Preparation and characterization of thick stoichiometric lithium tantalate crystals by vapor transport equilibration method

A stoichiometric lithium tantalate (SLT) crystal, 3.2 mm in the thickness and approximate 56 mm in the diameter, was prepared employing improved vapor transport equilibration (VTE) method. The chemical composition in SLT crystals is about 49.99 mol%. The compositional depth profile and uniformity along the radial direction were characterized. The composition deviation in the whole wafer is less than 0.02 mol%. The poling fields for ferroelectric domain reversal of SLT crystals were measured by applying ramped voltages using liquid electrodes. The forward and reverse poling fields are 159 V/mm and 145 V/mm, respectively, and their uniformity in the whole SLT crystal is promising.