•Lu-doped Bi2Te3 flower-like nanopowders were synthesized using hydrothermal method.•Optimal Lu-doped samples can have a higher power factor than the undoped sample.•Figure of merit (ZT) for the Lu0.1Bi1.9Te3 sample can reach 1.7 at 373 K.Lutetium-doped Bi2Te3 flower-like nanopowders were synthesized by hydrothermal method. The flower-like nanopowders were hot pressed into bulk pellets and the doping effects of lutetium on the thermoelectrical properties were investigated. The results show that the doping of lutetium can reduce the electrical resistivity greatly, while does not reduce the Seebeck coefficient too much, therefore results in a high power factor. Because the mass of the lutetium atom is close to the mass of the bismuth atom, replacing bismuth by lutetium will not increase the frequency of phonons greatly, which is helpful to remain a lower thermal conductivity. As a result of the combining effect of the lutetium doping and nanostructure of the sample, figure of merit (ZT) for the Lu0.1Bi1.9Te3 sample can reach a high value 1.7 at 373 K.

n-Type R0.2Bi1.8Se0.3Te2.7 (R = Ce, Y and Sm) nanopowders were synthesized by hydrothermal method and the thermoelectric properties of the bulk samples made by hot-pressing these nanopowders were investigated. The Ce, Y and Sm doping have significant effects on the morphologies of the synthesized nanopowders. The thermoelectric property results show that Ce, Y and Sm doping not only help to decrease the electrical resistivity, but also help to reduce the thermal conductivity. Among rare earth elements-doped samples, it seems that the Y0.2Bi1.8Se0.3Te2.7 bulk has a suitable microstructure, which scatters phonons effectively but does not scatter electronic carriers as much. As a result, the ZT values of Y0.2Bi1.8Se0.3Te2.7 can reach 1.21 at 413 K, which is higher than those of Bi2Se0.3Te2.7 ingots made by zone-melting method.

Yttrium-doped YxBi2−xTe3 (x = 0.15, 0.2, 0.25) flower-like nanopowders were synthesized by the hydrothermal method through careful adjustment of the amount of ethylenediaminetetraacetic acid surfactant. The flower-like nanopowders were hot pressed into bulk pellets, and the thermoelectric properties of the pellets were examined. The results showed that the optimized doped sample Y0.25Bi1.75Te3 had a relatively high Seebeck coefficient, a lower electrical resistivity, and a lower thermal conductivity. As a result, the figure of merit of the n-type Y0.25Bi1.75Te3 alloy reached 1.23 at 410 K.

Nanopowders of elements doped Bi2Te3 thermoelectric alloy R0.2Bi1.8Te3 (R=Ce, Y and Sm) were synthesized by the hydrothermal method. The nanopowders were hot-pressed into pellets and their thermoelectric properties were investigated. The results show that Ce, Y, and Sm doping has significant effects on the morphologies of the synthesized nanopowders and thermoelectric properties. Among the doping elements, Ce doping is a superiority dopant. Although the electrical conductivity and Seebeck coefficient are not improved much by Ce doping, the thermal conductivity is supressed greatly. As a result the figure of merit (ZT) of Ce0.2Bi1.8Te3 is improved and reaches 1.29 at 398 K, which is higher than the Bi2Te3 ingots made by the traditional zone-melting method

Nanostructure engineering and rare earths filling were employed to enhance the thermoelectric properties of the CoSb3 based skutterudite. The CoSb3 and the rare earths filled LaFe3CoSb12, CeFe3CoSb12, La0.5Ce0.5Fe3CoSb12 nano-powders were prepared via a hydro/solvo thermal method and then the nano-powders were used to make bulk samples by hot-press. Our results indicate that besides the nanostructure and the rare earths filling, the existence of a glassy phase in the samples is also an important factor for the enhancement of the thermoelectric properties. The Seebeck coefficients of the samples were improved obviously while their excellent electrical conductivities could be maintained, meanwhile the thermal conductivities of the samples were suppressed significantly. Therefore, the figures of merit were enhanced and ZT values could be reached at 773 K as 0.19, 0.43, 0.62 and 0.82 for CoSb3, LaFe3CoSb12, CeFe3CoSb12 and La0.5Ce0.5Fe3CoSb12 respectively.

