JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Lei Li,Wen Bin Hong,Shuang Yang,Han Yan,Xiang Ming Chen
NaCl ceramics were prepared by cold sintering at room temperature with the water content varying from 0 to 10 wt%. The relative density of the NaCl ceramics first decreases rapidly from 99.3% to 95.0% with increasing the water content from 0 to 3 wt%, and it decreases slowly to 93.4% with further increasing the water content up to 10 wt%. The decrease in relative density is mainly attributed to the volume increase caused by the evaporation of the residual water in NaCl ceramic body. The dielectric constant exhibits the same tendency as the relative density, while the Qf value increases from 27,600 GHz to 49,600 GHz with increasing the water content from 0 to 4 wt%, and it does not change much for higher water content. The improved Qf value is attributed to the improved microstructure homogeneity that benefits from the fast mass transport of the water-activated dissolution-precipitation mechanism. The results clearly show that the water content should be optimized but not determined arbitrarily or empirically to achieve the good combination of high density, microstructure homogeneity and good properties. To avoid the negative effect of the residual water, NaCl ceramics were also cold-sintered at 120 °C, in which both high relative density (98.8–99.6%) and high Qf value (48,100–56,000 GHz) were obtained.
研究领域:
材料科学
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陶瓷工程
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高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2022
·
IF 6.364
Bing Liu,Ke Sha,Meng Fei Zhou,Kai Xin Song,Cheng Chao Hu,Cheng Lu
A cold sintering process is adopted to pre-densify CaF 2 ceramics from 85.7% at 300 MPa to 91.7% at 750 MPa. Subsequent post-annealings at 1000–1150 °C lead to further improvements in densification, where great enhancements of grain size and crystallinity are also observed from the scanning and transmission electron micrographs. Significant advances in Qf values are achieved in the post-annealed CaF 2 ceramics. The optimum Qf value (80,522 GHz) is achieved after cold sintering at 750 MPa and post-annealing at 1000 °C, which is three times higher than the conventional sintered one at 1000 °C (26,448 GHz). Moreover, the obtained low- ε r (5.9–6.5) of CaF 2 ceramics suggests broad application prospects in the high-band microwave communications. A microstrip patch antenna is fabricated using the CaF 2 ceramics as the substrate, which operates at 7.89 GHz in the C-band, with an S 11 of −13.4 dB, simulated high gain and efficiency of 6.41 dBi and −0.56 dB, respectively.
研究领域:
材料科学
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电子工程
✓ 已验证
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2021
·
IF 5.302
Bing Liu,Ke Sha,Ying Qiang Jia,Yu Hui Huang,Cheng Chao Hu,Lei Li,Da Wei Wang,Di Zhou,Kai Xin Song
Cold sintering is adopted to pre-densify LiF ceramics, where the relative density increases significantly from 72.1 % at 125 MPa to 88.9 % at 500 MPa. The following post-annealings at 800 °C lead to further optimizations of densification, and near-full densifications with relative densities of 95.6 % and 97.6 % are achieved at 375 and 500 MPa, respectively. Qf value increased with increasing uniaxial pressure until it reaches the maximum value of 134,050 GHz at 375 MPa, which is 1.82 times higher than that via conventional sintering (73,800 GHz). ε r and τ f are mainly determined by the relative density, and the optimum microwave dielectric properties are obtained as follows: ε r = 8.45, Qf = 134,050 GHz, τ f =–135 ppm/°C. A microstrip patch antenna is designed and fabricated using the LiF ceramic as the substrate, which gives an S11 of –20.3 dB, a simulated high efficiency of 90.5 %, and a gain of 4.25 dB at the resonant frequency of 6.81 GHz.
研究领域:
材料科学
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电子工程
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DOI
高影响因子
CERAMICS INTERNATIONAL
·
2017
·
IF 2.986
Yuanming Lai,Caiyun Hong,Lichuan Jin,Xiaoli Tang,Huaiwu Zhang,Xin Huang,Jie Li,Hua Su
In this work, a series of low-temperature-firing (1− x )Mg 2 SiO 4 – x Li 2 TiO 3 –8 wt% LiF ( x = 35–85 wt%) microwave dielectric ceramics was prepared through conventional solid state reaction. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that the Li 2 TiO 3 phase was transformed into cubic phase LiTiO 2 phase and secondary phase Li 2 TiSiO 5 . Partial substitution of Mg 2+ ions for Ti 3+ ions or Li + Ti 3+ ions increased the cell volume of the LiTiO 2 phase. The dense microstructures were obtained in low Li 2 TiO 3 content ( x ≤ 65 wt%) samples sintered at 900 °C, whereas the small quantity of pores presented in high Li 2 TiO 3 content ( x ≥ 75 wt%) samples sintered at 900 °C and low Li 2 TiO 3 content ( x = 45 wt%) sintered at 850 and 950 °C. Samples at x = 45 wt% under sintering at 900 °C for 4 h showed excellent microwave dielectric properties of ε r = 10.7, high Q × f = 237,400 GHz and near-zero τ f = − 3.0 ppm/°C. The ceramic also exhibited excellent chemical compatibility with Ag. Thus, the fabricated material could be a possible candidate for low temperature co-fired ceramic (LTCC) applications.
