Effect of the addition of Ca2+ on the structure, microstructure and ferroelectric properties of (Pb1 − yCay)(Zr0.8Ti0.2)O3 system with y = 0.0, 0.02, 0.05 and 0.1

This work studies the relationship between ferroelectric properties and structural features of the (Pb1 − yCay)(Zr0.8Ti0.2)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 ap is seen with increasing the Ca2+ concentration with a subsequent decrease of lattice strain expressed by (90 − αp). Further, a sharp decline is also observed in the magnitudes of saturation polarization (Ps) 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 Pb2− 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.