Comparison of material properties between ultra low thermal expansion ceramics and conventional low thermal expansion glass

The material characteristics of various optical materials that are known to possess a low thermal expansion property were studied for mechanically and thermally ultra-stable optical applications. In this comparative study on material selection, the key mechanical and thermal properties of four potential low thermal expansion ceramics and three conventional low thermal expansion glass were evaluated under exactly the same testing configurations. This paper describes the results of basic material testing and outlines a comparison of material properties between the potential ceramics and conventional glass. The material testing results showed that the elastic modulus and thermal conductivity of cordierite ceramics were one-and-a-half or more times higher than those of conventional low thermal expansion glass, while ensuring the thermal expansion coefficient roughly matching that of compared glass materials. It was therefore revealed that the cordierite ceramics had most favorable physical properties and could be advantageous alternative materials to the conventional low thermal expansion glass for ultra-lightweight and thermally-stable optical applications.