PIEZOELECTRIC AND ELASTIC PROPERTIES OF ORTHORHOMBIC LIH2PO3 AND LIH2PO4

Single crystals of LiH2PO3 and LiH2PO4, both of space group symmetry P na2(1), with dimensions up to 40 mm were grown from aqueous solutions by controlled evaporation. Pyroelectric, dielectric, piezoelectric, el astic and thermoelastic properties were studied by standard methods. T he static piezoelectric constants d(333) exceed d(111) of alpha-quartz by only a factor 2. The pyroectric effects reach 3 times and 7 times, respectively, that of tourmaline. The mean elastic stiffness of the p hosphite is 13% smaller than that of the phosphate, a phenomenon also observed in the corresponding sodium and potassium salts.