Luminescence in trilanthanumtrichlorotungstate (La3WO6Cl3)

The luminescence properties of La₃WO₆Cl₃ are reported and discussed. The tungstate group occurs as a trigonal prismatic WO^6?₆ complex. The blue luminescence is, for the greater part, quenched at room temperature. No energy migration occurs in this lattice. The decay times are discussed in terms of a simple molecular-orbital (MO) scheme. The luminescence of the following activating ions was studied: Mo⁶⁺, Bi³⁺, Eu³⁺, Sm³⁺, Ce³⁺, and Tb³⁺. The molybdate group produces a red emission with low efficiency. The Bi³⁺ ion induces a narrow band emission with small Stokes shift. This is interpreted using a Bi³⁺O^2?W⁶⁺ charge-transfer state. Except for Ce³⁺, the rare earth activators show luminescence, but the total transfer efficiency from tungstate to the rare-earth ions is low. This is not due to the one-step tungstate-rare-earth transfer (which is efficient), but to the localized nature of the tungstate excitation. The Eu³⁺ charge-transfer band is at very low energies.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

基于第一性原理的无铅无机钙钛矿Cs3Bi2X9(X=Cl、Br、I)光电性能表面效应研究

用基于第一性原理的密度泛函理论方法,对Cs₃Bi₂X₉（X=Cl、Br、I）的光电特性进行理论计算,并系统阐述这3种晶体的表面效应对光电性能的影响。结果表明,3种材料的光学特性由铋原子和卤素原子最外层p轨道上的价电子主导。在可见光区中,材料的吸收峰会随卤素原子序数的增加呈现红移,其中一维结构的Cs₃Bi₂Cl₉表面结构在光吸收能力上尤为特别且敏感;二维结构的Cs₃Bi₂Br₉光吸收能力会受厚度影响;零维结构的Cs₃Bi₂I₉非常稳定,且几乎不受表面特性和晶体厚度的影响。     

基于第一性原理的无铅无机钙钛矿Cs3Bi2X9(X=Cl、Br、I)光电性能表面效应研究

用基于第一性原理的密度泛函理论方法,对Cs₃Bi₂X₉(X=Cl、Br、I)的光电特性进行理论计算,并系统阐述这3种晶体的表面效应对光电性能的影响。结果表明,3种材料的光学特性由铋原子和卤素原子最外层p轨道上的价电子主导。在可见光区中,材料的吸收峰会随卤素原子序数的增加呈现红移,其中一维结构的Cs₃Bi₂Cl₉表面结构在光吸收能力上尤为特别且敏感;二维结构的Cs₃Bi₂Br₉光吸收能力会受厚度影响;零维结构的Cs₃Bi₂I₉非常稳定,且几乎不受表面特性和晶体厚度的影响。     

Luminescence and crystal growth of Cs2NaYCl6Bi

The crystal growth of Cs₂NaYCl₆ doped with Bi³⁺ is described and its luminescence properties reported and discussed.     

Low temperature magnetic susceptibility and exchange interaction in Cs3Cr2Cl9

Magnetic susceptibility of Cs₃Cr₂Cl₉ as a single crystal is studied in the temperature range 4.2–77 K. A maximum is obtained at 25 ± 1 K. These experimental data are interpreted by considering the isotropic exchange interaction between two spin quadruplets. The exchange constant J is found to be equal to - 13 cm^?1.     

Hydrothermal synthesis of antimony oxychloride and oxide nanocrystals: Sb4O5Cl2, Sb8O11Cl2, and Sb2O3

We described herein a facile solution-phase route to three nanocrystals of antimony oxychlorides and oxides (Sb₄O₅Cl₂, Sb₈O₁₁Cl₂, and Sb₂O₃), whose morphologies and phases were varied with the pH value of a reaction mixture or composition of a mixed solvent. In particular, the solvent composition controlled the selective preparation of cubic Sb₂O₃ (senarmontite) and orthorhombic Sb₂O₃ (valentinite). Both cubic and orthorhombic Sb₂O₃ samples exhibited strong emission properties.     

