ESR AND ELECTRICAL-CONDUCTIVITY STUDIES OF (TEO2)(0.95)(CEO2)(0.05) SEMICONDUCTING GLASSES

Electron spin resonance (ESR) and d.c. conductivity measurements have been made on a prepared binary tellurite glass in the temperature rang e 200-400 K. The d.c. conductivity was found to be temperature depende nt and had two regimes. The data were consistent with the small polaro n transport mechanism and the polaron activation energy was 0.22 eV. T he ESR spectra at high temperatures were characterized by two overlapp ing lines, a broad line with g = 2.00 and a narrow line with g = 1.967 . At temperatures lower than 258 K, the narrow line disappeared and th e broad line remained. This suggests that carriers become localized at T < 258 K. At T > 273 K, the conductivity arises from hopping of carr iers between cerium sites. It was also found that the reduced valency ratio C (i.e., the ratio of the concentration of Ce4+ ions to the tota l Ce ion concentration in the glass) increases with temperature.