Formation mechanism of black LiTaO₃ single crystals through chemical reduction

Lithium tantalate (LiTaO₃, LT) wafers of different colors were prepared through chemical reduction of regular congruent LT wafers. Samples with different colors corresponding to different annealing temperatures were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and measurements of the Curie temperature and density. It was found that chemical reduction does not influence the basic LT structure. The Ta charge state change due to chemical reduction was found to be the main reason for the formation of black LT wafers.