Induced crystallization and physical properties of Li 2O–CaF 2–P 2O 5:TiO 2 glass system : Part II. Electrical, magnetic and optical properties

Abstract

The results of various physical properties namely, dielectric properties (dielectric constant, loss tan δ, ac conductivity σ, over a wide range of frequency and temperature and dielectric breakdown strength in air medium at room temperature), optical absorption, electron spin resonance (ESR) at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li 2O–CaF 2–P 2O 5:TiO 2 glass-ceramics have been reported. The optical absorption and magnetic susceptibility studies indicated that the titanium ions exist in Ti 3+ state in addition to Ti 4+ state in these samples. However, the reduction seems to be the lowest in the sample containing 0.6 mol% of TiO 2. The dielectric constant and loss variation with the concentration of TiO 2 have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analyzed by a pseudo Cole–Cole plot method and the spreading of dielectric relaxation has been observed. The ac conductivity in the high temperature region seems to be related both with electronic and ionic movements. The low temperature (or the nearly temperature independent) part of conductivity could be explained on the basis of quantum mechanical tunneling model. The studies on dielectric breakdown strength indicated the highest insulating strength for the sample containing 0.6 mol% of TiO 2.