Luminescence of yttrium oxide

Pulsed cathodoluminescence of pure and neodymium-activated Y₂O₃ ceramic and materials used for its synthesis (commercial Y₂O₃ micropowder and nanopowder obtained from it by laser evaporation) is investigated in a wavelength range of 350–850 nm. In the micropowder, four series of narrow electron-vibration bands of intrinsic luminescence centers are detected. In a ceramic with the same lattice, only one series is left, while the remaining series degenerate into broad bands. In the neodymium-activated ceramic, luminescence bands of the Na³⁺ ion located in the monoclinic lattice of the γ-Y₂O₃ phase are detected.     

Optical properties of anodic aluminum oxide produced in a complex electrolyte

Features of the absorption, transmission, photoluminescence, and infrared (IR) spectra of anodic aluminum oxide (AAO) formed in a complex electrolyte and annealed at 800, 900, 1000, and 1300°C are investigated. The variations in the phase composition changes of the anodic aluminum oxide are reflected in the respective features of its optical properties. A decrease in the transmission coefficient in the visible range of the spectrum is shown for the phase series: amorphous AOA → γ-Al₂O₃, γ-, θ-, δ-Al₂O₃ mixture → α-Al₂O₃. It is established that the highest absorption coefficient is characteristic of α-Al₂O₃, and the amorphous samples are the most transparent in the visible range. An intensive luminescence band in the red region of the spectrum with maxima at 678 and 694 nm is found for α-Al₂O₃. The emergence of this band is explained by the presence of octahedrally coordinated Mn₊₄ and Cr₊₃ impurity ions in the structure. A luminescence band at 700–800 nm is observed for the mixture of low-temperature phases. Intense luminescence in the region 350–500 nm is found for amorphous AAO and γ-Al₂O₃.     

Investigation of up-conversion luminescence properties of RE/Yb co-doped Y2O3 transparent ceramic (RE=Er, Ho, Pr, and Tm)

RE/Yb co-doped Y₂O₃ transparent ceramics (RE=Er, Ho, Pr, Tm) were fabricated and characterized from the point of up-conversion luminescence. All the samples exhibit high transparence not only in near-infrared band (NIR) band but also in visible region, which ensures the output of the up-conversion luminescence. Under 980 nm excitation, green and red emissions were observed in Er, Yb:Y₂O₃ transparent ceramic, while green emission was detected in Ho, Yb and Pr, Yb co-doped Y₂O₃ transparent ceramics. In Tm, Yb co-doped Y₂O₃ ceramic, very intense blue up-conversion luminescence was detected. The dependence of up-conversion emission intensity on the pumping power was measured for each RE/Yb co-doped Y₂O₃ transparent ceramic, and the up-conversion mechanism was discussed in detail. Meanwhile, the energy transfer efficiency was calculated.     

Luminescence of Cr<Superscript>3+</Superscript> impurity ions in Li<Subscript>2</Subscript>Ge<Subscript>7</Subscript>O<Subscript>15</Subscript> nanocrystals and clusters embedded in lithium germanate glasses

The properties of Cr³⁺-doped Li₂Ge₇O₁₅ (LGO) lithium germanate nanocrystals produced in lithium germanate glasses under isothermal heating were studied. The samples were characterized by x-ray diffraction and small-angle scattering, as well as by transmission electron microscopy. The luminescence spectra of the impurity chromium measured in lithium germanate glasses containing LGO crystals revealed transitions in Cr³⁺ ions residing in the glass phase and in LGO crystallites starting from extremely small clusters. This provided the possibility of following the process of crystallization of the lithium germanate glass from Cr³⁺ luminescence spectra. The effects observed in the Cr³⁺ luminescence spectrum revealed a ferroelectric phase transition in LGO nanocrystals embedded in the glass.     

Nanostructured layers of anion-defective gamma–alumina – New perspective TL and OSL materials for skin dosimetry. Preliminary results

Thin- layer material based on nanostructured Al₂O₃ of the surface density 5 mg/cm² was obtained. The material is characterized by high OSL and TL yields comparable with those for TLD-500 which is one of the leaders among the TL and OSL detectors. The dose response, fading and dependence of TL yield on heating rate was studied. It is established that high luminescence yield of the samples under study correlates with the content of anion vacancies and γ-phase of Al₂O₃. The data for time-resolved luminescent spectroscopy are presented, which evidence for possible correlation between high TL and OSL activity and the F-type centers. It is noted that the material needs to be modified for successful use in dosimetry. In addition further studies to decrease the contribution of unstable (at 300 К) components to OSL and TL yields are required.     

