Preparation and surface morphology analysis of near stoichiometric lithium tantalate crystals by the vapour transfer equilibrium method

In this paper, near stoichiometric lithium tantalate wafers with different Li contents were prepared by the vapour transfer equilibrium method, and the surface morphology of the diffused material and wafers were analyzed. X-ray diffraction and scanning electron microscopy tests were conducted on the diffused material and used diffused material, and it was found that the Li content in the used diffused material decreased, the crystal particle size increased, the lattice parameters decreased, and the crystallinity increased. By analyzing the Curie temperature, scanning electron microscopy, and atomic force microscopy tests of near stoichiometric lithium tantalate wafers prepared by different processes, it was found that the Li ions diffused into the wafers are related to the diffusion temperature, and the higher the diffusion temperature, the smaller the surface roughness of the wafer. When the Li/Ta ratio in the diffused material is equal to or exceeds 70/30, twins will appear on the wafer surface. Through the above analysis, the optimum diffusion temperature range for preparing near stoichiometric lithium tantalate wafers is 1160–1260 ℃, and the Li/Ta ratio in the diffused material should not exceed 70/30, which provides an empirical reference for the preparation of near stoichiometric lithium tantalate crystals with better performance by vapour transfer equilibrium method.