EFFECT OF AL ON ELECTRIC CONDUCTIVITY AND SUPERCONDUCTIVITY OF NB-Si-AL-O CERAMIC

Abstract

Metal-insulator transition and superconductivity with changing Al composition were observed in the Nb-Si-Al-O system. Semiconductor-like characteristic and normal conductive characteristic were observed for Al <40% and Al >50% respectively. Super-conductive compositions are distributed around the boundary between those two types of conductivity, such as Nb x SiAl (α–x) O z((α, x)=(1.5, 0.7), (2.0,0.8), (3.0, 0.7~1.4)). The superconductivity was confirmed by resistive transitions and diamagnetic transitions. The superconductors in this study have T c =10.0~11.5 K with resistive transitions, and the amplitudes of the diamagnetism reach 30~58% of that of pure Nb powder. X-ray diffraction patterns of any other superconducting Nb-systems such as Nb , Nb 3 Al , Nb 3 Si , NbN , and NbC , have not been observed in Nb-Si-Al-O .