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Di Zhou - One of the best experts on this subject based on the ideXlab platform.

  • crystal structure and microwave dielectric behaviors of scheelite structured 1 x bivo4 xla2 3moo4 0 0 x 1 0 ceramics with ultra low sintering temperature
    Journal of The European Ceramic Society, 2017
    Co-Authors: Lixia Pang, Di Zhou, Weiguo Liu, Zhenxing Yue
    Abstract:

    Abstract In the present work, a novel (1-x)BiVO4-xLa2/3MoO4 scheelite related solid solution ceramics were prepared via solid state reaction method. As revealed by X-ray diffraction data, the crystal structure changed continuously from monoclinic to tetragonal phase at x = 0.10 and then the tetragonal solid solution was kept in a wide composition range up to x = 0.70. Both the Raman and far infrared spectra supported this phenomenon. When x Value reached 0.9, the ceramic sample was found to composed of both scheelite tetragonal and monoclinic La2/3MoO4 phases. Large microwave permittivity Value between 68 ± 0.2–73 ± 0.3 can be achieved in compositions with 0.02 ≤ x ≤ 0.10 with high Qf Value about 10,000 ± 500 GHz. This series of solid solution ceramics might be candidate for both dielectric resonator and low temperature co-fired ceramic technology.

  • Phase Evolution, Phase Transition, Raman Spectra, Infrared Spectra, and Microwave Dielectric Properties of Low Temperature Firing (K0.5xBi1−0.5x)(MoxV1−x)O4 Ceramics with Scheelite Related Structure
    2016
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive R
    Abstract:

    ABSTRACT: In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic sample

  • phase composition crystal structure infrared reflectivity and microwave dielectric properties of temperature stable composite ceramics scheelite and zircon type in bivo4 yvo4 system
    Journal of Materials Chemistry C, 2015
    Co-Authors: Di Zhou, Lixia Pang, Guangsheng Pang
    Abstract:

    (1 − x)BiVO4–xYVO4 (x ≤ 0.65) ceramics were prepared using the solid state reaction method. X-ray diffraction, Raman spectra and scanning electron microscopy techniques were employed to study the phase composition and crystal structure. The ceramic samples were composed of both monoclinic scheelite and tetragonal zircon-type phases. The best microwave dielectric properties, with a permittivity ∼45, a Qf Value 14 000 GHz and a temperature coefficient of resonant frequency (TCF) +10 ppm °C−1, were obtained in the 0.81BiVO4–0.19YVO4 ceramic sintered at 870 °C for 2 h. Far-infrared spectra study showed that Bi–O oscillations dominate microwave dielectric polarizations in the (1 − x)BiVO4–xYVO4 ceramics. The (1 − x)BiVO4–xYVO4 ceramics might be potential candidates for microwave devices application and low temperature co-fired ceramic technology (LTCC).

  • microwave dielectric properties of low firing scheelite related na0 5la0 5 moo4 ceramic
    Materials Letters, 2015
    Co-Authors: Di Zhou, Huidong Xie
    Abstract:

    Abstract In this paper, the (Na 0.5 La 0.5 )MoO 4 ceramic with a scheelite structure was prepared via a solid state reaction method and its microwave dielectric properties were reported for the first time. The (Na 0.5 La 0.5 )MoO 4 ceramic sintered at 740 °C for 2 h possessed a low dielectric permittivity of 11.0, a quality factor ( Qf Value) of 25,050 GHz and a temperature coefficient of −59 ppm/ o C at 8.83 GHz. The (Na 0.5 La 0.5 )MoO 4 ceramic is chemically compatible with Ag electrode material at its sintering temperature. It can be a promising microwave dielectric material for low-temperature co-fired ceramics technology (LTCC).

