K2[B3O3(OH)5]: A new deep-UV nonlinear optical crystal with isolated [B3O3(OH)5]2- anionic groups

A new noncentrosymmetric material, namely, K 2 [B 3 O 3 (OH) 5 ] has been obtained by conventional solution reaction. It crystallizes in the orthorhombic space group Ama 2 (no. 40). In the structure of K 2 [B 3 O 3 (OH) 5 ], the BO 2 (OH) triangles and BO 2 (OH) 2 tetrahedra are linked via sharing corners forming the isolated [B 3 O 3 (OH) 5 ] 2- anionic groups with no dangling bonds in oxygen atoms. And K 2 [B 3 O 3 (OH) 5 ] is the first synthetic noncentrosymmetric borates with [B 3 O 3 (OH) 5 ] 2- anionic groups. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique showed that K 2 [B 3 O 3 (OH) 5 ] is type I phase-matchable, and the measured SHG coefficient is 0.32 times that of KH 2 PO 4 . The UV transmittance spectroscopy measurement indicated that the UV absorption edge was below 200 nm, suggesting that K 2 [B 3 O 3 (OH) 5 ] might be a promising deep-UV nonlinear optical material. Band structure and optical property calculations based on DFT methods were also performed.