Phase transition in Pb(Mn1/4Cd1/4W1/2)O3 ceramics

The polycrystalline samples of Pb(Mn1/4Cd1/4W1/2)O3 were synthesized by a high-temperature solid-state reaction technique. A preliminary X-ray structural study of the compound at room temperature shows the formation of a single-phase compound with a non-centrosymmetric space group P2221 of orthorhombic structure. Studies of dielectric constant (ε) and loss tangent (tan δ) both as a function of frequency (103–104 Hz) and temperature (20–350 °C) suggest that the compound undergoes a phase transition at 250 °C and has a very high value of dielectric constant ∼30,000 at transition temperature. Both ac and dc conductivity have been studied over a wide range of temperature. The activation energy (Ea) of the compound was calculated from both the plot of ac and dc conductivity versus inverse of absolute temperature. Variation of dc resistivity with electric field (0.55–53 kV m−1) at room temperature and variation of dc resistivity (106–103 Ω m) with temperature (26–350 °C) at a constant electric field of 11.2 kV m−1 showed the semiconductor characteristics of the material.