Comparison of Lanthanum and Bismuth modification of lead Zirconate-Lead Titanate PZT—A structural and dielectric study

Lead Zirconate Titanate (PZT) ceramics Pb 1−1.5 x Bi x V Pb ′′ 0.5 x Zr 0.90 Ti 0.10 O 3 containing Bismuth ( x = 0.005–0.12) were structurally and dielectrically characterized. Results are compared to Lanthanum modified Pb 1−1.5 x La x V Pb ′′ 0.5 x Zr 0.90 Ti 0.10 O 3 , ( x = 0.01–0.08) ceramics. For Bi a solubility limit is observed at x = 0.04. The Lanthanum-doped series proved to be single phase in the investigated range. Lanthanum doping leads to a continuous reduction of cell volume causing a change from rhombohedral to orthorhombic symmetry at x = 0.03 accompanied by switching from ferroelectric to antiferroelectric behaviour. Such a change was not observed with Bismuth. This might be due to the fact that a critical cell volume necessary for structural transition could not be achieved within the solubility range. For Lanthanum doped PZT with x = 0.03 orthorhombic structure was determined already at room temperature, but with ferroelectric polarization curve, which switched to antiferroelectric polarization at 120 °C. This raises new questions on the appearance and stability of antiferroelectric ordering.