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UV nonlinear optical materials require the simultaneous achievement of a large second harmonic generation (SHG) coefficient (≥1 × KH2PO4 (KDP), dij > 0.39 pmV−1), wide bandgap (λ < 300 nm, Eg > 4.2 eV), and moderate birefringence (0.05‐0.10@1064 nm) in a single structure. Therefore, designing UV nonlinear optical materials with excellent comprehensive performance is a challenging task. Herein, four UV transparent selenite materials are successfully obtained, namely, Al2(SeO3)3(H2O)3 (1), Ga2(SeO3)3(H2O)3 (2), NaGa3(HSeO3)6(SeO3)2 (3), and Cd5Ga4(HSeO3)2(SeO3)10 (4), through rational design and screening in the pure selenite system. Al2(SeO3)3(H2O)3 (1) and Ga2(SeO3)3(H2O)3 (2) are UV nonlinear optical materials with balanced properties, exhibiting moderate SHG responses (1.2 and 1.1 × KDP), appropriate birefringence (0.084 and 0.076@1064 nm), and wide bandgaps (5.5 and 5.3 eV). Such bandgaps are the largest in the reported pure selenite nonlinear optical (NLO) materials. This work further demonstrates that pure selenite is a good candidate for UV NLO materials. [ABSTRACT FROM AUTHOR]

Trigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular‐like moieties, a family of second‐order NLO‐active hybrid halides, MATX (X = Cl (1), Br (2), and I (3)), are achieved. MATX crystallizes in a nonpolar space group of P6¯$P\overline 6 $2c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX3 units enable segregation in layers of the three‐winged propeller‐like Me3TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/1, 6.5/2, and 7.6/3 times that of potassium dihydrogen phosphate), large birefringence (0.232/1, 0.252/2 and 0.260/3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first‐principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials. [ABSTRACT FROM AUTHOR]

Through systematic experiments, two novel mercury iodate sulfates, namely, Hg2(IO3)2(SO4)(H2O) and Hg2(IO3)2(SO4) were obtained. They crystallize in monoclinic space group C2 and C2/c, respectively. Hg2(IO3)2(SO4)(H2O) exhibits the [Hg(IO3)]+ polar cationic layer inherited from Hg(IO3)2 and the three‐dimensional (3D) framework inherited from HgSO4. This enables Hg2(IO3)2(SO4)(H2O) to generate a strong second harmonic generation (SHG) response of 6 times that of KH2PO4 (KDP). The structure of Hg2(IO3)2(SO4) is very similar to that of Hg2(IO3)2(SO4)(H2O), and they can be transformed into each other. Hg2(IO3)2(SO4)(H2O) shows a large optical band gap of 3.98 eV and a high dehydration temperature of 250 °C. This study indicates that by reasonable design, the introduction of multiple functional groups into a compound may combine their advantages to achieve good overall optical performance. [ABSTRACT FROM AUTHOR]

This paper comprehensively reviews 63 selenite compounds with bandgaps above 4.2 eV in four major categories. The focus is on their structures, optical properties, and design strategies, offering valuable insights for the future development of UV selenites. [Display omitted] • This article provides the first comprehensive review of UV selenite materials. • The article emphasizes the classification, structure, optical property, and design strategy of UV selenite. • We have summarized UV selenites' distribution by space group, symmetry, chemical composition, and optical properties. • We have offered guidance for UV selenites development, encompassing synthesis, design strategies, and so on. Nonlinear optical materials and birefringent materials are essential components of modern industrial technology. Selenites, owing to the unique stereochemical activity of the lone pair electrons, have a history spanning several decades as both linear and nonlinear optical materials. Up to now (January 16, 2024), nearly 1100 selenite materials have been discovered, some of which exhibit strong second-harmonic generation effects or large birefringence. With the strategic layout of nations and the rapid advancement of modern industrial technology, the demands on the transparency range of linear and nonlinear optical crystals have become increasingly stringent. Crystals transparent only in the visible spectrum are no longer adequate to meet current requirements. Selenites, which have a long history in the field, seem to have encountered a bottleneck in their recent development, primarily due to an excessive focus on their applications in the visible and near-infrared regions while neglecting their potential uses in the ultraviolet (UV) window. To explore new development directions of selenites, our research group is actively investigating their application as UV optical materials. Through a fluorination control strategy, we successfully synthesized a UV nonlinear optical crystal Y 3 F(SeO 3) 4 and a birefringent crystal CaYF(SeO 3) 2 , thereby developing the application of selenites in the UV region. Additionally, we found that some previously reported selenites with band gaps larger than 4.2 eV have not received sufficient attention from researchers, and their potential application in the UV region have been overlooked. To further promote the research progress of UV selenite materials, this paper comprehensively summarizes the reported selenite materials with bandgaps larger than 4.2 eV, totaling 63 compounds across 6 crystal systems and 19 space groups. We provide a detailed analysis of their structures, optical properties, and design strategies. These materials can be classified into four categories based on different anionic groups: simple selenites, fluoride selenites, selenites with tetrahedral groups, and other selenite compounds. Through a comprehensive review of UV selenites, we have identified ions or groups conducive to expanding the band gaps of selenites, proposed several reliable design methods for UV selenites, and offered useful suggestions for the development of UV selenites. Despite having a long history, selenite systems still hold significant untapped potential for further exploration. We hope this review provides valuable guidance and insights for the future development of inorganic selenites. [ABSTRACT FROM AUTHOR]