  • influence of ce substitution for bi in bivo4 and the impact on the phase evolution and microwave dielectric properties
    Inorganic Chemistry, 2014
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Xi Yao, Huidong Xie, Tao Shao, Qiu Ping Wang, Clive A Randall
    Abstract:

    In the present work, the (Bi1–xCex)VO4 (x ≤ 0.6) ceramics were prepared via a solid-state reaction method and all the ceramic samples could be densified below 900 °C. From the X-ray diffraction analysis, it is found that a monoclinic scheelite solid solution can be formed in the range x ≤ 0.10. In the range 0.20 ≤ x ≤ 0.60, a composite region with both monoclinic scheelite and tetragonal zircon solid solutions was formed and the content of the zircon phase increased with the calcined or sintering temperature. The refined lattice parameters of (Bi0.9Ce0.1)VO4 are a = 5.1801(0) A, b = 5.0992(1) A, c = 11.6997(8) A, and γ = 90.346(0)° with the space group I112/b(15). The VO4 tetrahedron contracts with the substitution of Ce for Bi at the A site, and this helps to keep the specific tetrahedron chain stable in the monoclinic structure. The microwave dielectric permittivity was found to decrease linearly from 68 to about 26.6; meanwhile, the quality factor (Qf) Value increased from 8000 GHz to around 23900 GHz ...

Lixia Pang - One of the best experts on this subject based on the ideXlab platform.

  • crystal structure and microwave dielectric behaviors of scheelite structured 1 x bivo4 xla2 3moo4 0 0 x 1 0 ceramics with ultra low sintering temperature
    Journal of The European Ceramic Society, 2017
    Co-Authors: Lixia Pang, Di Zhou, Weiguo Liu, Zhenxing Yue
    Abstract:

    Abstract In the present work, a novel (1-x)BiVO4-xLa2/3MoO4 scheelite related solid solution ceramics were prepared via solid state reaction method. As revealed by X-ray diffraction data, the crystal structure changed continuously from monoclinic to tetragonal phase at x = 0.10 and then the tetragonal solid solution was kept in a wide composition range up to x = 0.70. Both the Raman and far infrared spectra supported this phenomenon. When x Value reached 0.9, the ceramic sample was found to composed of both scheelite tetragonal and monoclinic La2/3MoO4 phases. Large microwave permittivity Value between 68 ± 0.2–73 ± 0.3 can be achieved in compositions with 0.02 ≤ x ≤ 0.10 with high Qf Value about 10,000 ± 500 GHz. This series of solid solution ceramics might be candidate for both dielectric resonator and low temperature co-fired ceramic technology.

  • Phase Evolution, Phase Transition, Raman Spectra, Infrared Spectra, and Microwave Dielectric Properties of Low Temperature Firing (K0.5xBi1−0.5x)(MoxV1−x)O4 Ceramics with Scheelite Related Structure
    2016
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive R
    Abstract:

    ABSTRACT: In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic sample

  • phase composition crystal structure infrared reflectivity and microwave dielectric properties of temperature stable composite ceramics scheelite and zircon type in bivo4 yvo4 system
    Journal of Materials Chemistry C, 2015
    Co-Authors: Di Zhou, Lixia Pang, Guangsheng Pang
    Abstract:

    (1 − x)BiVO4–xYVO4 (x ≤ 0.65) ceramics were prepared using the solid state reaction method. X-ray diffraction, Raman spectra and scanning electron microscopy techniques were employed to study the phase composition and crystal structure. The ceramic samples were composed of both monoclinic scheelite and tetragonal zircon-type phases. The best microwave dielectric properties, with a permittivity ∼45, a Qf Value 14 000 GHz and a temperature coefficient of resonant frequency (TCF) +10 ppm °C−1, were obtained in the 0.81BiVO4–0.19YVO4 ceramic sintered at 870 °C for 2 h. Far-infrared spectra study showed that Bi–O oscillations dominate microwave dielectric polarizations in the (1 − x)BiVO4–xYVO4 ceramics. The (1 − x)BiVO4–xYVO4 ceramics might be potential candidates for microwave devices application and low temperature co-fired ceramic technology (LTCC).

