Synthesis, structure, and characterization of a new promising nonlinear optical crystal: Cd5(BO3)3F

Abstract

A nonlinear optical crystal cadmium fluoroborate (Cd₅(BO₃)₃F) has been synthesized through high-temperature solid-state reactions. In the crystal structure, CdO_nF_m (n = 4, 5, 7; m = 0, 1, 2) distorted polyhedra interconnect via shared edges and corners to form a 3D framework with tunnels along the c axis. BO₃ planar triangles lie approximately parallel in the (001) plane. The combination of triangular BO₃ groups with π-conjugated systems and the d¹⁰ cation Cd²⁺ with polar displacement produces large SHG responses. The second harmonic generation (SHG) measurement shows that Cd₅(BO₃)₃F possesses a large SHG response about four times that of KH₂PO₄ (KDP) and is phase-matchable in the visible region. In addition, it exhibits a wide transparent region ranging from UV to near IR, which suggests that the material is a promising NLO material.