SnHPO₄: A Layered Tin(II) Phosphate with Enhanced Birefringence

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Phosphates are explored for short-wavelength optoelectronic applications, including ultraviolet (UV) and deep UV regions.
• Conventional phosphate materials often exhibit limited birefringence due to the symmetrical PO4 tetrahedra.

Purpose of the Study:

• To report a novel layered tin(II) phosphate with enhanced birefringence.
• To investigate the optical properties of this new material for UV applications.

Main Methods:

• Hydrothermal synthesis for growing single crystals of SnHPO4.
• Polarizing microscopy to measure refractive index difference.
• Density Functional Theory (DFT) calculations for theoretical refractive index difference.

Main Results:

• A layered tin(II) phosphate, SnHPO4, was synthesized with improved birefringence.
• Measured refractive index difference on a (010) wafer is 0.042@550 nm, closely matching DFT calculations (0.039@550 nm).
• The largest birefringence (0.078@550 nm) is theoretically predicted on the (100) plane. SnHPO4 exhibits UV transparency with a cutoff edge at 242 nm and a band gap of 4.50 eV.

Conclusions:

• The synthesized layered tin(II) phosphate demonstrates significantly improved birefringence compared to traditional phosphates.
• SnHPO4's UV transparency and birefringence make it a potential candidate for UV optoelectronic devices.
• The study highlights the potential of layered tin(II) phosphates for advanced optical material applications.