抄録
The contribution of piezoelectricity was taken into consideration in the elastic wave equation referred to the rotated coordinates, and investigated for all of the pure and semipure mode directions in the crystals of the piezoelectric point groups. In the point groups belonging to cubic, tetragonal I, trigonal I, orthorhombic, monoclinic and triclinic systems, pure and semipure mode directions are determined similarly to the case of neglecting the piezoelectric effect. In the points groups belonging to trigonal II, tetragonal II and hexagonal systems, it is found that the piezoelectric effect shows a remarkable contribution to pure and semipure mode directions. The pure and semipure mode directions can be derived taking account of the crystal symmetry elements.
