Abstract:

CaZrO₃ specimens were prepared by the high-temperature solid state method using analytically pure ZrO₂ and Ca(OH)₂ as raw materials,adding different amounts of Co₂O₃ (0,0.5%,1.0%,1.5% and 2% by mass),batching,molding,drying and firing at different temperatures (1 500,1 550 and 1 600 ℃ for 3 h).The results show that as the Co₂O₃ addition increases,the bulk density,the linear shrinkage and the average grain size of the prepared CaZrO₃ first increase and then decrease,while the apparent porosity changes in the opposite trend.CoO from the decomposition of Co₂O₃ has infinite displacement reaction with CaO,which reduces the activation energy of the reaction between CaO and ZrO₂,thus promoting the densification of the specimens.However,when the Co₂O₃ addition exceeds 1.5 mass%,more O₂ is produced during the decomposition of Co₂O₃,and the generated CoO cannot solid-dissolve with CaO crystals in a short time,which hinders the direct contact of reactants in the grain boundaries thus reducing the sintering performance.Therefore,the optimal addition of Co₂O₃ is 1.5 mass%,and in that case,the specimen has 4.25 g·cm^-3 of bulk density,3.3% of apparent porosity,and 6.13 μm of CaZrO₃ average grain size.

Key words: calcium zirconate, dicobalt trioxide, sintering property, phase composition, grain size

摘要：

以分析纯ZrO₂和Ca(OH)₂为原料,添加Co₂O₃(加入质量分数分别为0、0.5%、1.0%、1.5%和2%)粉末,经配料、成型、干燥和烧成(1 500、1 550和1 600 ℃分别保温3 h)后,通过高温固相法制备了CaZrO₃试样。结果表明:随Co₂O₃添加量的增加,制备CaZrO₃的体积密度、线收缩率和平均晶粒尺寸均先增大后减小,显气孔率的变化与之相反。Co₂O₃分解产生的CoO可以与CaO发生无限置换反应,降低CaO与ZrO₂的反应活化能,从而促进试样烧结致密性。但Co₂O₃添加量超过1.5%(w)时,可能由于Co₂O₃在分解过程产生较多O₂,同时产生的CoO短时间内不能固溶到CaO晶体中,处在晶界上,阻碍反应物的直接接触,降低了烧结性能。因此,Co₂O₃的最佳添加量为1.5%(w),此时CaZrO₃试样的体积密度为4.25 g·cm^-3,显气孔率为3.3%,CaZrO₃的平均晶粒尺寸为6.13 μm。

关键词: CaZrO₃, Co₂O₃, 烧结性能, 物相组成, 晶粒尺寸