ZnSiS4 display wide ranges of optical transparency, 1.4–25 and 0.7–25 μm, respectively, and have relatively large second-order nonlinearity as well as phase matchability for wide regions in the IR. The laser-damage threshold (LDT) for Cu2CdSnS4 is 0.2 GW/cm2, whereas α/β-Cu2ZnSiS4 has a LDT of 2.0 GW/cm2 for picosecond near-IR excitation. Both compounds also exhibit efficient third-order nonlinearity. Electronic structure calculations provide insight into the variation in properties.

•Up to 12.5% of the In3+ is replaced with Fe3+ in CuInS2.•Rietveld refinements using powder diffraction data show iron on the indium site.•CuIn0.875Fe0.125S2 is ferromagnetic below 95 K.•The thermal conductivity of CuIn0.875Fe0.125S2 is 1.37 W m−1 K−1 at 570 K.•The ZT of CuInS2 increased by over an order of magnitude with iron substitution.CuIn1−xFexS2 (x = 0–0.15) was synthesized via high-temperature, solid-state synthesis. Rietveld refinements using the neutron and synchrotron powder diffraction data indicate that all Fe-substituted materials are phase pure with the exception of the CuIn0.85Fe0.15S2 sample, which contains a minute secondary phase. These refinements also verify that iron resides on the indium site in the CuIn1−xFexS2 materials. CuIn0.875Fe0.125S2 displayed the lowest total thermal conductivity of the series, 1.37 W m−1 K−1 at 570 K, as well as the highest thermopower, −172 μV K−1 at 560 K. The electrical conductivity increases over six times upon going from CuInS2 to CuIn0.875Fe0.125S2. These improved properties result in an increase in the thermoelectric figure of merit (ZT) of CuInS2 by over an order of magnitude for the x = 0.125 sample. Magnetic measurements reveal the x = 0–0.10 samples to be paramagnetic, while the sample in which x = 0.125 displays ferromagnetic ordering below 95 K.

•Ag2FeSiS4, Li2FeGeS4, and Li2FeSnS4 possess a wurtz–kesterite structure (Pn).•These materials and others do not comply with Pauling’s radius ratio rule.•These materials and others do not comply with Pfitzner’s tetrahedral volume theory.•Five radii sets are assessed for accuracy in predicting M–S bonds.•A four-coordinate S2− radius of 1.63 Å is added to the Shannon radii set.Iron-containing diamond-like materials Ag2FeSiS4, Li2FeSnS4, and Li2FeGeS4 were synthesized for the first time via high-temperature, solid-state synthesis and found to adopt the wurtz–kesterite structure, crystallizing in the noncentrosymmetric space group Pn. These materials are considered in the broader context of design principles for new cubic- and hexagonal-derived diamond-like materials. All three of these new compounds violate Pauling’s radius ratio rule and Pfitzner’s tetrahedral volume theory. An evaluation of the adherence of over 40 published quaternary diamond-like structures to Pauling’s radius ratio rule and Pfitzner’s tetrahedral volume theory reveals that tetrahedral structures can often be generated even though these ideals are violated. To assess the radius ratios in diamond-like structures, an appropriate radii set must be selected. Accordingly, five radii sets have been investigated for accuracy in predicting metal–sulfur bond distances in diamond-like materials. Furthermore, a crystal radius of 1.63 Å for four-coordinate S2− has been calculated using the metal–sulfur bond lengths of quaternary diamond-like materials and is proposed as an addition to the popular Shannon radii set.Graphical abstract

