Pb2BO3Br: a novel nonlinear optical lead borate bromine with a KBBF-type structure exhibiting strong nonlinear optical response

Abstract

A potential ultraviolet (UV) nonlinear optical (NLO) material, Pb₂BO₃Br, has been successfully synthesized by a mild hydrothermal method. It crystallizes in the trigonal polar NCS space group P321 with lattice parameters a = 4.9601(8) Å, c = 6.733(2) Å, v = 143.46(6) ų and Z = 1. The title compound with a KBBF-type structure consists of a honeycomb-like [Pb₂BO₃] layer and Br anions. UV-Vis-NIR diffuse reflectance spectroscopy revealed that Pb₂BO₃Br exhibits wide transparent regions from UV to near-IR. The powder second harmonic generation (SHG) test showed that it is phase-matchable in the visible region and features a remarkable SHG effect of about 9.5 times that of KDP. In addition, the electronic structure calculations indicated that the prominent macroscopic SHG response of Pb₂BO₃Br mainly originated from the [BO₃]³⁻ trigonal-planar groups and distorted PbO₃ polyhedra.