METAL-INSULATOR-TRANSITION IN THE LIV2-XMXO3.8 (M = CU, TI) SPINEL SYSTEM

The electrical conductivity of LiV2-xMxO3.8 (M = Cu, Ti) was investiga ted as a function of dopant content (x). Polycrystalline samples of Li V2-xMxO3.8 were prepared from powders by sintering. The composition wa s determined by X-ray powder diffraction. Resistivity measurements in the temperature range of 300-12 K, were used to study the effects of d opant content on the metal-insulator transition (ha). Those measuremen ts reveal two common features of the MIT. First, the average valence o f the vanadium ions is almost the same at the MIT for both dopants. Se cond, the trend of the change in the position of the oxygen anion as a function of dopant is also the same for both dopants. These results l ead to the conclusion, that the main factor determining the MIT is the average valence of the V cations. In a previous study of the similar spinel system LiTi2-xMxO3.8.B it was also found that the average valen ce of the Ti ion is the determining factor. (C) 1998 Elsevier Science Ltd. All rights reserved.