双波长Pr3+掺杂12CaO·7Al2O3的光存储特性

采用化学共沉淀法制备了Pr3+掺杂的12CaO·7Al2O3(C12A7:Pr3+)材料.通过X射线衍射(XRD)、发射光谱、激发光谱、余辉衰减曲线、热释发光及光激励发光等测试手段系统研究了C12A7:Pr3+材料的微观结构和光学性质.结果表明,C12A7是一种理想的适合Pr3+掺杂的基质材料,C12A7:Pr3+具有...     

Oxygen ion conduction in 12CaO·7Al2O3: O2− conduction mechanism and possibility of O− fast conduction

12CaO·7Al₂O₃ (C12A7) with a unique nano-porous structure and free O^2? ions entrapped in sub-nanometer-sized cages is a fast oxygen-ion-conducting material. These free O^2– may be replaced by various oxygen-related species, OH^?, O^2? and O^?, by tuning the atmosphere during the heat treatment. We examined the conduction mechanism for stoichiometric C12A7 (C12A7:O^2?), in which O^2? ions exist as counter anions in sub-nanometer-sized cages, by Raman measurement of C12A7:O^2? annealed in a dry ¹⁸O₂ atmosphere. It was revealed that the primary ion conducting species is an O^2? ion which diffuses via exchange with O^2? in the cage wall. An experimental result on the sample containing O^? ions implied that O^? is more mobile than O^2? in C12A7. Ab initio calculations on the diffusion paths of O^2? and O^? ions in C12A7 supported the above experimental results.     

Blue upconversion luminescence in 12 CaO·7 Al2O3:Tm3 +/Yb3 + polycrystals

The effect of Yb^3 + concentration on the fluorescence of 12 CaO·7 Al₂O₃:Tm^3 +/Yb^3 + polycrystals is investigated. Under the excitation of 980 nm laser, the strong blue (477 nm) emission band is observed and attributed to ¹G₄ → ³H₆ of Tm^3 +. The ratio of blue to red emission increases with the increasing of Yb^3 + and remains constant at 10 mol% Yb^3 +. The pump dependence and upconversion mechanisms show that the two-photon cooperative upconversion process is responsible for the enhancement of the blue upconversion emission. The Commission Internationale de l'eclairage chromaticity coordinates (x, y) illustrate that the 12 CaO·7 Al₂O₃:1 mol% Tm^3 +/10 mol% Yb^3 + can emit high-purity blue light.     

Field-assisted sustainable O− ion emission from fluorine-substituted 12CaO·7Al2O3 with improved thermal stability

We examined the electric field-assisted thermionic emission of atomic oxygen radical anion (O^?) in a vacuum from fluorine-substituted derivatives of 12CaO·7Al₂O₃ (C12A7) with a composition of (12 ? x)CaO·7Al₂O₃·xCaF₂ (0 ≤ x ≤ 0.8). Unsubstituted C12A7 easily decomposed into 5CaO?3Al₂O₃ (C5A3) and 3CaO?Al₂O₃ (C3A) above 830 °C during the emission experiment in a vacuum. The decomposition temperature range became narrower as the amount of F^? ion substitution increased, e.g. the sample with x = 0.4 kept a single phase after the emission experiment at 900 °C. The emitted anionic species from the x = 0.4 sample were dominated by O^? ions (～ 92%) together with a small amount of O₂^? ions (～ 4%) and F^? ions (～ 4%). The absence of an O₂ gas supply to the opposite side of the emission surface led to a nearly steady co-emission of O^? ions and electrons with a ratio of < 1/1. The O₂ gas supply markedly enhanced the O^? ion emission, and suppressed the electron emission. A sustainable and high-purity O^? ion emission with a current density of 11 nA cm^? 2 was achieved at 830 °C with the supply of 40 Pa O₂ gas. The similarity in these emission features to the unsubstituted C12A7, together with the improved thermal stability demonstrates that the F^? ion-substituted C12A7 is a promising material for higher intensity O^? ion emission at higher temperatures.     

Sr-doping enhanced electrical transport and thermionic emission of single crystal 12CaO·7Al2O3 electride

Sr-doped single crystals (C_1-xS_x)12A7:e⁻ (x = 0, 0.01, 0.02, 0.03) were successfully fabricated by floating zone method. It is found that Sr-doping decreases the reduction time from 30 h to 20 h. The maximum emission current of (C_1-xS_x)12A7:e⁻ is greatly improved by 50% than that of the un-doped. The DFT calculations show Sr-doping in C12A7 contributed to the free O²⁻ in the cages spread out, leading to a short reduction time; increase the “window” between two adjacent cages that is conducive to the electrons in cages to escape. And the work function of the (C_1-xS_x)12A7:e⁻ is lower than that of C12A7:e⁻.     

K2O·CaO·4B2O3·12H2O∶Nd3+的合成及发光性能

以CaCl2、K2B4O7和Nd2O3为原料,采用易于工业化、无污染的水溶液法反应合成碱-碱土金属硼酸盐K2O·CaO·4B2O3·12H2O∶Nd3+晶体,利用X射线衍射、红外光谱、扫描电镜、荧光分光度计等现代分析测试手段,对所合成晶体进行了分析和表征.结果表明,所制备的K2O·CaO·4B2O3·12H2O∶Nd3...     

