Much effort has been devoted to the discovery of novel birefringent crystals that display considerable birefringence(Δn)in the infrared(IR)region.However,the simultaneous achievement of a wide energy gap(E_(g)>3.1...Much effort has been devoted to the discovery of novel birefringent crystals that display considerable birefringence(Δn)in the infrared(IR)region.However,the simultaneous achievement of a wide energy gap(E_(g)>3.1 eV)and a largeΔn(>0.2)in a heteroanionic chalcogenide system remains a formidable challenge.To address this bottleneck,we applied the partial-substitution strategy and successfully designed and synthesized two new quaternary oxychalcogenides,namely AEGe_(2)O_(4)Se(AE=Sr and Ba).These two isomorphic compounds belong to the monoclinic space group P2_(1)/c(no.14),featuring a structure composed of two-dimensional(2D)[Ge_(2)O_(4)Se]^(2−)layers with an antiparallel arrangement,which are separated by charge-balanced Ba^(2+)cations.Remarkably,they exhibit the coexistence of largeΔn values(0.209 and 0.238@2050 nm based on the generalized gradient approximation)and wide E_(g)values(3.57 and 3.81 eV).Furthermore,theoretical calculations were performed to elucidate the interplay between optical properties and electronic structures.These results reveal that the significantly improvedΔn value(approximately 15–17 times that of the parent compound BaGe_(2)O_(5))can mainly be attributed to the newly discovered[GeO_(3)Se]heteroanionic motif.In brief,this study provides a simple chemical substitution method to overcome the trade-off between wide E_(g)and largeΔn values in heteroanionic chalcogenides.展开更多
基金National Natural Science Foundation of China(21771179)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZR118)Natural Science Foundation of Fujian Province(2022L3092 and 2023H0041)。
文摘Much effort has been devoted to the discovery of novel birefringent crystals that display considerable birefringence(Δn)in the infrared(IR)region.However,the simultaneous achievement of a wide energy gap(E_(g)>3.1 eV)and a largeΔn(>0.2)in a heteroanionic chalcogenide system remains a formidable challenge.To address this bottleneck,we applied the partial-substitution strategy and successfully designed and synthesized two new quaternary oxychalcogenides,namely AEGe_(2)O_(4)Se(AE=Sr and Ba).These two isomorphic compounds belong to the monoclinic space group P2_(1)/c(no.14),featuring a structure composed of two-dimensional(2D)[Ge_(2)O_(4)Se]^(2−)layers with an antiparallel arrangement,which are separated by charge-balanced Ba^(2+)cations.Remarkably,they exhibit the coexistence of largeΔn values(0.209 and 0.238@2050 nm based on the generalized gradient approximation)and wide E_(g)values(3.57 and 3.81 eV).Furthermore,theoretical calculations were performed to elucidate the interplay between optical properties and electronic structures.These results reveal that the significantly improvedΔn value(approximately 15–17 times that of the parent compound BaGe_(2)O_(5))can mainly be attributed to the newly discovered[GeO_(3)Se]heteroanionic motif.In brief,this study provides a simple chemical substitution method to overcome the trade-off between wide E_(g)and largeΔn values in heteroanionic chalcogenides.