CuIn1−xFexS2(x=0–0.30) was synthesized via high-temperature, solid-state synthesis. Phase-pure materials were found in samples where x=0–0.15, after which a secondary phase became apparent. The materials were characterized with the use of X-ray powder diffraction (XRPD), and Reitveld refinement revealed a linear decrease in unit cell volume as the amount of iron substitution increases in accordance with Vegard’s Law. Inductively coupled plasma (ICP) confirms that the actual stoichiometry is close to the nominal composition of the materials. The temperature for both the chalcopyrite-to-sphalerite and the sphalerite-to-wurtzite phase transitions decreases with increasing iron substitution for indium. These findings suggest that the Fe is being randomly incorporated into the crystal structure of the CuInS2. X-ray photoelectron spectroscopy (XPS) measurements were used to determine the oxidation state of the ions (Cu1+, In3+, and S2−), and Fe57 Mössbauer spectroscopy verified that the iron is in the 3+ oxidation state. Band gaps of the solid solution were estimated to be in the range of 0.70–0.85 eV. Rietveld refinement of neutron diffraction data indicates that the iron is occupying the In site within the chalcopyrite structure.Graphical abstractCuIn1−xFexS2 samples were prepared by solid-state synthesis. X-ray photoelectron spectroscopy and Mössbauer spectroscopy indicate Cu+, In3+, Fe3+ and S2− in the samples. Rietveld refinement of neutron powder diffraction data shows Fe3+ residing on the indium site. The band gaps of the iron-containing samples decrease to ∼0.7 eV.Highlights► X-ray photoelectron spectroscopy confirms the presence of Cu+, In3+ and S2−. ► Mössbauer spectroscopy indicates the presence of Fe3+. ► Rietveld refinement of neutron powder diffraction data shows iron on the indium site. ► The band gap decreases to ∼0.7 eV with only 5% iron substitution. ► Additional characterization is reported.

The quaternary diamond-like semiconductor, Ag2CdGeS4, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag2CdGeS4 in the orthorhombic, noncentrosymmetric space group Pna21 with a=13.7415(8) Å, b=8.0367(5) Å and c=6.5907(4) Å, in contrast to a previously published model in Pmn21 from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna21 space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag2CdGeS4 exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material.Graphical abstractThe structure of the diamond-like semiconductor Ag2CdGeS4 has been solved and refined in the orthorhombic noncentrosymmetric space group Pna21. A view down the a-axis shows that all MS4 tetrahedra are pointing in the same direction along the c-axis. The structure can be derived from that of lonsdaleite.Highlights► The structure of Ag2CdGeS4 is solved from single crystal X-ray diffraction. ► The structure is supported by the Rietveld analysis of synchrotron diffraction data. ► Ag2CdGeS4 is a semiconductor with an optical band gap of 2.32 eV. ► Additional characterization is reported.

The Mn-substituted CuInS2 compounds (CuIn1–xMnxS2 with x = 0–0.20 and Cu1–yMnyInS2 with y = 0.05–0.10) were synthesized using high-temperature solid–state reactions. Single-phase materials with the chalcopyrite structure persist with up to 10% of the Cu/In sites being replaced with Mn. The introduction of manganese results in a linear expansion of the lattice parameters as a function of Mn concentration, following Vegard's law. Rietveld refinements on a combination of X-ray and neutron powder diffraction data reveal a site preference of Mn for the In site under In-poor conditions and the existence of cation anti-site occupation, CuIn and InCu. The Mn substitution increases the anion displacement, accentuating the cation-anion bond length mismatch. The greater variance in the bond alternation and the addition of Mn d–S p hybridization near the Fermi level result in a decrease in the bandgap by ∼0.1 eV. The CuInS2:Mn compounds display paramagnetic behavior with short-range antiferromagnetic interactions. X-ray photoelectron spectroscopy suggests the presence of Cu+, Mn2+, and In3+ in the samples.Graphical abstractHighlights► Up to 10% of the Cu/In sites is replaced with Mn in CuInS2. ► Mn prefers the In site under In-poor conditions for low-Mn-content samples. ► The oxidation states of Cu+, Mn2+ and In3+ are established. ► CuInS2:Mn is paramagnetic with short-range antiferromagnetic interactions. ► The bond alternation and p–d hybridization decrease the bandgap by ∼0.1 eV.

Ternary chalcopyrite systems are of interest for a number of applications, including host materials for dilute magnetic semiconductors and thin film photovoltaic cells. There are two cation sites, 4a and 4b, in the chalcopyrites, and the location of transition-metal ions in the chalcopyrites plays an important role in determining their magnetic and electrical properties. In this work, neutron and X-ray powder diffraction of the Mn-substituted CuInSe2 compounds, namely, CuIn1−xMnxSe2 (x = 0.05 and 0.10) and Cu1−yIn1−yMn2ySe2 (2y = 0.05, 0.15, and 0.20), has been carried out. Rietveld refinements using the neutron and X-ray diffraction data reveal a site preference of manganese ions on the copper site (4a) rather than the indium site (4b), in both series, namely, under In-poor conditions and under Cu-poor and In-poor conditions. The major fraction of Mn ions occupies the copper site, which thus pushes the expelled copper ions to the indium site, resulting in antisite CuIn defects. These results can help to explain why Mn-substituted CuInSe2 compounds display antiferromagnetic interactions instead of ferromagnetic coupling as predicted by first-principles calculations. High frequency electron paramagnetic resonance measurements suggest that the oxidation state of the manganese ions is divalent.

