Alpha-particle-induced luminescence of rare-earth-doped Y2O3 nanophosphors

The feasibility of utilizing Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺ as radioluminescent nanophosphors under alpha-particle excitation is investigated. Materials synthesized by the urea homogeneous precipitation method were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The XRD analysis of as-produced precipitates and nanophosphors fired at temperatures ranging from 950 to 1100 °C indicated the presence of highly crystalline cubic Y₂O₃ with crystallite sizes of ∼40 nm. SEM and TEM analysis revealed that particles with average diameters of ∼200 nm and comprised of ∼40 nm grains were obtained. High-resolution radioluminescence and photoluminescence spectra were used to investigate the unwanted radioluminescence saturation effects associated with the high ionization rate of alpha-particles. Additionally, the radioluminescence intensity as a function of rare-earth ion dopant concentration is investigated for these materials under alpha-particle excitation. The prospect for utilizing these materials as intermediate absorbers in indirect-conversion radioisotope batteries is discussed.     

Visible and infrared luminescence properties of Er-doped Y2Ti2O7 nanocrystals

Er³⁺-doped Y₂Ti₂O₇ nanocrystals were fabricated by the sol-gel method. While the annealing temperature exceeds 757 °C, amorphous pyrochlore phase Er_xY_2−xTi₂O₇ transfers to well-crystallized nanocrystals, and the average crystal size increases from ∼70 to ∼180 nm under 800-1000 °C/1 h annealing. Er_xY_2−xTi₂O₇ nanocrystals absorbing 980 nm photons can produce the upconversion (526, 547, and 660 nm; ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively) and Stokes (1528 nm; ⁴I_13/2→⁴I_15/2) photoluminescence (PL). The infrared PL decay curve is single-exponential for Er³⁺ (5 mol%)-doped Y₂Ti₂O₇ nanocrystals but slightly nonexponential for Er³⁺ (10 mol%)-doped Y₂Ti₂O₇ nanocrystals. For 5 and 10 mol% doping concentrations, the mechanism of up-converted green light is the two-photon excited-state absorption. Much stronger intensity of red light relative to green light was observed for the sample with 10 mol% dopant. This phenomenon can be attributed to the reduced distance between Er³⁺-Er³⁺ ions, resulting in the enhancement of the energy-transfer upconversion and cross-relaxation mechanisms.     

Yb/Er掺杂Y2O3纳米核壳颗粒的荧光性能及体内标定研究

为改善无机Y2O3上转换纳米粒子(UCNPs)的荧光性能,且同步实现其在生物体内的成像标定,通过共沉淀法及梯度合成工艺,制备出各组不同壳层厚度的Y2O3:Yb³⁺,Er³⁺@Y2O3:Yb³⁺ UCNPs。利用透射电子显微镜(TEM)扫描、X射线衍射(XRD)、上转换荧光(UCL)光谱、UCL寿命等对样品的形貌、结构及荧光性能进行了表征。结果表明：利用共沉淀法制得小尺寸Y2O3:Yb³⁺,Er³⁺@Y2O3:Yb³⁺纳米核壳颗粒,平均粒径范围在25.57~26.24 nm之间。通过调整Yb³⁺浓度和水浴时间优化合成工艺,获得高发射强度、长荧光寿命方案(80% Yb掺杂,8 h水浴)。高红绿比的荧光发射特征,决定其在小动物体内荧光标定检测时更宜采用红色信道。     

Synthesis and derivative chemistry of [Ru2(μ-PPh2) (μ-OH) 2(μ-p-cymene) 2]

The cationic diphenylphosphido-bridged compound [Ru₂(μ-PPh₂)(μ-OH)₂(η⁶-p-cymene)₂][PF₆) (2) has been prepared by reaction of the tri-μ-hydroxo complex [Ru₂(μ-OH)₃(η-p-cymene)₂][PF₆] (1) with diphenylphosphine. Complex 2 eliminates water on reaction with protic acids, incorporating the conjugate base of the added acid as a bridging ligand. Formic acid, acetic acid, phenol, and aniline react with 2 to give the monosubstituted compounds [Ru₂(μ-PPh₂)(μ-OH)(μ-L)(η⁶-p-cymene)₂]PF₆] (L = HCO₂, MeCO₂, OPh, or NHPH), whereas methanol, thiophenol, 1,2-benzenedithiol, hydrochloric acid and isopropanol afford the disubstituted derivatives [Ru₂(μ-PPh₂)(μ-L)₂(η⁶-p-cymene)₂]PF₆] (L = OMe, SPh, S₂C₆H₄, Cl, or H).     

