Dielectric and photoelectric properties of Pb(Mg1/3Ta2/3)O3 crystals

The temperature dependence of the dielectric constant epsilon and the spectral dependence of-the photoconductivity of Pb(Mg1/3Ta2/3)O-3 crystals are investigated. The width of the band gap (3.4 eV) is determined. It is found that above the temperature of the maximum of the dielectric constant, its reciprocal 1/epsilon varies with temperature first quadratically and then according to a linear law, as is characteristic of ferroelectrics with a smeared phase transition. The smearing parameter of the transition estimated from the experimental data is close to the value calculated assuming the-absence of long-range order in the arrangement of the Mg and Ta ions. (C) 1998 American Insitute of Physics.