Nanoindentation Based Estimates of Flexoelectric Properties of Piezoelectric Crystals
Flexoelectricity refers to coupling between electric polarization and strain gradients in crystalline dielectrics. Recent work has shown that stiffness data obtained by nanoindentation, combined with an analytical indentation model that predicts size dependent behavior attributable to flexoelectricity, may be used to characterize flexoelectric properties of piezoelectric crystals. In the present work this experimental-analytical method is used and evaluated based on nanoindentation of quartz, lithium niobate, lithium tantalate, lead magnesium niobate - 30% lead titanate, and barium titanate with Berkovich, cone, and cube corner indenters. Flexoelectric properties appear negligible in quartz and are estimated to be on the order of 10^-9C/m to 10^-8C/m in lithium niobate and lithium tantalate, and around 10^-4C/m for barium titanate and PMN-30%PT. The results for quartz agree with previous work, the results for barium titanate conflict, and those for the remaining materials are original and justifiable. Implications of the approach are discussed at length. The methodology in its current state is practical for specific types of dielectric crystals.