The Experts below are selected from a list of 1278 Experts worldwide ranked by ideXlab platform

Takashi Takeda - One of the best experts on this subject based on the ideXlab platform.

Shi-wei Wang - One of the best experts on this subject based on the ideXlab platform.

  • microstructure and optical properties of transparent Aluminum Oxynitride ceramics by hot isostatic pressing
    Scripta Materialia, 2014
    Co-Authors: Feng Chen, Jun Wang, Fang Zhang, Hailong Zhang, Run Tian, Zhao Zhang, Jian Zhang, Shi-wei Wang
    Abstract:

    Highly transparent Aluminum Oxynitride ceramic was fabricated by presintering at 1900 °C and further sintering by hot isostatic pressing (HIP) at 1900 °C under a 190 MPa argon atmosphere. For a 4.2 mm thick specimen doped with 0.1 wt.% Y2O3–La2O3, the inline light transmittance reached 78.8% at 600 nm and 84.4% at 1084 nm, respectively. Unlike the inhomogeneous microstructure of pressureless sintered specimen (grain size ∼150 μm), which contained substructure and twinning grains, the HIPed specimen had a homogeneous and refined microstructure with average grain size of ∼45 μm.

  • fabrication of Aluminum Oxynitride γ alon transparent ceramics with modified gelcasting
    Journal of the American Ceramic Society, 2014
    Co-Authors: Jun Wang, Fang Zhang, Feng Chen, Hailong Zhang, Run Tian, Manjiang Dong, Juan Liu, Zhao Zhang, Jian Zhang, Shi-wei Wang
    Abstract:

    Transparent Aluminum Oxynitride (AlON) ceramics have been prepared through aqueous gelcasting forming technique starting from the raw materials of single phase AlON powders. The powder was specially treated for anti-hydrolysis in ethanol before the shaping technique. The surface-treated AlON powders could then be dispersed in an aqueous-organic solution to prepare stable slurries containing 35 vol% solids loading. The obtained stable slurries were subsequently casted, calcined, and pressureless sintered at 1950°C for 8 h in nitrogen atmosphere. High transparent AlON ceramics with an average grain size of 112 μm and the in-line transmittance of 81% at wavelength 1100 nm have been obtained.

  • Fabrication of Aluminum Oxynitride (γ‐AlON) Transparent Ceramics with Modified Gelcasting
    Journal of the American Ceramic Society, 2014
    Co-Authors: Jun Wang, Fang Zhang, Feng Chen, Hailong Zhang, Run Tian, Manjiang Dong, Juan Liu, Zhao Zhang, Jian Zhang, Shi-wei Wang
    Abstract:

    Transparent Aluminum Oxynitride (AlON) ceramics have been prepared through aqueous gelcasting forming technique starting from the raw materials of single phase AlON powders. The powder was specially treated for anti-hydrolysis in ethanol before the shaping technique. The surface-treated AlON powders could then be dispersed in an aqueous-organic solution to prepare stable slurries containing 35 vol% solids loading. The obtained stable slurries were subsequently casted, calcined, and pressureless sintered at 1950°C for 8 h in nitrogen atmosphere. High transparent AlON ceramics with an average grain size of 112 μm and the in-line transmittance of 81% at wavelength 1100 nm have been obtained.

  • Preparation of Aluminum Oxynitride Powders by Solid-State Reaction: Preparation of Aluminum Oxynitride Powders by Solid-State Reaction
    Journal of Inorganic Materials, 2009
    Co-Authors: Xuejian Liu, Zhengren Huang, Shi-wei Wang, Dongliang Jiang
    Abstract:

