Ag₃In₃(SeO₃)₃(SO₄)F₄: A Sulfate Selenite Nonlinear Optical Material with a Wide Bandgap

Combining selenite and sulfate to design nonlinear optical (NLO) materials with wide bandgaps and strong second harmonic generation (SHG) response has been a long-standing challenge in this field, with only a few related achievements reported so far. In this work, we successfully incorporated sulfate groups into selenites via a simple hydrothermal method. Furthermore, we introduced In3+, which does not undergo d-d transitions, along with highly electronegative F- ion, and successfully synthesized the compound Ag3In3(SeO3)3(SO4)F4. This compound exhibits a honeycomb-like three-dimensional structure in which In6Se6 12-membered polyhedral ring tunnels extend along the c axis. Performance testing revealed that Ag3In3(SeO3)3(SO4)F4 demonstrates a moderate SHG response of 1.8 times that of KDP and a wide bandgap of 4.2 eV. This work offers practical and feasible ideas for the design of wide-bandgap NLO materials.