A neutron, X-ray and electron diffraction study of the structures of Pb3O2X2 (X = Cl, Br)

The crystal structures of the compounds Pb₃O₂Br₂ and Pb₃O₂Cl₂ have been re-refined from neutron powder diffraction data. They are found to be more closely isostructural than previous reports suggested. The major difference between the present refinements and previous refinements is in the oxygen position of the bromide compound which has moved significantly along b from y=0.024(5) to 0.9933(4), rather more in keeping with the previously reported structure of the chloride compound. Electron diffraction was used, prior to refinement, to determine the appropriate space group symmetry, given some previous ambiguity in the literature. The space group symmetry was thereby shown to be at least Pn2₁a, but most probably Pnma. Evidence for some displacive disorder along b was also found in the form of weak diffuse streaking perpendicular to b^∗.     

The thallous chalcogenides Tl6X4Y (X = Cl,Br, I; Y = S,Se)

Single crystals of Tl₆X₄Y(X = Cl, Br, I; Y = S, Se) were prepared by the Bridgman technique. The compounds were characterized by complete X-ray structural analyses. All are isotypic, space group $\text{P}\text{4}\text{mnc}$, with a = 843.3(2) pm, c = 917.2(2) pm for Tl₆Cl₄S, a = 872.1(2) pm, c = 932.8(1) pm for Tl₆Br₄S, a = 917.6(3) pm, c = 960.8(1) pm for Tl₆I₄S and a = 917.8(3) pm, c = 967.5(1) pm for Tl₆I₄Se. FIR spectra as well as photoacoustic spectra are given.     

Conductivite ionique dans les verres LiPO3LiX (X = I,Br, Cl)

The glass-forming regions in the systems LiPO₃LiX with X = I, Br, Cl were determined and the study of the electrical conductivity of glasses belonging to these systems was carried out. The conductivity increases with increasing halogen ion size and reaches maxima values of the order of 10^?6, 3, 2 10^?7, 10^?7 (ohm cm)^?1 at 25° C with LiI, LiBr, LiCl respectively : they are obtained at the limit of glass forming region. The Raman spectra do not show any modifications. The study of the electrical conductivity shows that the conduction is essentially ionic in nature.     

Preparation and characterisation of Rb2CrCl4-xXx (X=Br,OR I,x=1,2, or 3)

Several new compounds based on the ionic ferromagnet Rb₂CrCl₄ but with Br or I substituting for Cl have been prepared in powder and single crystal form. The compounds have been characterised by chemical and X-ray analysis. The ordering of the anions within the K₂NiF₄ type structure is discussed.     

Systemes CuX (X = Cl,Br)HgS. etude des composes CuHgSX (X = Cl,Br)

Powder samples of CuHgSCl and CuHgSBr have been synthesized, they crystallize in an orthorhombic structure, space group Pbam. The structure is built up of a three dimensional network of SHgS chains in z = 0 planes connected together with CuS₂X₂ (X = Cl, Br) tetrahedrons. S and X atoms build up a distorted cubic centered lattice.     

Conductivite ionique dans les verres AgPO3-AgX (X = I.Br.Cl)

The glass-forming regions in the systems AgPO₃- AgX with X = I.Br.Cl were determined and the study of the electrical conductivity of glasses belonging to these systems was carried out. The glass-forming region and conductivity increase with increasing halogen ion size. The conductivity reaches maxima values of the order of 10^?2, 10^?3, $\text{10}{}^{\mathrm{?4}}\text{(Ω ·}\text{cm}\text{)}{}^{\mathrm{?1}}$ with AgI, AgBr, AgCl respectively. The study of the electrical conductivity shows that the conduction is essentially ionic in nature and due to silver ions movements only.     

Etudes structurales et optiques des phases du type Cd2A3X (A = As,P; X = Cl,Br, I) et de leur solution solide

The structure of the compounds with general formula Cd₂A₃X (A = As, P; X = Cl, Br, I) was found from X-ray powder diffractograms. The variation of the cell parameter in Cd₂As_3?xP_xI solid solution was studied. The basic transition energy as well as its variation with temperature was obtained from transmission spectra on monocristals. Both results are discussed.     

Phase relations in Ga2X3-GaY3 systems (X=Se,Te; Y=Cl,Br,I) — Crystal growth,structural relations and optical absorption of intermediate compounds GaXY

The systems Ga₂X₃-GaY₃ (X=Se,Te; Y=Cl,Br,I) are quasibinary and include the intermediate compounds GaXY with incongruent melting behaviour. Crystals for structural and optical investigations were obtained by annealing. GaTeBr (orth., Pnnm; a=607, b=1518, c=413 pm; d_x=4.48 g/cm³; Z=4) is an isotype of GaTeCl, with a tetrahedral layer structure and Ga-Te-linking of the black phosphorous type; the remaining compounds are expected to form an isotypic series, with a crystal structure not yet determined. Optical absorption edges range from 2.55 eV (GaTeI) to 4.20 eV (GaSeCl).     

