CsY(SO₄)₂·4H₂O: A Deep-Ultraviolet Birefringent Crystal Induced by an Edge-Sharing Connection

Abstract

SO 4 tetrahedral groups have weak polarization anisotropy, which thus results in the small birefringence of sulfates. Here, we report new sulfate CsY(SO 4 ) 2 •4H 2 O with unprecedented birefringence among deep-ultraviolet (deep-UV) sulfates. Its single crystal (10 mm × 3.5 mm × 1.5 mm) was simply grown by an aqueous solution evaporation technique, and it features a rare layered structure composed of YO 9 polyhedra, SO 4 tetrahedra, and H 2 O molecules. Interestingly, each SO 4 group donates two oxygen atoms to edge-share with one adjacent YO 9 polyhedron and thus causes severe distortion of these groups. The characteristic edgesharing mode gives CsY(SO 4 ) 2 •4H 2 O a large birefringence of ∼0.045@546 nm, which is the maximum among deep-UV sulfates and phosphates with similar non-π-conjugated anionic groups. The ultraviolet−visible-near-infrared diffuse reflection and transmission spectra, infrared spectrum, thermal stability, and theoretical calculations are also presented. The fascinating results will improve our understanding of sulfates and may provide useful insights into the exploration of deep-UV sulfates with large birefringence.

H/F-Substitution-Induced Confinement Effect for Designing High-Phase-Transition-Temperature Organic–Inorganic Hybrid Materials

“…In order to deeply explore the relationship between the internal electronic structures and energy bands of compounds 1 and 2 , we study their band structures. − The band structures of compounds 1 and 2 were then investigated. When the conduction band minimum is at the same position as the valence band maximum, it is a direct band gap semiconductor; otherwise, it is an indirect band gap semiconductor. , As shown in Figure e,f, both compounds 1 and 2 are indirect band gap semiconductors. The band gap value of compound 1 is 4.325 eV.…”

“…When the conduction band minimum is at the same position as the valence band maximum, it is a direct band gap semiconductor; otherwise, it is an indirect band gap semiconductor. 55,56 As shown in Figure 5e,f, both compounds 1 and 2 are indirect band gap semiconductors. The band gap value of compound 1 is 4.325 eV.…”

RbCl·(H2SeO3)2: A Salt-Inclusion Selenite Featuring Short UV Cut-Off Edge and Large Birefringence

“…To widen the band gap and make blue-shift of the UV absorption edge, we selected alkali metal cations as the A-site cation in our design and synthesis strategy, because these kinds of cations have almost a sphere-like electron distribution that will contribute little to the optical birefringence, 39 but will be conducive to the transmission of UV light. 40 In addition, a highly electronegative Cl − was also introduced into the selenite system to broaden the band gap and increase structural distortion. Consequently, the UV cut-off edge of the title compound was successfully decreased to 230 nm.…”

“…Besides the large birefringence value, having a short cut-off edge is equally important for birefringent materials, which is related to the suitable spectral range and laser-induced damage threshold. To widen the band gap and make blue-shift of the UV absorption edge, we selected alkali metal cations as the A-site cation in our design and synthesis strategy, because these kinds of cations have almost a sphere-like electron distribution that will contribute little to the optical birefringence, but will be conducive to the transmission of UV light . In addition, a highly electronegative Cl – was also introduced into the selenite system to broaden the band gap and increase structural distortion.…”

(C3N6H7)2SiF6·H2O: an ultraviolet birefringent crystal exceeding the intrinsic energy gap of an organic reagent

“…31 Our group previously reported a yttrium sulphate (CsY (SO 4 ) 2 •4H 2 O) with the largest birefringence value among deep-UV sulphates, because the high coordinated YO 9 polyhedra make the [SO 4 ] 2− groups align uniformly. 32 Herein, combining the highly coordinated [SiF 6 ] 2− groups with the planar π-conjugated melamine, we synthesized a new hybrid compound of (C 3 N 6 H 7 ) 2 SiF 6 •H 2 O (1), which exhibits a large birefringence (Δn = 0.152@550 nm). Notably, optical measurements indicate that 1 has an enlarged energy gap compared to the melamine (4.76 eV vs. 4.41 eV), which is analyzed by theoretical calculations.…”