Two Short-Wave UV Antimony(III) Sulfates Exhibiting Large Birefringence

In the present work, we have successfully obtained two new UV antimony-based sulfates, NH4Sb­(SO4)2 and Ca2Sb2O­(SO4)4, by a conventional hydrothermal method. Interestingly, both compounds share similar structural building blocks, such as SbO4 seesaws and SO4 tetrahedra, yet they endow discrepant birefringence values measured at 546 nm with values of 0.150 and 0.114, respectively, owing to the different distortions of the SbO4 groups with SCALP electrons. Moreover, both compounds display large band gaps (4.32 and 4.43 eV, respectively), so they can be used as short-wavelength UV birefringent materials. Moreover, NH4Sb­(SO4)2 is a noncentrosymmetric compound, showing a frequency doubling effect of 0.2 × KDP. Detailed structural analyses and calculations confirm the source of superior optical performance and the reasons for the different birefringence of the two compounds. This work provides ideas for the following discovery of antimony-based optical materials with excellent properties

Yin–Yang Complementarity Strategy Achieving Giant Optical Anisotropy in a Metal-free Birefringent Material C(NH₂)₃(HC₄O₄)

The Yin–Yang complementarity strategy was first proposed to successfully develop a superior metal-free birefringent material C­(NH2)3(HC4O4), which was fabricated by two kinds of planar π-conjugated units containing triangle [C­(NH2)3]+ cations and square [HC4O4]− anions. C­(NH2)3(HC4O4) features a giant birefringence (0.313@546 nm), which is significantly enhanced compared to the commercially available birefringent materials

Sharp Enhancement of Birefringence in Antimony Oxalates Achieved by the Cation–Anion Synergetic Interaction Strategy

Birefringent materials with large birefringence play an important role in in laser science and technology owing to their ability to modulate polarized light. However, the lack of systematic and effective synthesis strategies severely hinders the development of novel superior birefringent materials. Herein, the cation–anion synergetic interaction strategy was proposed to successfully synthesize two excellent UV birefringent materials, RbSb­(C2O4)­F2·H2O and [C­(NH2)3]­Sb­(C2O4)­F2·H2O. Both compounds feature unprecedented [Sb­(C2O4)­F2]∞– anionic chains composed of planar π-conjugated [C2O4]2– units and a distorted SbO4F2 complex with stereochemically active lone pairs, which induce a large optical anisotropy. Remarkably, further enhancement of birefringence in [C­(NH2)3]­Sb­(C2O4)­F2·H2O was achieved via cation–anion synergetic interactions between the [C­(NH2)3]+ cationic groups and [Sb­(C2O4)­F2]∞– anionic chains. It exhibited a giant birefringence of 0.323@546 nm, twice larger than that of its analogue RbSb­(C2O4)­F2·H2O (0.162@546 nm). A detailed structural analysis and theoretical calculations revealed that the cation–anion synergetic interaction strategy is an effective strategy for the efficient exploration of superior birefringent materials, which will guide the further exploration of new structure-driven functional materials

Cd3(IO3)(IO4)F2·0.1CdO: A Nonlinear-Optical Crystal with the Introduction of Fluoride into Iodate Containing Both [IO3]^-and [IO4]^3-Groups

A new d10 transition-metal iodate fluoride, namely, Cd3(IO3)(IO4)F2·0.1CdO, was successfully designed and synthesized via the mid-infrared hydrothermal method. It crystallizes in the polar space group R3m and features the coexistence of the [IO3]- and [IO4]3- groups. Cd3(IO3)(IO4)F2·0.1CdO has a strong second-harmonic-generation response of about 3.0 times that of KDP(KH2PO4), large birefringence (0.133 at 546.1 nm), and a wide energy band gap (4.00 eV). In addition, the power laser damage threshold (LDT) measurement indicated that it possesses a high LDT of 84.29 MW/cm2, which is about 30 times that of AgGaS2. These superior properties showed that Cd3(IO3)(IO4)F2·0.1CdO may be an excellent nonlinear-optical crystal for visible and mid-infrared application

Hg₃(SeO₃)₂(SO₄): A UV Nonlinear Optical Mercury Selenite Sulfate Constructed by Neat [Hg₆O₈(SeO₃)₄]_∞ Layers and SO₄ Tetrahedra

