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

Abstract

A new noncentrosymmetric material, namely, K2[B3O3(OH)5] has been obtained by conventional solution reaction. It crystallizes in the orthorhombic space group Ama2 (no. 40). In the structure of K2[B3O3(OH)5], the BO2(OH) triangles and BO2(OH)2 tetrahedra are linked via sharing corners forming the isolated [B3O3(OH)5]2- anionic groups with no dangling bonds in oxygen atoms. And K2[B3O3(OH)5] is the first synthetic noncentrosymmetric borates with [B3O3(OH)5]2- anionic groups. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique showed that K2[B3O3(OH)5] is type I phase-matchable, and the measured SHG coefficient is 0.32 times that of KH2PO4. The UV transmittance spectroscopy measurement indicated that the UV absorption edge was below 200 nm, suggesting that K2[B3O3(OH)5] might be a promising deep-UV nonlinear optical material. Band structure and optical property calculations based on DFT methods were also performed.