The semiconductors Li2CdGeS4 and Li2CdSnS4, which are of interest for their nonlinear optical properties, were synthesized using high-temperature solid-state and polychalcogenide flux syntheses. Both compounds were found to crystallize in Pmn21, with R1 (for all data) = 1.93% and 1.86% for Li2CdGeS4 and Li2CdSnS4, respectively. The structures of both compounds are diamond-like with the tetrahedra pointing in the same direction along the c axis. The alignment of the tetrahedra results in the structure lacking an inversion center, a prerequisite for second-harmonic generation (SHG). A modified Kurtz nonlinear optical powder technique was used to determine the SHG responses of both compounds. Li2CdGeS4 displayed a type I phase-matchable response of approximately 70× α-quartz, while Li2CdSnS4 displayed a type I non-phase-matchable response of approximately 100× α-quartz. Diffuse-reflectance spectroscopy was used to determine band gaps of 3.10 and 3.26 eV for Li2CdGeS4 and Li2CdSnS4, respectively.

EuCu2SnS4 was prepared by a stoichiometric combination of the elements heated to 700 °C for 125 h. The structure was determined by single crystal X-ray diffraction methods. The compound crystallizes in the noncentrosymmetric, orthorhombic space group Ama2 with a=10.4793(1) Å, b=10.3610(2) Å, c=6.4015(1) Å, Z=4, R1=0.99% and wR2=2.37%. The structure type is that of SrCu2GeSe4. The structure can be described as a three-dimensional network built from near perfect SnS4 and distorted CuS4 tetrahedra together with EuS8 square antiprisms. The dark red compound is a semiconductor with an optical bandgap of 1.85 eV.EuCu2SnS4 crystallizes in the orthorhombic space group Ama2 and adopts the SrCu2GeSe4 structure-type. The structure can be described as a three-dimensional network built from near perfect SnS4 and distorted CuS4 tetrahedra together with EuS8 square antiprisms.

Mn-doped CuInSe2 compounds (CuIn1−xMnxSe2, x=0.0125–0.20 and Cu1−yIn1−yMn2ySe2, 2y=0.0125–0.60) were synthesized by high-temperature solid-state reactions. Single phase materials with chalcopyrite structure persist up to 0.10 and 0.20 doping for CuIn1−xMnxSe2 and Cu1−yIn1−yMn2ySe2, respectively. The chalcopyrite and sphalerite phases co-exist in the Cu1−yIn1−yMn2ySe2 system for 2y=0.25–0.50. Attempts to introduce greater manganese content, x=0.15–0.20 for CuIn1−xMnxSe2 and 2y=0.60 for Cu1−yIn1−yMn2ySe2, result in partial phase segregation. For the single-phase samples, the lattice parameters of both systems increase linearly with manganese concentration and thus follow Vegard's law. The temperature of the chalcopyrite–sphalerite phase transition is decreased by manganese substitution for all single-phase samples. The bandgap of the materials remains around 0.9 eV. Additionally, the Mn-doped CuInSe2 compounds display paramagnetic behavior, whereas pure CuInSe2 is diamagnetic at 5–300 K. All the CuIn1−xMnxSe2 and Cu1−yIn1−yMn2ySe2 compounds with chalcopyrite structure show antiferromagnetic coupling and measured effective magnetic moments up to 5.8 μB/Mn.The manganese solid solubility can reach up to 10% and 20% for CuIn1−xMnxSe2 and Cu1−yIn1−yMn2ySe2, respectively, while maintaining phase-pure, chalcopyrite-type materials. Lattice parameters increase linearly with increase manganese concentration suggesting that the manganese ions are distributed randomly on both the indium site and the copper and indium sites simultaneously.

