OH

OH- absorption bands of lithium tantalate crystals have been measured at room temperature, and the bands shape depending on the crystal composition has been observed. OH- absorption bands are fitted with three Lorentzian peaks by varying position, halfwidth, and area. Nearly constant peak positions (3461, 3475 and 3486 cm-1) for all samples are obtained. Hydrogenation is also performed to the crystals and its influence on the decomposed peaks (position, halfwidth and area) is investigated. The results show the fitting parameters of peaks have different values for crystals with different hydrogen concentration, which is interpreted by the different sites occupied by H+ in terms of the modified model about the location of Li-vacancy in the lattice. Additionally, it is shown that the halfwidth of peak at 3461 cm-1 remain unchanged regardless of hydrogen concentration, which make this parameter more suitable than other ones to determine the composition of LiTaO3 crystals. The quantitative relationship between the halfwidth of peak at 3461 cm-1 and the crystal composition is also presented