The effects of a thin RBaCo2O5 + δ (R= Pr, Nd, Sm, Gd) layer coating on the oxygen permeation flux through Ba0.5Sr0.5Co0.8Fe0.2O5 + δ(BSCF) membrane were investigated. Due to the high oxygen adsorption and desorption rate constants ka and kd of the RBaCo2O5 + δ (R112) materials and the porous structure of the coating layers, the oxygen permeation flux through the BSCF membranes can be enhanced remarkably. It was found that the reaction between Pr112 and BSCF also has significant influence on the oxygen permeation flux. The reaction between Pr112 and BSCF forms impurities which may block oxygen permeation flux. However, Nd112, Sm112, and Gd112 do not react seriously with BSCF, therefore, coating layers of these materials can significantly enhance the oxygen permeation flux of BSCF membranes.

Sintering behavior and crystallization of glass–ceramic using bauxite tailings as one constituent were investigated. Different heat-treatment schedules were used to study their sintering effect on the glass powder-coated tiles. The results show that different heat-treatment schedule will result different crystal shape of the glass–ceramic. It was found that applying a two-stage heat-treatment schedule, first sintered at the crystallization temperature and then sintered at a higher temperature can make the glass–ceramic-coating layer bond strongly with the tile body.

The doping effect of Ca, Al, and Fe on the oxygen adsorption properties of YBaCo4O7 was investigated by thermogravimetry (TG) method. It was found that the original YBaCo4O7 oxygen adsorption properties can be modified greatly by Ca, Al, and Fe doping. Ca doping in Y sites eliminates the oxygen adsorption at low temperature (~300 °C) but the oxygen adsorption properties at high temperature is almost unchanged. Minor Al doping in Co sites eliminates the oxygen adsorption hump at high temperature, but the hump at low temperature is preserved. Fe appearance in YBaCo3Al1−xFexO7 seems to weaken the effect of Al doping, so the oxygen hump at high temperature emerges again. The doping effect was discussed based on elements valence, binding energy between cations and oxygen ions, and distortion of crystal structure.

Electrical resistivity and Seebeck coefficients of Y BaCo4−xZnxO7 (x=0.0,0.5,1.0,2.0)(x=0.0,0.5,1.0,2.0) were investigated in the temperature range 350–1000 K. It was found that the electrical resistivity and activation energy increase with increasing Zn concentration, while Seebeck coefficients do not increase but decrease when electrical resistivity increases. We explained the increase of electrical resistivity and the drop of Seebeck coefficients for Zn-substituted samples by the decrease of carrier mobility, rather than of carrier concentration. The effect of oxygen absorption and desorption on the electrical resistivity and Seebeck coefficients was also investigated. An abrupt change of transport properties happens at about 650 K for x=0.0x=0.0 and 0.5 samples measured in oxygen. For x=1.0x=1.0 and 2.0 samples, however, such change disappears and the transport behavior in oxygen is almost same as that in nitrogen due to the significant suppression of oxygen diffusion caused by the higher Zn concentration in these samples.

The oxygen adsorption and desorption of newly found compounds RBaCo4O7 (R = Y, Dy–Lu, In) were investigated by thermogravimetry (TG) in the temperature range from room temperature to 1100 °C. The influence of Co replaced by Zn and Fe on the oxygen diffusion properties of YBaCo4O7 was also studied. TG results showed clearly that all RBaCo4O7 compounds basically experience two oxygen adsorption and desorption processes in the temperature range 20∼1100 °C in oxygen flow. One happens at about 200∼450 °C and the another happens at about 660∼1050 °C. The differences between the resulting states by adsorbing oxygen at lower and high temperature were discussed based on the X-ray diffraction (XRD) patterns and TG data. We showed evidence that the oxygen adsorption at the lower temperature has a small activation energy, while the oxygen adsorption at the higher temperature has a large activation energy. The oxygen adsorbed at high temperature will destroy the RBaCo4O7 structure. Zn substituting in the YBaCo4 − xZnxO7 influences the oxygen diffusion behavior prominently, the amount of oxygen adsorbed becomes increasingly weak with the increase of Zn content and disappears completely for the samples with x ≥ 2.0. However, replacement of Co by Fe has little effect on the oxygen absorption process.

