Eu₂MGe₂OS₆ (M = Mn, Fe, Co): Three Melilite-Type Rare-Earth Oxythiogermanates Exhibiting Balanced Nonlinear-Optical Behaviors

Sr2HgGe2OS6: A Hg-Based Oxychalcogenide Infrared Nonlinear Optical Material Exhibiting Favorable Balance between a Large Band Gap and Strong Second Harmonic Generation Response

“…It is clear that Sr 2 HgGe 2 OS 6 has a relatively high transmittance in the range of 4000–700 cm –1 , corresponding to 2.5–14.2 μm, covering the atmospheric transparent windows of “3–5” and “8–12 μm”. The only distinct absorption peak at 691 cm –1 in the IR spectrum is attributed to Ge–O stretching mode . The broad band at about 3300 cm –1 in the IR spectrum due to the symmetric O–H stretching mode of H 2 O adsorbed in the sample. , In addition, the experimental band gap of Sr 2 HgGe 2 OS 6 is concluded to be 2.9 eV (the inserted spectrum in Figure c) according to the Kubelka–Munk function, which is consistent with the yellow color of Sr 2 HgGe 2 OS 6 crystal.…”

“…The only distinct absorption peak at 691 cm −1 in the IR spectrum is attributed to Ge−O stretching mode. 29 The broad band at about 3300 cm −1 in the IR spectrum due to the symmetric O−H stretching mode of H 2 O adsorbed in the sample. 50,51 In addition, the experimental band gap of Sr 2 HgGe 2 OS 6 is concluded to be 2.9 eV (the inserted spectrum in Figure 2c) according to the Kubelka−Munk function, 43 which is consistent with the yellow color of Sr 2 HgGe 2 OS 6 crystal.…”

“…Notably, in recent studies, oxychalcogenides with mixed anionic moieties have attracted wide interest and are considered to be an important class of IR NLO candidates due to their ability to combine the strengths of oxides (wide band gap) and chalcogenides (large SHG response) effectively. Driven by the above strategy, a substantial amount of NLO materials have been synthesized and characterized, such as La 3 Ga 3 Ge 2 O 10 S 3 , Sr 5 Ga 8 O 3 S 14 , Ae 3 Q­[GeOQ 3 ] (Ae = Ba, Sr; Q = S, Se), AeGeS 2 O (Ae = Ba, Sr), A 2 MM 2 ′ OS 6 (A = Ca, Sr, Eu; M = Zn, Cd, Mn, Fe, Co, Ge; M′ = Ge, Sn, Ga), − Sr 3 Ge 2 O 4 Se 3 , Ae 3 Ge 2 O 4 Te 3 (Ae = Ba, Sr), , etc. − Most of them have demonstrated surprising performance. However, Hg-based oxychalcogenide IR NLO materials have never been reported, as far as we know.…”

Rational Design of Novel Promising Infrared Nonlinear Optical Materials: Structural Chemistry and Balanced Performances

“…Though much effort have been made by us to explore more chalcogenide borates, no NCS ones were obtained until the discovery of Eu 2 B 5 O 9 S (EBOS) and Eu 4.5 (B 5 O 9 ) 2 SI (EBOSI) . Both of them crystallize in the Pnn 2 space group, which is roughly isostructural with M II 2 B 5 O 9 X (M II = Eu, Pb, Ca, Sr, Ba; X = F, Cl, Br, I). , Ca, Sr, and Ba cations usually can be substituted with Eu 2+ on account of their similar ionic radii and coordination. , In the meantime, when the monovalent X – anion is substituted by the divalent S 2– anion, one of the two M II cation sites can be occupied by a Eu 3+ . Therefore, the structure of EBOS can be described in which the M II sites in M II 2 B 5 O 9 X are substituted with one Eu 2+ ion and one Eu 3+ ion, and the two X – sites are occupied by S 2– ions (Figure a).…”

Rare-earth-based chalcogenides and their derivatives: an encouraging IR nonlinear optical material candidate

“…In order to better illustrate the advantages of RE-based chalcogenide compounds and address the challenges in this field, this paper provides detailed explanations for 85 representative examples out of over 400 NCS compounds. 68–187 These examples are categorized into four groups based on the various asymmetric building motifs: (1) RE-based chalcogenides containing tetrahedral motifs; (2) RE-based chalcogenides containing lone-pair-electron motifs; (3) RE-based chalcogenides containing [BS 3 ] and [P 2 Q 6 ] motifs; and (4) RE-based chalcohalides and oxychalcogenides. Finally, the conclusions and perspectives for RE-based chalcogenides and their derivatives are provided for further exploration.…”