CsSbF₂ SO₄ : An Excellent Ultraviolet Nonlinear Optical Sulfate with a KTiOPO₄ (KTP)-type Structure

Area of Science:

• Solid-state chemistry
• Materials science
• Inorganic chemistry

Background:

• Noncentrosymmetric (NCS) polar materials are crucial for nonlinear optical (NLO) applications.
• Potassium titanyl phosphate (KTP) is a well-established NLO material, but research into new structures is ongoing.
• Metal sulfates and fluorides are classes of materials with potential NLO properties.

Purpose of the Study:

• To synthesize a novel NCS polar fluoride sulfate, CsSbF2SO4.
• To investigate the structural, optical, and NLO properties of the new compound.
• To explore the potential of fluoride sulfates as NLO materials.

Main Methods:

• Ionothermal synthesis was employed to obtain CsSbF2SO4.
• A co-substitution strategy was used, replacing [TiO6]8- and [PO4]3- groups in KTP with [SbO4F2]7- and [SO4]2- units.
• Structural characterization and second harmonic generation (SHG) measurements were performed.

Main Results:

• A novel NCS polar fluoride sulfate, CsSbF2SO4, was successfully synthesized.
• The compound exhibits a pseudo-3D framework of interconnected chains.
• CsSbF2SO4 shows a significantly enlarged band gap and a strong, phase-matchable SHG response (approx. 3.0 x KDP), the highest reported for a metal sulfate.

Conclusions:

• CsSbF2SO4 is a promising new material for near-ultraviolet nonlinear optical applications.
• The fluoride sulfate composition offers advantages for tuning optical properties.
• This work expands the scope of known NLO materials and synthetic strategies.