    Aluminum Oxynitride (AlON) powders were prepared by solid-state reaction processing with ¦�Al2O3 and AlN as starting materials in nitrogen atmosphere. The effects of reactive temperature, holding time, and Al2O3/AlN ratio on the resultant phase compositions were investigated systematically by XRD. In addition, the reactive mechanism was tentatively explored. The experimental results indicate that the solid-state reaction for AlON is mostly controlled by thermodynamics and the dynamic factors are also important to the reaction. The reaction can not be thoroughly processed neither only by prolonging holding time at lower reactive temperature nor only by increasing reactive temperature in a shorter holding time. Both reactive temperature and holding time are crucial to the reactive progress. By diffusing AlN into Al2O3 lattice, O-riched AlON formations begin between 1600¡䟡nd 1650¡䪠and finish at about 1750¡䬠Above 1800¡䪠O-riched AlON converts into Nª²riched AlON by further diffusing remnant AlN into Al2O3 lattice. Pure AlON is prepared by the solidª²state reaction of Al2O3 and AlN at 1950¡䟩n nitrogen atmosphere for 4h.

Jianjun Xie - One of the best experts on this subject based on the ideXlab platform.

  • photoluminescence of tb3 ce3 co doped Aluminum Oxynitride powders
    Materials Letters, 2011
    Co-Authors: Lianyun Deng, Jingxuan Lei, Ying Shi, Ting Lin, Yuying Ren, Jianjun Xie
    Abstract:

    Abstract Aluminum Oxynitride(AlON) phosphors co-doped by Tb3+ and Ce3+ were synthesized by nitridation of the precursor which was co-precipitated from Al(NO3)3 solution and nanosized carbon black at 1750 °C for 2 "hrs" in flowing nitrogen atmosphere. The obtained AlON based powders were composed of polycrystalline spinel typed particles with sizes in the range of 1–3 μm. Under an excitation of 275 nm, it was found that co-doping of Ce3+ could drastically enhance the luminescence of AlON:Tb3+ powder by energy transfer. The product with 0.5 mol% Ce3+ and 0.67 mol% Tb3+ exhibited a strong broad green emission at 540 nm. The critical quenching concentration of Tb3+ in AlON:0.5 mol% Ce3+/xmol% Tb3+ phosphor was determined to be 0.67 mol%. It was supposed that the mechanism of concentration quenching of Tb3+ in AlON:0.5 mol% Ce3+ xmol% Tb3+ phosphor was dipole–dipole interaction.

  • Photoluminescence of Tb3+/Ce3+ co-doped Aluminum Oxynitride powders
    Materials Letters, 2011
    Co-Authors: Lianyun Deng, Jingxuan Lei, Ying Shi, Ting Lin, Yuying Ren, Jianjun Xie
    Abstract:

    Abstract Aluminum Oxynitride(AlON) phosphors co-doped by Tb3+ and Ce3+ were synthesized by nitridation of the precursor which was co-precipitated from Al(NO3)3 solution and nanosized carbon black at 1750 °C for 2 "hrs" in flowing nitrogen atmosphere. The obtained AlON based powders were composed of polycrystalline spinel typed particles with sizes in the range of 1–3 μm. Under an excitation of 275 nm, it was found that co-doping of Ce3+ could drastically enhance the luminescence of AlON:Tb3+ powder by energy transfer. The product with 0.5 mol% Ce3+ and 0.67 mol% Tb3+ exhibited a strong broad green emission at 540 nm. The critical quenching concentration of Tb3+ in AlON:0.5 mol% Ce3+/xmol% Tb3+ phosphor was determined to be 0.67 mol%. It was supposed that the mechanism of concentration quenching of Tb3+ in AlON:0.5 mol% Ce3+ xmol% Tb3+ phosphor was dipole–dipole interaction.

David Horwat - One of the best experts on this subject based on the ideXlab platform.

  • From Blue to White Luminescence in Cerium-Doped Aluminum Oxynitride: Electronic Structure and Local Chemistry Perspectives
    The Journal of Physical Chemistry C, 2018
    Co-Authors: Alaa E. Giba, Philippe Pigeat, Stéphanie Bruyère, Hervé Rinnert, Flavio Soldera, Frank Mücklich, David Horwat
    Abstract:

    The excellent physical and chemical properties of Aluminum Oxynitride, Al(O)N, along with the tunable luminescence features of cerium ions (Ce) hold a promising future in white light sources based ...