Nanocrystals formation on Ho doped strontium barium niobate glass

The study of two different methods to obtain strontium barium niobate nanocrystals immersed in a glass matrix has been carried out. Ho₂O₃-doped SrO-BaO-Nb₂O₅-B₂O₃ glasses were fabricated using the melt quenching method. Glass ceramic samples were obtained from the precursor glass by thermal treatment in a furnace and by laser irradiation. These glass ceramic samples are formed by a glassy phase and a crystalline phase of strontium barium niobate nanocrystals. This structure was confirmed by X-ray diffraction and Atomic Force Microscope images. The incorporation of Ho³⁺ ions in the strontium barium niobate nanocrystals were corroborated by optical measurements, which produced an increment in the luminescence intensity compared to the precursor glass.     

Luminescence properties of Pr3+-doped transparent oxyfluoride glass–ceramics containing BaYF5 nanocrystals

Transparent oxyfluoride glass–ceramics containing BaYF₅ nanocrystals were successfully synthesized by appropriate heat-treatment on the SiO₂–Al₂O₃–Na₂O–BaF₂–Y₂O₃–Pr₆O₁₁ precursor glass. The structure and luminescence properties of the precursor glass and glass–ceramics were investigated by DSC, XRD, TEM, optical transmission, photoluminescence, decay time and radioluminescence spectra. The XRD results indicate that the BaYF₅ nanocrystals can percitated in the precursor glass and the sharper emission peaks of Pr³⁺ in glass ceramic suggests that Pr³⁺ ions are incorporated into the BaYF₅ nanocrystals. The higher the heat-treatment temperature is, the more the Pr³⁺ ions are centered into BaYF₅ nanocrystals, which results in the optimal concentration of Pr³⁺ in glass ceramic changes on heat-treatment temperature. It is notable that the emission intensity of both photoluminescence and radioluminescence for 0.1 mol% Pr³⁺ in the glass ceramic (GC665) are stronger than those in the precursor glass. The mechanism of enhanced luminescence is also discussed.     

Influence of grain size on luminescence properties of micro- and nanopowder Zn2V2O7 vanadate

Micro- and spongiform nanocrystalline Zn₂V₂O₇ compounds were synthesized by hydrothermal and solid-state reaction techniques, and their morphological features were investigated by scanning electron microscopy (SEM). The grain size ranges of the produced powders were 3–15, 0.5–2 μm, and 50–500 nm. The luminescence spectra of these compounds were measured under pulse cathode beam and photoexcitation (200–400 nm). The luminescence decay properties of Zn₂V₂O₇ were studied.It is found that the intensity, maximum position of luminescence spectra and luminescence decay time of Zn₂V₂O₇ samples depend considerably on the grain size of the synthesized powders. The processes of energy relaxation in Zn₂V₂O₇ and the observed size effect on the luminescence properties are also discussed.     

Investigation of structural features of the Y3Al5O12: Ce3+/Lu2O3 crystal phosphors formed by the colloidal chemical method

The specific features of the crystal structure of crystal phosphors Y₃Al₅O₁₂: Ce³⁺/Lu₂O₃ (Lu₂O₃: Ce) synthesized by the colloidal chemical method have been investigated by neutron diffraction at room temperature. The influence of the method used for introducing Lu₂O₃ into the system on the structure and luminescence properties of the samples has been analyzed. The investigation has revealed that the spectra of the samples prepared under the most nonequilibrium conditions are characterized by the Stokes shift and high photoluminescence intensity. This has been explained by the disorder of their crystal structure due to the formation of stable associates of defects.     

Yb:Y2O3透明陶瓷的光学性能研究

介绍了一种基于纳米粉末真空烧结技术的新型固体激光材料——Yb：Y₂O₃多晶陶瓷的制备工艺、物理化学特性、能级结构和光谱特性，并与Yb：YAG单晶进行了对比.采用紧凑型有源镜激光器(CAMIL)的抽运方式，验证了Yb：Y₂O₃透明陶瓷的激光输出性能.在35W的最大抽运功率下，得到波长1078 nm，功率10.5 W 的连续激光输出，斜率效率达到37.5%.实验中还观察到激光输出波长随抽运功率增加而红移以及随输出耦合镜变化而漂移的现象.Yb：Y₂O₃多晶陶瓷是一种理想的激光材料，不仅具有与Yb：YAG单晶同样优秀的物理化学性能和光谱特性，而且其热导率和发射带宽约为Yb：YAG单晶的两倍，非常适合于高亮度激光器和超短脉冲激光器领域的发展应用. 关键词： 2O₃陶瓷')" href="#">Yb:Y₂O₃陶瓷 陶瓷激光器 透明陶瓷     

Luminescence of CdSe/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> quantum wires at high photoexcitation levels

Nonlinear dependence of the CdSe/Al₂O₃ quantum wire luminescence intensity on the photoexcitation level and an asymmetric broadening of luminescence spectra accompanied by a high-frequency shift of the maximum are observed and explained in terms of the dominant filling of exciton phase space in wires with different cross sections.     

