TRAPPED-HOLE CENTERS IN IRRADIATED LI3VO4

Defects in lithium vanadate (Li3VO4) exposed to x rays were studied by electron spin resonance (ESR). 77 K irradiation produces two types of trapped-hole centers. One is supposed to be carbonate radical CO3-, which is thermally stable even at room temperature. Another, having a hyperfine interaction with a vanadium nucleus (I = 7/2, 99.76% natural abundant) is attributable to an intrinsic O- type center with one neighboring vanadium ion. The center is thermally unstable and anneals out around 200 K. In spite of the prominent detection of trapped-hole centers, ESR signals due to trapped-electron centers have not been clearly observed.