Synthesis of CsPbX3 (X = Cl/Br,Br, and Br/I)@SiO2/PMMA composite films as color-conversion materials for achieving tunable multi-color and white light emission

All-inorganic cesium lead halide based perovskite nanocrystals(PNCs)exhibit promising optoelectronic properties,but their poor stability and anion exchange reaction limit their broad commercial applications.Herein,we demonstrated the successful synthesis of blue-green-red emitting CsPbX₃(X=Cl/Br,Br,and Br/I)PNCs via hot injection method,followed by silica-coating and embedding in poly(methylmethacrylate)(PMMA)matrix.The photoluminescence(PL)spectra of SiO₂/PMMA-coated PNCs can be tuned continuously by regulating precursor composition ratio,from blue(CsPb(Cl_0.5/Br_0.5)₃;460 nm)to red(CsPb(Br_0.4/I_0.6)₃via green(CsPbBr₃;519 nm).The PNCs composite films exhibit improved stability(thermal-,moisture-,and photo-stability)because of the barrier formed by Si0₂/PMMA coating and also displayed exceptional photoluminescent quantum yield(PLQY of blue,green,and red-emitting Si0₂/PMMA coated PNCs are 37%,86%,and 71%,respectively)with longer lifetimes inhibiting anion exchange.Eventually,the PNCs-encapsulated Si0₂/PMMA composite films were integrated into the UV LED chip as down-converting materials to construct a prototype white-peLED unit.The designed white-peLED unit demonstrated bright white light generating CIE coordinates(0.349,0.350),a luminous efficiency(LE)of 39.2%and a color rendering index(CRI)of 84.7.The wide color gamut of 121.47%of NTSC and 98.56%of Rec.2020 is also achieved with the built w-LED system.Therefore,the results demonstrated that CsPbX₃(X=Cl/Br,Br,and Br/I)PNCs@SiO₂/PMMA composite films can be employed as efficient UV to visible color conversion materials for white-LEDs and backlighting.     

Cu magic angle spinning (MAS) nuclear magnetic resonance (NMR) study of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I)

⁶³Cu MAS NMR spectra of CuX crystals (X=Cl, Br, and I) and CuX-based glasses (X=Cl, Br, and I) have been measured. The CuCl and CuI crystals gave the isotropic chemical shift values around 0 ppm, and the CuBr crystal, around −55 ppm. The peak positions of the chlorocuprate(I), bromocuprate(I), and iodocuprate(I) glasses were very close to those of the CuX crystals, respectively. This result indicates that these glasses mainly consist of CuX₄ tetrahedra (X=Cl, Br, and I). The halogen coordination environments around Cu⁺ in bromochlorocuprate(I) glasses were dependent on the kind of modifying cation and the Br⁻/(Cl⁻+Br⁻) ratio. The bromochlorocuprate(I) glasses were mainly composed of CuCl_mBr_4−m or CuCl_nBr_4−n tetrahedra (m=0, 1, 2, and 4; n=0, 1, and 4).     

Electrical relaxation of superionic conducting glasses AgX-AgPO3 (X=I,Br, Cl)

The complex impedance of superionic conducting glasses (AgX)_0.3-(AgPO₃)_0.7 (X = I, Br, Cl) was measured in the frequency range 5 Hz–500 kHz and temperatures between 299 K and 348 K. The frequency dependence of (the real part of complex conductivity) shows two regions: low and high frequencies. The first is attributed to the electrode-electrolyte polarization, while the second is attributed to the bulk conduction. The replacement of AgCl by AgBr or Agl at the same molar fraction is found to improve the bulk conductivity of the studied glasses. The electrical conductivity spectra exhibit one relaxation peak associated with dielectric loss which arises from the thermally activated jumps of Ag⁺ ions. The dependence of the relaxation time upon the halogen type is discussed in terms of the structural aspects, where the silver halides tend to form microdomains. The special characteristic of fast ionic conduction depending upon halide type is emphasized.     

0D Cs3Cu2X5 (X = I,Br, and Cl) Nanocrystals: Colloidal Syntheses and Optical Properties

0D lead‐free metal halide nanocrystals (NCs) are an emerging class of materials with intriguing optical properties. Herein, colloidal synthetic routes are presented for the production of 0D Cs₃Cu₂X₅ (X = I, Br, and Cl) NCs with orthorhombic structure and well‐defined morphologies. All these Cs₃Cu₂X₅ NCs exhibit broadband blue‐green photoluminescence (PL) emissions in the range of 445–527 nm with large Stokes shifts, which are attributed to their intrinsic self‐trapped exciton (STE) emission characteristics. The high PL quantum yield of 48.7% is obtained from Cs₃Cu₂Cl₅ NCs, while Cs₃Cu₂I₅ NCs exhibit considerable air stability over 45 days. Intriguingly, as X is changed from I to Br and Cl, Cs₃Cu₂X₅ NCs exhibit a continuous redshift of emission peaks, which is contrary to the blueshift in CsPbX₃ perovskite NCs.     

