METAL-INSULATOR-TRANSITION IN THE LIV2O4-DELTA SPINEL SYSTEM

We have investigated the electrical conductivity of LiV2O4-delta as a function of oxygen deficiency in the stoichiometric composition of the starting materials. Polycrystalline samples of LiV2O4-delta were prep ared;from powders by sintering and exhibit metallic behaviour. It is t he first time that polycrystalline samples of LiV2O4 show such behavio ur. The composition was determined by X-ray powder diffraction. Resist ivity measurements in the temperature range of 300-12 K, were used to study the effects of oxygen deficiency and sample preparation conditio ns, on the metal-insulator transition (MIT). These measurements show m etallic conductivity in the range delta = 0.7-1.1, outside this range the system displays non-metallic behaviour. The results indicate that the main factor determining the MIT is the average valence of the V ca tions. (C) 1997 Elsevier Science Ltd.