  • influence of ce substitution for bi in bivo4 and the impact on the phase evolution and microwave dielectric properties
    Inorganic Chemistry, 2014
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Xi Yao, Huidong Xie, Tao Shao, Qiu Ping Wang, Clive A Randall
    Abstract:

    In the present work, the (Bi1–xCex)VO4 (x ≤ 0.6) ceramics were prepared via a solid-state reaction method and all the ceramic samples could be densified below 900 °C. From the X-ray diffraction analysis, it is found that a monoclinic scheelite solid solution can be formed in the range x ≤ 0.10. In the range 0.20 ≤ x ≤ 0.60, a composite region with both monoclinic scheelite and tetragonal zircon solid solutions was formed and the content of the zircon phase increased with the calcined or sintering temperature. The refined lattice parameters of (Bi0.9Ce0.1)VO4 are a = 5.1801(0) A, b = 5.0992(1) A, c = 11.6997(8) A, and γ = 90.346(0)° with the space group I112/b(15). The VO4 tetrahedron contracts with the substitution of Ce for Bi at the A site, and this helps to keep the specific tetrahedron chain stable in the monoclinic structure. The microwave dielectric permittivity was found to decrease linearly from 68 to about 26.6; meanwhile, the quality factor (Qf) Value increased from 8000 GHz to around 23900 GHz ...

  • phase evolution phase transition raman spectra infrared spectra and microwave dielectric properties of low temperature firing k0 5xbi1 0 5x moxv1 x o4 ceramics with scheelite related structure
    Inorganic Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10). (K0.5xBi1−0.5x)(MoxV1−x)O4 compositions (x = 0, 0.04, 0.08, 0.09, 0.10, 0.19, 0.28, 0.46, 0.64, 0.82, 0.85, 0.86, 0.87, 0.88, 0.91, and 1.00, denoted as KBMVx). Powders were mixed and milled for 4 h using a planetary mill (Nanjing Machine Factory, Nanjing, China) by setting

Xi Yao - One of the best experts on this subject based on the ideXlab platform.

  • Phase Evolution, Phase Transition, Raman Spectra, Infrared Spectra, and Microwave Dielectric Properties of Low Temperature Firing (K0.5xBi1−0.5x)(MoxV1−x)O4 Ceramics with Scheelite Related Structure
    2016
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive R
    Abstract:

    ABSTRACT: In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic sample

  • influence of ce substitution for bi in bivo4 and the impact on the phase evolution and microwave dielectric properties
    Inorganic Chemistry, 2014
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Xi Yao, Huidong Xie, Tao Shao, Qiu Ping Wang, Clive A Randall
    Abstract:

    In the present work, the (Bi1–xCex)VO4 (x ≤ 0.6) ceramics were prepared via a solid-state reaction method and all the ceramic samples could be densified below 900 °C. From the X-ray diffraction analysis, it is found that a monoclinic scheelite solid solution can be formed in the range x ≤ 0.10. In the range 0.20 ≤ x ≤ 0.60, a composite region with both monoclinic scheelite and tetragonal zircon solid solutions was formed and the content of the zircon phase increased with the calcined or sintering temperature. The refined lattice parameters of (Bi0.9Ce0.1)VO4 are a = 5.1801(0) A, b = 5.0992(1) A, c = 11.6997(8) A, and γ = 90.346(0)° with the space group I112/b(15). The VO4 tetrahedron contracts with the substitution of Ce for Bi at the A site, and this helps to keep the specific tetrahedron chain stable in the monoclinic structure. The microwave dielectric permittivity was found to decrease linearly from 68 to about 26.6; meanwhile, the quality factor (Qf) Value increased from 8000 GHz to around 23900 GHz ...