Our exploration of novel inorganic solids with large birefringence in the d10 Metal–Te4+–SO42− system afforded four new sulfate tellurites, Ga2(TeO3)(SO4)(OH)2, In2(TeO3)2(SO4)(H2O), Zn4(Te3O7)2(SO4)2(H2O) and Hg3(Te3O8)(SO4). Notably, Hg3(Te3O8)(SO4) exhibits the largest birefringence at 532 nm (0.184) and 1064 nm (0.166) among the reported metal sulfate tellurites. [ABSTRACT FROM AUTHOR]

Large birefringence (Δn = 0.277 at 546 nm) and strong second-harmonic generation (SHG) intensity (4.3 × KDP) achieved a remarkable balance in a potential ultraviolet nonlinear optical crystal: 2(C3H7N6)+·2Cl−·H2O. Theoretical calculations showed that planar benzene-like π-conjugated [C3N6] groups had important optical properties. [ABSTRACT FROM AUTHOR]

We report a new strongly birefringent material, [Al(H2O)6](IO3)2(NO3) (AINO). Based on a detailed analysis, we concluded that its enhanced birefringence (0.253 at 546 nm) predominantly resulted from a synergy of the effects of its (NO3)− and (IO3)− functional motifs, combined with an equally important and indispensable optimal arrangement of these two groups in the structure. This work has provided insight for discovering new birefringent materials. [ABSTRACT FROM AUTHOR]

The first divalent-metal iodate-phosphate, Pb2(IO3)(PO4), has been prepared via the strategy of introducing (IO3)− into phosphate. The structure features a unique 3D network where [Pb(IO3)]∞+ and [Pb(PO4)]∞− layers are alternatively interconnected. The birefringence of Pb2(IO3)(PO4) is greatly increased to 0.060 at 1064 nm. [ABSTRACT FROM AUTHOR]

Birefringent materials are very important in the laser industry. By combining the hexathiodiphosphate(IV) [P 2 S 6 ]4- unit and the highly polarizable Hg2+, a mercury hexathiodiphosphate(IV) Hg 2 P 2 S 6 was designed and synthesized by using solid-state synthesis. Hg 2 P 2 S 6 crystallizes in P 1 ¯ space group. It has a layered structure as in many hexathiodiphosphates(IV) such as ZnPS 3 , CdPS 3. Its crystal structure, electronic structure and optical properties are investigated by experimental methods and first-principle calculations. Hg 2 P 2 S 6 has a very large birefringence of 0.50 ​at 1064 ​nm and 0.48 ​at 2050 ​nm. Theoretical studies show the large birefringence comes from the synergistic effect of [P 2 S 6 ]4- and [HgS 4 ]6- groups with strong polarizability anisotropy. By combining the hexathiodiphosphate (IV) [P 2 S 6 ]4- unit and the highly polarizable Hg2+, a mercury hexathiodiphosphate (IV), namely, Hg 2 P 2 S 6 with large birefringence was designed and synthesized. It's found that the synergistic effect of the favourably arranged [P 2 S 6 ]4- and [HgS 4 ]6- groups with high polarizability anisotropy leads to its large birefringence. [Display omitted] • The properties of a mercury hexathiodiphosphate (IV), Hg 2 P 2 S 6 has been studied by experimental and theoretical methods. • Hg 2 P 2 S 6 has a very large birefringence compared with most of its counterparts. • The synergistic effect of the favourably arranged [P 2 S 6 ]4- and [HgS 4 ]6- groups leads to its large birefringence. [ABSTRACT FROM AUTHOR]

• NaMoO 3 (IO 3) is the first example of molybdenum(VI) iodate with 1D chain-like structure featuring a large birefringence (0.208@1064 nm). • Both 1D [MoO 3 (IO 3)]- anionic chain in NaMoO 3 (IO 3) and 3D [MoO 3 (IO 3)]- anionic framework in γ-KMoO 3 (IO 3) are assembled from 0D Λ-shaped cis -MoO 4 (IO 3) 2 units. • The polar 3D γ-KMoO 3 (IO 3) exhibits the largest SHG response (12 × KDP) among AMoO 3 (IO 3) family as well as a high LIDT value (52 × AGS). [Display omitted] Herein, we reported two alkali metal molybdenum(VI) iodates, namely, NaMoO 3 (IO 3) and γ-KMoO 3 (IO 3) with 1D and 3D [MoO 3 (IO 3)]− anionic architectures, respectively. The novel 1D chain in NaMoO 3 (IO 3) and the 3D network in γ-KMoO 3 (IO 3) are constructed by the 0D Λ-shaped cis -[MoO 4 (IO 3) 2 ]4− building units interconnected by bridging IO 3 − anions as well as the corner-sharing of oxo anions. Importantly, the polar γ-KMoO 3 (IO 3) exhibits a very large second-harmonic generation (SHG) effect of 12 × KH 2 PO 4 (KDP) under 1064 nm laser radiation, a high laser-Induced damage threshold value (52 × AgGaS 2), and a moderate birefringence of 0.087@1064 nm, whereas the centrosymmetric NaMoO 3 (IO 3) has a large birefringence of 0.208@1064 nm. This study further proves the useful route of exploring promising optical materials via assembling the 0D basic building units into higher dimensional anionic architectures. [ABSTRACT FROM AUTHOR]