KMBP₂O₈ (M = Sr, Ba): A new kind of noncentrosymmetry borophosphate with the three-dimensional diamond-like framework

Two new isotypic anhydrous borophosphates, KMBP₂O₈ (M=Sr, Ba), have been prepared under high temperature solution growth (HTSG). Investigation of single-crystal X-ray diffraction shows that they crystallize In noncentrosymmetric space group /4̄2d with the following lattice parameters: a = 7.1095(18), c= 13.882(5)Á for KSrBP₂O ₈ and a = 7.202(2), c= 14.300(6)Å for KBaBP₂O ₈. The fundamental building block (FBB) of title borophosphates with B:P ratio = 1:2 is 12□:(12□) (symbol □ represents BO₄ and PO₄ tetrahedra). The FBBs are further interlocked together to form the final 3D diamond-like architecture. Second-harmonic generation (SHG) on powder samples has been measured using Kurtz and Perry technique, which Indicates that they are phase-matchable materials, and their SHG coefficients are measured to be about 1/5 (for KSrBP₂O₈) and 1/3 (for KBaBP₂O₈) times as large as that of KDP.