  • phase evolution phase transition raman spectra infrared spectra and microwave dielectric properties of low temperature firing k0 5xbi1 0 5x moxv1 x o4 ceramics with scheelite related structure
    Inorganic Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10). (K0.5xBi1−0.5x)(MoxV1−x)O4 compositions (x = 0, 0.04, 0.08, 0.09, 0.10, 0.19, 0.28, 0.46, 0.64, 0.82, 0.85, 0.86, 0.87, 0.88, 0.91, and 1.00, denoted as KBMVx). Powders were mixed and milled for 4 h using a planetary mill (Nanjing Machine Factory, Nanjing, China) by setting

  • phase transition raman spectra infrared spectra band gap and microwave dielectric properties of low temperature firing na0 5xbi1 0 5x moxv1 x o4 solid solution ceramics with scheelite structures
    Journal of Materials Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    A scheelite based structure that could host the solid solution (Na0.5xBi1−0.5x)(MoxV1−x)O4 (0.0 ≤ x ≤ 1.0) was prepared via the solid state reaction method. All the compositions can be sintered well below a temperature of 800 °C. A structural phase transition occurs from the monoclinic scheelite structure to a tetragonal scheelite structure at x = 0.10 at room temperature. This structural transition is related to a displacive ferroelastic–paraelastic phase transition. This phase transition was also confirmed by in situhigh temperature XRD and Raman studies, and a room temperature infrared spectra study. The compositions near the phase boundary possessed high dielectric permittivities (>70), and large Qf Values (>80 000 GHz) with variable temperature coefficients of frequency and capacitance. For example, a temperature stable dielectric made as a composite with compositions of x = 0.05 and x = 0.10 was designed and co-sintered at 720 °C for 2 h to produce a dielectric with a permittivity of ∼77.3, a Qf Value between 8 000 GHz–10 000 GHz, and a temperature coefficient of <±20 ppm/°C at 3.8 GHz over a temperature range of 25–110 °C. This material is a candidate for dielectric resonators and low temperature co-fired ceramics technologies. Near the phase boundary at x = 0.10 in the monoclinic phase region, the samples show strong absorption in the visible light region and we determine a band gap energy of about 2.1 eV, which means that it might also be useful as a visible light irradiation photocatalyst.

  • microwave dielectric characterization of a li3nbo4 ceramic and its chemical compatibility with silver
    Journal of the American Ceramic Society, 2008
    Co-Authors: Di Zhou, Lixia Pang, Hong Wang, Xi Yao
    Abstract:

    A Li3NbO4 ceramic has been prepared using the solid-state reaction method and well sintered at around 930°C. The best microwave dielectric properties were obtained in the ceramic sintered at 930°C for 2 h with permittivity 15.8, Qf Value about 55 009 GHz, and temperature coefficient about −49 ppm/°C. From X-ray diffraction, backscattered electron imaging, and energy-dispersive X-ray spectroscopy results of the ceramic co-fired with 20 wt% silver additive, the Li3NbO4 ceramic was found not to react with Ag at 900°C. The Li3NbO4 ceramic is a promising dielectric material for low-temperature co-fired ceramic technology.

Clive A Randall - One of the best experts on this subject based on the ideXlab platform.

  • influence of ce substitution for bi in bivo4 and the impact on the phase evolution and microwave dielectric properties
    Inorganic Chemistry, 2014
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Xi Yao, Huidong Xie, Tao Shao, Qiu Ping Wang, Clive A Randall
    Abstract:

    In the present work, the (Bi1–xCex)VO4 (x ≤ 0.6) ceramics were prepared via a solid-state reaction method and all the ceramic samples could be densified below 900 °C. From the X-ray diffraction analysis, it is found that a monoclinic scheelite solid solution can be formed in the range x ≤ 0.10. In the range 0.20 ≤ x ≤ 0.60, a composite region with both monoclinic scheelite and tetragonal zircon solid solutions was formed and the content of the zircon phase increased with the calcined or sintering temperature. The refined lattice parameters of (Bi0.9Ce0.1)VO4 are a = 5.1801(0) A, b = 5.0992(1) A, c = 11.6997(8) A, and γ = 90.346(0)° with the space group I112/b(15). The VO4 tetrahedron contracts with the substitution of Ce for Bi at the A site, and this helps to keep the specific tetrahedron chain stable in the monoclinic structure. The microwave dielectric permittivity was found to decrease linearly from 68 to about 26.6; meanwhile, the quality factor (Qf) Value increased from 8000 GHz to around 23900 GHz ...