Synchrotron-radiation photoemission study of the V–VI layered compounds Bi2Te3, Bi2Se3, Sb2 Te3 and Sb2Te2Se

The valence band (VB) density of states and the binding energies of the weakly bound core levels have been measured by XUV photoelectron spectroscopy using synchrotron radiation for four V–VI layered compounds. Chemical shifts of the core levels are determined which support the partial ionicity of the bonds involved. The chemical shifts of the emission from two unequivalent crystal sites were shown to differ by less than 30 meV for the compounds Bi₂Te₃, Bi₂Se₃ and Sb₂Te₃.VB and core-level photoemission spectra for the V–VI compounds Bi₂Te₃, Bi₂Se₃, Sb₂Te₃ and Se₂Te₂Se have been presented. Chemical shifts of the Te 4d, Bi 5d, Sb 4d and Se 3d levels were determined, indicating partial ionicity of the mainly covalent bonds involved. Chemical-shift differences originating from atoms at two different crystal sites are <30 meV. In a simple model this implies that similar charge transfers do occur even though completely different bond orbitals were proposed for the and the AB⁽²⁾ bonds. Finally, the fact that no surface core-level shifts were observed tends to confirm the very weak influence of the van der Waals-like bonds on the B⁽²⁾ atoms.     

Emission spectra of Cs2NaTbCl6 and Cs2NaYCl6: Tb3+

The emission spectra of microcrystalline Cs₂NaTbCl₆ and Cs₂Na(Y_0.99Tb_0.01)Cl₆ have been measured at room temperature and at 77 K. The crystal structures of these compounds are face-centered cubic and the terbium (III) ions lie at sites of octahedral (O_h) symmetry surrounded by six chloride ions. Emission is observed from both the ⁵D₃ and ⁵D₄ excited states of Tb³⁺. Assignments have been made for nearly all of the magnetic-dipole transitions split out of the Tb³⁺⁷F₆, ⁷F₅, ⁷F₄, ⁷F₃, ⁷F₂, ⁷F₁ ← ⁵D₄ and ⁷F₄, ⁷F₂ ← ⁵D₃ transitions. These assignments are based on the calculated transition energies and relative magnetic-dipole strengths and intensities obtained from a weak-field crystal-field analysis of octahedral TbCl₆^3? units. Magnetic-dipole lines dominate the spectra for transitions of ΔJ = ±1 free-ion parentage, whereas both magnetic-dipole lines and vibronically induced electric-dipole lines contribute significantly to the emission intensities of the ΔJ = 0, ±2 transitions. The crystal-field sub-levels of both ⁵D₃ and ⁵D₄ appear to reach a Boltzmann thermal equilibrium prior to emission. Emission from ⁵D₃ is partially quenched in going from low temperature to high temperature and in going from Cs₂NaYCl₆: Tb³⁺ (1%) to Cs₂NaTbCl₆.This study has led to the identification and assignment of nearly all of the pure magnetic-dipole transitions split out of the Tb³⁺⁷F₆, ⁷F₅, ⁷F₄, ⁷F₃, ⁷F₂, ⁷F₁ ← ⁵D₄ and ⁷F₄, ⁷F₂ ← ⁵D₃ transitions in crystal-line Cs₂NaTbCl₆. The assignments were based on calculated transition energies and relative magnetic-dipole strengths (and intensities) obtained from a (weak-field) crystal-field analysis of octahedral (O_h) TbCl₆^3? clusters. Excellent agreement between the calculated and observed relative intensities of the magnetic-dipole lines was achieved by assuming a Boltzmann equilibrated set of crystal-field sub-levels for both the ⁵D₄ and ⁵D₃ emitting states. Furthermore, the experimental results suggest that ⁵D₄ ← ⁵D₃ relaxation is temperature-dependent.The energy levels calculated and displayed in table 1 appear to be qualitatively correct and are in semiquantitative agreement with the emission results (as interpreted in section 4). Calculated and observed transition energies for the assigned magnetic-dipole transitions generally agree to within 0.2%.One of the most remarkable features of the emission spectra obtained on Cs₂NaTbCl₆ is the absence of any vibrational structure in the ΔJ = ± 1 transitions (⁷F₆, ⁷F₃ ← ⁵D₄ and ⁷F₄, ⁷F₂ ← ⁵D₃), and the presence of extensive vibrational structure in the ΔJ = O, ±2 transitions (⁷F₆, ⁷F₄, ⁷F₂ ← ⁵D₄). If other than OO vibronic transitions do contribute to the ΔJ = ±1 emissions, their intensities must be at least two or three orders-of-magnitude weaker than the OO magnetic-dipole lines. Vibronically induced electric-dipole transitions appear, however, to make substantial contributions to the ⁷F₆, ⁷F₄, ⁷F₂ ← ⁵D₄ emission spectra. A clear-cut theoretical explanation for the absence of vibrational structure in the ΔJ = ±1 transitions is not readily apparent. We are presently examining this problem in greater detail.     

