Elastic properties of langasite-type crystals determined by bulk and surface acoustic waves

We have determined the elastic constants of langasite-type crystals (La3Ga5 SiO14, La3Ga5.5Nb0.5O14, and La3Ga5.5Ta0.5O14) from measurements of the sou nd velocity of acoustic waves. Starting with the elastic tensor determined from bulk acoustic waves, we optimized the data set by investigating the in fluence of the elastic tensor components on the angular dispersion of surfa ce guided waves. This procedure is particularly useful for accurate determi nation of the nondiagonal elements of the elastic tensor. Phase velocity ca lculations based on the new set of constants show an increased agreement wi th experimental data compared to the data set derived from bulk waves and p reviously published material data. (C) 2001 American Institute of Physics.