Deformation anisotropy of Y + 128° –cut single crystalline bidomain wafers of lithium niobate

Abstract

Bidomain single crystals of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) are promising material for usage as actuators, mechanoelectrical transducers and sensors working in a wide temperature range. It is necessary to take into account anisotropy of properties of crystalline material when such devices are designed. Inthis study we investigated deformations of bidomain round shapedY+ 128°-cut wafers of lithium niobate in an external electric field. Dependencies of piezoelectric coefficients on rotation angles were calculated for lithium niobate and lithium tantalate and plotted for the crystal cuts which are used for bidomain ferroelectric structure formation. In experiment, we utilized external heating method and long-time annealing with lithium out-diffusion method in order to create round bidomain lithium niobate wafers. In order to obtain dependencies of the bidomain crystals’ movements on the rotation angle with central fastening and external electric field application optical microscopy was used. We also modeled a shape of the deformed bidomain wafer with a suggestion that the edge movement depends on the radial distance to the fastening point quadratically. In conclusion, bidomainY+ 128°-cut lithium niobate wafer exhibits saddle-like deformation when DC electric field is applied.