Microwave Dielectric Ceramics

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Polycrystalline Ceramics".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 9423

Special Issue Editors

School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: microwave dielectric ceramics; ferroelectrics; LTCC; MLCC; transparent ceramics; 3D printing
College of Electronics Information, Hangzhou Dianzi University, Hangzhou 310018, China
Interests: 5G; microstrip patch antenna; WLAN applications; ceramics

Special Issue Information

Dear Colleague,

Microwave dielectric ceramics are widely used for the manufacturing of microwave substrates and components such as capacitors, resonators, filters and antennas in the field of microwave communication. To satisfy miniaturization and integration in the 5G era, low-temperature cofiring ceramics (LTCCs) and high-temperature cofiring ceramics (HTCCs) are required to achieve LTCC components/modules and HTCC substrate/packaging housing, respectively. Generally, a low permittivity can minimize the cross-coupling effect between air and dielectrics and improve signal transmission speed; a high quality factor can increase the frequency selectivity; and a near-zero temperature coefficient of the resonant frequency can ensure the stability of the frequency against temperature. Sometimes, anti-reduction characteristics of the LTCC for multi-layer ceramic capacitors (MLCCs) with base metal electrodes (BMEs, copper/nickel) are also required in order to reduce the cost. Moreover, electrical (dielectric properties, breakdown voltage, insulation resistance), mechanical (flexural strength), and thermal (coefficient of thermal expansion, thermal conductivity) properties should be considered.  

In order to better promote the development and application of microwave dielectric ceramics, this Special Issue on “Microwave Dielectric Ceramics” is being launched in Crystals. It will focus on synthesis procedures, crystal structures, and electrical/mechanical/thermal properties of microwave dielectric materials and their relationships. Original works, perspectives, and reviews for this Special Issue are all welcomed.

Dr. Wen Lei
Dr. Kaixin Song
Guest Editors

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Keywords

  • microwave dielectric properties
  • anti-reduction characteristics
  • dielectric ceramics
  • microcrystalline glass
  • glass ceramics
  • low-temperature cofiring ceramics (LTCCs)
  • multi-layer ceramic capacitors (MLCCs)
  • microwave substrate
  • microwave components and design method

Published Papers (9 papers)

