Contribution to the measurement of the material constants on domain-engineered ferroelectric crystals

Technique based on the combination of the methods (interferometric, resonant and hydrostatic)for measuring material constants for the domain-engineered crystal has been developed. All measured material properties were obtained on one sample with the same domain structure, which is very important because the same domain structure is not reproducible on domain-engineered crystals sample by sample. Technique is demonstrated on [001](C)-poled PMN-30 %PT square crystal plate. The temperature dependencies of piezoelectric coefficients d(31), sum of elastic constants s(11)(E)+s(12)(E), elastic constant C(33)(E), electromechanical thickness coupling factor k(1) and free dielectric constant were studied in the wide temperature range. Different methods give somewhat different material constants (especially piezoelectric). They must be used critically with respect to the used measurement method and its sensitivity to the local crystal domain structure. Hydrostatic piezoelectric coefficient shows different values if measured directly (108pC/N) or calculated (300 pC/N) from d(33)(int) and dn(31)(int) measured by the interferometer.