Evaluation of Pyrex Glasses by the Line-Focus-Beam Ultrasonic Material Characterization System

The line-focus-beam ultrasonic material characterization (LFB-UMC) system is applied to evaluation of commercial Pyrex glasses (C-7740, Corning Inc.). Twenty-eight specimens were prepared at random from different lots. Velocities of leaky surface acoustic waves (LSAWs), VLSAW, were measured at 225 MHz around 23°C. VLSAW was 3121.85-3149.83 m/s. To understand the velocity variations, bulk acoustic properties, viz., longitudinal and shear velocities (Vl and Vs), and density (ρ), and chemical compositions were measured for eight specimens extracted from the twenty-eight specimens. It is clarified that the VLSAW changes are related to the changes in elastic constants (c11 and c44) rather than in ρ and mainly to the changes in chemical composition ratio of B2O3/SiO2. Thus, we demonstrated that the LFB-UMC system is very useful and effective for evaluation of glasses and control of the production processes.