Remarkable Piezophoto Coupling Catalysis Behavior of BiOX/BaTiO3 (X = Cl,Br, Cl0.166Br0.834) Piezoelectric Composites

Polarization field engineering of piezoelectric materials is considered as an advisable strategy in fine‐tuning photocatalytic performance which has drawn much attention recently. However, the efficient charge separation that determines the photocatalytic reactivities of these materials is quite restricted. Herein, a judicious combination of piezoelectric and photocatalytic performances of BiOX/BaTiO₃ (X = Cl, Br, Cl_0.166Br_0.834) to enable a high piezophotocatalytic activity is demonstrated. Under the synergic advantages of chemical potential difference and piezoelectric potential difference in BiOX/BaTiO₃ composites, the photoinduced carriers recombination is largely halted, which directly contributes to the significantly promoted piezophotocatalytic activity of piezoelectric composites. Inspiringly, the BiOBr/BaTiO₃ composites under light irradiation with auxiliary ultrasonic activation result in an ultrahigh and stable photocatalytic performance, which is much higher than the total of those by isolated photocatalysis and piezocatalysis, and can rival current excellent photocatalytic system. In fact, the theoretical piezoelectric potential difference of BiOBr/BaTiO₃ composites reaches 100 mV, which far exceeds the pure BaTiO₃ of 31.21 mV and BiOBr of 30 mV, respectively. First, fabrication of BiOX/BaTiO₃ piezoelectric composites and its remarkable piezophoto coupling catalysis behavior lays new ground for developing high‐efficiency piezoelectric photocatalysts in purifying wastewater, killing bacteria, and other piezophototronic processes.     

Preparation of AgX (X = Cl, I) nanoparticles using ionic liquids

Nanoparticles of silver halides have been prepared by mixing silver halide powder with a single liquid phase consisting of an ionic liquid, isooctane, n-decanol and water. Much higher nanoparticle concentrations may be formed with ionic liquids using this new simple method than are found with conventionally applied surfactants. This method also emphasizes the applicability of ionic liquids as versatile components in microemulsions and as solvents for the synthesis of nanomaterials. The effect on the nanoparticles of changing the composition of the liquid mixtures and the nature of the ionic liquid is analysed. High nanoparticle concentrations were only found with chloride based ionic liquids, indicating the importance of the ionic liquid anion in the mechanism of the reaction.     

基于BiOX(X=Cl、Br、I)新型高性能光催化材料的最新研究进展

铋系半导体BiOX(X=Cl、Br、I)因其独特的层状结构和合适的禁带宽度而表现出优异的光催化活性与稳定性, 已成为光催化材料领域极具应用前景的材料体系。本文首先针对BiOX(X=Cl、Br、I)光催化材料研究中的关键科学问题进行了深入分析, 进一步综述了国内外解决上述关键问题所采取的有效措施, 包括: 微结构调控、半导体复合、贵金属沉积、离子掺杂和表面敏化等, 并针对纳米结构BiOX(X=Cl、Br、I)负载于合适载体上实现固载的研究进展进行了概述, 从而对基于BiOX(X=Cl、Br、I)新型高性能光催化材料的最新研究进展进行了全面深入的综述, 最后展望了BiOX光催化材料的研究方向与趋势。     

PbX2（X：I,Br,Cl）基非氟卤化物玻璃的形成行为

为了获得具有实用意义的非氟卤化物玻璃，有必要探索新的玻璃形成系统，本文获得了 新的Ｃ ＰｂＸ２（Ｘ：Ｉ，Ｂｒ，Ｃｌ）为基质的三元非氟卤化物玻璃形成系统，并且首次发现ＰｂＩ２可以单独形成玻璃，所得的三元玻璃形成系统均表现出了良好的玻璃形成能力，此外，还从晶体结构，化学键的特怀，离了半径应电负性等角度探讨了各卤化物在玻璃形成过程中所坊的作用，结果表明，这些因素对玻璃形成均具有重要的作用。     

New halide glasses of the CdX2-PbX2-KI (X=Cl,Br) systems

The glass forming regions and some properties of the CdBr₂-PbBr₂-KI (10 to 50 mol % CdBr₂, 10 to 70 mol % PbBr₂, 20 to 40 mol % KI), CdCl₂-PbBr₂-KI (10 to 50 mol % CdCl₂, 10 to 80 mol % PbBr₂, 10 to 70 mol % KI) and CdCl₂-PbCl₂-KI (20 to 50 mol % CdCl₂, 10 to 70 mol % PbCl₂, 5 to 60 mol % KI) ternary systems were studied. Glasses exhibit remarkably high transmittance (up to 80%) in the visible and IR region (down to 250 cm^–1 for CdBr₂-PbBr₂-KI, 300 cm^–1 for CdCl₂-PbBr₂-KI and 400 cm^–1 for CdCl₂-PbCl₂-KI for 1 mm thick plates). The values of glass transition temperature lie between 343 to 353 K and crystallization temperature between 343 to 403 K.