  • phase evolution phase transition raman spectra infrared spectra and microwave dielectric properties of low temperature firing k0 5xbi1 0 5x moxv1 x o4 ceramics with scheelite related structure
    Inorganic Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10). (K0.5xBi1−0.5x)(MoxV1−x)O4 compositions (x = 0, 0.04, 0.08, 0.09, 0.10, 0.19, 0.28, 0.46, 0.64, 0.82, 0.85, 0.86, 0.87, 0.88, 0.91, and 1.00, denoted as KBMVx). Powders were mixed and milled for 4 h using a planetary mill (Nanjing Machine Factory, Nanjing, China) by setting

  • phase transition raman spectra infrared spectra band gap and microwave dielectric properties of low temperature firing na0 5xbi1 0 5x moxv1 x o4 solid solution ceramics with scheelite structures
    Journal of Materials Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    A scheelite based structure that could host the solid solution (Na0.5xBi1−0.5x)(MoxV1−x)O4 (0.0 ≤ x ≤ 1.0) was prepared via the solid state reaction method. All the compositions can be sintered well below a temperature of 800 °C. A structural phase transition occurs from the monoclinic scheelite structure to a tetragonal scheelite structure at x = 0.10 at room temperature. This structural transition is related to a displacive ferroelastic–paraelastic phase transition. This phase transition was also confirmed by in situhigh temperature XRD and Raman studies, and a room temperature infrared spectra study. The compositions near the phase boundary possessed high dielectric permittivities (>70), and large Qf Values (>80 000 GHz) with variable temperature coefficients of frequency and capacitance. For example, a temperature stable dielectric made as a composite with compositions of x = 0.05 and x = 0.10 was designed and co-sintered at 720 °C for 2 h to produce a dielectric with a permittivity of ∼77.3, a Qf Value between 8 000 GHz–10 000 GHz, and a temperature coefficient of <±20 ppm/°C at 3.8 GHz over a temperature range of 25–110 °C. This material is a candidate for dielectric resonators and low temperature co-fired ceramics technologies. Near the phase boundary at x = 0.10 in the monoclinic phase region, the samples show strong absorption in the visible light region and we determine a band gap energy of about 2.1 eV, which means that it might also be useful as a visible light irradiation photocatalyst.

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

  • Phase Evolution, Phase Transition, Raman Spectra, Infrared Spectra, and Microwave Dielectric Properties of Low Temperature Firing (K0.5xBi1−0.5x)(MoxV1−x)O4 Ceramics with Scheelite Related Structure
    2016
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive R
    Abstract:

    ABSTRACT: In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic sample

  • phase evolution phase transition raman spectra infrared spectra and microwave dielectric properties of low temperature firing k0 5xbi1 0 5x moxv1 x o4 ceramics with scheelite related structure
    Inorganic Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    In the present work, the (K0.5xBi1−0.5x)(MoxV1−x)O4 ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO4 scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1−0.19, a BiVO4 scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO4 type and the other phase is a (K,Bi)1/2MoO4 type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)1/2MoO4 tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)1/2MoO4 monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf Value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10). (K0.5xBi1−0.5x)(MoxV1−x)O4 compositions (x = 0, 0.04, 0.08, 0.09, 0.10, 0.19, 0.28, 0.46, 0.64, 0.82, 0.85, 0.86, 0.87, 0.88, 0.91, and 1.00, denoted as KBMVx). Powders were mixed and milled for 4 h using a planetary mill (Nanjing Machine Factory, Nanjing, China) by setting