K2O·CaO·4B2O3·12H2O∶Nd3+的合成及发光性能

以CaCl2、K2B4O7和Nd2O3为原料,采用易于工业化、无污染的水溶液法反应合成碱-碱土金属硼酸盐K2O·CaO·4B2O3·12H2O∶Nd3+晶体,利用X射线衍射、红外光谱、扫描电镜、荧光分光度计等现代分析测试手段,对所合成晶体进行了分析和表征.结果表明,所制备的K2O·CaO·4B2O3·12H2O∶Nd3+晶型发育良好、形貌规整.基质本身具有上转换发光特性,K2O·CaO·4B2O3·12H2O∶Nd3+的发光强度较基质弱.当激发源为828 nm时,材料呈橙红色光.     

Luminescence and absorption of Tb3+in mo·Al2O3·B2O3·Tb2O3 glasses

Quantum yields of the green Tb luminescence for 254 nm excitation of glass compositions in the system MO·Al₂O₃· B₂O₃·Tb₂O₃ (M = Mg, Ca, Sr, Ba and Zn) were studied in relation to absorption and excitation spectra. Yields as high as 80% were observed. The Tb 4f-5d absorption maximum ranges from 218 to 232 nm, always at a longer wavelength than the glass matrix absorption. The yield strongly depends on the spectral position of the 4f-5d absorption, due to competing impurity absorption at 254 nm.     

Photoluminescence quenching in zinc oxide modified by Al2O3 and Al2O3 · CeO2 Nanopowders under proton irradiations

The photoluminescence spectra of initial ZnO powder and that modified by Al₂O₃, Al₂O₃ · CeO₂ nanopowders are investigated in the range 360–660 nm before and after 100-keV proton irradiation. It is found that the introduction of nanoparticles causes a decrease in the UV-band intensity and a change in the luminescence bands in the visual spectrum due to V _O ⁺ oxygen vacancies, O _int ^- interstitial oxygen, and V _Zn ^- zinc vacancies. Luminescence quenching in the UV and visible spectra occurs under the effect of protons. The decomposition of the spectra into elementary defects and analysis of changes in their integrated intensity during modification and irradiation of the powders are carried out.     

(CaO · Al2O3 · SiO2): Eu phosphors for violet/ultraviolet-to-white radiation conversion

(2CaO · 0.5Al₂O₃ · 5SiO₂): Eu and (CaO · 0.2Al₂O₃ · SiO₂): Eu phosphors doped with B₂O₃ in an amount of 3 wt % are obtained by direct solid-phase synthesis at 1350°C. When excited by LED radiation with a maximum at 380 nm, these phosphors emit white light with color coordinates, which are close to those in the EBU and NTSC TV standards and fall into the field of white light corresponding to light warning systems according to the International Commission on Illumination (CIE).     

Simple identification of Al2O3 and MgO·Al2O3 spinel inclusions in steel using X-ray-excited optical luminescence

Nonmetallic inclusions in steel cause problems in steel products and steel production. In particular, an analysis of Al₂O₃ and MgO·Al₂O₃ spinel inclusions is important since they are one of the most harmful inclusions. A rapid and simple analysis of nonmetallic inclusions is required as the conventional analytical methods for nonmetallic inclusions are time-consuming. In this study, we propose a simple method to identify Al₂O₃ and MgO·Al₂O₃ spinel inclusions in steels. X-ray-excited optical luminescence (XEOL) analysis was selected as a promising method because it can rapidly identify sizes, shapes, and compositions of nonmetallic inclusions and can be performed in air. A model steel sample prepared by heating a mixture of Fe, Al, and MgO powders at 1550°C in argon atmosphere was used. XEOL images of the model steel sample showed that Al₂O₃ inclusions emitted blue and red luminescences. Using a filter attached to the camera, blocking light in the wavelength region above 650 nm, only the blue luminescence of the Al₂O₃ inclusions was observed. This was implemented as the luminescences of the Al₂O₃ inclusions appeared in both blue and red regions at wavelengths of 350, 485, 695, and 750 nm; consequently, the luminescences at 695 nm and 750 nm were blocked by the filter. In contrast, MgO·Al₂O₃ spinel inclusions emitted green luminescence (peak at 520 nm), unaffected by the filter. This indicates that we can simply identify Al₂O₃ and MgO·Al₂O₃ spinel inclusions by an XEOL image in the wavelength range of 420–650 nm.     

