Structural investigations on ferroelectric Pb1-3/2xLaTiO3 using the x-ray Rietveld method

The structures of the defect perovskite Pb1-3/2xLaxTiO3 prepared by the solid-state method were investigated in the solubility range of 0.05 less than or equal to x less than or equal to 0.30 with 0.05 increment by x-ray Rietveld method. In the system Pb1-3/2xLaxTiO3, the atom displacements of Ti (delta(Ti)) and Pb/La (delta(Pb/La)) along the spontaneous polarization (P-s) direction (c axis) decrease nonlinearly with increasing La content, while the value of delta(Ti)/delta(Pb/La) decreases linearly. The shape of oxygen octahedron of compounds Pb1-3/2xLaxTiO3 is independent of the La content. The calculated value of P-s decreases linearly in the solubility range of 0.05 less than or equal to x less than or equal to 0.30. In the refinement process, the hkl dependence of diffraction line broadening was also taken into account. The anisotropy of microstrain-like broadening observed in Pb1-3/2xLaxTiO3 might be ascribed to occurrence of compositional inhomogeneity between the crystallites.