Date: 30 Sep 2008

Effect of Mn4+ substitution on thermal, structural, dielectric and impedance properties of lead titanate

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Polycrystalline samples of Mn-modified lead titanate (Pb Mn x Ti1−x O3 (PMT) with x = 0, 0.04, 0.07, 0.10) were prepared by a high-temperature solid-state reaction method. Calcination and sintering temperatures were optimized by thermal gravimetric analysis and repeated firing. Preliminary structural studies using an X-ray diffraction technique (at room temperature) suggest that compounds are formed in a single phase with tetragonal crystal system. Scanning electron micrographs show uniform grain distribution throughout the surface of the samples. Detailed studies of dielectric and impedance properties of the compounds in a wide range of temperature (35 °C–500 °C) and frequency range (1 kHz–1 MHz) exhibit that phase transition temperature of the PMT compounds depends on Mn concentration. The real and imaginary part of complex impedance plots exhibit semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of both bulk and grain boundary effects at high-temperature. The bulk resistance of the material decreases with rise in temperatures. This exhibits a typical negative temperature coefficient of resistance behaviour of the material.