ORCID Profile
0000-0003-0652-3956
Current Organisation
University of Aberdeen
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Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7TC00965H
Abstract: The anion order of Y 4 Al 2 O 9 –Y 4 Si 2 O 7 N 2 solid solutions has been studied by the Rietveld refinement of neutron powder diffraction data. The luminescence properties of Ce 3+ doped Y 4 Al 2−2x Si 2x O 9−2x N 2x are also investigated.
Publisher: Wiley
Date: 26-06-2009
Publisher: Wiley
Date: 27-09-2010
Publisher: The Electrochemical Society
Date: 2009
DOI: 10.1149/1.3106058
Publisher: AIP Publishing
Date: 08-2008
DOI: 10.1063/1.2966717
Abstract: MgTiO 3 ceramic s le was synthesized and its Raman spectra were recorded. The Raman-active vibrational modes of MgTiO3 were calculated using first-principle calculations (density functional theory). Based on experimental data and calculation results, the Raman peaks were assigned as 225 cm−1 (Ag), 306 cm−1 (Ag), 398 cm−1 (Ag), 500 cm−1 (Ag), 715 cm−1 (Ag) and 281 cm−1 (Eg), 328 cm−1 (Eg), 353 cm−1 (Eg), 486 cm−1 (Eg), 641 cm−1 (Eg). The assignment was supported by the polarized Raman spectrum. Meanwhile, the symmetry coordinates of MgTiO3 primitive cell were analyzed and employed to expand the Raman-active modes.
Publisher: Wiley
Date: 02-07-2013
DOI: 10.1111/JACE.12429
Publisher: AIP Publishing
Date: 17-03-2014
DOI: 10.1063/1.4868226
Abstract: 1:2 B-site cation ordered Ba(Mg1/3Nb2/3)O3 ceramic was synthesized using conventional solid-state reaction at 1600 °C for 12 h. The structure parameters were obtained through Rietveld refinement of X-ray diffraction data. The Raman peak frequencies were obtained by Lorenz fitting on Raman spectrum. Four-parameter semiquantum model was used to fit the infrared (IR) reflectivity spectrum, and the fitted parameters were used to calculate the dielectric permittivity ε and dielectric loss tanδ. A total of 9 active Raman and 16 active IR modes were obtained using first-principle calculations based on density functional theory with local density approximation. All of the vibrational modes were assigned and represented by linear combinations of the symmetry coordinates deduced using group theory analysis. The Raman mode with the highest frequency A1g(4) (789 cm−1) can be described as the breathing vibration of NbO6. The IR modes Eu(1) (149 cm−1) and A2u(2) (212 cm−1), which can be described as the twisting vibrations of Ba–MgO6/Ba–NbO6 on the a–b plane and the stretching vibrations of Ba–MgO6/Ba–NbO6 along the c direction, respectively, are the dominant contributing modes to ε and tanδ. The dielectric property parameters obtained using IR spectrum fittings, first-principal calculations, and microwave measurements were compared.
Publisher: Elsevier BV
Date: 08-2012
Publisher: AIP Publishing
Date: 04-2008
DOI: 10.1063/1.2903913
Abstract: A MgTiO3 ceramic s le was synthesized by solid-state reactions and its far infrared (IR) reflection spectrum recorded. The IR-active vibrational modes of MgTiO3 were calculated using first-principle calculations and the modes were represented by linear combinations of the symmetry coordinates. Using the eigenfrequencies obtained by the density functional theory calculations as initial values, we fitted the infrared reflection spectrum using the four-parameter semiquantum (FPSQ) model and the Lorentz three-parameter classical model. The parameters (ΩjTO, ΩjLO, γjTO, γjLO in FPSQ fitting and Ωj, Sj, γj in the three-parameter model fitting) of seven of the eight modes predicted by group theory analysis were obtained. The transverse optical modes (in FPSQ) are assigned as 279cm−1 (Au), 383cm−1 (Au), 472cm−1 (Au), 673cm−1 (Au) and ∼262cm−1 (Eu), 317cm−1 (Eu), 416cm−1 (Eu), 531cm−1 (Eu). The modes Au (279cm−1), Eu (317cm−1), Au (472cm−1), and Eu (531cm−1), which contain larger components of cation vibrations, contribute most to the microwave dielectric constant and dielectric loss.