Elaboration of nanostructured Eu3+-doped Gd2O3 phosphor fine spherical powders using polyol-mediated synthesis

Red-emitting Eu³⁺-doped Gd₂O₃ spherical powders were directly precipitated using a polyol method. The as-synthesized powders consist of agglomerates with a spherical shape and a size ranging between 0.4 and 0.6 μm. Each agglomerate is nanostructured and consists of a packing of nanocrystallites (3–5 nm) of a bcc oxide phase whose luminescence presents original features in comparison with bulk materials. The powders were further calcinated and the size of both crystallites and agglomerates, the crystalline structure and the luminescence were studied as a function of the annealing temperature. For temperatures lower than 900 °C, the samples obtained are highly crystalline and possess the classical Eu³⁺ red luminescence. For optimized temperature, the morphology of the particles can be preserved leading to spherical, dense, luminescent and almost monodisperse oxide powders, 0.5 μm in size. PACS 81.07.Bc; 81.07.Wx; 81.16.Be; 75.50.-y; 42.70.-a     

Luminescence of Thin Bismuth Germanate Films Having the Structure of Eulitine and Benitoite

The luminescence and luminescence excitation spectra of thin films of Bi₄Ge₃O₁₂ and Bi₂Ge₃O₉ were investigated. The spectra were decomposed into elementary components by the Alentsev-Fok method. It has been established that the luminescence spectra of thin Bi₄Ge₃O₁₂ and Bi₂Ge₃O₉ films have a similar structure and that each contains three luminescence bands with maxima at 2.70, 2.40, and 2.05 eV and at 2.73, 2.40, and 1.95 eV, respectively. Comparison of the results obtained with the well-known results of investigation of the luminescence of Bi₁₂GeO₂₀ and Bi₂O₃ suggests that the luminescence in the compounds considered is caused by the radiation processes that proceed in structural complexes of similar configuration that contain the bismuth ion in the nearest oxygen environment. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 377–380, May–June, 2005.     

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO,Ca(OH)2 and CaCO3

In microscopy studies of 19^th‐century cement stone, we found free lime in the form of darkened spherical structures, as they were described in the literature already. When trying to determine their phase composition by Raman spectroscopy, we encountered contradictive assignments in literature spectra of the lime phases CaO, Ca(OH)₂ and CaCO₃ and observed strong spectral features that have been ignored or erroneously assigned so far. In this study we present Raman spectra of pure lime phases and of a naturally grown calcite crystal, burnt limestone (quick lime, mainly CaO), aged slaked lime putty (mainly Ca(OH)₂), and carbonated lime putty (mainly CaCO₃). Based on the results, we shed light mainly onto these two questions: (1) Does CaO have a Raman spectrum? (2) Which features in the spectra are luminescence bands that could be (and already have been) misinterpreted as Raman bands? We proof our assignment of luminescence bands in lime phases by using three different laser wavelengths for excitation, and give hypotheses on the origin of the luminescence as well as practical advices on how to identify these misleading features in Raman spectra. This article is mainly addressed to users of Raman spectroscopy in different fields of material analysis who might not be aware of the presence of interfering bands in their spectra. Copyright © 2014 John Wiley & Sons, Ltd.     

Intrinsic luminescence centers in scandia,yttria, and their solid solutions

Pulsed cathodoluminescence (PCL) of Y₂O₃ and Sc₂O₃ powders, as well as of ceramic samples of binary (11 mol % Sc₂O₃–ZrO₂ and 10 mol % Y₂O₃–ZrO₂) and ternary (xSc₂O₃–(10–x)Y₂O₃–ZrO₂) (x = 5, 6, 7, 8 mol %) solid solutions are studied in the range of 300–850 nm at room temperature. In Y₂O₃ and Sc₂O₃, series of strong narrow luminescence bands emitted by surface bound radicals _...0^...0>-Y=O and _...0^...0>-Sc=O are found. The PCL spectra of xSc₂O₃–(10–x)Y₂O₃–ZrO₂ ceramic samples showed the same series of narrow bands at 543, 551, 555, 572, 583, 594, 614, and 639 nm as the yttrium oxide spectra. The existence of these luminescence bands, which correspond to the emission of the _...0^...0>-Y=O radical, and the absence of the emission lines of the _...0^...0>-Sc=O radical indicate that yttrium ions, due to their larger radius, are the first that are displaced to the surface of crystallites in these systems, which is accompanied by the formation of the second phase in subsurface layers.     

