Synthesis and optical properties of the first lead borate bromide with isolated BO3 groups: Pb2Ba3(BO3)3Br.

Single crystals of a new compound Pb2Ba3(BO3)3Br have been grown by a spontaneous crystallization method. They crystallize in the noncentrosymmetric orthorhombic space group C2221 with isolated BO3 triangles and distorted PbO polyhedra. UV-Vis-NIR diffused reflectance spectroscopy measurements indicate that the absorption edge is at 326 nm. Second-harmonic generation (SHG) measurements using 1064 nm radiation show that Pb2Ba3(BO3)3Br exhibits relative large NLO response about 3.1× that of KH2PO4 (KDP) and is type I phase-matchable. First-principles electronic structure calculations show that the isolated BO3 groups and PbO4 polyhedra play an important role in the total SHG response.