Dielectric and Structural Characterization of Pb_1–x A _x Zr _0.40Ti_0.60O₃ (A = Sr, Ca) Ferroelectric Ceramics

This paper reports the influence of Sr- and Ca-substitution on the structural and ferroelectric properties of Pb_1–x Sr _x Zr _0.40Ti_0.60O₃ (PSZT) and Pb_1–x Ca _x Zr _0.40Ti_0.60O₃ (PCZT) ceramic systems. The dielectric measurements show that these substitutions cause a diffuse behavior in the dielectric permittivity curves for all samples. According to the X-ray absorption near-edge structure (XANES) spectra collected at Ti K- and L_III -edge, when Pb was replaced by Sr or Ca, a decrease in the local distortion around Ti atoms in the TiO₆ octahedron could be observed. The O K-edge XANES spectra also revealed that the hybridization between O 2p and Pb 6sp states decreased as the amount of Sr or Ca atoms increased. Based on these results, it was possible to ascertain that the ferroelectric behavior in PSZT and PCZT samples bears a close correlation to the hybridization weakening between O 2p and Pb 6sp states.