Controlled synthesis of bismuth oxo nanoscale crystals (BiOCl, Bi12O17Cl2, α-Bi2O3, and (BiO)2CO3) by solution-phase methods

We present the controlled solution-phase synthesis of several sheet- or rod-like bismuth oxides, BiOCl, Bi₁₂O₁₇Cl₂, α-Bi₂O₃ and (BiO)₂CO₃, by adjusting growth parameters such as reaction temperature, mole ratios of reactants, and the base used. BiOCl, Bi₁₂O₁₇Cl₂, and α-Bi₂O₃ could be prepared from BiCl₃ and NaOH, whereas (BiO)₂CO₃ was prepared from BiCl₃ and urea. BiOCl and Bi₁₂O₁₇Cl₂ could also be prepared from BiCl₃ and ammonia. The α-Bi₂O₃ sample exhibited strong emission at room temperature.     

Crystal structure and magnetic properties of Co2TeO3Cl2 and Co2TeO3Br2

The crystal structures of the two new synthetic compounds Co₂TeO₃Cl₂ and Co₂TeO₃Br₂ are described together with their magnetic properties. Co₂TeO₃Cl₂ crystallize in the monoclinic space group P2₁/m with unit cell parameters a=5.0472(6) Å, b=6.6325(9) Å, c=8.3452(10) Å, β=105.43(1)°, Z=2. Co₂TeO₃Br₂ crystallize in the orthorhombic space group Pccn with unit cell parameters a=10.5180(7) Å, b=15.8629(9) Å, c=7.7732(5) Å, Z=8. The crystal structures were solved from single crystal data, R=0.0328 and 0.0412, respectively. Both compounds are layered with only weak interactions in between the layers. The compound Co₂TeO₃Cl₂ has [CoO₄Cl₂] and [CoO₃Cl₃] octahedra while Co₂TeO₃Br₂ has [CoO₂Br₂] tetrahedra and [CoO₄Br₂] octahedra. The Te(IV) atoms are tetrahedrally [TeO₃E] coordinated in both compounds taking the 5s² lone electron pair E into account. The magnetic properties of the compounds are characterized predominantly by long-range antiferromagnetic ordering below 30 K.     

An extended open framework based on disordered [Nb6Cl9O3(CN)6] cluster units: Synthesis and crystal structure of Cs3Mn[Nb6Cl9O3(CN)6]0.6H2O

The synthesis and crystal structure of Cs₃Mn[Nb₆Cl₉O₃(CN)₆]0.6H₂O are described in this work. It crystallizes in the cubic system (space group Fm-3m; a=15.708(5) Å) and is characterized by a static orientational disorder of the [Nb₆Cl₉O₃(CN)₆]⁵⁻ cluster units. It results in a framework structurally related to that encountered in the well known Prussian Blue family prepared for different hexacyanometallates. The charge of the framework is compensated by cesium cations that are located in the tetrahedral cavities of the c.f.c. lattice of units along with water molecules. We will evidence the features that act in the crystallization of solid state compounds built up from ordered or disordered units as well as the influence of orientational disorder on interatomic distances obtained from single-crystal X-ray diffraction investigations.     

