LAUSR

Inorganic phosphates are of great interest, because of their rich structural chemistry and multiple functional properties. Compared with the phosphates that only contain the solely condensed P-O groups, the phosphates with various condensed P-O groups are less reported, especially for the noncentrosymmetric (NCS) ones. Here, two new bismuth phosphates, Na6Sr2Bi3(PO4)(P2O7)4 and Cs2CaBi2(PO4)2(P2O7), were synthesized by the solid-state reaction and both structures contain two types of isolated P-O groups. Remarkably, Na6Sr2Bi3(PO4)(P2O7)4 crystallizes in the tetragonal space group P4̅21c, which represents the first NCS bismuth phosphate with PO4 and P2O7 groups. Detailed structural comparisons among Bi3+-containing alkali/alkaline-earth metal phosphates show that the ratios of cations/phosphorus profoundly influence the condensed degree of P-O groups. Ultraviolet-visible-near-infrared (UV-vis-NIR) diffusion spectra show that both compounds have the relatively short UV cutoff edges. And Na6Sr2Bi3(PO4)(P2O7)4 has a second-harmonic generation response of 1.1 × KDP. The first-principles calculations are carried out to understand the structure-performance relationship.