Ultra-high quality factor of transparent Al2O3 ceramics fabricated by vacuum sintering and post hot isostatic pressing

Abstract

Transparent polycrystalline Al2O3 (PCA) ceramics were prepared by vacuum sintering followed by hot isostatic pressing (HIP) using MgO as a sintering aid. The prepared sample with thickness of 0.8 mm exhibits a transmittance of 50% (λ = 640 nm) and 78% (λ = 4.5 μm) in the entire visible band and infrared band, respectively. Effects of additive content, sintering temperature as well as HIP method on the microstructure of Al2O3 ceramics were systematically investigated. The experimental results show that the effect of HIP on the transmittance of PCA in the visible light region is particularly obvious, which can increase the transmittance by almost two times. In particular, the quality factor of pure Al2O3 ceramics prepared by the same process is as high as 1,120,970 GHz (at 13.6 GHz) owing to extremely high density and reduction of the grain boundary, which render Al2O3 ceramics potential candidates for fabrication of multilayer electronic devices.