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

Two new isotypic anhydrous borophosphates, KMBP(2)O(8) (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 I42d with the following lattice parameters: a = 7.1095(18), c = 13.882(5)A for KSrBP(2)O(8) and a = 7.202(2), c = 14.300(6)A for KBaBP(2)O(8). The fundamental building block (FBB) of title borophosphates with B:P ratio = 1:2 is 12square:<12square> (symbol square represents BO(4) and PO(4) 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 KSrBP(2)O(8)) and 1/3 (for KBaBP(2)O(8)) times as large as that of KDP.