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Research

11 pages, 3719 KiB  
Article
The Structure and Microwave Dielectric Properties of MgTi1−x(Mn1/3Nb2/3)xO3 Ceramics
by Huan Huang, Baoyang Li, Fanshuo Wang, Yuanming Lai and Gang Jiang
Crystals 2023, 13(7), 1050; https://doi.org/10.3390/cryst13071050 - 02 Jul 2023
Cited by 3 | Viewed by 864
Abstract
MgTi1−x(Mn1/3Nb2/3)xO3 (x = 0–0.30) ceramics were prepared via the solid-state reaction method. The phase composition, microstructure, bond characteristics, and microwave dielectric properties of MgTi1−x(Mn1/3Nb2/3)x [...] Read more.
MgTi1−x(Mn1/3Nb2/3)xO3 (x = 0–0.30) ceramics were prepared via the solid-state reaction method. The phase composition, microstructure, bond characteristics, and microwave dielectric properties of MgTi1−x(Mn1/3Nb2/3)xO3 (x = 0–0.30) were systematically investigated. The MgTi1−x(Mn1/3Nb2/3)xO3 ceramics presented an ilmenite type with an R-3 space group, and the secondary-phase MgTi2O5 only existed at x = 0 and 0.30. The introduction of (Mn1/3Nb2/3)4+ effectively suppressed the formation of the MgTi2O5 phase. The variation trend of the dielectric constant (εr) was the same as relative density. The quality factor (Qf) value was enhanced by the stable microstructure, which was caused via the lattice energy of Ti/(Mn1/3Nb2/3)-O bonds. And a high Qf value (353,000 GHz) was obtained for MgTi1−x(Mn1/3Nb2/3)xO3 (x = 0.04) ceramics sintered at 1250 °C. In addition, the introduction of Mn2+ ions with a larger ionic radius exacerbates the distortion of TiO6 octahedra, leading to significant fluctuations in the temperature coefficient of the resonance frequency (τf) value. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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11 pages, 4689 KiB  
Article
Phase Compositions and Microwave Dielectric Properties of Na1+xSrB5O9+0.5x Ceramics
by Xuepeng Lu, Peng Wu, Huimin Yang, Min Yang and Yong Zheng
Crystals 2023, 13(7), 1042; https://doi.org/10.3390/cryst13071042 - 30 Jun 2023
Viewed by 755
Abstract
Microwave dielectric ceramics composed of Na1+xSrB5O9+0.5x (0 ≤ x ≤ 0.125) were synthesized via a traditional solid-state reaction approach. The effects of non-stoichiometric Na on the crystal structures, phase compositions, chemical bond characteristics, and microwave dielectric properties of [...] Read more.
Microwave dielectric ceramics composed of Na1+xSrB5O9+0.5x (0 ≤ x ≤ 0.125) were synthesized via a traditional solid-state reaction approach. The effects of non-stoichiometric Na on the crystal structures, phase compositions, chemical bond characteristics, and microwave dielectric properties of the Na1+xSrB5O9+0.5x ceramics were systematically studied. All Na1+xSrB5O9+0.5x ceramics sintered at optimum temperatures consisted of a NaSrB5O9 solid-solution phase and a SrB2O4 phase. Appropriate excess Na could suppress the generation of the SrB2O4 phase, and the lowest content of the SrB2O4 phase was achieved at x = 0.075. The εr values of the Na1+xSrB5O9+0.5x ceramics were primarily affected by the relative density and molecular polarization. The Q × f values showed a positive correlation with the lattice energy. The τf value was correlated to the SrB2O4 phase content, bond valence, and bond energy. Typically, the Na1.075SrB5O9.0375 ceramic sintered at 825 °C possessed good microwave dielectric properties of εr = 5.61, Q × f = 31, 937 GHz, and τf = −3.09 ppm/°C, which are suitable for high-frequency, low-temperature co-fired ceramics (LTCCs) substrate applications. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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13 pages, 4713 KiB  
Article
Effects of LiF-Addition on Sintering Behavior and Dielectric Response of LaPO4 Ceramics at Microwave and Terahertz Frequency for LTCC Applications
by Hu Li, Dongfeng Wang, Kainan Zhang, Weijia Guo, Xiaoyu Xu, Yanbin Zhang, Yan Sun, Xingqi Xu, Jialun Du, Haitao Wu, Guangbin Duan and Zhenxing Yue
Crystals 2023, 13(7), 1035; https://doi.org/10.3390/cryst13071035 - 29 Jun 2023
Viewed by 851
Abstract
This paper reports on the successful preparation of LaPO4-x wt.% LiF (x = 0–5) ceramics using the traditional solid-state reaction method. The crystal structures, sintering behaviors, and dielectric response at microwave and terahertz frequencies were investigated. XRD results indicate [...] Read more.
