Investigation of the origin of abnormal grain growth in the sintering process of Sr_(0.5)Ba_(0.5)Nb2O6 ceramics without eutectic liquid-phase

摘要

Abnormal grain growth in the traditional sintering process of (Sr_xBa_(x-1))Nb2O6 limites its application and the localized liquid-phase exsisting is regarded the main reason for the presence of abnormal grain growth. To prevent the presence of a localized liquid-phase, the sol-gel method was employed to synthesize nano-sized powders of Sr_(0.5)Ba_(0.5)Nb2O6, which was followed by a pure solid-phase sintering process of nano-sized powders to observe the evolution of the grain morphology. SEM observation revealed that the abnormal and preferential rod-like grain growth along the c-axis existed in the pure state-phase sintering for the Sr_(0.5)Ba_(0.5)Nb2O6 material companied with some of the smaller grains being diminished or consumed. This behavior would exist in the traditional solid-phase sintering with or without the localized liquid-phase. This would be another important factor to aid the abnormal grain growth and should be prevented in the manufacturing process. The effects of grain sizes on the dielectric constant, Tc and diffuse phase transion (DPT) were observed in the Sr_(0.5)Ba_(0.5)Nb2O6 ceramics.