Cu-coated Al2O3 powders were prepared by the heterogeneous method starting with Al2O3 and CuSO4·5H2O raw materials. Nanometer Al particles were used to reduce Cu resulting in a uniform coating of Cu particles on the Al2O3 grains. TEM, XRD and XPS were used to analyses the status of the nano-sized Cu particles on the surface of Al2O3 grains. The mechanical properties of the composite were investigated after hot press sintering at different temperatures. Samples with enhanced fracture toughness about 5.75 MPa m1/2 were obtained after hot press sintering at temperature 1500 °C, which is much higher than that of monolithic Al2O3 ceramics.

The solid–gas phase oxygen ions exchange of the superconducting material YBa2Cu3O7−δ (YBCO) powder at high temperature subject to an instantaneous change of surrounding gas between pure oxygen and nitrogen was studied by a transient thermogravimetric analysis (TGA) method. The dependence of equilibrium oxygen vacancy of YBCO sample on surrounding partial oxygen pressure at temperature region 500–800 °C was measured by a homemade static oxygen absorption instrument. A rapid weight gain in the oxygen absorption period and a slow weight loss in the oxygen desorption period were observed in the transient experiment. The surface reaction rate constants both for the oxygen absorption and desorption periods were calculated by considering the surface reaction as the rate-limiting step. The result shows that rate constant for the oxygen desorption period is much smaller than that of the oxygen absorption period.

Alumina particles with plate-like shape were prepared successfully by a wet chemical processes with nano-size aluminum additive. The seed-effect of nano-size aluminum and its effect on the final α-Al2O3 particle size and shape were investigated. TEM, XRD, XPS, Zeta potential and DSC/TG were used to observe the microstructure of the α-Al2O3 particle and analysis this wet chemical processes. It was found that aluminum additive not only helps to produce the nano-size plate-like α-Al2O3 particles effectively but also reduces the formation temperature of α-Al2O3.

The oxygen in-diffusion, out-diffusion, and permeability of layered perovskite-type-like YBa2Cu3O7−x (YBCO) were investigated by thermogravimetry, oxygen static adsorption, and oxygen permeability experiment. The results show that the oxygen in-diffusion at higher oxygen partial pressure is very faster, while the oxygen out-diffusion at lower oxygen partial pressure is relatively slow due to the formation of surface barrier. Oxygen permeation rate increases with temperature and arrives at 3.36×10−7 mol/s cm2 at 900 °C for a YBCO membrane with thickness 1.00 mm.

The geometric and electronic structures of the PbS, PbSe and PbTe(0 0 1) surfaces were investigated by using the density functional theory. The calculations show that the (0 0 1) surfaces of these semiconductors do not reconstruct but exhibit oscillatory geometric relaxation to some extent. The interlayer distance shift and the intralayer rumpling have some obvious regularity. The calculations also show that the electronic structures of these semiconductors are very similar. The direct surface band gap locates at the X point and there are no new surface states appearing in the fundamental band gap. Some p characters surface resonance states appear mainly in the valence and the conduction band, and the other surface state with the anions s character also appears in the deep band gap below −10.0 eV.

We proposed a simple double sensor circuit to enhance the ratio of output signals of the resistance type sensors. In this circuit, one sensor (sensor 1) is used to control the current through another sensor (sensor 2). Thus, when the environment atmosphere is changed, both the resistance and the current through sensor 2 are changed and result in a great enhancement of the ratio of output signals. Resistance oxygen sensor YBa2Cu3O7−x (YBCO) was used to demonstrate this proposal. Actually, it shows that the ratio of output signals increase from 20 to 360.