钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

KEu2Cl6 und K1, 6Eu1, 4Cl5: Zwei neue gemischtvalente Europiumchloride

KEu₂Cl₆ and K_1.6Eu_1.4Cl₅: Two New Mixed‐Valent Europium Chlorides The reaction of the binary chlorides EuCl₃, EuCl₂ and KCl yields the mixed‐valent compounds KEu₂Cl₆ and K_1.6Eu_1.4Cl₅. KEu₂Cl₆ (hexagonal, P6₃/m, Z = 1, a = 788.87(13), c = 411.41(6) pm, R₁ = 5.40 %) crystallizes with an addition‐variant of the UCl₃‐type of structure with tricapped trigonal prismatic coordination for the europium cations. The K⁺ ions reside in channels along [001] and exhibit extremely large displacement parameters U₃₃. The crystal structure of K_1.6Eu_1.4Cl₅ (orthorhombic, Pnma, Z = 4, a = 1260.49(12), b = 871.05(9), c = 787.18(10) pm, R₁ = 4.77 %) is closely related to that one of K₂EuCl₅ if the K⁺ and the Eu³⁺ ions are partly substituted for Eu²⁺. Absorption spectra show transitions, which can be assigned to Eu²⁺ and Eu³⁺ ions, and additional transitions due to interaction of both cations occupying common positions.     

Luminescence de l'Europium Divalent dans les Fluosilicates MSiF6 (M = Sr,Ba)

Luminescence of Eu²⁺ Ions in Fluosilicates MSiF₆ (M = Sr, Ba) A pure f → f emission is detected in Eu²⁺ doped SrSiF₆ and BaSiF₆. Because of the strong ionic bonding of europium a large gap occurs between the bottom of the 5d band and the ⁶P_7/2 emission level (3000 cm^?1 at 300 K). The emission is very intense under low pressure mercury excitation and decreases slowly with temperature.     

A study of the near infrared emission bands of the hydroperoxyl radical at medium resolution

Emissions of the hydroperoxyl radical HO₂ in the spectral range from 1.0 to 1.6 μm were studied at low and medium resolution. The resolved spectrum shows the expected parallel band structure for the vibrational ovetone transition ²A″ (200-000); in the case of the vibronic transitions ²A′, 000 → ²A″, 000 and ²A′, 001 → ²A″, 000, however, comparison of experimental and computer simulated spectra shows that there also occur intense subbands with ΔK = 0, in addition to the ordinary ΔK = ± 1 transitions. The cause for the break-down of the type-C selection rule is not well known. In the reaction system of ethylene with discharged oxygen vibronic bands could be observed originating from ²A′ levels up to at least ν′₃ = 6. The most probable excitation mechanism for these high vibronic levels is the chemiluminescent reaction HCO + O₂ (¹Δ_g) → HO₂(²A′, 00ν′₂) + CO. From the computer fits to the spectra of HO₂ and DO₂ at medium resolution the origins of the 000-000 bands and the fundamental frequencies $\text{ν}$_3′ of the excited ²A′ state could be determined; the values are $\text{ν}$_o(HO₂)=7028 ± 3 cm^?1, $\text{ν}$_o(DO₂)=7034 ± 8 cm^?, $\text{ν}$_3′(HO₂)=927 ± 10 cm^?, and $\text{ν}$_3′(DO₂)=940 ± 28 cm^?1.     

Transition probabilities of europium(III) in zirconium and beryllium fluoride glasses,phosphate glass,and pentaphosphate crystals

Eigenvectors of Eu³⁺ were obtained by a least-squares fitting procedure to the measured transitions from the two lowestJ levels to a multitude of excited levels up to 41 000 cm^?1. The Judd-Ofelt parametersΩ_t(t = 2, 4, 6) were obtained by comparison between theU^(t) calculated from the eigenvectors, and the observed oscillator strengths. Radiative transition probabilities and branching ratios were evaluated for the excited states⁵D_J(J = 0, 1, 2, 3) and⁵L₆ to⁷F_J. The agreement between the calculated and observed lifetimes and branching ratios is better in oxide glasses than in the pentaphosphate crystal and fluoride glasses. This can be understood on the basis of the higher variety of sites and hence, better averaging.     

