Study of OH- absorption mode due to domain inversion in lithium niobate crystals

Recently, the significant change of OH spectra of highly Mg-doped LiNbo₃ during polarization reversal process have been found experimentally. However, there is no proper theory and model to explain the unusual phenomena. Based on the Nb-vacancy model, the OH absorption band for highly Zn and Mg doped LiNbo₃ single crystals under coercive field were calculated. Theoretical investigation of OH absorption band under the forward and back coercive field are also investigated. Our result shows the Zn²⁺ and Mg²⁺ ions sit at Li lattice sites for highly doped LiNbo₃ single crystals. The theoretical prediction of the disappearing and the reappearing of the OH absorption band after polarization reversal agrees well with the experimental result, and this indicates that Zn²⁺ and Mg²⁺ ions do not substitute the Nb-lattice sites.