Dielectric, elastic and piezoelectric properties of RCa 4O(BO 3) 3 ( R=rare-earth elements) crystals with monoclinic structure of point group m

Abstract

Rare-earth calcium oxoborate RCa 4O(BO 3) 3 ( R=La, Gd, Y) piezoelectric single crystals were successfully grown by a conventional RF-heating Czochralski (Cz) technique. They belong to the monoclinic system with point group m, and have 27 independent material constants. We developed the determination scheme (cuts and vibration modes) of the material constants in point group m. Their material constants were evaluated on the basis of the determination scheme and systematically compared. Also, the Rayleigh surface acoustic wave (RSAW) velocities v and coupling factors K 2 for the fundamental X-, Y- and Z-cuts were theoretically simulated in their crystals by Campbell and Jones's method, which showed a good agreement with the measured values. Moreover, from the calculated result in their all propagation direction, it was confirmed that (180°, 120°, 167°)-cut of the RCa 4O(BO 3) 3 ( R=Y) and (180°, 146°, 167°)-cut of the RCa 4O(BO 3) 3 ( R=La), indicated excellent RSAW propagation properties when compared with existing piezoelectric crystals.