Low temperature phase transition studies on Pb(Mg0.5W0.5)O3 ceramic

We present here the results of X-ray diffraction (XRD), dielectric and calorimetric studies on lead magnesium tungustate, Pb(Mg0.5W0.5)O3 (PMW) ceramic. It is shown that the low temperature antiferroelectric phase of PMW having orthorhombic structure (space group Pmcn) transforms to paraelectric cubic (space group Fm3m) phase at 281 K. The phase transition is of first order character as confirmed by coexistence of Pmcn and Fm3m phases over wide temperature range ∼50 K. The first order character of phase transition is also revealed by the observation of thermal hysteresis in the real part of dielectric permittivity and calorimetric studies. We do not find any evidence for the additional intermediate phase between antiferroelectric (Pmcn) and paraelectric (Fm3m) phases as reported in the literature. Anomalies in the heat flow and dielectric measurements support the finding of our XRD results and reveals that the phase transition temperature (Tc) is 281 K instead of 312 K reported in the literature.

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