Energy levels and intensities of the absorption spectrum of the U3+ ion in anhydrous formic acid

The absorption spectrum of the U³⁺ ion in anhydrous formic acid was recorded in the range 4100–23,000 cm^?1. The electrostatic, spin-orbit and configuration interaction parameters obtained from a least-squares fit to eight observed levels are: E¹ = 2882.7 cm^?1, E² = 13.8 cm^?1, E³ = 285.4 cm^?1, ξ_5f = 1654 cm^?1, α = 19.8 cm^?1, β = ?380.3 cm^?1 and γ = 1000.0 cm^?1. Intensity calculations gave good agreement with the oscillator strengths of observed bands only if some of the experimental band areas were combined.     

Ternäre Chloride in den Systemen ACl/GdCl3 (A = Na?Cs)

Ternary Chlorides in the Systems ACl/GdCl₃ (A = Na? Cs) The phase diagrams of the pseudobinary systems ACl/GdCl₃ (A = Na? Cs) were investigated by DTA. Their powder diffractograms were indexed in analogy to known structure families. By solution calorimetry and measurements of e.m.f. = f(T) in galvanic cells for solid electrolytes the enthalpies ΔH⁰ and free enthalpies ΔG⁰ for the formation of the ternary chlorides from the compounds adjacent in the systems were determined. The systems with A = K, Rb, Cs are analogous to those with Sm³⁺ and Eu³⁺. There exist compounds A₃GdCl₆, A₂GdCl₅ and AGd₂Cl₇. Cs₂GdCl₅ is crystallysing in the Cs₂DyCl₅ type; the Rb- and K-compounds and also Na₂GdCl₅ have the K₂PrCl₅?structure. In the system NaCl/GdCl₃ additionally the compounds NaGdCl₄ and Na₃GdCl₆ were found. L? Na₃GdCl₆ is metastable compared with (NaCl + Na₂GdCl₅); above 265°C stable H? Na₃GdCl₆ is existing (cryolite-structure).     

Spectrum analysis of U-doped LaBr3 single crystals. Part 1: crystal-field analysis

Single crystals of U³⁺:LaBr₃ were grown by the Bridgman-Stockbarger technique. High-resolution polarized absorption spectra of the crystals were recorded at 4.2 K in the 4000-50,000 cm⁻¹ range. Sixty-four experimental crystal-field energy levels of the U³⁺ ion were fitted to a semiempirical Hamiltonian employing free-ion, one-electron crystal-field as well as two-particle correlation crystal-field (CCF) operators with an r.m.s. deviation of 28 cm⁻¹. The performed analysis of the spectra enabled the determination of crystal-field parameters and assignment of the observed 5f³→5f³ transitions. The effects of selected CCF operators on the splitting of some specific U³⁺ multiplets have been investigated and the obtained values of Hamiltonian parameters are discussed and compared with those reported in previous analyses.     

Luminescence and vibrational spectra of Ba5Li2W3O15

The infrared and Raman spectra of Ba₅Li₂W₃O₁₅ are reported down to 200 cm^?1. From the internal stretching modes of the tungstate octahedra the crystallographic order between lithium and tungsten in the face-sharing octahedra can be derived. The green tungstate luminescence shows a low quenching temperature that is described with the Dexter-Klick-Russell model. The U⁶⁺ ion shows a yellow emission in Ba₅Li₂W₃O₁₅. There is ample evidence for two different U⁶⁺ centers with different decay times (10 and 80 μsec) and different emission and excitation spectra. One of these is located in a single layer of tungstate octahedra, the other in a double layer of octahedra.     

Hydrogen bonding: VII. Low temperature infrared spectral studies of potassium dihydrogen trifluoride,trihydrogen tetrafluoride,and tetrahydrogen pentafluoride; structure of the H3F−4 ION

We have recorded the infrared spectra of crystalline K⁺H₂F₃^?, K⁺H₃F₄^?, and K⁺H₄F₅^? at room temperature and 12–18 K. The broad (4̃00 cm^?1) anion F-H stretching bands for these three salts are not resolved at low temperature; however, in each case the F-H-F bending region is resolved into the maximum number of bands predicted by theory. The complexity of the F-H-F bending mode region shows the H₄F₅^? ion to be of lower symmetry than predicted by X-ray studies. The H₃F₄^? ion has three hydrogen fluorides hydrogen bonded to a central fluoride ion, rather than a chain type structure. The F-H stretching bands for the three ions have very similar frequencies (1750–1800 cm^?1), which shows the hydrogen bonds in the three ions to be of about the same strength, and to be significantly weaker than the hydrogen bond in the HF₂^? ion.     

