A novel UV nonlinear optical crystal material: K21Yb8B45O90

Abstract

A new noncentrosymmetric (NCS) rare earth borate crystal K₂₁Yb₈B₄₅O₉₀ has been grown using the K₂O–CdO–B₂O₃ flux and its structure was determined by single crystal X-ray crystallographic study. The compound crystallizes in the NCS trigonal space group R32. In the structure, BO₃ and BO₄ polyhedra interconnect via sharing corners to form the basic structure unit B₅O₁₀ groups, which are bridged by YbO₆ triangular prisms to build up a three-dimensional framework with one-dimensional channels occupied by K atoms. Second harmonic generation (SHG) measurement indicates that K₂₁Yb₈B₄₅O₉₀ possesses an SHG response close to KDP with a particle size of 50–61 μm. In addition, thermal analyses suggest that the compound melts at 955 °C incongruently. The band gap of K₂₁Yb₈B₄₅O₉₀ deduced from diffuse reflectance spectroscopy measurement is 5.90(2) eV.