Mechanism of the piezoelectricity of langasite based on the crystal structures

Langasite family crystals (R3Ga5SiO14, R=rare earth) are expected as the new piezoelectric material for SAW filter. La3Ga5SiO14 has the largest piezoelectric modulus in these crystals. It is reported that the piezoelectric properties of these crystals improved with the increase of the ionic radius of R. In this work, we clarified the crystal structures of three kinds of langsite family crystals (R=La, Pr and Nd) by X-ray diffraction analysis. We investigated the differences among these crystal structures and clarified the reason why the piezoelectric properties improved with the increase of the ionic radius of R on the basis of these structural differences.