A novel mercury selenite sulfate named Hg3(SeO3)2(SO4) has been successfully synthesized under a mild hydrothermal method. Hg3(SeO3)2(SO4) crystallizes in a monoclinic space group P21 and features a unique three-dimensional (3D) frame structure formed by [Hg6O8(SeO3)4]∞ layers and SO4 tetrahedra, which enables it to exhibit a comprehensive performance of a moderate second-harmonic generation (SHG) response of approximately 1.3 times that of baseline KH2PO4 (KDP), a moderate birefringence (0.118@546 nm), and a wide band gap (4.70 eV), which indicates that it has potential for application as an ultraviolet (UV) nonlinear optical material. Detailed theoretical calculations show that the Hg2+-based polyhedra with large polarizability and deformability and the SeO3 groups with stereochemically active lone pair (SCALP) electrons are the main contributors to moderate optical properties

A₂Hg_<i>x</i>(SeO₃)_<i>y</i> (A = K, Rb, Cs): Three Alkali Metal Mercury Selenites Featuring Unique 1D [HgO_<i>m</i>(SeO₃)_<i>n</i>]_∞ Chains

Herein, three alkali metal mercury selenites, K2Hg2(SeO3)3, Rb2Hg2(SeO3)3, and Cs2Hg3(SeO3)4, were successfully obtained by a hydrothermal method. The three compounds featured same one-dimensional (1D) [HgOm(SeO3)n]∞ chain structure that consisting of distorted Hg–O polyhedra and SeO3 triangular pyramids with stereochemically active lone pair (SCALP) electrons. Interestingly, the rich coordination environment of Hg atoms and the size difference of alkali metal cations lead to diverse arrangement of SeO3 groups, which makes them exhibit different birefringence. The band gaps of the three compounds indicate that they are potential ultraviolet (UV) optical materials. Detailed theoretical calculations demonstrate that the combined effects of SeO3 triangular pyramids and Hg–O polyhedra are responsible for the optical characteristics of the reported compounds

Refractive Index Modulates Second-Harmonic Responses in RE₈O(CO₃)₃(OH)₁₅X (RE = Y, Lu; X = Cl, Br): Rare-Earth Halide Carbonates as Ultraviolet Nonlinear Optical Materials

The first series of rare-earth chloride/bromine carbonate nonlinear optical (NLO) crystals, RE8O­(CO3)3(OH)15X (RE = Y, Lu; X = Cl, Br), have been synthesized with a facile hydrothermal method. All of the title compounds were isostructural with the noncentrosymmetric space group P63 (no. 173), and their structures can be described as the [REO4(CO3)3] units connect the adjacent infinite [RE7O25]∞ layers in the a–b plane to form an intricate three-dimensional framework, and the Br– or Cl– anions were located in the center of equilateral triangles formed by the RE(3)­O7 polyhedra. The measured second-harmonic generation (SHG) effects of Y8O­(CO3)3(OH)15Cl, Lu8O­(CO3)3(OH)15Cl, Y8O­(CO3)3(OH)15Br, and Lu8O­(CO3)3(OH)15Br were 1.65, 2.22, 1.83, and 3.00 times that of KH2PO4, respectively. Our study revealed that the difference of SHG efficiency was mainly derived from the different refractive indices of crystals when the orientation of [CO3]2– groups that had a relationship with the SHG coefficient was almost identical. Furthermore, the birefringences of the four crystals were successively measured to be 0.045, 0.062, 0.073, and 0.088 (λ = 546.1 nm), which were very favorable for realizing phase-matching in the visible and UV region. In addition, with a wide transparent region from UV to near infrared, they can be excellent UV NLO materials

Refractive Index Modulates Second-Harmonic Responses in RE₈O(CO₃)₃(OH)₁₅X (RE = Y, Lu; X = Cl, Br): Rare-Earth Halide Carbonates as Ultraviolet Nonlinear Optical Materials