Dilatometric studies of Y2W3O12 with added Al2O3

Y₂W₃O₁₂ exhibits negative thermal expansion along the three crystallographic directions due to the transverse thermal vibrations perpendicular to the Y-O-W linkage. It is highly hygroscopic and forms a trihydrate structure at room temperature. Dilatometric studies of Y₂W₃O₁₂ show large thermal expansion hysteresis due to large grain size and a large initial positive thermal expansion due to the removal of water molecules. Al₂O₃ has been added to Y₂W₃O₁₂ upto 10 wt% in an attempt to overcome the hygroscopicity and reduce the particle size and thereby the thermal expansion hysteresis. Thermo gravimetric, dilatometric and electron microscopic studies are presented to support these observations. Dedicated to Professor C N R Rao on his 70th birthday     

添加Y2O3的ZrO2—Al2O3复相陶瓷力学性能的研究

采用工业ZrO2, Al2O3原料, 以Y2O3作为稳定剂, 通过适当的工艺制备出ZrO2-Al2O3复相陶瓷. 研究结果表明, Y2O3添加量为3.5%(摩尔分数)的ZrO2基陶瓷中加入Al2O3可有效地抑制ZrO2晶粒的生长, 有利于使ZrO2晶粒以亚稳四方相存在, 从而提高材料的强度与断裂韧性. Al2O3含量为20%(质量分数)时, 复相陶瓷的抗弯强度、断裂韧性分别为676.7和10 MPa*m1/2, 其值接近湿化学法制备的复相陶瓷的力学性能. 相变增韧与颗粒弥散增韧作用相互叠加提高了复相陶瓷材料的力学性能.     

Solvothermal synthesis and luminescence properties of monodisperse Gd2O3:Eu and Gd2O3:Eu@SiO2 nanospheres

A series of uniform, monodispersed Gd(OH)³:Eu³⁺ nanospheres less than 100 nm were successfully synthesized with iron ions as catalyst and DMF as solvent under the solvothermal condition. Cetyltrimethyl ammonium bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as co-surfactant during this facile procedure should be changed as A series of uniform, monodisperse Gd(OH)³:Eu³⁺ nanospheres less than 100 nm in diameter were successfully synthesized with solvothermal method. Iron ion was used as catalyst and Dimethylformamide (DMF) as solvent, Cetyltrimethyl Ammonium Bromide (CTAB) and Polyvinylpyrrolidone (PVP) were performed as surfactants. Further calcination process was applied to prepare Gd₂O₃:Eu³⁺ nanoshpheres during this facile procedure.     

Optical properties of (Y1−xTmx)3GaO6 and subsolidus phase relation of Y2O3-Ga2O3-Tm2O3

A serial of samples in Y₂O₃-Ga₂O₃-Tm₂O₃ pseudo-ternary system are prepared by solid-state chemical reaction method. The range of solid solution in (Y_1−xTm_x)₃GaO₆ is 0<x<0.384. Powder X-ray diffraction shows that the compounds crystallize in Gd₃GaO₆ (Cmc2₁)-type structure. The solid solubilities of Y_3+xGa_5−xO₁₂ (x=0-0.77) and Tm_3+xGa_5−xO₁₂ (x=0-0.62) are 37.5-47.11 at% Y₂O₃, and 37.5-45.26 at% Tm₂O₃, respectively. PL spectra of Tm-doped Y₃GaO₆ show that there is a sharp blue emission at ∼456 nm from the ¹D₂→³F₄ transition at room temperatures with two lifetimes (∼5 and ∼15 μs) and a narrow saturation range of PL intensity for the Tm³⁺ content from x=0.005 to 0.03. The sharp emission and long lifetime of (Y_1−xTm_x)₃GaO₆ indicate that Y₃GaO₆ is a potential phosphor and laser crystal host material.     