  • Ultraviolet optical excitation of near infrared emission of Yb-doped crystalline Aluminum Oxynitride thin films
    Journal of Applied Physics, 2018
    Co-Authors: Alaa E. Giba, Philippe Pigeat, Stéphanie Bruyère, Hervé Rinnert, Frank Mücklich, Raúl Gago, David Horwat
    Abstract:

    Yb3+ ions hold promises for high power emission in the near infrared (NIR). Yet, relevant matrices, comprising mediators to excite Yb3+, have to be found and the optical mechanisms have to be studied in detail. The purpose of this study is to report on the optical excitation and emission mechanisms of NIR photoluminescence (PL) of Yb-doped crystalline Aluminum Oxynitride thin films prepared at room temperature using reactive magnetron sputtering. Crystal structure and chemical composition are analyzed by transmission electron microscope and Rutherford backscattering spectrometry, respectively. Photoluminescence spectroscopies are used to investigate the excitation and emission mechanisms. NIR emission at 985 nm is obtained under indirect optical excitation using the 325 nm line of a He-Cd laser, the excitation mechanism is explored by photoluminescence excitation measurement (PLE), and the fine structure of the emitted energy levels is investigated by performing PL measurements at low temperature (LTPL). PLE shows that the host defects play the role of mediators to transfer the excitation energy to Yb ions. This offers different possibilities for the development of multiple excitation channels for Yb3+. Stark splitting of the energy levels of the 2F5/2 and 2F7/2 transitions is evidenced using LTPL in the 78 to 295 K range. Electronic transitions are ascribed to experimental emission lines based on good agreement with theoretical values. Moreover, the activation energies for PL thermal quenching are determined and correspond to the energy difference between highest energy quenched lines and thermally activated “hotlines.”Yb3+ ions hold promises for high power emission in the near infrared (NIR). Yet, relevant matrices, comprising mediators to excite Yb3+, have to be found and the optical mechanisms have to be studied in detail. The purpose of this study is to report on the optical excitation and emission mechanisms of NIR photoluminescence (PL) of Yb-doped crystalline Aluminum Oxynitride thin films prepared at room temperature using reactive magnetron sputtering. Crystal structure and chemical composition are analyzed by transmission electron microscope and Rutherford backscattering spectrometry, respectively. Photoluminescence spectroscopies are used to investigate the excitation and emission mechanisms. NIR emission at 985 nm is obtained under indirect optical excitation using the 325 nm line of a He-Cd laser, the excitation mechanism is explored by photoluminescence excitation measurement (PLE), and the fine structure of the emitted energy levels is investigated by performing PL measurements at low temperature (LTPL). ...

  • From Blue to White Luminescence in Cerium-Doped Aluminum Oxynitride: Electronic Structure and Local Chemistry Perspectives C
    The Journal of Physical Chemistry, 2018
    Co-Authors: Alaa E. Giba, Philippe Pigeat, Stéphanie Bruyère, Hervé Rinnert, Flavio Soldera, Frank Mücklich, David Horwat
    Abstract:

    The excellent physical and chemical properties of Aluminum Oxynitride, Al(O)N, along with the tunable luminescence features of cerium ions (Ce) hold a promising future in white light sources based on chip technology. Manipulation of the emission color from blue to green, to yellow, and finally to white is demonstrated for the first time in Ce-doped Al(O)N thin films by tuning of the local structure, electronic structure, and film thickness. Analysis of the electronic structure by electron energy loss spectroscopy at the Ce-M₄,₅, Al-L₂,₃, O-K, and N-K edges and photoluminescence spectroscopies highlights the essential role of oxygen and postdeposition annealing in changing the valence state of Ce ions from Ce⁴⁺ (optically inactive) to Ce³⁺ (optically active) as well as the local field around Ce³⁺ and, finally, in activating excitation pathways through generation of specific defect complexes in the Oxynitride matrix.

Rongjun Xie - One of the best experts on this subject based on the ideXlab platform.