Ag／YB12Cu3O7—x,Al／YBa2Cu3O7—x界面特性分析

利用电学测量方法结合二次离子质谱（ＳＩＭＳ）技术对金属Ａｇ与Ａｌ与ＹＢａ２Ｃｕ３Ｏ７－ｘ（ＹＢＣＯ）超导薄膜接触界面电学性质和扩散特征进行了测试分析，分析结果显示由于Ａｇ和Ａｌ具有不同的化学性质，二与ＹＢＣＯ界面的互扩散特性有明显不同，这些不同影响到接触界面的电学性质和接触窗口下ＹＢＣＯ超导性能，在Ａｇ／ＹＢＣＯ样品中，在高于３５０℃以上的温度下氧气氛中退火将引起Ａｇ和Ｏ的界面互扩散，但对ＹＢＣ     

Crystallization and conductivity of 2CaO–La2O3–5P2O5 glass–ceramic with Al2O3 addition

Al₂O₃ was added to a 2CaO–La₂O₃–5P₂O₅ metaphosphate, to replace 10% of the Ca²⁺ ions by Al³⁺, forming a phosphate with the nominal composition 1.8CaO–0.1Al₂O₃–La₂O₃–5P₂O₅. The effect of Al₂O₃ addition and heat treatment on the microstructure and conductivity of the resulting glass–ceramics was investigated by XRD, SEM, TEM, and AC impedance spectroscopy. Upon transformation from glass to glass–ceramic, conductivities increased significantly. The glasses were isochronally transformed at 700 and at 800 °C for 1 h or 5 h, in air, following heating at 3 or 10 °C/min. With Al₂O₃ addition, after a heat treatment at 700 °C, 100–300 nm nano-domains of LaP₃O₉ crystallized from the glass matrix. Annealing at 800 °C produced a further order of magnitude conductivity increase for the Al-free glass, but less so for the Al-containing glass.     

Eu（C8H7O3）3·C12N2·H2O配合物的合成与表征

合成了新的Eu(C8H7O3)3·C12H8N2·H2O配合物.并经元素分析、摩尔电导、IR、UV、1H NMR等表征,初步确定配体3-甲氧基苯甲酸以桥式双齿形式和Eu(Ⅲ)配位.     

Relaxation phenomena in Cr3+ doped Al2O3−Fe 2 57 O3 systems

Mössbauer absorption spectra have been measured for Cr³⁺ doped Al₂O₃?Fe ₂ ⁵⁷ O₃ systems for different values of the Cr³⁺ concentration at room temperature. The cross relaxation between Fe³⁺ and Cr³⁺ ions, which destroys the paramagnetic hyperfine structure of Fe⁵⁷ observed in undoped Al₂O₃?Fe ₂ ⁵⁷ O₃, is thoroughly studied. The experimental results suggest a new kind of cross-relaxation process involving three spins, i.e. two Fe³⁺.ions and one Cr³⁺. The process, though it is a higher-order one, is highly effective because it is energy-conserving.     

12CaO·7Al_2O_3∶Ce~(3+)透明陶瓷的制备及其闪烁特性研究

采用高温固相法制备了不同Ce3+掺杂浓度的12Ca O·7Al2O3(C12A7∶x%Ce3+)陶瓷样品。在350 nm紫外光激发下,样品的发射光谱呈现为主峰位于440 nm的宽带,来源于Ce3+的5d1→2F5/2和2F7/2的辐射跃迁。随着Ce3+掺杂浓度的增加,发射强度增大;当Ce3+摩尔分数超过0.7%时,有杂质相出现。为了进一步提高光致发光强度,采用自蔓延燃烧法合成了C12A7∶0.5%Ce3+陶瓷样品。在H2气氛下热处理,通过改变笼中阴离子基团的种类和数目提高了陶瓷闪烁特性(发光强度和衰减时间)。结果表明,C12A7∶Ce3+陶瓷是可应用于闪烁体的潜在材料。     

KNO3／Al2O3和K2CO3／Al2O3的强碱性研究

采用ＣＯ２－ＴＰＤ及Ｈａｍｍｅｔｔ批示剂法测定了ＫＮＯ３／Ａｌ２Ｏ３及Ｋ２ＣＯ３／Ａｌ２Ｏ３样品的碱量和碱强度。当ＫＮＯ３，Ｋ２ＣＯ３的负载量低于其单层分散阈值时，能在ＡｌＯ３均匀分布并产生强度为１８．４的强碱位；高于其单层分散阈值后则能生成强度为２７．０的超强碱位。     

Eu(C8H7O3)3·C12H8N2·H2O配合物的合成与表征

合成了新的Eu(C8H7O3)3·C12H8N2·H2O配合物.并经元素分析、摩尔电导、IR、UV、1H NMR等表征,初步确定配体3-甲氧基苯甲酸以桥式双齿形式和Eu(Ⅲ)配位.     

The role of surface hydroxils of Al2O3·xH2O in the luminescence of adsorbed fluorescein molecules

Acta physica Academiae Scientiarum Hungaricae - Producing various surface hydroxil concentrations on Al2O3 films by surface reactions it was found that there is a distinct relation between the...     

Birefringence in YA1O3∶Nd between 2–4·7 eV

The paper presents original spectra of the birefringence of the orthorhombic YAlO₃Nd single crystal in the region from 2 to 4·7 eV, describes a reflection method of null ellipsometry which was used for the measurement of the spectra and, in conclusion, makes a comparison between the measured spectra and the values predicted from the values measured over the region of lower energies 1·1 – 2·2 eV.The authors are grateful to J. Kvapil for samples preparation.