Oscillator strengths of the bands of the B̃2 A′1—X̃2 A″2 system of CD3 and a spectroscopic measurement of the recombination rate comparison with CH3

Absolute CD₃ concentrations were measured in the flash photolysis of d₆-HgMe₂. An oscillator strength of (0.99 ± 0.10) × 10^?2 was recorded for the 0O band of the B?—X? system, and a recombination rate coefficient of (4.9 ± 0.4) × 10^?11 cm³ molecule^?1 s^?1 was derived. It is suggested that the probability of recombination per collision is virtually the same as for the CH₃ radical.Some new bands of the B?—X? system have been discovered and tentatively assigned: from a study of the temperature dependence of the intensity of the 47300 cm^?1 transition, Herzberg's scheme ‘b’ has been established for the vibrational assignment.     

Absorption spectra of dysprosium compounds in nonaqueous solutions. Spectral intensity analysis

Absorption spectra of dysprosium compounds were measured in amides and D₂O within the 5500–35000 cm^?1 region and in alcohols within the 7000–34300 cm^?1 region. The oscillator strengths of f-f absorptions bands below 35000 cm^?1 were determined. The intensities of the Dy³⁺ ground state absorption were analyzed according to the Judd-Ofelt theory of forced electric dipole transitions.A good fit to the measurements was obtained with the intensity parameter given in Tables 4–6. The polarizability effect on the intensity of the f-f transition with high value matrix elements U⁽⁴⁾ and U⁽⁶⁾ were considered.     

Darstellung,Eigenschaften und elektronische Raman-Spektren von Bis(chloro)phthalocyaninatoferrat(III), -ruthenat(III) und -osmat(III)

Preparation, Properties and Electronic Raman Spectra of Bis(chloro)-phthalocyaninatoferrate(III), -ruthenate(III) and -osmate(III) Bis(chloro)phthalocyaninatometalates of Fe^III, Ru^III and Os^III [MCl₂Pc(2-)]^?, with an electronic low spin ground state are formed by the reaction of [FeClPc(2-)] resp. H[MX₂Pc(2?)] (M = Ru, Os; X = Cl, I) with excess chloride in weakly coordinating solvents (DMF, THF) and are isolated as (n-Bu₄N) salts. The asym. M? Cl stretch (ν_as(MCl)) is observed in the f.i.r. at 288 cm^?1 (Fe), 295 cm^?1 (Ru), 298 cm^?1 (Os), ν_as(MN) at 330 cm^?1 (Fe), 327 cm^?1 (Ru), and 317 cm^?1 (Os); only ν_s(OsCl) at 311 cm^?1 is resonance Raman (r.r.) enhanced with blue excitation. The m.i.r. and FT-Raman spectra are typical for hexacoordinated phthalocyanines of tervalent metal ions. The UV-vis spectra show besides the characteristic π-π* transitions (B, Q, N, L band) of the Pc ligand a number of extra bands at 12–15 kK and 18–24 kK due to trip-doublet and (Pc→M)CT transitions. The effect of metal substitution is discussed. The r.r. spectra obtained by excitation between the B and Q band (λ₀ = 476.5 nm) are dominated by the intraconfigurational transition Γ₇ Γ ₈ arrising from the spin-orbit splitting of the electronic ground state for Fe^III at 536 cm^?1, for Ru^III at 961 cm^?1 and Os^III at 3 028 cm^?1. Thus the spin-orbit coupling constant increases very greatly down the iron group: Fe^III (357 cm^?1)< Ru^III (641 cm^?1)< Os^III (2 019 cm^?1). The Γ₇ Γ ₈-transition is followed by a very pronounced vibrational finestructure being composed in the r.r. spectra by the coupling with ν_s(MCl), δ(MClN) and the most intense fundamental vibrations of the Pc ligand. In absorption only vibronically induced transitions are observed for the Ru and Os complex at 1 700-2800 rsp. 3100-5800 em^?1 instead of the 0-0 phonon transitions. The most intense lines are attributed to combinations of the intense odd vibrational mo-des at ≈ 740 and 1120 cm^?1 with ν₅(MCI), δ(MClN).     

