Synthesis, Crystal Growth, Electronic Properties and Optical Properties of Y₆IV_2.5S₁₄ (IV=Si, Ge)

Abstract

Two isostructural ternary acentric sulfides, Y 6 Si 2.5 S 14 (1) and Y 6 Ge 2.5 S 14 (2) were re-investigated to understand the origin of the chemical flexibility of RE 6 B x C y Ch 14 (RE=Y, LaÀ Lu; B=Si, Ge, Sn, Al, Ga; C = monovalent M + (Ag, Na, Li, etc.), divalent M 2 + (Mg, Cr, Ni, Zn, etc.), trivalent M 3 + (Al, In, Ga, etc.), tetravalent M 4 + (Si, Ge, Sn) and pentavalent M 5 + (Sb), Ch=S, Se), which consists of ~444 isostructural compounds. Y 6 IV 2.5 S 14 (IV=Si, Ge) were synthesized by a high-temperature salt flux method. The crystal structures of Y 6 IV 2.5 S 14 (IV=Si, Ge) are constructed by [YS 8 ] polyhedra, [Si1S 6 ] octahedra, and [Si2S 4 ] tetrahedra. The Si1 atom displaces from the center of [Si1S 6 ] octahedra with partial occupancy, which can be replaced by various metals, and mainly accounts for the chemical flexibility of the RE 6 B x C y Ch 14 family. The bonding pictures of Y 6 Si 2.5 S 14 were studied by electron localization function (ELF) and crystal orbital Hamilton population (COHP) calculations. Y 6 Si 2.5 S 14 is evaluated as an indirect semiconductor with a bandgap of 2.4(1) eV measured by UV-Vis. The indirect bandgap of Y 6 Ge 2.5 S 14 is 1.7(1) eV. Y 6 IV 2.5 S 14 (IV=Si, Ge) are not type-I phase-matchable materials. For samples of 47 μm particle size, Y 6 Si 2.5 S 14 and Y 6 Ge 2.5 S 14 own good second harmonic generation (SHG) responses of ~3.0 × AGS and ~2.8 × AGS respectively. Y 6 Si 2.5 S 14 and Y 6 Ge 2.5 S 14 possess high laser damage threshold (LDT) of ~5.5 × AGS and ~5.2 × AGS respectively.

Synthesis, Crystal and Electronic Structures, and Nonlinear Optical Properties of Y4Si3S12

“…Hence the SiÀ S bonds within Y 4 Si 3 S 12 are expected to be strong covalent bonds, which are verified by ELF calculations (vide infra). The SiÀ S distances (2.103(5)-2.156(5) Å) within Y 4 Si 3 S 12 agree well with many silicon-sulfides such as Y 6 Si 2.5 S 14 (2.11-2.13 Å), [36] Mg 2 SiS 4 (2.155-2.200 Å), [52] BaLa 2 Si 2 S 8 (2.108-2.157 Å), [53] SiS 2 (2.131 Å), [54] Tl 2 PbSiS 4 (2.045-2.256 Å), [55] Li 2 ZnSiS 4 (2.113-2.123 Å), [56] Na 2 In 2 SiS 6 (2.115-2.145 Å), [57] and Sm 3 Al 0.33 SiS 7 (2.088-2.137 Å) [34] etc. Y 4 Si 3 S 12 is the third member of the ternary YÀ SiÀ S system with another two previously reported compounds YSi 0.25 S 0.75 [58] and Y 6 Si 2.5 S 14 .…”

“…The Si−S distances (2.103(5)–2.156(5) Å) within Y 4 Si 3 S 12 agree well with many silicon‐sulfides such as Y 6 Si 2.5 S 14 (2.11–2.13 Å), [36] Mg 2 SiS 4 (2.155–2.200 Å), [52] BaLa 2 Si 2 S 8 (2.108–2.157 Å), [53] SiS 2 (2.131 Å), [54] Tl 2 PbSiS 4 (2.045–2.256 Å), [55] Li 2 ZnSiS 4 (2.113–2.123 Å), [56] Na 2 In 2 SiS 6 (2.115–2.145 Å), [57] and Sm 3 Al 0.33 SiS 7 (2.088–2.137 Å) [34] etc. Y 4 Si 3 S 12 is the third member of the ternary Y−Si−S system with another two previously reported compounds YSi 0.25 S 0.75 [58] and Y 6 Si 2.5 S 14 [35,36] . The crystal structure of Y 4 Si 3 S 12 is quite different than YSi 0.75 S 0.25 [58] and Y 6 Si 2.5 S 14 [35,36] .…”

“…Y 4 Si 3 S 12 is the third member of the ternary YÀ SiÀ S system with another two previously reported compounds YSi 0.25 S 0.75 [58] and Y 6 Si 2.5 S 14 . [35,36] The crystal structure of Y 4 Si 3 S 12 is quite different than YSi 0.75 S 0.25 [58] and Y 6 Si 2.5 S 14 . [35,36] The three dimensional structure of YSi 0.75 S 0.25 is constructed by [YSi 3.5 Si 1.5] octahedra via sharing edges and surfaces, where Si atoms jointly mix with S atoms.…”

“…[35,36] The crystal structure of Y 4 Si 3 S 12 is quite different than YSi 0.75 S 0.25 [58] and Y 6 Si 2.5 S 14 . [35,36] The three dimensional structure of YSi 0.75 S 0.25 is constructed by [YSi 3.5 Si 1.5] octahedra via sharing edges and surfaces, where Si atoms jointly mix with S atoms. Within Y 6 Si 2.5 S 14 , [35,36] [YS 8 ] polyhedra, [Si1S 6 ] octahedra, and [Si2S 4 ] tetrahedra are interlinked to form the three dimensional framework of Y 6 Si 2.5 S 14 .…”

“…[23][24][25][26][27][28] The Y metal, with an electronegativity value of 1.2, located between Mg (1.3) and Ca (1.0), and ionic radius of 1.04 Å residing between Mg 2 + (0.86 Å) and Ca 2 + (1.14 Å), was underexplored as a constituent element for NLO materials. Some yttriumcontaining NLO compounds such as YCOB, [29,30] Ba 2 YGaSe 5 , [31] Ba 2 YInSe 5 , [31] Ba 2 YGaTe 5 , [32] Ba 2 YInTe 5 , [32] Y 4 GaSbS 9 , [33] Y 6 ZnSi 2 S 14 , [34] Y 6 Si 2.5 S 14 [35,36] etc. have demonstrated their potential as NLO materials.…”