Li2ZnSnS4 is a new diamond-like semiconductor, which is of interest as a host structure for the creation of potentially interesting electronic, magnetic and photovoltaic materials. The compound was synthesized via traditional high-temperature solid-state methods and was predicted to adopt a wurtz-stannite structure with all atoms possessing tetrahedral environments. Initial analysis of single-crystal X-ray diffraction data indicated crystallographic disorder that upon closer examination violated basic chemical principles. The structure was subsequently re-evaluated and the apparent “disorder” problem was found to be the result of pseudo-merohedral twinning. The crystal structure was finally solved in the monoclinic space group Pn, which resulted in a chemically reasonable model. The refinement converged with R1=1.68% (for all data). Additional characterization of the sample, including diffuse reflectance, thermal analysis and second harmonic generation measurements, was also performed.Li2ZnSnS4 is a new diamond-like semiconductor synthesized via high-temperature solid-state methods. Analysis of single-crystal X-ray diffraction data indicated that the structure was a pseudo-merohedral twin crystallizing in space group Pn and related to the wurtz-stannite structure. Additional characterization of the sample is reported.

This paper describes the synthesis and characterization of two, new rare earth monothiophosphate materials, LaPO3S·xH2O and NdPO3S·yH2O, and their properties in comparison to the corresponding orthophosphates prepared by a similar aqueous metathesis reaction. Each of these new materials was found to exist in an amorphous phase similar to a corresponding orthophosphate mineral. The new rhabdophane-type oxythiophosphates were found to display reversible dehydration and rehydration under mild conditions. The materials were found to be thermally unstable. Disproportionation was found to occur at less than 450 °C under vacuum. Sulfur is lost during heating in air between 450 and 650 °C, according to thermogravimetric analysis (TGA) experiments, yielding the orthophosphate. The monothiophosphate hydrates display broad photoluminescence in the visible under excitation by a 325 nm laser. The compounds were also analyzed using differential thermal analysis, FT-IR and UV/vis/NIR spectroscopy.This paper describes the synthesis and characterization of two, new rare earth monothiophosphate materials, LaPO3S·xH2O and NdPO3S·yH2O. Each of these was found to exist in a phase similar to the orthophosphate mineral, rhabdophane. The monothiophosphate hydrates displayed broad photoluminescence in the visible under excitation by a 325 nm laser.

Solid-state microwave synthesis was found to provide a simple, rapid and economical route to prepare Sb2Se3, Sb2Te3, Bi2Se3 and Bi2Te3. These technologically important materials were prepared via solid-state microwave synthesis in as little as 4 min. Through the process of finding the ideal synthetic conditions with which to produce each of these compounds, the effects that several synthetic variables have on the reaction outcomes were explored. Scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, differential thermal analysis and diffuse reflectance measurements, when appropriate, were used to characterize the materials.Solid-state microwave synthesis offers a fast, economical and green route for the preparation of Sb2Se3, Sb2Te3, Bi2Se3 and Bi2Te3 (shown in graphic) in only 4 min. Through the process of preparing these materials in pure form, the effects that several reaction variables, including sample quantity, irradiation time and sample geometry, have on the outcome of the reactions were documented.

Two new lithium-containing diamond-like semiconductors, Li2ZnGeSe4 and Li2ZnSnSe4, have been prepared by high-temperature, solid-state synthesis. Single crystal X-ray diffraction reveals that both compounds adopt the wurtz–kesterite structure type, crystallizing in the noncentrosymmetric space group Pn. X-ray powder diffraction coupled with Rietveld refinement indicates the high degree of phase purity in which the materials are prepared. Both compounds display optical bandgaps around 1.8 eV, wide optical transparency windows from 0.7 to 25 μm and type-I phase matched second harmonic generation starting at 2500 nm and persisting deeper into the infrared. Using the Kurtz powder method, the second-order nonlinear optical coefficient, χ(2), was estimated to be 19 and 23 pm V−1 for Li2ZnGeSe4 and Li2ZnSnSe4, respectively. Using a 1064 nm incident laser beam with a pulse width (τ) of 30 ps both compounds exhibit a laser damage threshold of 0.3 GW cm−2, which is higher than that of the AgGaSe2 reference material measured under identical conditions. Differential thermal analysis shows that the title compounds are stable up to 684 and 736 °C, respectively. These properties collectively demonstrate that Li2ZnGeSe4 and Li2ZnSnSe4 have great potential for applications in tunable laser systems, especially in the infrared and even up to the terahertz regime. Electronic structure calculations using a plane-wave pseudopotential method within density functional theory provide insight regarding the nature of the bandgap and bonding.

Correction for ‘Infrared nonlinear optical properties of lithium-containing diamond-like semiconductors Li2ZnGeSe4 and Li2ZnSnSe4’ by Jian-Han Zhang et al., Dalton Trans., 2015, 44, 11212–11222.