RbSe₃B₂O₉(OH) and CsSe₃B₂O₉(OH): one dimensional boroselenite-based anionic frameworks with second harmonic...

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Materials Science

Background:

• Alkali boroselenites are a class of inorganic compounds with potential applications in optics.
• Exploring novel structures and properties of these materials is crucial for advancing optical technologies.

Purpose of the Study:

• To synthesize and characterize two new alkali boroselenites: RbSe3B2O9(OH) and CsSe3B2O9(OH).
• To investigate their crystal structure, optical properties, and electronic band structures.

Main Methods:

• Solid-state synthesis reactions.
• Single-crystal X-ray diffraction for structural analysis.
• Optical diffuse reflectance spectroscopy for optical transitions.
• Theoretical calculations for electronic and optical properties.

Main Results:

• Successful synthesis of isostructural RbSe3B2O9(OH) and CsSe3B2O9(OH) crystallizing in the noncentrosymmetric space group P212121.
• Both compounds show indirect optical transitions with band gaps of 3.79 eV (RbSe3B2O9(OH)) and 4.17 eV (CsSe3B2O9(OH)).
• A broad transparency window (0.3-8.5 μm) and second-harmonic-generation (SHG) responses were observed, with CsSe3B2O9(OH) showing a notable SHG response.

Conclusions:

• The new alkali boroselenites possess unique noncentrosymmetric structures and exhibit favorable optical properties.
• Their broad transparency and SHG response suggest potential applications in nonlinear optics.
• Theoretical calculations provide insights into the structure-property relationships.