Dielectric and ferroelectric properties of lanthanum modified lead titanate ceramics

Lanthanum (La) modified lead titanate ceramics (Pb1-xLaxTi1-2yMoyFeyO3 with x = 0.02, 0.05, 0.10, 0.15, 0.20 and y = 0.02) were prepared by high temperature solid state reaction method. Cold pressed pallets were sintered at 1200 degreesC for 2 h. Single phase formation has been confirmed by X-ray diffraction studies. It has been observed that the dielectric constant decreases with poling. Dielectric constant at room temperature is found to increase with increase in La content. In all compositions dielectric constant showed peak at transition temperature and the magnitude of peak width is found to depend on the frequency of measurement. It has been observed that the transition temperature decreases at the rate of 14 degreesC per mol% of La substitution. Coercive field and c/a ratio continuously decreases with increase in La addition. Polarization shows a peak in 15 mol% La composition for which value is 14.07 muC cm(-2). (C) 2002 Published by Elsevier Science B.V.