Publisher: Elsevier BV
Date: 05-2015
Publisher: American Chemical Society (ACS)
Date: 29-02-2012
DOI: 10.1021/IC202340Q
Abstract: A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa ̅3, Z = 24, and cell parameter a = 15.6593(1) Å. The structure of Sr(3)Si(2)O(4)N(2) is constructed by isolated and highly corrugated 12 rings which are composed of 12 vertex-sharing [SiO(2)N(2)] tetrahedra with bridging N and terminal O to form three-dimensional tunnels to accommodate the Sr(2+) ions. The calculated band structure shows that Sr(3)Si(2)O(4)N(2) is an indirect semiconductor with a band gap ≈ 2.84 eV, which is close to the experimental value ≈ 2.71 eV from linear extrapolation of the diffuse reflection spectrum. Sr(3-x)Si(2)O(4)N(2):xEu(2+) shows a typical emission band peaking at ~600 nm under 460 nm excitation, which perfectly matches the emission of blue InGaN light-emitting diodes. For Ce(3+)/Li(+)-codoped Sr(3)Si(2)O(4)N(2), one excitation band is in the UV range (280-350 nm) and the other in the UV blue range (380-420 nm), which matches emission of near-UV light-emitting diodes. Emission of Sr(3-2x)Si(2)O(4)N(2):xCe(3+),xLi(+) shows a asymmetric broad band peaking at ~520 nm. The long-wavelength excitation and emission of Eu(2+) and Ce(3+)/Li(+)-doped Sr(3)Si(2)O(4)N(2) make them attractive for applications in phosphor-converted white light-emitting diodes.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM13852B
Publisher: IOP Publishing
Date: 02-2013
Abstract: A new spinel compound, MgFeVO 4 , was prepared by solid-state reactions. On the basis of the Mössbauer spectrum, it can be deduced that both Fe and V in MgFeVO 4 are trivalent. Structure refinements based on X-ray and neutron diffraction data indicated that V 3+ ions are likely to occupy the octahedral site, whereas Fe 3+ and Mg 2+ ions take both octahedral and tetrahedral sites. The formula of the compound can be represented as (Mg 1- x Fe x )[Mg x Fe 1- x V]O 4 ( x =0.638). The transport measurements indicate that MgFeVO 4 is an n-type semiconductor with the hopping mechanism below 170 K and thermally activated mechanism at high temperatures. The DC and AC magnetic data show the antiferromagnetic interactions and spin glass behavior in MgFeVO 4 . The time-dependent magnetic relaxation and the exchange bias effect related to the spin glass phase are also analyzed. The curve fittings give long flipping times and large n values, indicating that strongly interacting clusters rather than in idual spins are the predominant spin glass features.
Publisher: Wiley
Date: 30-08-2007
Publisher: The Electrochemical Society
Date: 2008
DOI: 10.1149/1.2898897
Publisher: Elsevier BV
Date: 10-2013
Publisher: Elsevier BV
Date: 03-2011
Publisher: Springer Science and Business Media LLC
Date: 07-05-2008
Publisher: IOP Publishing
Date: 06-2011
Abstract: MgTiO 3 ceramics were annealed in various atmospheres of air, O 2 and N 2 at a low temperature of 800 °C and the influences of annealing on the conductivity and microwave dielectric loss were investigated. The conductivity variation with the annealing atmosphere is consistent with the defect equilibrium 2O O × ↔2V O •• + O 2 ↑+ 2e', indicating n-type conductance for MgTiO 3 . Annealing in air/O 2 is favorable for eliminating oxygen vacancies and electron defects and thus decreases the conductivity. The N 2 -annealing increases the contents of oxygen vacancies and electron defects as well as the conductivity. Annealing in air/O 2 /N 2 reduced the microwave dielectric loss irrespective of the contrary effects of air/O 2 -annealing and N 2 -annealing on the defects and conductivity, suggesting the frozen defects associated with the oxygen loss during the high-temperature sintering and the low-temperature N 2 -annealing have negligible effects on microwave dielectric loss. Other factors, such as the release of thermally induced strain, may be responsible for the reduction of microwave dielectric loss due to the low-temperature annealing in air/O 2 /N 2 .
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Xiping Jing.