Effects of extra Ba2+ and two-step sintering on the crystal structure, microstructure, and dielectric properties of (Ba, Ca)(Ti, Zr)O3

This study investigated how extra Ba2+ and two-step sintering affect the crystal structure, microstructure, and dielectric properties of (Ba, Ca)(Ti, Zr)O3 (BCTZ). XRD results indicate that no secondary phase formed in any of the BCTZ samples after sintering. Raman spectra reveal that Ca2+ ions were pushed from the Ba-site to the Ti-site when extra Ba2+ was added after sintering. The Curie temperatures of all BCTZ samples decreased due to the smaller tetragonality caused by the addition of extra Ba2+. SEM micrographs revealed that two-step sintering decreased the grain size from 5.0 μm to 0.5 μm compared with normal sintering. Furthermore, samples with fine-grain microstructures exhibited flat curves for the temperature coefficient of capacitance.