Abstract
Transparent MgAl2O4 spinel ceramics were fabricated by hot isostatic pressing of the sintered materials composed of fine grains. Since the fine-grained sintered materials were difficult to obtain from pure powders at low temperatures, the additives reducing sintering temperatures were examined. As a result, a small addition of boron oxides (0.05-0.5 mass%-B2O3) was found to be very effective. The influence of boron oxides on the microstructure was investigated. The restriction of anomalous grain growth was important for transparency. The samples added with 0.15 mass%-B2O3 showed high optical transmittance (80% with 1 mm thick).
