A novel UV nonlinear optical crystal material: K21Yb8B45O90

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.