An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various eur...An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.展开更多
The phase constitution of a composite consisting of 12 at. pct CeO_2-3 at. pct Y_2O_3-ZrO_2/2.5 wt pct Al_2O_3 (3Y12Ce2.5Al)was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase ...The phase constitution of a composite consisting of 12 at. pct CeO_2-3 at. pct Y_2O_3-ZrO_2/2.5 wt pct Al_2O_3 (3Y12Ce2.5Al)was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase and 63.1 at. pct tetragonalphase at 1450℃. Green compacts were fabricated by cold isostatic pressing with powder synthesized by coating technique,and pressureless sintered at 1450℃. The fracture toughness and Vickers hardness, evaluated by the micro-indentation method,are 2.02 MPa·m^(1/2) and 11.395 GPa, respectively. The addition of 3 at. pct Y_2O_3 to 12 at. pct CeO_2-ZrO_2 ceramic leads todrastically decrease in toughness compared to composites without yttria stabilizer. No monoclinic phase is detected on thesudece of all the ground samples. The high content of cubic phase and lack of phase transformation can be attributed to thelow toughness based on the thermodynamic prediction.展开更多
β-GaOis an ultra-wide band-gap semiconductor with promising applications in UV optical detectors,Schottky barrier diodes, field-effect transistors and substrates for light-emitting diodes. However, the preparation of...β-GaOis an ultra-wide band-gap semiconductor with promising applications in UV optical detectors,Schottky barrier diodes, field-effect transistors and substrates for light-emitting diodes. However, the preparation of large β-GaOcrystals is undeveloped and many properties of this material have not been discovered yet. In this work, 2-inch β-GaOsingle crystals were grown by using an edge-defined film-fed growth method. The high quality of the crystal has been proved by high-resolution X-ray diffraction with 19.06 arcsec of the full width at half maximum. The electrical properties and optical properties of both the unintentionally doped and Si-doped β-GaOcrystals were investigated systematically.展开更多
This work is a study of the effect of co-doping(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)solid solution with yttria and/or ceria on the phase composition,local structure and transport properties of the crystals.The solid solu...This work is a study of the effect of co-doping(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)solid solution with yttria and/or ceria on the phase composition,local structure and transport properties of the crystals.The solid solution crystals were grown using directional melt crystallization in cold crucible.We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk,unlike yttria codoping.Ceria co-doping of the(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)crystals increases their conductivity,whereas the addition of 1 mol.%yttria tangibly reduces the conductivity.Equimolar co-doping of the(ZrO_(2))0.9(-Sc_(2_O_(3))0.1 crystals with ceria and yttria changes the conductivity but slightly.Optical spectroscopy of the local structure of the crystals identified different types of optical centers.We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals.展开更多
基金NSFC (50272063)The Sci-Tec Project of Jiangmen City Nanocomposites (2006-10 &No .2007-11)
文摘An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.
基金This work is financiallv supported by the Flanders-China bilateral project(BIL 99/10 and 02/16)the Science and Technology Committee of Shanghai Municipalityand the Commission of the.European Communities in the framework of the Growth Project“BIOGRAD”(G5RD-CT2000-00354).
文摘The phase constitution of a composite consisting of 12 at. pct CeO_2-3 at. pct Y_2O_3-ZrO_2/2.5 wt pct Al_2O_3 (3Y12Ce2.5Al)was determined by thermodynamic calculation. It is a combination of 36.9 at. pct cubic phase and 63.1 at. pct tetragonalphase at 1450℃. Green compacts were fabricated by cold isostatic pressing with powder synthesized by coating technique,and pressureless sintered at 1450℃. The fracture toughness and Vickers hardness, evaluated by the micro-indentation method,are 2.02 MPa·m^(1/2) and 11.395 GPa, respectively. The addition of 3 at. pct Y_2O_3 to 12 at. pct CeO_2-ZrO_2 ceramic leads todrastically decrease in toughness compared to composites without yttria stabilizer. No monoclinic phase is detected on thesudece of all the ground samples. The high content of cubic phase and lack of phase transformation can be attributed to thelow toughness based on the thermodynamic prediction.
文摘β-GaOis an ultra-wide band-gap semiconductor with promising applications in UV optical detectors,Schottky barrier diodes, field-effect transistors and substrates for light-emitting diodes. However, the preparation of large β-GaOcrystals is undeveloped and many properties of this material have not been discovered yet. In this work, 2-inch β-GaOsingle crystals were grown by using an edge-defined film-fed growth method. The high quality of the crystal has been proved by high-resolution X-ray diffraction with 19.06 arcsec of the full width at half maximum. The electrical properties and optical properties of both the unintentionally doped and Si-doped β-GaOcrystals were investigated systematically.
基金Financial support from the Russian Science Foundation(Project 17-79-30071“Scientifically grounded optimization of power and mass-dimensional characteristics of planar SOFC stacksdevelopment of fuel processor for highly-efficient transport and stationary power plants”)is gratefully acknowledged.A part of experimental facilities used for this research were developed in framework of Project 14.B25.31.0018 funded by the Russian Ministry of Education and Science。
文摘This work is a study of the effect of co-doping(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)solid solution with yttria and/or ceria on the phase composition,local structure and transport properties of the crystals.The solid solution crystals were grown using directional melt crystallization in cold crucible.We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk,unlike yttria codoping.Ceria co-doping of the(ZrO_(2))_(0.9)(Sc_(2)O_(3))_(0.1)crystals increases their conductivity,whereas the addition of 1 mol.%yttria tangibly reduces the conductivity.Equimolar co-doping of the(ZrO_(2))0.9(-Sc_(2_O_(3))0.1 crystals with ceria and yttria changes the conductivity but slightly.Optical spectroscopy of the local structure of the crystals identified different types of optical centers.We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals.
