Accurate Velocity Measurement of Periodic Striae of TiO2–SiO2 Glasses by the Line-Focus-Beam Ultrasonic Material-Characterization System

Abstract

The evaluation of periodic striae layers in TiO2–SiO2 ultra-low-expansion glasses, formed during production, is discussed through the measurement of leaky surface acoustic-wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material-characterization system. The averaging effect associated with an LSAW propagation region interacting with periodic striae on a specimen surface was examined at 225 MHz, taking several specimens prepared with inclination angles of θ=0, 2, 5, 10, 20, and 90° to the plane of striae layers with a periodicity of 0.16 mm. LSAW velocities corresponding to TiO2 concentrations in the glass were properly measured for the specimens with θ less than 10°, and the perpendicular specimen (θ=90°) was suitable for accurate determination of the striae periodicities for LSAW propagation perpendicular to the striae plane.