New Fluoride Carbonates: Centrosymmetric KPb2(CO3)2F and Noncentrosymmetric K2.70Pb5.15(CO3)5F3

Two new potassium lead fluoride carbonates, KPb2(CO3)2F and K2.70Pb5.15(CO3)5F3, have been synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. KPb2(CO3)2F and K2.70Pb5.15(CO3)5F3 were structurally characterized by single crystal X-ray diffraction and exhibit two-dimensional crystal structures consisting of corner-shared PbO6F and PbO6F2 polyhedra. K2.70Pb5.15(CO3)5F3 is noncentrosymmetric, and crystallizes in the achiral and nonpolar space group P6̅m2 (crystal class −6m2). Powder second-harmonic generation (SHG) measurements using 1064 nm radiation revealed a SHG efficiency of approximately 40 × α-SiO2, whereas a charge constant, d33, of approximately 20 pm/V was obtained through converse piezoelectric measurements. For the reported materials, infrared, UV–vis, thermogravimetric, and differential thermal analysis measurements were performed.