We investigated the transport properties of isoelectronic substitution of Yb by Ca for Zintl phase YbCd2Sb2 below 300 K.The p-type Yb1-xCaxCd2Sb2(0.2≤x≤0.8) samples were synthesized via a solid-state reaction followed by suitable cooling,annealing,grinding,and spark plasma sintering(SPS) densification processes.For samples with x=0.2,0.4,0.5,0.6,0.8,the electrical conductivity,Seebeck coefficient,thermal conductivity,heat capacity and Hall effect measurements were carried out in the temperature range from 1.9 to 300 K.It was found that the Ca substitution effectively lowered the thermal conductivity at low temperature,while the electrical resistivity and the Seebeck coefficient in the compounds were found to increase with increasing Ca concentration.As a result,the dimensionless figure of merit ZT of 0.18 was attained at 300 K for sample with x=0.2.
A photoanode structure for dye-sensitized solar cells has been applied into the photocatalytic/electrochemical cooperative degradation of methylene blue solutions.The low eutectic point of titanium dioxide(TiO2)with a fluorine-doped tin dioxide(FTO)conductive layer results in a high reactivity of TiO2for the photocatalytic process as well as a good electron transfer for the electrochemical process.The porous TiO2layer maintains a large surface area for the degradations.Through the combinational process,the degradation velocity was improved by*36%,compared to a pure photocatalytic process.
Min YangXinling LiuJikun ChenFanqi MengYuliang ZhangHelmut BrandlThomas LippertNuofu Chen
Previous reports about the thermal conductivities of VO2 showed various temperature dependences across metal-insulator transition (MIT) temperature. In this work, polycrystalline VO2 samples were fabricated by spark plasma sintering of VO2 powder. Temperature dependences of their thermal conductivities were investigated using laser flash technique, and the thermal conductivity showed a significant decrease trend from metal-phase to insulator phase. Electrical transport properties were investigated to confirm both carrier and lattice contribution to the thermal conductivity. It is found that the lattice thermal conductivity decreased significantly across MIT point, which may be caused by soft phonon mode in metal phase of VO2 .
