铝酸盐长余辉材料研究进展

文章系统地介绍了铝酸盐长余辉发光材料的发展历史、发光机制以及制备方法,对近年众多的研究进行了对比分耩,展望铝酸盐长余辉材料的研究和发展趋势以及应用前景。     

Preparation of sodium aluminate from the leach liquor of diasporic bauxite in concentrated NaOH solution

A new process to produce monosodium aluminate hydrates (MAH) by fast crystallization from the leach liquor of a diasporic bauxite in concentrated NaOH solution is presented. The crystallization of MAH was carried out easily compared to the precipitation of gibbsite and the effect of agitation, initial concentration of sodium aluminate, seed amount and the presence of red mud were systematically studied in a batch crystallizer. The apparent kinetics of crystallization followed a second order rate law with an apparent activation energy for MAH crystallization of 38.0 kJ/mol which implies a surface-diffusion controlled mechanism. X-Ray diffraction and scanning electron microscopy identified the structure of MAH as Na₂O·Al₂O₃·2.5H₂O with a flake crystal morphology. The molar ratio α of Na₂O to Al₂O₃ in the MAH products was < 1.2 after a simple wash by dilute sodium aluminate.     

HfO2 Gate Dielectrics for Future Generation of CMOS Device Application

The material and electrical properties of HfO2 high-k gate dielectric are reported.In the first part,the band alignment of HfO2 and (HfO2)x(Al2O3)1-x to (100)Si substrate and their thermal stability are studied by X-ray photoelectron spectroscopy and TEM.The energy gap of (HfO2)x(Al2O3)1-x,the valence band offset,and the conduction band offset between (HfO2)x(Al2O3)1-x and the Si substrate as functions of x are obtained based on the XPS results.Our XPS results also demonstrate that both the thermal stability and the resistance to oxygen diffusion of HfO2 are improved by adding Al to form Hf aluminates.In the second part,a thermally stable and high quality HfN/HfO2 gate stack is reported.Negligible changes in equivalent oxide thickness (EOT),gate leakage,and work function (close to Si mid-gap) of HfN/HfO2 gate stack are demonstrated even after 1000℃ post-metal annealing(PMA),which is attributed to the superior oxygen diffusion barrier of HfN as well as the thermal stability of the HfN/HfO2 interface.Therefore,even without surface nitridation prior to HfO2 deposition,the EOT of HfN/HfO2 gate stack has been successfully scaled down to less than 1nm after 1000℃ PMA with excellent leakage and long-term reliability.The last part demonstrates a novel replacement gate process employing a HfN dummy gate and sub-1nm EOT HfO2 gate dielectric.The excellent thermal stability of the HfN/HfO2 gate stack enables its use in high temperature CMOS processes.The replacement of HfN with other metal gate materials with work functions adequate for n- and p-MOS is facilitated by a high etch selectivity of HfN with respect to HfO2,without any degradation to the EOT,gate leakage,or TDDB characteristics of HfO2.     

Effect of heat treatment on photoluminescence behavior of BaMgAl10O17:Eu phosphors

The blue phosphor of BaMgAl₁₀O₁₇:Eu²⁺ (BAM) powders were prepared by solid-state reaction. The thermal degradation of BAM phosphor significantly reduces the intensity of the blue emission. BAM is reduced by an amount of 50% after heating at around 800 °C for 1 h. Photoluminescence (PL) excitation and emission spectra showed that the blue emission of 450 nm peak decreased with increasing annealing temperature. The ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transition of Eu³⁺ were observed at 590 and 615 nm emission lines over 1100 °C. Electron paramagnetic resonance (EPR) spectrum also detected two signals of Eu²⁺, corresponding to g=3.7156(9) for 88 mT, and g=2.9507(9) for 133 mT. X-ray absorption near edge structure (XANES) spectrum decreased the intensity of Eu²⁺ for 6977 eV with increasing annealing temperature, while high-energy peak of Eu³⁺ for 6984 eV was increased. The combined use of X-ray and neutron data by the Rietveld refinement appears to support that the secondary phase of EuMgAl₁₁O₁₉ magnetoplumbite structure in BAM may be formed by heat treatment.     

