Characterization and identification of berlinite crystals by acoustic microscopy

Berlinite crystals grown in H₃PO₄, HCl, H₃PO₄/HCl, H₂SO₄/HCl, or H₃PO₄/HCl/H₂SO₄ solvents are characterized by acoustic microscopy techniques. Surface and subsurface defects can be visualized via acoustical images, whereas elastic parameters of the crystal can be measured on a microscopic scale. They prove to be of great importance in the identification of not only crystal orientations but of preparation methods as well. We show, for example, that a growth in sulfuric and phosphoric mediums improves mechanical behavior of berlinite crystals. Moreover, it seems that anisotropy plays a fundamental role in this characterization technique with an appearance or a disappearance of specific modes.