THEORETICAL-ANALYSIS OF THE ELECTRICAL-PROPERTIES OF TELLURITE GLASSES

The most important parameters of the process of charge transport by po larons and the polarizability of oxide glassy semiconductors (OGS) bas ed on TeO2 when modified with transition metal ions (TMI) such as tung sten are determined from the analysis of the temperature dependence of d.c. conductivity and static dielectric constant: a) The high tempera ture activation energy for conduction with this type of glass and TMI doping is found to dominate the magnitude of conductivity. The behavio ur at high temperature can be described by non-adiabatic small radius polaron hopping (SRP) between nearest neighbours. Hopping, binding ene rgies of the polarons and disorder energies have been calculated. b) F or intermediate temperatures a simple model is used in which excitatio ns by optical phonons is considered to make independent contributions to the jump frequency. The electron coupling coefficient has been calc ulated. The macroscopically observed dielectric constant epsilon has b een related to the microscopic quantities; number of polarisable atoms per unit volume and the polarizability of these atoms. c) The low tem perature electrical conductivity can be described by using Mott's vari able range hopping to calculate the density of states near the Fermi e nergy level. Partial derivative epsilon/partial derivative T could be attributed to the change of polarizability with temperature and with v olume.