Electrical and optical properties of new Pr³⁺-doped PbWO₄ ceramics

Polycrystalline samples of new scheelite-type tungstates, Pb_{1−3x x}Pr_2xWO₄ with 0.0098 ⩽ x ⩽ 0.20, where denotes cationic vacancies have been successfully prepared by a high-temperature solid-state reaction method using Pr₂(WO₄)₃ and PbWO₄ as the starting reactants. The influence of the Pr³⁺ substitution in the scheelite framework on the structure and optical properties of prepared new ceramic materials has been examined using powder X-ray diffraction method (XRD) and UV-Vis-NIR spectroscopy. The results of dielectric studies of Pb_{1−3x x}Pr_2xWO₄ samples showed both low values of dielectric constant (below 14) and loss tangent (below 0.2). The electrical conductivity and thermoelectric power measurements revealed a low conductivity (∼2 × 10⁻⁹ S/m) and the sign change of thermoelectric power around the temperature of 366 K suggesting the p-n transition. These results are discussed in the context of vacancy, acceptor and donor levels as well as the Maxwell-Wagner model.