Heteroanion-introduction-driven birefringence enhancement in oxychalcogenide (Ba3MGe3O2S8)-Ge-II (M-II = Mn, Cd)

Birefringent crystals play a crucial role in regulating the polarization of light and are widely used in optoelectronic fields. However, the effective design of novel infrared (IR) birefringent crystals with large birefringence (& UDelta;n) still face significant challenges. In this study, we present the rational design and successful synthesis of two novel quinary oxychalcogenides with the formula (Ba3MGe3O2S8)-Ge-II (M-II = Mn, Cd), employing a heteroanion-introduction strategy via high-temperature solid-state reactions. (Ba3MGe3O2S8)-Ge-II (M-II = Mn, Cd) crystallized in the monoclinic space group P2(1)/n (no. 14) and the structures comprised one-dimensional (1D) [(MGe3S8O2)-Ge-II](6-) chains arranged in an antiparallel manner and separated by Ba2+ cations. The coexistence of multiple heteroanionic ligands ([(MOS5)-O-II] octahedra, [GeOS3], and [GeO2S2] tetrahedra) in one material was surprisingly discovered for the first time in the realm of oxychalcogenides. It was revealed that the heteroanion-introduction strategy not only leads to a reduction in the structural dimensionality but also enhances the optical anisotropy significantly. Notably, (Ba3MGe3O2S8)-Ge-II (M-II = Mn, Cd) demonstrated large ?n values of 0.11 and 0.14, which represent a remarkable improvement compared to the three-dimensional (3D) parent AE(3)M(II)M(2)(IV)Q(8) system (?n = 0). Furthermore, theoretical calculations suggest that the significant ?n of (Ba3MGe3O2S8)-Ge-II (M-II = Mn, Cd) resulted primarily from the combination of polarizabilities from the various heteroanionic groups. Overall, these results highlight the potential of the heteroanion-introduction strategy for designing novel IR birefringent materials for optoelectronic applications.

Automated summary

In this study, two novel infrared birefringent crystals were successfully designed and synthesized using a heteroanion-introduction strategy. These crystals are important for regulating the polarization of light and have potential applications in optoelectronics.