New nonlinear optical potassium iodate K[IO3] and borates K3[B6O10]Br, KTa[B4O6(OH)4](OH)2·1.33H2O—Synthesis, structures and relation to the properties

NH4IO2F2 and (NH4)3(IO2F2)3·H2O: A Series of Ammonium-Containing Fluoroiodates with Wide Band Gaps

A series of ammonium-containing fluoroiodates, NH₄IO₂F₂ and (NH₄)₃(IO₂F₂)₃·H₂O, with isolated [IO₂F₂] units have been fabricated by a fluorine-oxygen substitution strategy from NH₄IO₃. The two compounds crystallize in the orthorhombic system, but in different space groups, noncentrosymmetric Pca2₁ for NH₄IO₂F₂ and centrosymmetric Pnma for (NH₄)₃(IO₂F₂)₃·H₂O, and show wide band gaps of 4.53 eV for (NH₄IO₂F₂) and 4.55 eV for ((NH₄)₃(IO₂F₂)₃·H₂O). In addition, NH₄IO₂F₂ exhibits a 1.2 × KDP second harmonic generation response, a short ultraviolet cutoff edge in iodates, and a good crystal growth habit. The crystal of NH₄IO₂F₂ with a size of 11 × 5 × 2 mm³ was obtained by the aqueous solution method. The results enrich the structural diversity of iodate and supply a greater understanding of the design of new functional materials based on the fluoroiodates.

Bi3TeBO9: A Promising Mid-Infrared Nonlinear Optical Crystal with a Large Laser Damage Threshold

Mid-infrared (mid-IR) nonlinear optical (NLO) crystals are key materials in the field of laser technology. Nevertheless, the applications of these significant optical materials are always limited by their low laser damage threshold (LDT). Here, an oxide mid-IR NLO crystal, Bi₃TeBO₉, with a large LDT was discovered. The centimeter-sized Bi₃TeBO₉ single crystal was successfully grown by the top-seeded solution growth (TSSG) method. The Bi₃TeBO₉ features a high LDT of 450 MW/cm² (∼15 × AgGaS₂) and the widest transparent range (0.35-7.10 μm) among known borate crystals. The second-harmonic generation (SHG) effect is about 1.6 times that of KDP. First-principles calculations and structural analysis show that the optical characteristics of Bi₃TeBO₉ are mainly affected by distorted [BiO₆] groups. Furthermore, its thermal characteristics including specific heat, thermal diffusivity, thermal conductivity, and thermal expansion were also measured.

BaLiTe2O5X (X = Cl, Br): mixed alkali/alkaline-earth metal tellurite halides with [Te2O5]∞ chains

Isostructural BaLiTe₂O₅X (X = Cl, Br) feature [BaLiTe₂O₅]_∞ double layers, demonstrating wide optical bandgaps and large birefringence.