Evaluation of internal stresses in the surface layers of BaTiO₃ crystals by data of acoustic emission measurements

The work continues a complex study of BaTiO₃ crystals, possessing an involved domain structure of the `Forsberg grid' type. Earlier, the crystals were studied by measuring thermal expansion, dielectric constant, and acoustic emission in the region of phase transition. The curves exhibited additional anomalies at temperatures a few Kelvins below the Curie point T_C. As the surface layers containing growth defects were removed by etching, the domain structure of crystals simplified, and the extra anomalies disappeared, while their temperatures T_AE determined from the acoustic emission data gradually approached the T_C value. The present work is concerned with the dependence of T_AE on the layer thickness Δl removed, which was not studied earlier.