Abstract Transparent magnesium aluminate spinel (MgAl2O4) ceramics were successfully fabricated from commercial spinel powders via air presintering and hot isostatic pressing (HIP) using CaO as sintering additive. The influence of the CaO content on microstructure, densification process and optical quality of MgAl2O4 ceramics were investigated. It was found that using CaO as sintering additive would prompt the sintering process significantly. The relative densities of MgAl2O4 ceramics presintered at 1525 °C change from 92.1% to 97.8% with the amount of CaO increasing from 0 to 0.15 wt%, and the average grain sizes of presintered MgAl2O4 ceramics increase from 0.4 μm to 0.8 μm, correspondingly. However, when the CaO content increases to 0.15 wt%, the secondary phase grains (calcium aluminate) occur in MgAl2O4 ceramics, which severely reduces the optical quality. The transparent MgAl2O4 ceramic with 0.125 wt% CaO presintered at 1525 °C for 3 h and HIP post-treated at 1600 °C for 3 h shows the best in-line transmittance of 86.3% at 1100 nm and 83.7% at 600 nm, the average grain size of 2.9 μm.

中文翻译：

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CaO对MgAl2O4透明陶瓷微观结构和性能的影响

摘要 以商业尖晶石粉末为原料，以CaO为烧结添加剂，通过空气预烧结和热等静压(HIP)成功制备透明镁铝尖晶石(MgAl2O4)陶瓷。研究了CaO含量对MgAl2O4陶瓷显微组织、致密化过程和光学质量的影响。发现使用 CaO 作为烧结添加剂会显着促进烧结过程。1525 ℃下预烧结的MgAl2O4陶瓷的相对密度随着CaO含量从0增加到0.15wt%而从92.1%变为97.8%，预烧结MgAl2O4陶瓷的平均晶粒尺寸也相应地从0.4μm增加到0.8μm。然而，当CaO含量增加到0.15wt%时，MgAl2O4陶瓷中出现第二相晶粒（铝酸钙），这严重降低了光学质量。含有 0.125 wt% CaO 的透明 MgAl2O4 陶瓷在 1525°C 下预烧结 3 小时并在 1600°C 下进行 3 小时 HIP 后处理显示出最佳在线透射率，1100 nm 处为 86.3%，600 nm 处为 83.7%平均晶粒尺寸为 2.9 μm。