Growth and characterization of thin films of Y2O3, La2O3 and La2CuO4

Films of Y₂O₃, La₂O₃, and La₂CuO₄ were prepared by an ultrasonic nebulization and pyrolysis method using acetylacetonates of the corresponding metals in alcohol solvents as source materials. Homogeneous, uniform films with good adherence have been obtained using this simple technique. As-deposited yttrium and lanthanum oxide films were poorly crystallized. After postannealing in oxygen at higher temperature, they crystallized into cubic and hexagonal phases, respectively. Transparent yttrium and lanthanum oxide films have high electric breakdown voltages. Single phase polycrystalline La₂CuO₄ thin films were obtained from a source solution with a La:Cu ratio of 2:1.     

Formation of β- and β″-Al2O3 by the solid state reaction between NaAlO2 and γ-Al2O3

The solid state reaction of NaAlO₂ with γ-Al₂O₃ was investigated kinetically. Powdered compacts with various compositions (Al₂O₃/NaAlO₂ = 1–5) were fired at 700–1200°C for 1–768 hr. The amounts of the reaction product were determined by peak heights of X-ray diffraction patterns. β″-Al₂O₃ was formed predominantly from the sample with Al₂O₃/NaAlO₂ = 2. The firing time for the β″-Al₂O₃ formation was shortened as the firing temperature was raised, and the activation energy, E_a, for formation was about 130–135 kcal/mole. The sample of Al₂O₃/NaAlO₂ = 5 formed m-Al₂O₃ with the mullite structure and was observed to transform gradually to β-Al₂O₃. E_a for the m-Al₂O₃ formation and for the transition were about 55–60 and 40 kcal/mole, respectively, which resulted in E_a of about 95–100 kcal/mole for the β-Al₂O₃ formation. The mechanism of the m-Al₂O₃ formation is discussed briefly.     

Standard free energy of formation of YFeO3, Y3Fe5O12, and a new compound YFe2O4 in the FeFe2O3Y2O3 system at 1200°C

The phase equilibria in the FeFe₂O₃Y₂O₃ system have been established at 1200°C. The following phases were stable: yttria, hematite, magnetite, wüstite, metallic iron, yttrium-iron perovskite, yttrium-iron garnet, and a new phase YFe₂O₄, belonging to a rhombohedral crystal system. The YFe₂O₄ compound has a solid solution from YFe₂O_3.905 to YFe₂O_4.000. The standard free energies of formation of YFe₂O_3.905, YFeO₃, and Y₃Fe₅O₁₂ have been determined to be ?96 800 ± 200 cal, ?59 800 ± 200 cal, and ?143 700 ± 600 cal, respectively, from metallic iron, Y₂O₃, and oxygen.     

Synthesis of SiO2/Y2O3:Eu core-shell materials and hollow spheres

The SiO₂/Y₂O₃:Eu core-shell materials and hollow spheres were first synthesized by a template-mediated method. X-ray diffraction patterns indicated that the broadened diffraction peaks result from nanocrystals of Y₂O₃:Eu shells and hollow spheres. X-ray photoelectron spectra showed that the Y₂O₃:Eu shells are linked with silica cores by Si-O-Y chemical bond. SEM and TEM observations showed that the size of SiO₂/Y₂O₃:Eu core-shell structure is in the range of 140-180 nm, and the thickness of Y₂O₃:Eu hollow spherical shell is about 20-40 nm. The photoluminescence spectra of SiO₂/Y₂O₃:Eu core-shell materials and Y₂O₃:Eu hollow spheres have better red luminescent properties, and the broadened emission bands came from the size effects of nanocrystals composed of Y₂O₃:Eu shell.     

The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

Synthesis, crystal structures and luminescence properties of the Eu-doped yttrium oxotellurates(IV) Y2Te4O11 and Y2Te5O13

Y₂Te₄O₁₁:Eu³⁺ and Y₂Te₅O₁₃:Eu³⁺ single crystals in sub-millimeter scale were synthesized from the binary oxides (Y₂O₃, Eu₂O₃ and TeO₂) using CsCl as fluxing agent. Crystallographic structures of the undoped yttrium oxotellurates(IV) Y₂Te₄O₁₁ and Y₂Te₅O₁₃ have been determined and refined from single-crystal X-ray diffraction data. In Y₂Te₄O₁₁, a layered structure is present where the reticulated sheets consisting of edge-sharing [YO₈]¹³⁻ polyhedra are interconnected by the oxotellurate(IV) units, whereas in Y₂Te₅O₁₃ only double chains of condensed yttrium-oxygen polyhedra with coordination numbers of 7 and 8 are left, now linked in two crystallographic directions by the oxotellurate(IV) entities. The Eu³⁺ luminescence spectra and the decay time from different energy levels of the doped compounds were investigated and all detected emission levels were identified. Luminescence properties of the Eu³⁺ cations have been interpreted in consideration of the now accessible detailed crystallographic data of the yttrium compounds, providing the possibility to examine the influence of the local symmetry of the oxygen coordination spheres.     

