Method for reducing transparency and resistivity of lithium niobate or lithium tantalate wafer

The invention discloses a method for reducing transparency and resistivity of a lithium niobate or lithium tantalate wafer, which comprises the following steps of: alternately arranging the pretreated lithium niobate or lithium tantalate wafer and pure cotton paper or fiber cloth to form a laminated structure, and performing reduction blackening treatment on the wafer under a specific annealing furnace process condition to obtain the lithium niobate or lithium tantalate wafer. By adjusting the ratio of the thickness of the pure cotton paper or the fiber cloth to the thickness of the wafer, the lithium niobate or lithium tantalate yellow black wafer/grey wafer with different reduction degrees can be controllably prepared, the problems that the wafer blackening speed is too high, the reduction degree of the wafer is difficult to control, and the wafer is completely blackened are effectively solved, meanwhile, the resistivity and the light penetration rate of the wafer are effectively reduced, and the service li