PHASE-TRANSITIONS AND THE DOPING EFFECT IN TI3O5

The electronic stares of the (Ti1-xVx)(3)O-5 system, where 0 less than or equal to x less than or equal to 0.33, have been explored through measurements of the x-ray diffraction, magnetization, electrical resis tivity, and thermoelectric power. Three structural phases appear as th e composition and temperature are varied: the high-temperature orthorh ombic (HO) phase with a pseudobrookite-type structure and the slightly deformed monoclinic (HM) one, and the low-temperature monoclinic (LM) one which is completely different from the former two phases. For 0 l ess than or equal to x less than or equal to 0.08, the HO-HM transitio n with a small magnetic anomaly and the HM-LM transition with signific ant spin-singlet Ti-Ti pairs successively take place, but for 0.1 less than or equal to x less than or equal to 0.33, no transition to the L M phase exists there. While the MO-phase Ti3O5 is like a highly correl ated metal, the MO-phase compounds with 0.1 less than or equal to x le ss than or equal to 0.33 have a strongly localized state due to the di sorder and the polaron formation, and exhibit a spin-glass-like phase at low temperatures.