Dielectric Study of the Phase Transitions in Pb_{1 − x}Ba_x(Yb_1/2Ta_1/2)O₃Ceramics

The structure and low frequency dielectric properties of Pb 1 − x Ba x (Yb 1/2 Ta 1/2 )O 3 solid solutions with x = 0.00, 0.10, 0.15, 0.20 and 0.30 have been investigated using X-ray diffraction and dielectric constant measurements. As Ba 2+ concentration increases beyond x = 0.15, the crystal structure changes from monoclinic to pseudocubic at room temperature. The sharp paraelectric-antiferroelectric phase occuring in pure Pb(Yb 1/2 Ta 1/2 )O 3 , remarkably decreases and simultaneously the weak ferroelectric phase gets enhanced with increase in x. The maximum value of the dielectric constant (K max ) varies with x, showing a peak value at x = 0.20 whereas dielectric maximum temperature (T max ) continuously decreases with increase in x. The diffuseness exponent and degree of diffuseness are calculated for x = 0.15, 0.20 and 0.30 by fitting the dielectric data to the modified Curie-Weiss law and the values indicate that the compounds exhibit diffuse phase transition. The paper also discusses the influence of calcination and sintering temperature on the dielectric properties of pure Pb(Yb 1/2 Ta 1/2 )O 3 .