CERAMICS INTERNATIONAL
·
2022
·
IF 5.532
Yucheng Cao,Liangbin Zhang,Hongrong Mei,Zhenggang Rao,Tingfang Tian,Chunchun Li
The monoclinic diopside structured CaMgGe 2 O 6 dielectric ceramics were synthesized by the traditional solid-phase reaction method, and their microwave dielectric properties were characterized. X-ray diffraction (XRD) and Rietveld refinement revealed that CaMgGe 2 O 6 belongs to the monoclinic system of space group C2/c. SEM images showed that dense CaMgGe 2 O 6 ceramics could be formed at the optimum sintering temperature of 1300 °C. Typically, ceramic sintered at 1300 °C for 6 h possessed outstanding microwave dielectric properties with ε r ∼7.96, Q × f ∼41,280 GHz, and τ f ∼ −46.6 ppm/°C. Far-infrared spectra analysis revealed the intrinsic microwave dielectric properties of CaMgGe 2 O 6 ceramics. These findings demonstrate promising application prospects of CaMgGe 2 O 6 in microwave substrate materials.
研究领域:
材料科学
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陶瓷
·
微波工程
·
介电材料
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2023
·
IF 5.2
Sen Peng,Lei Xiao,Lianwen Deng,Jun He,Yecheng Xi,Jiahui Zhu
In this work, two novel CaASbWO 8 (A = Gd, La; named CGSWO and CLSWO) microwave dielectric ceramics were synthesized by a classical solid-state method. Remarkably, the outstanding microwave dielectric properties ( ε r = 12.97, Q×f = 45,034 GHz, and τ f = −16.29 ppm/°C) were achieved for CGSWO ceramics sintered at 1440 °C, and CLSWO ceramics sintered at 1300 °C possessed the excellent microwave dielectric properties of ε r = 9.89, Q×f = 61,326 GHz, and τ f = 0.55 ppm/°C. Bond valence, ionic polarizability, Raman spectroscopy and Phillips–Vechten–Levine (P-V-L) theory were used to study the internal lattice vibration and chemical bonds in detail, and the dielectric properties were explored from the internal factors. In comparison to the ε r , the ε theo of CGSWO was found to be consistently underestimated, whereas CLSWO exhibited a contrasting pattern. This discrepancy was primarily attributed to the rattling and compressed effects of A-site cation. According to the analysis of P-V-L theory, W-O bond played an important role in regulating the Q×f value. Moreover, the τ f values of CGSWO and CLSWO ceramics were opposite, which provided an opportunity to manufacture microwave ceramic devices with good temperature stability.
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DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2023
·
IF 5.7
Weijia Guo,Zhiyu Ma,Yutian Lu,Zhenxing Yue
High- Q and temperature-stable ceramics are indispensable in microwave engineering. However, medium-permittivity ( ε r ∼ 60, named as K60) microwave dielectric ceramics that meet the above demands are yet to be synthesized. High- Q Ba 4 Sm 9.33 Ti 16.5 Al 2 O 54 (BSTA) and Ca 0.6 Sm 0.27 Ti 0.8 Al 0.27 O 3 (CSTA) ceramics have large resonant frequency temperature coefficients ( τ f ) with opposite signs. The composites of the two are expected to have good dielectric properties , but there will be obvious diffusion when they are compounded with each other by sintering after directly mixing the raw powder, which would lead to severe deterioration in dielectric properties. In this work, the undesired diffusion can be effectively avoided by stacking two or three ceramic layers together, which are achieved by two methods named adhesive bonding and spark-plasma-sintering (SPS) cofiring. The finite element method (FEM) analysis with COMSOL Multiphysics proposed in this work can precisely predict the microwave dielectric properties of layered ceramics, helping to determine the ratio of different layers to reach near-zero τ f . The adhesive-bonded layered ceramics exhibit excellent dielectric properties: ε r = 62.2, Q × f = 21,400 GHz, and τ f = –0.7 ppm/°C. The SPS-cofired layered ceramics can be fabricated in one time, partially solving the problem of sintering mismatch between different layers, together with superior properties of ε r = 59.8, Q × f = 19,780 GHz, and τ f = –0.6 ppm/°C. These layered ceramics could fill the gap of high- Q and temperature-stable K60 microwave dielectric ceramics. The layer-stacking process and related FEM simulations can be used to design more high- Q and temperature-stable microwave dielectric ceramics and devices.
研究领域:
材料科学
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陶瓷
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微波工程
·
介电材料
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DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2023
·Vol. 107
·期 1
·223-233
·
IF 3.9
Zhenjun Qing,Huapeng Zou,Xin Zhou,Haiyan Li,An Liu,Shumin Duan,Yingxiang Li,Sen Peng
Li 2 Co 2 Mo 3 O 12 (LCMO) ceramics were synthesized using the solid-state reaction method. X-ray diffraction analysis results indicated that the sole crystalline phase present in the ceramics was LCMO, which belongs to the orthorhombic structure of the Pnma space group. The sample, which was sintered at 850°C, demonstrated outstanding microwave dielectric properties, with an ε r value of 8.95, a Q × f value of 43 200 GHz, and a τ f value of –71.3 ppm/°C. It was found that while the main factor influencing ε r was ionic polarizability, sintering density had a lesser effect on it. Furthermore, Q × f was primarily affected by relative density, and there was no significant relationship between packing fraction and this property. The higher the degree of distortion of the [Li/CoO 6 ] octahedron is, the poorer the τ f value of LCMO ceramics. Additionally, the microwave dielectric properties of LCMO ceramics were intrinsically linked to ionicity, lattice energy, bond energy, and thermal expansion coefficient of chemical bonds, with Mo–O bonds being the primary factor affecting these properties, as supported by analysis using chemical bonding theories. Mo–O bond vibration dominated the Raman spectra. Good chemical compatibility between silver and LCMO ceramics was demonstrated through our co-firing experiment.
研究领域:
材料科学
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陶瓷
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微波介质
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固态化学
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拉曼光谱
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）