Elastic piezoelectric and dielectric constants of poly-domain and non-stoichiometric crystals of lithium niobate

The pulse-phase method was used to measure the velocities of longitudinal and lateral ultrasonic waves in the X, Y, Z directions of lithium niobate crystals. The measurements were made zero-orientation monodomain, polydomain and non-stoichiometric samples. As a result of these measurements, elastic moduli Csub(11)sup(E), Csub(33)sup(D), Csub(44)sup(E), Csub(66)sup(E), Csub(12)sup(E), Csub(14)sup(D), piezoelectric moduli esub(15), esub(22) and dielectric susceptibilities epsilonsub(11)sup(S), epsilonsub(11)sup(T) have been determined. The composition nonstoich has been found to affect the domain structure, as well as the elastic and piezoelectric properties. Polydomain crystals with different geometry of domain configurations differ in magnitude of some physical constants from monodomain configurations. In lithium niobate crystals, an increase in elastic shear moduli Csub(44)sup(E) and Csub(66)sup(E) and a decrease in the piezoelectric moduli are observed with a lower degree of unipolarity (increase in the number of domain boundaries)