TEMPERATURE-DEPENDENCE OF THE STRUCTURE OF LI-1-XHXIO3 STUDIED BY HIGH-RESOLUTION NEUTRON POWDER DIFFRACTION BETWEEN 10 AND 380-K

Thermal variations of structural parameters of Li1-xHxIO3 are reported between 10 and 380 K, and are compared to isotypic α-LiIO3 in the same temperature range. Beside the presence of a weakly bound, randomly distributed proton in general position of P63, differences appear concerning the thermal expansion coefficient along the polar axis and a significant shift of the Li position is observed from 210 K to the decomposition temperature (≈400 K). This predicts differences in the Li1-xHxIO3 pyroelectric and piezoelectric effects when compared to the α-LiIO3 crystal widely used for technological applications. © 1993 Academic Press, Inc.