Structure-property relationships in BaTiO3-(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 lead-free ceramics

Dense (1 − x)BaTiO3−x(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 [(1 − x)BT-xNBMT] polycrystalline ceramics were prepared by solid-state reaction method. The detailed structure analysis was performed by X-ray diffraction (XRD) and Raman spectroscopy, confirming that the Ba and Ti sites were partially replaced by Na+/Bi3+ and Mg2+ ions, respectively. An obvious structural variation from tetragonal to pseudocubic was observed for sample with x = 0.08-0.12. The lattice parameter for sample with x ≥ 0.12 decreased linearly with x value. Three changing modes in frequency, width and intensity were observed with x value in the Raman spectra, indicating intense changes of local structure, accounting for evolved dielectric and ferroelectric macroscopic properties. The subgrain microstructures were observed by conventional transmission electron microscopy (TEM) imaging with an energy-dispersive X-ray spectroscopy (EDS) attachment. A large number of core-shell grains were detected by TEM dark field, for x = 0.20, which were attributed to the dissolution-precipitation mechanism. In this present study, (1 − x)BT-xNBMT ceramics are considered promising for high temperature capacitor applications.