Sr 6 Cd 2 Sb 6 O 7 S 10 : Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups

A new nonlinear optical (NLO) oxysulfide, Sr 6 Cd 2 Sb 6 O 7 S 10 , which contains the functional groups [SbO x S 5− x ] 7− ( x =0, 1) with a 5s 2 electron configuration, is synthesized by a solid‐state reaction. This compound displays a phase‐matchable second harmonic generation (SHG) response four times stronger than AgGaS 2 (AGS) under laser irradiation at 2.09 μm. Single‐crystal‐based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS 4 ] 7− and [SbS 5 ] 7− pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS 4 ] 7− units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an n s 2 electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.