Williamson-Hall analysis and the dielectric behavior of complex perovskites (BaM0.9M′0.1)0.984O3 (M=Ti, Zr; M′=Nb, Ta)

The long range average structure and local distortions of perovskite type solid solutions (BaTi0.9M′0.1)0.984O3 and (BaZr0.9M′0.1)0.984O3 (M′=Nb, Ta) were examined by high-resolution synchrotron X-ray diffraction. A Rietveld refinement indicated that all four solid solutions had simple cubic symmetry, where the lattice volume varied according to the size of the cationic constituents. As revealed by Williamson-Hall analysis and scanning electron microscopy, both (BaTi0.9M′0.1)0.984O3 had denser and enlarged grains than the parental BaTiO3, and had anisotropic microstrain that are indicative of the non-periodic atomic displacements along the [100] directions of the cubic cell. (BaTi0.9Nb0.1)0.984O3 and (BaTi0.9Ta0.1)0.984O3 exhibited relaxor-like dielectric behavior with Curie temperatures of 230 K and 195 K, respectively. On the other hand, (BaZr0.9Nb0.1)0.984O3 and (BaZr0.9Ta0.1)0.984O3 showed almost unchanged dielectric behavior compared to that of BaZrO3.