This paper reports on the successful preparation of LaPO4-x wt.% LiF (x = 0–5) ceramics using the traditional solid-state reaction method. The crystal structures, sintering behaviors, and dielectric response at microwave and terahertz frequencies were investigated. XRD results indicate that all the diffraction peaks were attributed to LaPO4, and no secondary phase was observed. Rietveld refinement was conducted to analyze the variation of the crystal structure of LaPO4-x wt.% LiF. SEM indicates that the addition of LiF significantly decreased the grain size while increasing the apparent density of the ceramics. When x = 3, the optimum microwave dielectric properties εr = 10.03, Q × f = 81,467 GHz, and τf = −43.79 ppm/°C were achieved in LaPO4-3 wt.% LiF ceramic at 750 °C. The infrared reflectance spectrum and terahertz time-domain spectroscopy were analyzed and compared with the dielectric properties measured at microwave frequency to investigate the inherent dielectric response. The findings indicate that the dielectric constant attributed to ionic displacement polarization and oxygen vacancy is an essential factor affecting dielectric loss. Moreover, it is worth noting that the LaPO4-3 wt.% LiF ceramic demonstrates excellent compatibility with silver powders, suggesting its immense potential as a dielectric material in LTCC applications. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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14 pages, 3841 KiB  
Article
Photoluminescence and Temperature Sensing Properties of Bi3+/Sm3+ Co-Doped La2MgSnO6 Phosphor for Optical Thermometer
by Qingliang Xu, Wanqing Qian, Raz Muhammad, Xinhua Chen, Xueqing Yu and Kaixin Song
Crystals 2023, 13(7), 991; https://doi.org/10.3390/cryst13070991 - 21 Jun 2023
Cited by 2 | Viewed by 891
Abstract
The optical temperature sensor utilizing the fluorescence intensity ratio (FIR) has garnered significant attention in the past few years due to its rapid response, robust anti-interference capability, remote control feature, and other advantages. In this study, the high-temperature solid-phase approach was used to [...] Read more.
The optical temperature sensor utilizing the fluorescence intensity ratio (FIR) has garnered significant attention in the past few years due to its rapid response, robust anti-interference capability, remote control feature, and other advantages. In this study, the high-temperature solid-phase approach was used to fabricate a variety of double perovskite-structured La2MgSnO6: Bi3+, Sm3+ (LMS: Bi3+, Sm3+) phosphors. The Rietveld refinement data of XRD and the Gaussian fitting of the emission peak of LMS: 0.02Bi3+ phosphor indicated Bi3+ occupies three lattice sites. The calculation and analysis of average lifetime and energy transfer efficiency substantiated the presence of energy transfer from Bi3+ to Sm3+, with a transfer efficiency of up to 59.07%. The emission intensity of LMS: 0.02Bi3+, 0.05Sm3+ at 403 K maintains 50.2% at the condition of room temperature. The FIR fitting and calculation demonstrated that LMS: 0.02Bi3+, 0.05Sm3+ phosphor possessed good optical temperature sensitivity, with a maximum absolute sensitivity Sa-max of 0.0055 K−1 and a maximum relative sensitivity Sr-max of 0.88% K−1, demonstrating its valuable potential applications for optical temperature sensors. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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15 pages, 6688 KiB  
Article
Phase Structures and Dielectric Properties of (n + 1)SrO − nCeO2 (n = 2) Microwave Ceramic Systems with TiO2 Addition
by Qi Su, Jingjing Qu, Fei Liu, Changlai Yuan, Xiao Liu, Mingwei Su, Liufang Meng and Guohua Chen
Crystals 2023, 13(6), 955; https://doi.org/10.3390/cryst13060955 - 15 Jun 2023
Viewed by 793
Abstract
Ti4+-ion-doped (n + 1)SrO − nCeO2 (n = 2) ceramic systems were prepared with the conventional solid-state reaction method, and the effects of the phase structures and compositions, sintering behaviors, microstructures and microwave dielectric properties of these [...] Read more.
