Zn atoms in lithium niobate and mechanism of their insertion into crystals

Precision X-ray structural studies were carried out for LiNbO3 : Zn-x singl e crystals with x = 0.0, 2.87, 5.20, and 7.60 at. %. It was found that the insertion of the Zn atoms into the Li position was accompanied by a decreas e in the concentration of intrinsic Nb-Li defects. At x = 7.6%, the Zn atom s change their locations in the lattice and partially occupy the Nb positio ns. This clarifies the structural nature of the "threshold" Zn concentratio n, which manifests itself as singularities in the concentration dependences of various optical properties. The structural origin of the threshold conc entration is likely a common feature of all nonphotorefractive impurities ( Mg, Zn, In, and Sc) in LiNbO3. A change in the intrinsic defect structure o f the LiNbO3 crystals with different Zn concentrations is discussed. (C) 20 01 MAIK "Nauka/Interperiodica".