Effect of electrostatic and size on dopant occupancy in lithium niobate single crystal

摘要

We proposed a simple and an effective method to predict the site occupancy and threshold concentration of metal ions in lithium niobate (LiNbO_3, LN) single crystal. The ionic energy parameter E_i, defined by the ionic electronegativity and ionic radius, was proposed to describe the electrostatic and size effects of cations on the structural stability of LN. The dopant location can be easily identified by comparing the E_i deviation of dopant from those of host cations Li~+ and Nb ~(5+), and the dopant prefers to occupy the lattice site with the smaller deviation of E_i. Our calculated occupancies agree well with those experimental results, which demonstrate the predictive power of our present method. We in this work predicted the preferred occupancies of 60 metal ions in LN single crystal. Further, the threshold concentrations of some frequently used dopants were calculated on the basis of the assumption that all doped LN crystals can endure the same variation of E_i.