Interface Structure and Bond Strength of Copper-Bonded Alumina Substrates

Copper-bonded alumina substrates with different interface structures were studied to elucidate their effect on the bond strength and the resistance to hydrogen embrittlement and thermal cracking. The substrates were made by bonding copper either directly to alumina using Cu-O eutectic reaction or indirectly with an interlayer of cuprous aluminate between the metal and the ceramic. The substrate with the aluminate interlayer shows somewhat lower bond strength, still adequate for its use, than the directly bonded substrate. However, the substrate with the aluminate layer has greater resistance to hydrogen embrittlement and thermal cracking. The cause of such improvement is ascribed to the porosity of the aluminate layer and the compressive stress induced in alumina.     

Formation Kinetics of Calcium Aluminates

The kinetics of formation of calcium aluminates was studied by firing the reaction mixes in the temperature range 12000° to 1460°C for reaction times from 15 to 360 min. Phases formed were determined by taking X-ray diffractograms of the samples. It was observed that all stable calcium aluminates were formed and that monocalcium aluminate (CA) grew with calcium dialuminate (CA₂) in a 1:2 reaction mix of CaO and Al₂O₃. CA reacted further with Al₂O₃ to form CA₂. The formation of CA₂ obeyed the rate law equation 1 - (1 - x )^1/3= Kt / r ². The activation energy for the system (140 kJ·mol⁻¹ (33.4 kcal · mol⁻¹)) was determined by the Arrhenius equation.     

稀土铝酸盐夜光丝的网络加工技术

对稀土铝酸盐夜光丝进行了网络加工。阐明了不同的喂入率、加工气压、加工速度对夜光丝网络加工影响的规律。对网络加工后的稀土铝酸盐夜光丝进行了小样试织，从满足夜光丝的织造要求和发光性能的角度优选了网络加工工艺参数。     

Microstructure and photoluminescence of Eu-doped Sr3Al2O6 phosphors calcined with and without H3BO3 flux

The development of highly efficient and stable red phosphors fabricated using cost-effective and simple mass-production methods is essential for applications in future displays and lighting devices. Herein, we investigate the phase formation, microstructures, and luminescence properties of Sr₃Al₂O₆:Eu powders synthesized using a solid-state reaction process. Single-phase Sr₃Al₂O₆:Eu phosphors exhibiting excellent photoluminescence with color-tunable orange-red and red colors under different excitation wavelengths were successfully synthesized. The optimal Eu doping concentration of Sr₃Al₂O₆, yielding strong photoluminescence with phase stability, was 5 at. %, with the concentration quenching point determined by systematic exploration. The addition of H₃BO₃ as a flux significantly affected the grain size and improved the emission intensity of the synthesized (Sr_0.95Eu_0.05)₃Al₂O₆ phosphors up to 12.5 wt %, while secondary phases were formed at higher flux concentrations. The photoluminescence intensities of the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions of 12.5 wt % H₃BO₃ added (Sr_0.95Eu_0.05)₃Al₂O₆ increased by 3.4 and 4.2 times compared with the flux-free powders under the 394 nm-wavelength excitation, while the decay time decreased from 7.35 to 5.40 ms. Our report of the enhanced photoluminescence intensity and shortened decay time of (Sr_0.95Eu_0.05)₃Al₂O₆ phosphors following the flux addition is promising for production of single-phase phosphors emitting multi-colors, which is needed for optical devices activated by various excitation frequencies.     

国内外耐酸性碳酸钙的研究进展

回顾了国内外碳酸钙在耐酸性处理方面的研究进展及应用。叙述了其处理方法经历了从制备耐酸性碳酸钙组合物，到对碳酸钙进行表面改性及复合的过程，并着重介绍了用磷酸盐、铝酸盐或铝盐、硅酸盐及钡盐等对碳酸钙进行表面改性或复合。     

Preparation of CuAlO2 Films by Wet Chemical Synthesis

CuAlO₂ is a delafossite-type compound and is a known p -type semiconductor. Transparent CuAlO₂ thin films were prepared using a sol–gel technique. The films with an Al/Cu atomic ratio of 1.0 consisted of CuAlO₂, Cu₂O, and CuO after heat treatment at 800°–900°C in nitrogen gas. The electrical resistivity of the film heated at 800°C was 250 Ω·cm.