On existence of one-partial bulk waves in semi-infinite piezoelectric media

The conditions for the existence of one-partial bulk waves satisfying the b oundary conditions on a mechanically free surface of a semi-infinite piezoe lectric medium have been analyzed. In purely elastic media, similar wave so lutions are known to exist along the propagation directions m which form li nes on the sphere m m = 1, passing through all the available degeneracy poi nts (acoustic axes). It is shown that in a triclinic piezoelectric half-spa ce with a metallized surface, one-partial bulk waves may exist sorely along isolated propagation orientations, whereas for a nonmetallized surface, su ch waves can exist only if an additional condition for the material constan ts of the medium is fulfilled. It is also shown that the one-partial bulk s olution may not exist along an arbitrary acoustic axis in a piezoelectric. These conclusions are valid in the general case of unrestricted anisotropy, i.e., they do not take into account the material symmetry. In addition, th e orientations providing the propagation of one-partial hulk waves because of the existing symmetry are specified for piezoelectric media of various s ymmetry classes. (C) 2000 MAIK "Nauka/Interperiodica".