The luminescence of α- and β-LaNb3O9

The luminescence of undoped and rare-earth-doped LaNb₃O₉ is reported. The two modifications (α and β) show striking differences. Whereas undoped β-LaNb₃O₉ does not luminesce at all (down to 4.2 K), α-LaNb₃O₉ emits efficiently with a quenching temperature of 250 K. Energy transfer from niobate to rare-earth dopants is observed for the α, but not for the β modification. The rare-earth dopant emission consists of sharp lines for the α modification, but is considerably broadened for the β modification. The luminescence properties are discussed in terms of the crystal structure. In addition results for α-NbPO₅ will be given.     

Electrical conductivity and phase transitions of the solid electrolyte system (Cs1−yRby)Cu4Cl3(I2−xClx)

Results of electrical conductivity measurements, thermal analysis, and X-ray diffraction studies indicate the existence of four phases, between 295 K and the melting points, in the system (Cs_1?yRb_y)Cu₄Cl₃I₂. These phases are designated α, á β, γ in order of decreasing temperature. The α phase is isostructural with α-RbAg₄I₅; the á phase is also cubic and very likely belongs to space groupP2₁3, a subgroup ofP4₁32 andP4₃32 to which the α phase belongs. There is a high probability that the á → α transition is continuous. The á → α transition is not discernible in the conductivity measurements or thermal analysis; therefore the line of á-α transitions is presently unknown. The β phase transforms to the á and the γ phase transforms to the β phase wheny ≤ 0.36; the γ phase transforms to the α phase wheny ≥ 0.36. That is, there is a triple point aty = 0.36, T = 399K. The γ-β, β-α′, and γ-α transitions are all hysteretic and are therefore first order. The conductivities of the β phases are relatively low and the enthalpies of activation relatively high. The conductivity of the β phase decreases with increasingy. The β phase probably belongs to space groupR3, in which the Cu⁺ ions can be ordered. The α and á phases are the true solid electrolytes; the conductivities are high, >0.73 Ω^?1cm^?1 at 419 K, and the enthalpies of activation of motion of the Cu⁺ ions low, 0.11 eV.In the system CsCu₄Cl₃(I_2?xCl_x), 0 ≤ x ≤ 0.25, the Cl^? for I^? substitutions affect the transitions to only a small extent relative to the stoichiometric compound. The β phase occurs for allx and transforms to á.     

K+掺杂双钙钛矿Cs2AgInCl6的发光性质

采用固相球磨法制备了K⁺掺杂双钙钛矿Cs₂AgInCl₆纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射谱和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs₂AgInCl₆为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K⁺掺杂主要取代Ag⁺的位置,引起Cs₂AgInCl₆的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs₂AgInCl₆的光致发光强度显著增强。K⁺的最佳掺杂比例为40%,Cs₂Ag_0.6K_0.4InCl₆发出中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K⁺掺杂比例超过60%,K⁺开始取代Cs⁺的位置,产物发生相变,出现立方相的Cs_2-xK_1+x-yAg_yInCl₆和单斜相的Cs_2-xK_1+xInCl₆产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。     

Layered perovskite-related ruthenium oxychlorides: crystal structure of two new compounds Ba5Ru2Cl2O9 and Ba6Ru3Cl2O12

