From oxides to oxysulfides: the mixed-anion GeS₃O unit induces huge improvement in the nonlinear optical effect and optical anisotropy for potential nonlinear optical materials

Abstract

The mixed-anion GeS3O unit induces huge improvement in the optical anisotropy and NLO response from Sr2ZnGe2O7 oxide to Sr2MGe2S6O oxysulfides.

Oxychalcogenides as Promising Ultraviolet Nonlinear Optical Candidates: Experimental and Theoretical Studies of AEGeOS2(AE = Sr and Ba)

“…The repeated measurements with freshly prepared samples lead to the reproducible results. This phenomenon may be caused by the distinct crystal quality based on the different experimental methods, and some similar examples can also be found in other NLO oxychalcogenides (see Table for details). − ,,− As illustrated in Figure S1a,b, the UV cutoff edges (λ UV ) of SrGeOS 2 and BaGeOS 2 are about 263 and 260 nm, respectively, which are comparable to other UV-NLO materials such as CsSbF 2 SO 4 (λ UV = 240 nm), La 3 SnGa 5 O 14 (λ UV = 270 nm), Pb 3 Mg 3 TeP 2 O 14 (λ UV = 250 nm), Li 2 ZrTeO 6 (λ UV = 290 nm), and KCsMoP 2 O 9 (λ UV = 260 nm) . Meanwhile, their infrared absorption edges can reach the far infrared wavelength (12.11 μm for SrGeOS 2 and 12.18 μm for BaGeOS 2 ), indicating that AEGeOS 2 (AE = Sr and Ba) have a wide transparent window from the UV range to far-IR spectral region (Figure S1c,d).…”

“…Up to now, there are 24 NCS oxychalcogenides known, which are summarized in Table in an ascending sort order of E g . The same compounds are put together and arranged according to the reported maximum E g . − ,,− The vast majority of the studies used infrared NLO materials, such as AEGeOSe 2 (AE = Sr and Ba), , Sr 3 Ge 2 O 4 Se 3 , and AEGeGa 2 OS 6 (AE = Ca and Sr) . Only few can reach the ultraviolet band, such as AEGeOS 2 (AE = Sr and Ba), La 3 Ga 3 Ge 2 S 3 O 10 , Sr 5 Ga 8 O 3 S 14 , SrZn 2 OS 2 , and α-Na 3 PO 3 S. , From Figure S5a, it is clear that most of the reported oxychalcogenides are oxysulfides (∼70.8%) and only one oxytelluride (∼4.2%), Ba 3 Ge 2 O 4 Te 3 , has been found to date.…”

Characterizations and Nonlinear-Optical Properties of Pentanary Transition-Metal Oxysulfide Sr2CoGe2OS6

“…As shown in Figure b, the SHG intensity of Sr 2 CoGe 2 OS 6 is increasing along with the increased particle sizes and reaches to a plateau, indicating a PM behavior. For the 200–250 μ m sample, the SHG intensity of Sr 2 MnGe 2 OS 6 is around 0.34 × AGS, a moderate value and smaller than those of Sr 2 MGe 2 OS 6 . This difference may be induced by the relatively stronger covalence character of M–O/S (M = Zn, Cd) bonds because covalent bonds can contribute larger microscopic susceptibilities than ionic bonds.…”

“…In this work, the 2 b site cation is occupied by a transition-metal Co 2+ ion, and the oxidation state is confirmed by X-ray photoelectron spectroscopy analysis (Figure S3). In contrast, most of the reported melilite-type NLO oxysulfides contain nonmagnetic d 10 metal M 2+ (M = Zn, Cd) ions . By a comparison of these structural features, it can be deduced that Sr 2 CoGe 2 OS 6 should have a smaller optical band gap than the Zn or Cd analogues, which may have an important influence on the NLO properties.…”

“…In fact, several NLO oxysulfides have already been studied, including La 3 Ga 3 Ge 2 S 3 O 10 , Sr 6 Cd 2 Sb 6 O 7 S 10 , Eu 4.5 (B 5 O 9 ) 2 SI, K 2 Ba 0.5 Ga 9 O 2 S 13 , Gd 3 NbS 3 O 4 , and Ba 2 SnSSi 2 O 7 . Very recently, a family of melilite-type oxysulfides with the formulas Sr 2 M II M IV 2 OS 6 (M II = divalent metal; M IV = Si, Ge, Sn) were investigated as IR NLO materials . As is well-known, melilite-type oxides A 2 M II M IV 2 O 7 (A = alkali-earth metal, Eu, Pb) possess abundant physical properties, including ionic conductive, antiferromagnetic, and NLO properties .…”