Mechano-chemical synthesis K2MF6 (M = Mn,Ni) by cation-exchange reaction at room temperature

In order to establish the power of mechanochemistry to produce industrially important phosphors, synthesis of K₂MnF₆ has been attempted by the successive grinding reactions of manganese (II) acetate with ammonium fluoride and potassium fluoride. The progress of reaction was followed by ex-situ characterization after periodic intervals of time. Cubic symmetry of K₂MnF₆ was evident from its powder X-ray diffraction pattern which was refined successfully in cubic space group (Fm-3m) with a = 8.4658 (20) Å. Stretching and bending vibration modes of MnF₆²⁻ octahedral units appeared at 740 and 482 cm⁻¹ in the fourier transformed infrared spectrum. Bands at 405 and 652 cm⁻¹ appeared in the Raman spectrum and they were finger-print positions of cubic K₂MnF₆. Other than the ligand to metal charge transfer transition at 242 nm, transitions from ⁴A_2g to ⁴T_1g, ⁴T_2g and ²T_2g of Mn⁴⁺-ion appeared at 352, 429, 474 and 569 nm in the UV–visible diffuse reflectance spectrum of the sample. Red emission due to Mn⁴⁺ was observed in the photoluminescence spectrum with a decay time of 0.22 ms. Following the success in forming cubic K₂MnF₆, this approach has been extended to synthesize cubic K₂NiF₆ at room temperature. All these results confirmed the susceptibility of acetate salts of transition metals belonging to first-row of the periodic table to facile fluorination at room temperature aided by mechanical forces.     

Electronic absorption spectrum of copper formate tetrahydrate

Single crystals of copper formate tetrahydrate were grown at room temperature. Spectra in the near infrared at room temperature and in the visible at room and liquid air temperatures were recorded on a Unicam SP-700 spectrophotometer and Hilger medium quartz spectrograph respectively. The observed absorption bands have been attributed to an ion of Cu²⁺ in tetragonal symmetry with ²B_1g as the ground state. Taking into consideration the spin—orbit coupling associated with the tetragonal field, a successful interpretation of all the observed bands has been made. The band observed in the near infrared at 11000 cm^?1 has been indentified with a vibrational overtone mode of CO₂. The crystal parameters derived are Dq = ?1380 cm^?1, Ds = ?1950 cm^?1, Dt = ?205 cm^?1 and λ = ?830 cm^?1.     

Electronic absorption spectroscopy of alkaline earth metal uranate compounds

Summary Electronic absorption spectra have been measured by diffuse reflectance for MgUO_4–x, MgU₃O₉, CaUo)_4–x, Ca₂UO₅, Ca₃UO₆, Ca₂U₃O₁₁, CaU₂O₇, CaU₄O₁₂, SrUO₃, SrUO₄, SrUO_3.67, Sr₂U₃O₁₁, SrU₄O_12.8, Sr₂UO₅, Sr₃UO₆, BaUO₄, Ba₃UO₆, BaU₂O₇, Ba₂U₂O₇ and Ba₂U₃O₁₁.Measurements in the near i.r. region of the spectrum have identified transitions arising within the manifold of the 5f electronic levels which indicate the presence of uranium(V) in certain compounds. The portion of the spectrum between 20 000 and 30 000 cm^–1 is shown to contain charge-transfer transitions and, in certain instances, vibrational progressions which are characteristic of the symmetry of the UO₆ octahedron in the solid state structure.     

A4N2O5 (A = Na,K), neue Oxidnitrite der Alkalimetalle und eine Bemerkung zum quasi-binären System K3NO3/K3OBr

A₄N₂O₅ (A = Na, K) Novel Alkali Metal Oxide Nitrites, and a Comment on the System K₃NO₃/K₃OBr K₄N₂O₅ and Na₄N₂O₅ have been prepared for the first time: the respective alkali metal nitrites and -oxides in molar ratios 2 : 1 have been reacted in the solid state. Their crystal structure (for crystallographic data see ?Inhaltsübersicht”?) derive from the anti-K₂NiF₄ type of structure. Na₄N₂O₅ undergoes two phase transitions (at ?15°C and ?60°C) upon cooling. The behavior of solid solutions in the system K₃NO₃/K₃OBr at cooling gives support for the phase transition being driven by the OK₃-framework, where as in Na₃NO₃ order-disorder transitions of the NO₂^? group seem to induce the phase transitions.     

