Effect of the addition of Ca²⁺ on the structure, microstructure and ferroelectric properties of (Pb_{1 - y}Ca_y)(Zr_0.8Ti_0.2)O₃ system with y = 0.0, 0.02, 0.05 and 0.1

Author： Beitollahi A.

Publisher： Springer Publishing Company

ISSN： 0022-2461

Source： Journal of Materials Science, Vol.38, Iss.6, 2003-03, pp. : 1219-1229

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Abstract

This work studies the relationship between ferroelectric properties and structural features of the (Pb_{1 - y}Ca_y)(Zr_0.8Ti_0.2)O₃ system with y = 0.0, 0.02, 0.05 and 0.1. All of the samples were prepared by hot-pressing of PZT calcined powder, prepared by conventional ceramic route. Single phase compositions of rhombohedral (RH) structure were observed for the whole series of the samples studied in this work. However, a linear decrease of RH lattice constant a_p is seen with increasing the Ca²⁺ concentration with a subsequent decrease of lattice strain expressed by (90 - α_p). Further, a sharp decline is also observed in the magnitudes of saturation polarization (P_s) of the samples doped with 2 mol% Ca²⁺. However, the rate of decrease slows down for Ca²⁺ concentrations above this level. A diffuse phase transition was observed in the case of 10 mol% Ca²⁺-doped PZT(0.8) which is believed to be possibly due to the distribution in coupling strengths created from a random compositional fluctuations of Ca²⁺ and Pb^2- ions on A-sites. The results are interpreted on crystal-chemical grounds. It is proposed that the long range coupling of (Zr/Ti)O₆ coordination octahedra and Pb²⁺ ions, due to the covalency of the Pb–O bond, is interrupted by the incorporation of Ca²⁺. By considering the effect of calcium on coupling strength and coupling distribution, the observed dielectric response for the above compositions is qualitatively explained.