Study of CaO–WO3–P2O5 glass system by dielectric properties, IR spectra and differential thermal analysis

Dielectric constant ε′, loss tanδ and ac conductivity σac of 40CaO–xWO3–(60−x)P2O5 (with 0⩽x⩽15) glasses are studied over a range of frequencies and temperature. The dielectric breakdown strength of these glasses is also determined at room temperature. The values of dielectric parameters, viz., ε′, tanδ and σac of CaO–P2O5 glasses are found to decrease with the introduction of WO3 up to 3 mol% and increase with further increase in the concentration of WO3; the probable reasons for such an increase are identified and explained with the aid of IR spectra and differential thermal analysis of these glasses. The variation of tanδ with temperature at different frequencies of CaO–P2O5 glasses has exhibited dielectric relaxation effects with decreasing relaxation intensity with increase in the concentration of WO3 from 0 to 3 mol%; such relaxation effects seem to have been absent in glasses containing WO3 beyond 3 mol%. The relaxation phenomenon has been analysed by a pseudo-Cole–Cole plot method and the possible mechanism responsible for such relaxation effects has been suggested.