Chemical composition characterization of Ca3Ta(Ga0.5Al0.5)3Si2O14 single crystal by the line-focus-beam ultrasonic material characterization system

A new method for evaluation of homogeneity of Ca3Ta(Ga0.5Al0.5)3Si2O14 (CTGAS) single crystals was established based on leaky surface acoustic wave (LSAW) velocity measurements performed by the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Three plate specimens cut perpendicular to X-, Y-, and Z-axes were prepared from the CTGAS crystal ingot and LSAW velocity distributions were examined for these specimens. LSAW velocity changes due to Al-substitution effect were successfully extracted by using a relationship between two LSAW velocities propagating along different directions for Ca3TaGa3Si2O14 (CTGS) and Al-substituted CTGS. Comparison of measured LSAW velocities and the results of chemical composition analysis performed by electron probe microanalysis (EPMA) demonstrated that LSAW velocity is mainly affected by Al-content change in CTGAS. Maximum velocity variation was observed in radial direction of the crystal ingot through the Z-axis propagating LSAW velocity measurements for Y-cut CTGAS specimen corresponding to Al-content change of 0.226 mol%. Accuracy of evaluation of Al content by velocity measurement for Y-cut Z-propagating LSAW is estimated to be ±0.0047 mol% and is superior to that by EPMA.