Teiichi Ueno

Solid phase condensation reaction of lead cyclo-tetraphosphate

Abstract When aqueous solutions of lead nitrate and sodium cyclo-tetraphosphate were mixed, α and β type crystals were found in the precipitated solids. The structure and properties of the crystals were investigated by X-ray diffractometry, scanning electron microscope and thermal analysis. Lead cyclo-tetraphosphate of α type changed to cyclo-octaphosphate by heating at 150°C for 2 h and by successive heating at 350°C for 30 min in the yield of 100%. This solid state condensation reaction mechanism of lead cyclo-tetraphosphate of α type was discussed.

Possible high Tc superconductivity and large fluctuation effect in Nb3Ge films

Abstract The electrical resistivity ϱ( T ) of RF sputter-deposited Nb 3 Ge films has been investigated in detail in the neighborhood of the transition temperature. After cooling to below room temperature, many samples exhibited a semiconductive type of increase in the resistivity before undergoing the transition to superconductivity. These films have very large resistivity in the normal state (ϱ n =10 3 -10 5 μΩ cm) and show fairly high onset temperatures. The maximum value of the onset temperature T c-on reaches 32 K. On the other hand, the films with rather small resistivity exhibited a metallic behavior in the normal state. However, the fluctuation effect on the electrical conductivity starts from a higher temperature than the usual onset temperature where we can see a clear drop of the resistivity. The films were examined by EPMA and SEM to reveal the correlation between the superconductive properties and the microstructure.