研究领域:
材料科学
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电子材料
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DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2025
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IF 6.2
Caidan Hou,Zhuo Wang,Jinteng Kang,Ying Xue,Zhuang Liu,Zeyu Ning,Junke Xie,Xin Li
The microwave dielectric properties of SrLa₂Al₂O₇ ceramic, specifically the quality factor ( Qf ) and temperature coefficient of resonant frequency ( τ f ), were enhanced through substituting La 3+ with Sr 2+ at the A-site and Al 3+ with Ti 4+ at the B-site. Pure-phase Sr/Ti co-substituted Sr 1+2 x La 2−2 x Al 2−2 x Ti 2 x O 7 ceramics were synthesized via solid-phase reaction route. Remarkably, at an optimal substitution level of x = 0.55, the resulting Sr 2.1 La 0.9 Al 0.9 Ti 1.1 O 7 ceramic exhibited superior microwave dielectric properties: ε r = 25.94 ± 0.32, Qf = 117,300 ± 5700 GHz ( f 0 = 6.40 GHz), τ f = 3.28 ± 0.17 ppm/°C. The increase of Qf value was highly associated with the low interlayer polarization effect caused by the small absolute value of interlayer polarization charges. The τ f value was jointly dominated by both τ ε and the bond valence of B-site bonds.
研究领域:
材料科学
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电子材料
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高影响因子
Journal of Materials Chemistry C
·
2021
·Vol. 9
·期 40
·14359-14370
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IF 7.393
Lingxia Li,Xubin Wang,Weijia Luo,Shun Wang,Tian Yang,Ji Zhou
Miniaturization, power dissipation and temperature stability are the most critical factors restricting the microwave use of ceramic-based devices. Balancing them, especially for the ceramics with high dielectric constant, is a great challenge. Herein, a new strategy by trivalent ion (Al3+ and Ga3+) co-substitution is put forward in tungsten bronze structural Ba4Nd9.33Ti18O54 ceramics for millimeter-wave metamaterials, and a nearly 40% increase in Qf values with stable temperature characteristics is obtained. The crystal symmetry, morphology and the vibration modes are characterized by XRD, EDS and Raman spectroscopy, suggesting the varied internal strain and oxygen octahedron tilt from the mismatch of different cations. The best performance of Ba4Nd9.33Ti18−x(Al0.4Ga0.6)xO54−0.5x (BNT-AGx) is observed when x is 2.4: εr = 67.71, Qf = 13 675 GHz, τf = +4.4 ppm °C−1. Considering the dispersion relationship of BNT-AGx ceramics further, the structure of BNT-AGx metamaterials is uniquely designed, and the sub-wavelength BNT-AGx blocks are also fabricated to demonstrate the frequency selection filtering function with high temperature stability at the millimeter-wave band (>30 GHz), which is of great significance to achieve some eMBB (Enhanced Mobile Broadband) scenes of 5G (the 5th Generation) technology, from a metal loaded cavity to free space.
研究领域:
材料科学
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电子工程
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高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2024
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IF 5.8
Yang Gao,Weishuang Fang,Tianyi Xie,Haiyi Peng,Xiaogang Yao,Huixing Lin
Mg 1–3 x (CoNiZn) x Ta 2 O 6 ceramics ( x = 0.00, 0.05, 0.10, 0.20, and 0.25) were synthesized by the solid-phase reaction method. The XRD and Rietveld refinement results suggest that the Mg 1–3 x (CoNiZn) x Ta 2 O 6 ceramics have a pure tri-rutile structure. (Co 1/3 Ni 1/3 Zn 1/3 ) 2+ can significantly broaden the sintering temperature range of ceramics. The chemical bonding theory reveals that the A-O bond (A = Mg, Co, Ni, or Zn) ionicity and Ta-O bond ionicity are closely related to the porosity corrected relative permittivity ( ε r -corr. ). The increase in A-O bond energy contributes to the greater stability of the AO 6 octahedron , resulting in a decrease in | τ f |. Additionally, the Raman spectroscopy reveals that there is a negative relationship between the Qf value and the full width at half maximum ( FWHM ) of the strongest peak of the A 1g mode. Correspondingly, Mg 0.4 (CoNiZn) 0.2 Ta 2 O 6 ceramic has excellent microwave dielectric properties after sintering at 1450°C for 4 h: ε r = 28.9, Qf = 91,900 GHz (at 7.4 GHz), and τ f = 44 ppm/°C. Furthermore, Mg 0.4 (CoNiZn) 0.2 Ta 2 O 6 ceramic can maintain a stable Qf value (∼ 91,000 GHz) across a broad range of sintering temperatures (150°C), which is a result of the combination of densification and FWHM . This characteristic facilitates adaptation to changes in furnace temperature in large-scale production. The strategy of multiple-element substitution to extend the sintering temperature range is expected to be applied to other ceramic systems.
研究领域:
材料科学
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陶瓷工程
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DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2024
·
IF 5.8
Mo Wei,Meng Fei Zhou,Bing Liu,Cheng Chao Hu,Yu Hua Cheng,Kai Xin Song
In this work, MgF 2 – x wt%LiF ( x = 0.5, 1.0, 2.5, 4.0, 5.0) ceramics have been prepared through the standard solid-state reaction method. X-ray diffraction patterns and scanning electron micrographs revealed the successful preparation of dense MgF 2 –LiF composite ceramics at an exceptionally low sintering temperature range of 525–600°C. The optimal microwave dielectric properties ( ε r = 5.09 ± 0.03, Qf = 100,733 ± 1646 GHz, τ f = −67.4 ± 3.3 ppm/°C) were achieved in MgF 2 –0.5 wt%LiF ceramics after sintering at 550 °C for 3 h. The present ceramics exhibited an outstanding combination of low- ε r , high Qf , and an ultra-low sintering temperature, surpassing the performance of most low-temperature-fired dielectric materials. Moreover, the theoretical Qf value, extrapolated from the fitting of infrared reflectivity spectra, was calculated to be 326,583 GHz, indicating significant potential for further Qf improvement. Additionally, the chemical compatibility with Al electrodes was confirmed, suggesting promising potential for ultra-low temperature co-fired ceramic (ULTCC) applications.
研究领域:
材料科学
·
陶瓷
·
介电材料
·
微波工程
✓ 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）