The first series of rare-earth chloride/bromine carbonate nonlinear optical (NLO) crystals, RE8O­(CO3)3(OH)15X (RE = Y, Lu; X = Cl, Br), have been synthesized with a facile hydrothermal method. All of the title compounds were isostructural with the noncentrosymmetric space group P63 (no. 173), and their structures can be described as the [REO4(CO3)3] units connect the adjacent infinite [RE7O25]∞ layers in the a–b plane to form an intricate three-dimensional framework, and the Br– or Cl– anions were located in the center of equilateral triangles formed by the RE(3)­O7 polyhedra. The measured second-harmonic generation (SHG) effects of Y8O­(CO3)3(OH)15Cl, Lu8O­(CO3)3(OH)15Cl, Y8O­(CO3)3(OH)15Br, and Lu8O­(CO3)3(OH)15Br were 1.65, 2.22, 1.83, and 3.00 times that of KH2PO4, respectively. Our study revealed that the difference of SHG efficiency was mainly derived from the different refractive indices of crystals when the orientation of [CO3]2– groups that had a relationship with the SHG coefficient was almost identical. Furthermore, the birefringences of the four crystals were successively measured to be 0.045, 0.062, 0.073, and 0.088 (λ = 546.1 nm), which were very favorable for realizing phase-matching in the visible and UV region. In addition, with a wide transparent region from UV to near infrared, they can be excellent UV NLO materials

Refractive Index Modulates Second-Harmonic Responses in RE₈O(CO₃)₃(OH)₁₅X (RE = Y, Lu; X = Cl, Br): Rare-Earth Halide Carbonates as Ultraviolet Nonlinear Optical Materials

The first series of rare-earth chloride/bromine carbonate nonlinear optical (NLO) crystals, RE8O­(CO3)3(OH)15X (RE = Y, Lu; X = Cl, Br), have been synthesized with a facile hydrothermal method. All of the title compounds were isostructural with the noncentrosymmetric space group P63 (no. 173), and their structures can be described as the [REO4(CO3)3] units connect the adjacent infinite [RE7O25]∞ layers in the a–b plane to form an intricate three-dimensional framework, and the Br– or Cl– anions were located in the center of equilateral triangles formed by the RE(3)­O7 polyhedra. The measured second-harmonic generation (SHG) effects of Y8O­(CO3)3(OH)15Cl, Lu8O­(CO3)3(OH)15Cl, Y8O­(CO3)3(OH)15Br, and Lu8O­(CO3)3(OH)15Br were 1.65, 2.22, 1.83, and 3.00 times that of KH2PO4, respectively. Our study revealed that the difference of SHG efficiency was mainly derived from the different refractive indices of crystals when the orientation of [CO3]2– groups that had a relationship with the SHG coefficient was almost identical. Furthermore, the birefringences of the four crystals were successively measured to be 0.045, 0.062, 0.073, and 0.088 (λ = 546.1 nm), which were very favorable for realizing phase-matching in the visible and UV region. In addition, with a wide transparent region from UV to near infrared, they can be excellent UV NLO materials

Refractive Index Modulates Second-Harmonic Responses in RE₈O(CO₃)₃(OH)₁₅X (RE = Y, Lu; X = Cl, Br): Rare-Earth Halide Carbonates as Ultraviolet Nonlinear Optical Materials

The first series of rare-earth chloride/bromine carbonate nonlinear optical (NLO) crystals, RE8O­(CO3)3(OH)15X (RE = Y, Lu; X = Cl, Br), have been synthesized with a facile hydrothermal method. All of the title compounds were isostructural with the noncentrosymmetric space group P63 (no. 173), and their structures can be described as the [REO4(CO3)3] units connect the adjacent infinite [RE7O25]∞ layers in the a–b plane to form an intricate three-dimensional framework, and the Br– or Cl– anions were located in the center of equilateral triangles formed by the RE(3)­O7 polyhedra. The measured second-harmonic generation (SHG) effects of Y8O­(CO3)3(OH)15Cl, Lu8O­(CO3)3(OH)15Cl, Y8O­(CO3)3(OH)15Br, and Lu8O­(CO3)3(OH)15Br were 1.65, 2.22, 1.83, and 3.00 times that of KH2PO4, respectively. Our study revealed that the difference of SHG efficiency was mainly derived from the different refractive indices of crystals when the orientation of [CO3]2– groups that had a relationship with the SHG coefficient was almost identical. Furthermore, the birefringences of the four crystals were successively measured to be 0.045, 0.062, 0.073, and 0.088 (λ = 546.1 nm), which were very favorable for realizing phase-matching in the visible and UV region. In addition, with a wide transparent region from UV to near infrared, they can be excellent UV NLO materials