  • phase transition raman spectra infrared spectra band gap and microwave dielectric properties of low temperature firing na0 5xbi1 0 5x moxv1 x o4 solid solution ceramics with scheelite structures
    Journal of Materials Chemistry, 2011
    Co-Authors: Di Zhou, Lixia Pang, Jing Guo, Hong Wang, Xi Yao, Clive A Randall
    Abstract:

    A scheelite based structure that could host the solid solution (Na0.5xBi1−0.5x)(MoxV1−x)O4 (0.0 ≤ x ≤ 1.0) was prepared via the solid state reaction method. All the compositions can be sintered well below a temperature of 800 °C. A structural phase transition occurs from the monoclinic scheelite structure to a tetragonal scheelite structure at x = 0.10 at room temperature. This structural transition is related to a displacive ferroelastic–paraelastic phase transition. This phase transition was also confirmed by in situhigh temperature XRD and Raman studies, and a room temperature infrared spectra study. The compositions near the phase boundary possessed high dielectric permittivities (>70), and large Qf Values (>80 000 GHz) with variable temperature coefficients of frequency and capacitance. For example, a temperature stable dielectric made as a composite with compositions of x = 0.05 and x = 0.10 was designed and co-sintered at 720 °C for 2 h to produce a dielectric with a permittivity of ∼77.3, a Qf Value between 8 000 GHz–10 000 GHz, and a temperature coefficient of <±20 ppm/°C at 3.8 GHz over a temperature range of 25–110 °C. This material is a candidate for dielectric resonators and low temperature co-fired ceramics technologies. Near the phase boundary at x = 0.10 in the monoclinic phase region, the samples show strong absorption in the visible light region and we determine a band gap energy of about 2.1 eV, which means that it might also be useful as a visible light irradiation photocatalyst.

  • microwave dielectric characterization of a li3nbo4 ceramic and its chemical compatibility with silver
    Journal of the American Ceramic Society, 2008
    Co-Authors: Di Zhou, Lixia Pang, Hong Wang, Xi Yao
    Abstract:

    A Li3NbO4 ceramic has been prepared using the solid-state reaction method and well sintered at around 930°C. The best microwave dielectric properties were obtained in the ceramic sintered at 930°C for 2 h with permittivity 15.8, Qf Value about 55 009 GHz, and temperature coefficient about −49 ppm/°C. From X-ray diffraction, backscattered electron imaging, and energy-dispersive X-ray spectroscopy results of the ceramic co-fired with 20 wt% silver additive, the Li3NbO4 ceramic was found not to react with Ag at 900°C. The Li3NbO4 ceramic is a promising dielectric material for low-temperature co-fired ceramic technology.

  • dielectric behavior and cofiring with silver of monoclinic bisbo4 ceramic
    Journal of the American Ceramic Society, 2008
    Co-Authors: Di Zhou, Hong Wang, Xi Yao, Lixia Pang
    Abstract:

    Pure monoclinic phase of BiSbO4 ceramic was synthesized using the solid-state reaction method. BiSbO4 ceramics can be well sintered between 960° and 1080°C. The dielectric constant of BiSbO4 ceramic was about 20.1 and dielectric loss was about 0.055–2.5 × 10−4 at 1 MHz. With the measured frequencies increasing from 100 to 900 kHz, the temperature coefficients of permittivity decreased from +224.1 to +95.9 ppm/°C. At the microwave range, the best microwave dielectric properties were obtained in the ceramic sintered at 1080°C/2 h with a permittivity of 19.3, a Qf Value of about 70 000 GHz, and a temperature coefficient of resonant frequency of −62 ppm/°C. Cofiring between BiSbO4 ceramic and 20 wt% Ag was also investigated, and it was found that after cofiring at 900°C for 5 h only very little unknown phase containing a little amount of Ag was formed and most Ag was scattered in grain boundaries.