Optimization of Ca additive and HIP condition in fabrication of the transparent MgAl₂O₄ ceramics

The amount of Ca addtive as well as the sintering condition on the in -line transmittance and the flexural strength of the transparent MgAl2O4 spinel ceramics were optimized. In -line transmittance and mechanical properties were also dependent on the hot-isostatic-press(HIP) temperature. Elevated HIP temperature induced the abnormal grain growth, which resulted the large trapped pores inside the grain, which resulted the in -line transmittance degraded. Elevated HIP together with larger Ca amount accelerated the generation of abnormal grain growth (AGG) and the secondary phases, hence the optical and mechanical properties degraded. The optimized condition was the addition of 800 ppm Ca with HIP at 1500 C-degrees. Big scattering sources, pore clusters as well as the secondary calcium aluminate phases, were restricted and homogeneous microstructure without AGG was revealed. Hence, both the in -line transmittance and the strength were optimized as 84% and 323 MPa, simultaneously.