Microstructure and optical properties of transparent alumina

The microstructure and optical properties are evaluated for alumina sintered by spark plasma sintering at temperatures between 1100 and 1550 degrees C. With increasing sintering temperature, grain growth and densification occur Lip to 1250 degrees C, and above 1300 degrees C, rapid grain growth and pore growth Occur. Light transmission increases with the densification and decreases with the grain/pore growth. It is found that the total forward transmission and the reflection of light are related to the porosity and the pore growth, whereas the in-line transmission and the light absorption are related to the grain size and the defects, respectively. The relationships are explained by using the Mie scattering theory, model prediction and observed microstructural characteristics. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.