Evaluation of long-term stability of low thermal expansion coefficient materials using gauge block interferometers

Abstract

The long-term stability of NEXCERA™ ceramics having a low coefficient of thermal expansion was evaluated over a period of eight years. Several gauge blocks of differing lengths were prepared, using two types of NEXCERA. Each gauge block was kept wrung to a platen and its absolute length was periodically measured by gauge block interferometer during the eight years. Relative uncertainties of measurement of changes in gauge block length were estimated as 4.1 × 10−8 and 2.9 × 10−8 for 200 mm and 800 mm gauge blocks, respectively. The experimental results show the trend of expansion and a relative change of less than 0.1 × 10−6/year for every gauge block.