Optical properties of Sm3+ and Dy3+ ions in Gd2MoB2O9 host lattice

Gd₂MoB₂O₉ doped with Sm³⁺ and Dy³⁺ were used for this study. The photoluminescence behaviors of Sm³⁺ and Dy³⁺ in this phosphor material were investigated by the excitation and emission spectra. The Sm³⁺-doped Gd₂MoB₂O₉ phosphor powders show a red luminescence, whereas the Dy³⁺-doped Gd₂MoB₂O₉ phosphor powders show a yellow luminescence. In addition, the optimum doping concentration and the time-resolved luminescence spectroscopy were also investigated.     

Electronic structure of an oxygen vacancy in Al<Subscript>2</Subscript>O<Subscript>3</Subscript> from the results of Ab Initio quantum-chemical calculations and photoluminescence experiments

The electronic structure of an oxygen vacancy in α-Al₂O₃ and γ-Al₂O₃ is calculated. The calculation predicts an absorption peak at an energy of 6.4 and 6.3 eV in α-Al₂O₃ and γ-Al₂O₃, respectively. The luminescence and luminescence excitation spectra of amorphous Al₂O₃ are measured using synchrotron radiation. The presence of a luminescence band at 2.9 eV and a peak at 6.2 eV in the luminescence excitation spectrum indicates the presence of oxygen vacancies in amorphous Al₂O₃.     

Nonlinear Luminescence Quenching in Eu2O3

We report a laser spectroscopic investigation of saturation effects in the spectra and dynamics of Eu₂O₃. The saturation effects occur at high laser intensity and appear as dips in the center of the fluorescence excitation lines and as a shortening of the ⁵D₀ excited‐state decay curve. The saturation effects are observed in nanoparticles, micrometer‐sized particles, and a fused crystal of monoclinic‐phase Eu₂O₃ and in micrometer‐sized particles of cubic‐phase Eu₂O₃. We attribute the mechanism of the nonlinear luminescence quenching to upconversion by energy transfer.     

Luminescence spectroscopy of Ti ions in Li2O-CaF2-P2O5 glass ceramics

Li₂O-CaF₂-P₂O₅ glasses mixed with different concentrations of TiO₂ (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The photo luminescence spectra of these samples excited with the wavelengths corresponding to their absorption edges have been recorded at room temperature. The spectra exhibited an emission band in the wavelength region 470-500 nm. The emission band is identified due to the charge transfer from O²⁻ ion in to empty 3d orbital of octahedrally positioned Ti⁴⁺ ions. The analysis of the results further indicates the highest luminescence efficiency for the glass ceramic sample crystallized with 0.6 mol% of TiO₂.     

Er,Yb:YAG微晶玻璃发光特性的研究

高温熔制Er³⁺，Yb³⁺离子掺杂CaO-Y₂O₃-Al₂O₃-SiO₂系统玻璃，并进行微晶化处理，研究了微晶玻璃中Er³⁺离子的发光及上转换发光特性，分析了微晶玻璃上转换发光机理.结果表明：原始玻璃经热处理得到了Er,Yb:YAG微晶玻璃，微晶玻璃中Er³⁺离子在室温下⁴I_13/2→⁴I_15/2跃迁产生横盖1450—1650nm区间的超宽带荧光，荧光半高宽达180nm，这可能由于YAG微晶相中Er³⁺离子与玻璃相中残留Er³⁺离子的共同发光；Er³⁺与Yb³⁺离子局域基质声子能量的降低使微晶玻璃Er³⁺离子上转换发光强度与原始玻璃相比显著提高，绿光、红光上转换荧光强度比玻璃样品分别增强约7和3倍；微晶化后Er³⁺，Yb³⁺离子局域环境发生变化也导致微晶玻璃中Er³⁺离子绿光、红光上转换发光相对强度发生变化. 关键词： 铒 镱:钇铝石榴石 微晶玻璃 荧光光谱