Zerodur® — A Low Thermal Expansion Glass Ceramic for Optical Precision Applications

A Super-Precise CTE Evaluation Method for Ultra-Low-Expansion Glasses Using the LFB Ultrasonic Material Characterization System

“…For temperatures from 0 to 50 C, Class-0 glass has a CTE of AE20 ppb/K; Class-1 glass, AE50 ppb/K; and Class-2 glass, AE100 ppb/K. 14) All specimens were optically polished on both sides with a parallelism within 10 seconds.…”

“…At present, it is very difficult to state definitely what chemical elements mainly cause the velocity variations because Zerodur glasses consist of 10 elements, as shown in Table III. Second, the variations in the process temperature and time for the crystallization 11,14) to realize the ultra-low-expansion characteristics are considered to provide the velocity changes. The elastic constants would vary remarkably because the glass volume shrinks by 3 percent in this process.…”

“…The elastic constants would vary remarkably because the glass volume shrinks by 3 percent in this process. 14) In order to apply the LFB-UMC system to improve the Zerodur glass production process, we have to make further investigations. Since the characteristic differences among the four Zerodur ingots could be detected as changes of LSAW velocities measured with a high accuracy, the LFB-UMC system is very useful for quality control and selection of Zerodur products.…”