Extraction studies of metal complexes with some macrocyclic tetraaza ligands and xanthene dyes : Spectrophotometric determination of Cadmium(II) with Tetramethyltetraazacyclotetradecane and Erythrosin A

The liquid-liquid extraction of ion-pair complexes of zinc(II), copper(II) and cadmium(II) is described. The macrocyclic ligands 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4Me-cyclam-14) and rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet b) are used with xanthene dyes as the counter ions. The apparent extraction constants (D′_c) are reported. The sequences of extraction efficiency of both ligands are related to the structure of the complexes. The apparent molar absorptivity of the Cd(4Me-cyclam-14)—erythrosin A ion-associate is 1.1 × 10⁵ l mol^? cm^?1. The calibration graph is linear over the range 0—10^?5 M, which allows even 0.05 μg ml^?1 cadmium to be determined in a 0.5 M sodium hydroxide medium. No interference was observed from Ni²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Sn⁴⁺, Ga³⁺, Al³⁺ and Fe³⁺. Interferences were Cu²⁺, Hg²⁺, Ag⁺ and large anions.     

Synthesis and structure of the cluster μ3-sulfido-μ-–(diethylphosphorodithioato-S,S'-)-allylthioureocyclo-tris-[ (μ-sulfido)-χ-(diethylphosphorodithioato-S,S')-molybdenum(IV)], Mo3S4(C4H10O2S2P)4(C4H8N2S)

Title compound, M_r =1273.16, was synthesized by a substitution reaction and its crystal is triclinic belonging to space group P1 with cell parameters: a =13.944(2), b =14.143(7), c =14.233(3) Å, α =77.35(3)°, β =69.94(2)°, γ =63.50(3)°, V=2351(1) ų, Z=2, D_c =1.799g cm^?2. Room temperature, graphite-filtered Mo K_α radiation (λ =0.71073Å) was used for data collection. μ =14.988 cm^?1, F(000) =1280, R=0.051 for 7025 observed reflections. The crystal consists of decrete cluster molecules containing a cluster core [Mo₂(μ₃-S)]¹⁰⁺ with three μ-S, one μ-dtp(dtp =[S₂P(OC₂H₅)]^2-), three χ-dtp and one allylthioureo to form a local six-coordinated sphere around each Mo atom. The bonds of cluster skeleton [Mo₃(μ₃-S)(μ-S)₃]⁴⁺, Mo? Mo 2.744～2.766, Mo—(μ₂-S) 2.340～2.342 and Mo—(μ-S)2.272～2.296 Å, are comparable with those found in the related analogues.     

Lanthanide‐Based Layer‐Type Two‐Dimensional Coordination Polymers Featuring Slow Magnetic Relaxation,Magnetocaloric Effect and Proton Conductivity

Three lanthanide‐based two‐dimensional (2D) coordination polymers (CPs), [Ln(L)(H₂O)₂]_n, {H₃L=(HO)₂P(O)CH₂CO₂H; Ln=Dy³⁺ (CP 1 ), Er³⁺ (CP 2 )} and [{Gd₂(L)₂(H₂O)₃}^.H₂O]_n, (CP 3 ) were hydrothermally synthesized using phosphonoacetic acid as a linker. Structural features revealed that the dinuclear Ln³⁺ nodes were present in the 2D sheet of CP 1 and CP 2 while in the case of CP 3 , nodes were further connected to each other forming a chain‐type arrangement throughout the network. The magnetic studies show field‐induced slow magnetic relaxation property in CP 1 and CP 2 with U_eff values of 72 K (relaxation time, τ₀=3.05×10^?7 s) and 38.42 K (relaxation time, τ₀=4.60×10^?8 s) respectively. Ab‐initio calculations suggest that the g tensor of Kramers doublet of the lanthanide ion (Dy³⁺ and Er³⁺) is strongly axial in nature which reflects in the slow magnetic relaxation behavior of both CPs. CP 3 exhibits a significant magnetocaloric effect with ?ΔS_m=49.29 J kg^?1 K^?1, one of the highest value among the reported 2D CPs. Moreover, impedance analysis of all the CPs show high proton conductivity with values of 1.13×10^?6 S cm^?1, 2.73×10^?3 S cm^?1 and 2, 6.27×10^?6 S cm^?1 for CPs 1 – 3 , respectively, at high temperature (>75 °C) and maximum 95 % relative humidity (RH).