Abstract
Translucent polycrystalline aluminas with different grain sizes were obtained by sintering the green compact, which was fabricated by using slip casting methods for high-purity α-alumina (99.99 %) powder of 0.24 μm in grain size, at 1,373 ∼ 2,073 K and by applying HIP method. Effect of average grain size on transmittance and mechanical strength of sintered bodies was investigated. For sintered bodies with average grain size of less than 2 μm, transmittance increased because of the effect by Rayleigh scattering. Non-translucent alumina with average grain size about 2 ∼ 7 μm is considered to follow Mie scattering. For average grain sizes larger than 7 μm, the transmittance was slightly increased based on the law of Fresnel. Mechanical strength of sintered body increased with decreasing the grain size, and depended on the inverse-square law of the grain size. Polycrystalline alumina with the average grain size of 0.8 μm showed the excellent properties of high transmittance and high mechanical strength, compared with that of lucalox.
