TOP SEEDED SOLUTION GROWTH OF RB-DOPED KNBO3 SINGLE-CRYSTALS

We report the growth of Rb-doped potassium niobate (KRN) single crysta ls using the top seeded solution growth (TSSG) technique. Colorless an d transparent KRN single crystals have been successfully grown from me lt comprising up to 15 mol% of Rb. Atomic absorption measurements indi cate that the Rb content in the KRN solid solution is rather low, the Rb segregation coefficient being on the order of 0.05. Based on crysta l energy considerations, the most probable Rb location in the host lat tice is expected to be the lattice site of the K+ cation. It is believ ed that the substitution of K+ by a much larger Rb+ has given rise to a lattice misfit in the doped bulk crystal, and thereby increased the total free energy of the crystal. From the thermodynamics point of vie w, the segregation phenomenon tends to reduce the lattice strain withi n the bulk crystals, hence, resulting in the segregation coefficient o f Rb being rather small.