The effect of BaO addition on the sintering properties and grain growth behavior of CaZrO3 ceramics

In the present work, dense CaZrO₃ ceramics were prepared by a conventional solid-state reaction using high-purity commercial ZrO₂ and Ca(OH)₂ as raw materials, and BaO as a sintering aid. The effect of BaO addition on the sinterability, phase composition, and microstructures of CaZrO₃ ceramics was investigated. The grain growth kinetics was also analyzed based on the classical Brook model. The results showed that an appropriate amount of BaO addition has a significant positive contribution to the densification and grain growth of CaZrO₃ ceramics. However, excess addition gives rise to the formation of BaZrO₃ at the grain boundary, which dramatically hinders the grain growth and thus degrades the sinterability of CaZrO₃ ceramics. The enhanced sintering mechanism is related to lattice distortion generated from the substitution of Ca²⁺ sites by larger Ba²⁺ ions. The grain growth kinetics analysis demonstrated that the grain growth activation energy is affected by the BaO addition, and the value is decreased from 65.5 to 55.4 kJ·mol⁻¹ as the BaO content increases from 0 to 1 wt%.