Ti4+-ion-doped (n + 1)SrO − nCeO2 (n = 2) ceramic systems were prepared with the conventional solid-state reaction method, and the effects of the phase structures and compositions, sintering behaviors, microstructures and microwave dielectric properties of these ceramic systems were investigated in detail as a function of TiO2 content. The analytical results of the XRD patterns show that the pure (n + 1)SrO − nCeO2 (n = 2) system is a composite-phase ceramic system with coexisting SrCeO3 and Sr2CeO4 phases (represented as a SrCeO3 + Sr2CeO4 system), which belong to the orthogonal structures of the Pmcn (62) and Pbam (55) space groups, respectively. For the xTiO2-(1 − x) (SrCeO3 + Sr2CeO4) (x = 0.1–0.4) ceramic samples, the secondary phase Sr2TiO4 can also be detected within the range of the investigated components. Meanwhile, the Raman spectroscopy, SEM-EDS, and HRTEM (SAED) analysis results also verified the correctness and consistency of the phase structures and compositions for all the given specimens. In addition, complex impedance spectroscopy was used to detect the conductive behavior of these compound ceramic systems, and the calculation results show that the appropriate addition of Ti4+-ions can make the SrCeO3 + Sr2CeO4 system have better thermal stability. The composition of x = 0.2 multiphase structural ceramic sample sintered at 1330 °C for 4 h has a near zero τf value of ~−4.6 ppm/°C, a moderate εr of ~40.3 and a higher Q × f~44,020 GHz (at 6.56 GHz). The relatively superior-performing ceramics developed in this work are expected to provide a promising microwave dielectric material for communication components. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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8 pages, 6333 KiB  
Article
Microwave Dielectric Properties of Li3TiO3F Oxyfluorides Ceramics
by Guoguang Yao, Jiuyan Zhao, Ya Lu, Hongkai Liu, Cuijin Pei, Qian Ding, Miao Chen, Yaming Zhang, Ding Li and Fu Wang
Crystals 2023, 13(6), 897; https://doi.org/10.3390/cryst13060897 - 31 May 2023
Cited by 10 | Viewed by 1049
Abstract
Using a solid-state reaction strategy, nominal Li3TiO3F oxyfluorides ceramics were fabricated, and its sintering behavior, microstructure, phase assemblages, as well as microwave dielectric performances were all investigated. The main phase of Li3TiO3F with cubic structures [...] Read more.
Using a solid-state reaction strategy, nominal Li3TiO3F oxyfluorides ceramics were fabricated, and its sintering behavior, microstructure, phase assemblages, as well as microwave dielectric performances were all investigated. The main phase of Li3TiO3F with cubic structures accompanied with small amounts of the LiF or Li2TiO3 secondary phase was identified by XRD analysis. SEM analysis showed that a uniform and dense microstructure was obtained for 750 °C-sintered samples. The dielectric constant (εr) and quality factor (Q × f) were found to be strongly correlated with porosity and grain size distribution, whereas the temperature coefficient of resonance frequency (τf) was mainly dominated by the phase assemblages. In particular, the 750 °C-sintered Li3TiO3F samples exhibited good microwave dielectric performances: εr = 18, Q × f = 57,300 GHz (under 9.2 GHz), τf = −43.0 ppm/°C. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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8 pages, 5334 KiB  
Article
Microwave Dielectric Properties of CaB2O4-CaSiO3 System for LTCC Applications
by Changzhi Yin, Zhengyu Zou, Mingfei Cheng, Yiyang Cai, Jiaqing Yang, Weicheng Lei, Wenzhong Lu, Xiaoqiang Song and Wen Lei
Crystals 2023, 13(5), 790; https://doi.org/10.3390/cryst13050790 - 09 May 2023
Cited by 4 | Viewed by 1280
Abstract
A novel composite ceramic with low densification temperature was fabricated using the conventional solid-state method. The XRD and Rietveld refinement results indicated that the two phases of CaB2O4 and CaSiO3 can coexist in all compositions. Furthermore, a phase transition [...] Read more.
A novel composite ceramic with low densification temperature was fabricated using the conventional solid-state method. The XRD and Rietveld refinement results indicated that the two phases of CaB2O4 and CaSiO3 can coexist in all compositions. Furthermore, a phase transition of CaSiO3 ceramic from α-phase to β-phase was observed. A dense ceramic with excellent microwave dielectric properties (εr~6.4, Q × f~75,600 GHz, and a negative τf~26.9 ppm/°C) was obtained at x = 0.5 when sintered at 925 °C at the frequency of 14.2 GHz. A good chemical compatibility between the composite ceramic and Ag electrode was improved by elemental mapping results. A patch antenna was fabricated based on the simulated result. All results indicated that the 0.5 CaB2O4 + 0.5 CaSiO3 ceramic has large application potential in the LTCC field. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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11 pages, 5761 KiB  
