Sr6 Cd2 Sb6 O7 S10 : Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups.

A new nonlinear optical (NLO) oxysulfide, Sr6 Cd2 Sb6 O7 S10 , which contains the functional groups [SbOx S5-x ]7- (x=0, 1) with a 5s2 electron configuration, is synthesized by a solid-state reaction. This compound displays a phase-matchable second harmonic generation (SHG) response four times stronger than AgGaS2 (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 [SbOS4 ]7- and [SbS5 ]7- pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS4 ]7- units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns2 electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.