Single crystals of the title compounds were prepared using a BaCl₂ flux and investigated by X-ray diffraction methods using MoKα radiation and a charge coupled device (CCD) detector. The crystal structures of these two new compounds were solved and refined in the hexagonal symmetry with space group P6₃/mmc, a=5.851(1) Å, c=25.009(5) Å, ρ_cal=4.94 g cm⁻³, Z=2 to a final R₁=0.069 for 20 parameters with 312 reflections for Ba₅Ru₂Cl₂O₉ and space group , a=5.815(1) Å, c=14.915(3) Å, ρ_cal=5.28 g cm⁻³, Z=1 to a final R₁=0.039 for 24 parameters with 300 reflections for Ba₆Ru₃Cl₂O₁₂. The structure of Ba₅Ru₂Cl₂O₉ is formed by the periodic stacking along [001] of three hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The BaO₃ stacking creates binuclear face-sharing octahedra units Ru₂O₉ containing Ru(V). The structure of Ba₆Ru₃Cl₂O₁₂ is built up by the periodic stacking along [001] of four hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The ruthenium ions with a mean oxidation degree +4.67 occupy the octahedral interstices formed by the four layers hexagonal perovskite slab and then constitute isolated trinuclear Ru₃O₁₂ units. These two new oxychlorides belong to the family of compounds formulated as [Ba₂Cl₂][Ba_n+1Ru_nO_3n+3], where n represents the thickness of the octahedral string in hexagonal perovskite slabs.     

K+掺杂双钙钛矿Cs2AgInCl6的发光性质

采用固相球磨法制备了K⁺掺杂双钙钛矿Cs₂AgInCl₆纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs₂AgInCl₆为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K⁺掺杂主要取代Ag⁺的位置,引起Cs₂AgInCl₆的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs₂AgInCl₆的光致发光强度显著增强。K⁺的最佳掺杂比例为40%,Cs₂Ag_0.6K_0.4InCl₆材料发射中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K⁺掺杂比例超过60%,K⁺开始取代Cs⁺的位置,产物发生相变,出现立方相的Cs_2-xK_1+x-yAg_yInCl₆和单斜相的Cs_2-xK_1+xInCl₆产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。     

On the crystal field of Cs2NaY0.99Eu0.01Cl6

Crystal field parameter for cubic Cs₂NaEu_xY_1?xCl₆ (with x = 0.01) are reported. The values are A⁰₄ = 225 cm^?1 and A⁰₆ = 15 cm^?1.     

Multimode Luminescence Tailoring and Improvement of Cs2NaHoCl6 Cryolite Crystals via Sb3+/Yb3+ Alloying for Versatile Photoelectric Applications

Lead-free halide double perovskites are currently gaining significant attention owing to their exceptional environmental friendliness, structural adjustability as well as self-trapped exciton emission. However, stable and efficient double perovskite with multimode luminescence and tunable spectra are still urgently needed for multifunctional photoelectric application. Herein, holmium based cryolite materials (Cs₂NaHoCl₆) with anti-thermal quenching and multimode photoluminescence were successfully synthesized. By the further alloying of Sb³⁺ (s-p transitions) and Yb³⁺ (f-f transitions) ions, its luminescence properties can be well modulated, originating from tailoring band gap structure and enriching electron transition channels. Upon Sb³⁺ substitution in Cs₂NaHoCl₆, additional absorption peaking at 334 nm results in the tremendous increase of photoluminescence quantum yield (PLQY). Meanwhile, not only the typical NIR emission around 980 nm of Ho³⁺ is enhanced, but also the red and NIR emissions show a diverse range of anti-thermal quenching photoluminescence behaviors. Furthermore, through designing Yb³⁺ doping, the up-conversion photoluminescence can be triggered by changing excitation laser power density (yellow-to-orange) and Yb³⁺ doping concentration (red-to-green). Through a combined experimental-theoretical approach, the related luminescence mechanism is revealed. In general, by alloying Sb³⁺/Yb³⁺ in Cs₂NaHoCl₆, abundant energy level ladders are constructed and more luminescence modes are derived, demonstrating great potential in multifunctional photoelectric applications.     

[Bi2Cl10(H2-Norf)4(H2O)8](H-Norf是诺氟沙星)(英)

The crystal structure of [Bi2Cl10(H2-Norf)4(H2O)8] (1) comprises [H2-Norf]^ cations and [Bi2Cl10]4^- anions, that are loosely associated via H-bonding interactions, as well as water molecules that also participate in H-bonding interactions. Strong blue-fluorescent emission of 1 at solid state is observed at the room temperature. CCDC:238237.