Effects of A/B cation ratio on the microstructure and lifetime of (Ba1-xCax)(z)(Ti0.99-y ZryMn0.01)O-3 (BCTZM) sintered in reducing atmosphere

Abstract

Microstructure and dielectric properties of (Ba1-xCax)(z)(Ti0.99-yZry Mn-0.01)O-3 (BCTZM) with various cation ratios (A/B) sintered in reducing atmosphere and then annealed to reoxidize the ceramic bodies were investigated. With decreasing A/B cation ratio, concurrent with the grain size reduction, the insulation resistance and lifetime of the BCTZM are both increased. The degradation of insulation resistance is closely related to oxygen partial pressure used during annealing and the resulting microstructure of the ceramics. Within the same volume, the specimen with fine grain size provides more grain boundaries, in comparison to large grain size specimens, which helps in providing an efficient diffusion pathway for oxygen during annealing. The result of oxidation of the Mn, that is, a change in the valence state of Mn from Mn+2 to Mn+3 is confirmed from thermogravimetric analysis and electron paramagnetic resonance analysis.