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...
The microstructure and coupling between structural and magnetic domains of ferromagnetic shape memory alloy Ni55Mn20.6Ga24.4 were investigated by scanning electron acoustic microscopy （SEAM）. Stripe ferroelastic domains （martensite variants） exist in every grain, and exhibit the configurations of the typical self-accommodation arrangement. Magnetic domain structure of Ni55Mn20.6Ga24.4 was observed by the Bitter method and magnetic force microscopy （MFM）. Due to the unique subsurface imaging capability of SEAM, combined with the Bitter method, the ferroelastic domain structure can be compared with in situ ferromagnetic domain structure. It is found that the martensitic variant boundaries coincide well with the ferromagnetic domain walls, which is beneficial for the understanding of the correlation between two kinds of ferroic domains.
Low-frequency （below 100 kHz, even down to several hundred Hz） near-field scan- ning probe acoustic microscopy （SPAM） was successfully developed based on the commer- cial atomic force microscope, providing a subsurface depth profile information and as well as nanoscale spatial resolution up to several nm. SPAM was successfully used to image locally domain configurations of ferroelectric materials and subsurface structures of other materials. Ferroelectric domain structures and the buried structures were clearly visualized by scanning probe acoustic microscopy. The acoustic imaging origin is discussed in terms of interaction between the excited acoustic wave and local structures beneath the SPAM tip. It is expected that the scanning probe acoustic microscopy in application to ferroelectrics and other materials undoubtedly enrich our understanding the nature of ferroelectricity and elasticity at submicro-, even nano-meter scale.
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 .
