Piezoelectric, dielectric, and pyroelectric constants of LiH3(SeO3)2

The complete sets of dielectric, piezoelectric, and pyroelectric constants and a partial set of elastic constants are given for ferroelectric lithium trihydrogen selenite, the first crystal of monoclinic class m for which such data have been obtained. The ferroelectric moment is 15/~coul/cm/ directed 3 from the normal to the (001) plane. It decreases by 6"6% in magnitude and shifts to an angle of 1.1 at 85 C. The two principal axes of the dielectric tensor in the symmetry plane are nearly 45 from t ! t the ferroelectric axis and the principal dielectric constants are Q/e0 = 13.0, %/e0 = 12.9, and e3/e 0 --46.