Self-diffusion of yttrium in monocrystalline yttrium oxide: Y2O3

Yttrium self-diffusion in monocrystalline yttrium oxide (Y₂O₃) is studied by means of the classical radio tracer technique. The few reliable diffusion data obtained in the temperature range 1600–1700°C lead to the following diffusion coefficient

$\text{D=3.5×10}{}^{\mathrm{?9}}\text{exp}\text{?}\text{72}\text{RT}\text{(}\text{kcal/mole}\text{)}\text{m}{}^2\text{sec}{}^{\mathrm{?1}}$

.Experimental errors on the above numerical values are large and give, for the preexponential and energy terms, respectively:

$\text{2.10}{}^{\mathrm{?7}}\text{<D}{}_0\text{<3.10}{}^{\mathrm{?10}}\text{m}{}^2\text{sec}{}^{\mathrm{?}}$

$\text{62<Q<82}\text{kcal/mole}$

.Nevertheless these results seem in good agreement with those deduced from high-temperature and low-stress creep experiments. The theoretical aspect of self-diffusion of yttrium in Y₂O₃ is studied in terms of point defects and lattice disorder due to the equilibrium between the oxide and its environment. This last part is confined to the restricted range of high oxygen partial pressure in which oxygen interstitials are supposed to be majority defects. Intrinsic and extrinsic diffusion behavior are both considered on the basis of a vacancy diffusion mechanism.     

Polymorphism in yttrium molybdate Y2Mo3O12

Yttrium molybdate (Y₂Mo₃O₁₂) has been prepared by non-hydrolytic sol–gel chemistry. The phase evolution upon heating was investigated using in situ and ex situ heat treatments combined with powder X-ray diffraction. This method has led to the isolation of two orthorhombic phases with different atomic connectivity. Yttrium adopts 6- and 7-coordinate sites in the Pbcn and Pba2 structures, respectively. Cocrystallization of both phases was observed in a narrow temperature range, suggesting that crystallization kinetics play a major role in phase formation. It was found that the Pba2 phase is the stable polymorph below 550 °C, and converts to Pbcn at higher temperatures.     

Sm2O3Ga2O3 and Gd2O3Ga2O3 phase diagrams

Four definite compounds exist in the Sm₂O₃Ga₂O₃ binary phase diagram, namely: Sm₃GaO₆, Sm₄Ga₂O₉, SmGaO₃, and Sm₃Ga₅O₁₂. The $\text{3}\text{1}$ compound is orthorhombic (space group Pnna - Z.4) with the cell parameters: a = 11.40₀Å, b = 5.51₅Å, c = 9.07Å and belongs to the oxysel family. Sm₃GaO₆ and SmGaO₃ melt incongruently at 1715 and 1565°C; Sm₄Ga₂O₉ and Sm₃Ga₅O₁₂ have a congruent melting point at 1710 and 1655°C. With regard to the Gd₂O₃Ga₂O₃ system three definite compounds have been identified: Gd₃GaO₆, Gd₄Ga₂O₉, and Gd₃Ga₅O₁₂. Only the garnet melts congruently at 1740°C with the following composition: Gd_3.12Ga_4.88O₁₂. Gd₃GaO₆, and Gd₄Ga₂O₉ melt incongruently at 1760 and 1700°C. GdGaO₃ is only obtained by melt overheating which may yield an equilibrium or a metastable phase diagram.     

XPS study of carbonation of Mn/Y2O3 catalysts

XPS spectra in the Ols range of binding energy demonstrate a steady decline of concentration of surface carbonate groups as Mn loading in Mn/Y2O3 oxide catalysts increases from 0 to 50 at.%.