RESUMEN
Enhancing anisotropy through an effective synergistic arrangement of anionic and cationic groups is crucial for improving the birefringence optical properties of materials. In this work, by transforming I-O into I-F through the fluorination strategy, two metal-free guanidine fluorooxoiodates (C(NH2)3)2(I2O5F)(IO3)(H2O) and C(NH2)3IO2F2 and one guanidine iodate C(NH2)3IO3 were successfully synthesized using the hydrothermal method. An unprecedented dimer [I2O5F] formed by [IO3F] and [IO3] in (C(NH2)3)2(I2O5F)(IO3)(H2O) was found, which greatly enriches the structural diversity of fluorooxoiodates. All three compounds feature a relatively large birefringence (Δn = 0.068, 0.110 and 0.075 at 546 nm) and a short ultraviolet cutoff edge. The theoretical calculation was carried out to understand the electronic structures and linear optical properties.
RESUMEN
Fluorooxoborates are promising yet largely untapped crystal materials for linear and nonlinear optical applications. The introduction of a strong electronegative F atom into an oxyboron anionic group offers a virtually unlimited chance for structural engineering and ultimately purposeful tuning of the macroscopic optical properties of the crystal. Herein, a new mixed alkali/alkaline-earth fluorooxoborate, Na2BaB12O18F4, was synthesized in a closed system. Na2BaB12O18F4 features a [B6O11F2] fundamental building unit (FBB), which polymerizes into two new (first example) independent interpenetrating three-dimensional (3D) B-O/F anionic networks constructed entirely from BO3 and BO3F units. Based on optical characterizations and the first-principles calculations, Na2BaB12O18F4 exhibits a moderate birefringence (0.054 @ 1064 nm) and a short ultraviolet (UV) cutoff edge (below 190 nm). The successful synthesis and characterization of Na2BaB12O18F4 may speed up the subsequent discovery of other mixed alkali/alkaline-earth metal fluorooxoborates.
RESUMEN
The first zinc iodate fluoride, ZnIO3F, was synthesized by the Zn2+ cation, the IO3 group, and fluorine ion, where Zn2+ is coordinated by O atoms from iodate and F atoms to form the ZnO4F2 polyhedron. It has outstanding optical characteristics, including large birefringence (Δ = 0.219 at 546 nm), wide band gap (Eg = 4.2 eV), and good thermal stability (over 475 °C), showing a subtle balance between the wide band gap and birefringence.
RESUMEN
In minerals and artificial crystals, the OH and F groups often coexist and have a high probability of disordered structure. The OH/F position cannot be determined accurately in the crystal structure only by the direct X-ray diffraction method because of the poor contrast between O and F and the weak diffractivity of hydrogen atoms. In this work, a new fluorooxoborate Ba[B2OF3(OH)2]2, with a size of up to 12 × 4 × 3 mm3, has been synthesized successfully by a facile hydrothermal reaction. The BOF3 units with well-ordered OH/F positions are observed for the first time in alkali/alkaline earth metal fluorooxoborates. Owing to the selective fluorination of BO4, Ba(B2OF3(OH)2)2 exhibits a large birefringence and hence can be used as a DUV birefringent material. This work will guide the study of the structural chemistry of oxyfluorides.