Dielectric properties of ZnF2-PbO-TeO2 glasses

The dielectric constant epsilon, loss tan delta and a.c. conductivity sigma of four compositions of ZnF2-PbO-TeO2 glasses with successive decrease in PbO and TeO2 concentration were measured in the frequency range 5 x 10(2)- 10(5) Hz and in the temperature range 30 to 200 degrees C. The dielectric breakdown strength of these glasses were also determined at room temperature in the air medium. The variation of dielectric loss with temperature for these has glasses has exhibited dielectric relaxation effects. The rate of increase of epsilon and tan delta with temperature beyond the relaxation region has been found to increase with an increase:in the PbO concentration whereas the dielectric breakdown strength, the activation energy for dipoles and for a.c. conduction in the high-temperature region, has been found to decrease with an increase in the concentration of PbO. These results have been understood due to the increase in the degree of depolymerization of the glass network with increase in the modifier concentration PbO. An attempt has also be made to expain conduction in these glasses on the basis of quantum mechanical tunneling (QMT) model. (C) 1997 Elsevier Science Ltd. All rights reserved.