Physical properties of single crystals of KTiPO₄, K_xRb_1−xTiOPO₄ (x = 0.85; 0.75), KGeOPO₄ and KTiOAsO₄

Abstract

Abstract Single crystals of the title compounds of optical quality and dimensions up to 30 × 25 × 25 mm were grown by the flux method. During the growth process the formation of twins consisting of bicrystals was observed, even in the case of single‐crystalline seeds. The twinning boundaries could be detected by etching with hot KOH solutions. The following physical properties were investigated: refractive indices, dielectric constants, thermal expansion, piezoelectric, and electrooptic effects, elastic and thermoelastic constants. The crystals exhibit a quite similar behaviour. The anisotropy of all properties is quasi‐tetragonal. In respect to polar properties only small differences within the mixed crystals K x Rb 1– x TiOPO 4 are found. Replacement of P by As does only slightly affect the polar properties, whereas the replacement of Ti by Ge leads to a drastic reduction of polar effects.