Dopant Occupancy in MgO-Codoped Lithium Niobate Crystals

On the basis of the bond valence model, the preferential occupancy of various dopant such as Mn2+, Eu3+, Er3+, Nd3+, Lu3+, Yb3+, In3+, Cr3+, Fe3+ and Ti4+ in the ideal stoichiometric lithium niobate (SLN) crystallographic frame was investigated in a viewpoint of chemical bonds. Theoretical analysis indicates that the dopant occupancy is significantly influenced by the anti-site Nb4+Li. Our work also shows that Mg-like ions (Mg2+, Zn2+, In3+, Sc3+) have a repulsive effect on Nb4+Li ions. When removing Nb4+Li ion by codoping Mg-like ions, the dopant occupancy in the LN crystallographic frame is determined by the natural characteristics of dopant, which is consistent well with the result in the ideal SLN crystals.