, Volume 7, Issue 3-4, pp 291-307

Superconductivity in the TiO and NbO systems

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Abstract

This paper presents electrical resistivity and superconductivity studies for the B1 (NaCl) structure oxides of titanium, vanadium, and niobium. In samples of nominal composition TiO x , VO x , and NbO x ,x was varied from 0.8 to 1.2. It was found that all three of these oxides exhibit room-temperature electrical resistivities characteristic of metallic behavior. With decreasing temperature, the resistivity drops steeply in the case of NbO x , but remains steady or rises somewhat in the case of TiO x and VO x , depending on the exact value ofx. It is suggested that in TiO x and VO x there is a large resistivity component due to scattering of carriers by disordered vacancies. Superconductivity was observed in NbO x (T c=1.38 K,x=1.0) and TiO x (T c=1.0 K,x=1.07). In the latter case the material showed a well-defined maximum ofT c as a function of composition, withT c<0.05 K forx<0.85 andx>1.20. Several VO x samples remained normal to 0.07 K.