Jiang-Gao Mao

Two novel cadmium antimonites, Cs ₄ Cd(SbF ₅ ) ₃ (H ₂ O) ₂ and Cd[Sb ₇ O ₁₀ (OH)](SO ₄ ), have been successfully synthesized by room-temperature solution evaporation and hydrothermal methods. Cs ₄ Cd(SbF ₅ ) ₃ (H ₂ O) ₂ features the first cadmium fluoroantimonite compound.

The development of high‐performance second‐order nonlinear optical (NLO) crystals with novel structural architectures remains a significant challenge. In this study, we present a new cocrystal, PZA‐IA (C ₅ H ₅ N ₃ O∙HIO ₃ ), which was synthesized by combining pyrazinamide (PZA) and iodic acid (IA). The cocrystal crystallizes in the polar space group Pca 2 ₁ . Its asymmetric unit comprises one C ₅ H ₅ N ₃ O molecule and one HIO ₃ molecule, which are linked by a strong hydrogen bond between the HIO ₃ molecule's O─H group and the aromatic nitrogen atom of the C ₅ H ₅ N ₃ O molecule. PZA‐IA exhibits exceptional comprehensive NLO properties: a strong second harmonic generation (SHG) response of 6.0 × KH ₂ PO ₄ , a wide band gap of 3.55 eV, a suitable birefringence of 0.143 at 1064 nm enabling phase matching, and a high laser‐induced damage threshold of 380.1 MW cm ⁻² . First‐principles calculations reveal that both molecular components contribute synergistically to the SHG effect. PZA and IA account for 59.96% and 39.51% of the total response, respectively. This work provides a new strategy for designing NLO materials in the future.

A symmetry-engineered γ-Ag ₄ P ₂ S ₆ crystal features large birefringence, high thermal stability (>750 °C), and a wide IR transmission range (0.4–18.2 μm).

Birefringent crystals with transparency spanning the mid‐ to far‐infrared regions are critical for infrared optical technologies. However, their development remains constrained by the inherent challenge of simultaneously achieving high birefringence and a broad IR transmission window. Taking the thiophosphate Nb ₄ P ₂ S ₂₁ , characterized by birefringence‐active S–S units, as a template, we developed a linear‐matching strategy to enhance its optical anisotropy. This approach involves retaining the strongly anisotropic [Nb ₂ PS ₁₀ ] backbone while replacing the highly flexible C _{2 v} ‐symmetric [S ₃ ] ²⁻ bridging units with D _{∞ h} ‐symmetric [LiS ₂ ] ³⁻ and [S ₂ ] ²⁻ groups, which possess lower polarizability anisotropy. Although such a high‐to‐low substitution typically reduces birefringence, the rigid linear groups couple effectively with the chain, resulting in enhanced birefringence of 0.45 and 0.53 at 546 nm for CsLiNb ₄ P ₂ S ₂₀ and Nb ₄ P ₂ S ₂₀ , respectively. Moreover, both crystals exhibit broad infrared transparency (2.5–16.7 µm), and are air stable, highlighting their potential applications as mid‐ to far‐infrared birefringent optical materials. Our design strategy provides a new perspective for the design of crystals with large birefringence.

Two phenylphosphonate salts, [C(NH ₂ ) ₃ ] ₂ (PhPO ₃ )·2H ₂ O (1) and (C ₅ H ₇ N ₂ ) ₂ (PhPO ₃ )·5H ₂ O (2), were synthesized. Both exhibit strong second-harmonic generation and proton conductivity.

A polar ionic cocrystal, (C ₄ H ₈ N ₅ )(PhPHO ₂ )·H ₂ O, exhibits strong second-harmonic generation, a high laser damage threshold, a wide band gap, and high birefringence, highlighting phosphinate salts as promising ultraviolet materials.

Five facile designing routes for non-centrosymmetric NLO iodates are outlined, including polymerization, aliovalent substitution, fluorine substitution, and hybrid integration with π-conjugated or tetrahedral units.

The PZA–IBr organic–inorganic hybrid crystal, synthesized through halogen bond-driven assembly, exhibits an ultrahigh birefringence of 0.524, making it an ideal material for optical applications.

A birefringent anionic group [ICl ₄ ] ⁻ with giant anisotropy was discovered. Its combination with the organic [C ₅ H ₇ N ₂ ] ⁺ cation led to the formation of C ₅ H ₇ N ₂ ICl ₄ , which exhibited a giant birefringence (1.162 at 546 nm) and moderate band gap (2.29 eV).

Two novel tin iodates, Ba[Sn(IO ₃ ) ₆ ] and Ba[Sn(IO ₃ ) ₄ F ₂ ], were synthesized, and fluoride regulation improved the birefringence and band gap of Ba[Sn(IO ₃ ) ₄ F ₂ ], offering a strategy for high-performance birefringent materials.