Article
The Influence of CaF2 Doping on the Sintering Behavior and Microwave Dielectric Properties of CaO-B2O3-SiO2 Glass-Ceramics for LTCC Applications
by Chao Dong, Hua Wang, Tingnan Yan, Jianwei Zhao, Jiwen Xu and Dawei Wang
Crystals 2023, 13(5), 748; https://doi.org/10.3390/cryst13050748 - 30 Apr 2023
Cited by 6 | Viewed by 1261
Abstract
With the rapid development of microelectronic information technology, microelectronic packaging has higher requirements in terms of integration density, signal transmission speed, and passive component integration. Low temperature co-fired ceramics (LTCC) exhibit excellent dielectric properties and low temperature sintering properties, which meets the above-mentioned [...] Read more.
With the rapid development of microelectronic information technology, microelectronic packaging has higher requirements in terms of integration density, signal transmission speed, and passive component integration. Low temperature co-fired ceramics (LTCC) exhibit excellent dielectric properties and low temperature sintering properties, which meets the above-mentioned requirements. This work investigates the effects of CaF2 doping (0–16 mol%) on the glass structure, sintering behavior, crystallization, microstructure, and microwave dielectric properties of the CaO-B2O3-SiO2 (CBS) glass-ceramic system. Glass-ceramics were prepared using the conventional melting and quenching method. The physical and chemical properties of the glass-ceramics were analyzed using various techniques including TMA, SDT, FTIR, XRD, SEM, and a network analyzer. The results indicate that CaF2 doping can effectively reduce the sintering temperature and softening temperature of CBS ceramics. It also substantially improves the densification, dielectric, and mechanical properties. The appropriate amount of CaF2-doped CBS glass-ceramics can be sintered below 800 °C with a low dielectric constant and loss at high frequency (εr < 6, tanδ < 0.02 @ 10~13 GHz). Specifically, 8 mol% CaF2 doped CBS glass-ceramics sintered at 790 °C exhibit excellent microwave dielectric and thermal properties, with εr ~ 5.92 @ 11.4 GHz, tanδ ~ 1.59 × 10−3, CTE ~ 7.76 × 10−6/°C, λ ~ 2.17 W/(m·k), which are attractive for LTCC applications. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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10 pages, 4727 KiB  
Article
Sintering Characteristics and Microwave Dielectric Properties of BaTi4O9 Ceramics with CuO–TiO2 Addition
by Haoxuan Guo, Peishu Zhu, Qingping Lin, Min Gao, Deping Tang and Xinghua Zheng
Crystals 2023, 13(4), 566; https://doi.org/10.3390/cryst13040566 - 27 Mar 2023
Cited by 3 | Viewed by 1089
Abstract
Sintering characteristics, phase evolutions, microstructures, and microwave dielectric properties have been investigated for BaTi4O9 ceramics prepared by traditional low temperature sintering using CuO–TiO2 (CT) additions as aids. The sintering temperature of BaTi4O9 ceramics was found to [...] Read more.
Sintering characteristics, phase evolutions, microstructures, and microwave dielectric properties have been investigated for BaTi4O9 ceramics prepared by traditional low temperature sintering using CuO–TiO2 (CT) additions as aids. The sintering temperature of BaTi4O9 ceramics was found to evidently reduce from 1350 °C to about 1100 °C with a very small amount of 0.5 wt% CT addition. When the CT addition increased to beyond 0.5 wt%, however, it was not expected to further lower the sintering temperature. Meantime, the secondary phases of Ba4Ti13O30, BaTiO3, and TiO2 were observed in these BaTi4O9-based ceramics when the CT content was beyond 2 wt%. With the introduction of the CT addition, the permittivity (ε) had little enhancement, and the temperature coefficient of the resonant frequency (τf) was improved to near zero. The BaTi4O9 ceramics with 0.5 wt% CT additions, sintered at 1100 °C, exhibited excellent microwave dielectric properties, such as ε = 36.9, Q × f = 23100 GHz, and τf = 2.5 ppm/°C. In addition, the densification mechanism and variations of the microwave dielectric properties have also been discussed with the crystal phase and microstructure’s evolution. Full article
(This article belongs to the Special Issue Microwave Dielectric Ceramics)
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