Hydroxyl-induced structural reconstruction: Two new potassium hepta-borates with deep-UV transparency and enhanced birefringence

Abstract

As the critical component of polarization devices and optical devices, birefringent crystals are widely used in high-tech fields such as laser communication, laser polarization engineering, and high-precision scientific research instruments. In this study, two new hydroxyl borates KB 7 O 9 (OH) 4 and KB 7 O 10 (OH) 2 were synthesized successfully by hydrothermal method From KB 7 O 9 (OH) 4 to KB 7 O 10 (OH) 2 , two hepta-borates show different functional units of [B 7 O 10 (OH) 4 ] and [B 7 O 12 (OH) 2 ], respectively, which are further polymerized to form 1D [B 7 O 9 (OH) 4 ] infinite chain and 2D [B 7 O 10 (OH) 2 ] infinite layer via hydroxyl-induced structural reconstruction, respectively. For the 1D [B 7 O 9 (OH) 4 ] infinite chain of KB 7 O 9 (OH) 4 , which was first found in inorganic hydrated hepta-borates based on ICSD database. The performance characterization shows that two compound has a deep-UV transparency (shorter than 200 nm), and exhibits a moderate birefringence of 0.041 to 0.078 at 546 nm, indicating their potential as a deep-UV birefringent crystals.