Electrical conductivity and 125Te nuclear spin relaxation measurements were performed on monocrystals of ultra-pure paratellurite at temperatures of between about 50K and the melting point (1007K), under O partial pressures ranging from 0.0001 to 1bar. At high temperatures, the nuclear spin relaxation rate and the conductivity were attributed to the diffusive motion of point defects. From the observed O partial pressure dependence of the nuclear spin relaxation rate and the conductivity, a defect model was developed which involved ionic O interstitials, doubly-charged O vacancies and charge-compensating electron holes. The observed pressure dependence suggested that the nuclear spin relaxation rate reflected the motion of doubly-charged O vacancies, while the conductivity was due to the mobility of charge-compensating electron holes. An analysis of the data indicated a value of 3.3eV for the incorporation enthalpy of O at interstitial sites and of 4.5eV for the formation enthalpy of O Frenkel pairs of ionic O interstitials and doubly-charged O vacancies. The chemical diffusion coefficient was found to reflect the ambipolar diffusion of ionic O interstitials and charge-compensating electron holes. At 950K, the nuclear spin relaxation and conductivity data yielded a chemical diffusivity of about 10-5cm2/s.

Point-Defects and Diffusion in Paratellurite. J.Wegener, O.Kanert, R.Küchler, A.Watterich: Zeitschrift für Naturforschung, 1994, 49a[12], 1151-8