Structure and optical properties of a noncentrosymmetric borate RbSr4(BO3)3

A new noncentrosymmetric borate, RbSr4(BO3)3 (abbreviated as RSBO), has been grown from Rb2OB2O3RbF flux and its crystal structure was determined by single crystal x-ray diffraction. It crystallizes in space group Ama2 with cell parameters of a=11.128(10) Å, b=12.155(15) Å, c=6.952(7) Å, Z=4. The basic structural units are isolated planar BO3 groups. Second harmonic generation (SHG) test of the title compound by the Kurtz–Perry method shows that RSBO can be phase matchable with an effective SHG coefficient about two-thirds as large as that of KH2PO4 (KDP). Finally, based on the anionic group approximation, the optical properties of the title compound are compared with those of the structure-related apatite-like compounds with the formula “A5(TOn)3X”.