With the rapid development of 5G and 6G communication technologies, microwave dielectric ceramics have become essential materials widely used in microwave components such as filters, oscillators, and dielectric antennas. To meet the demands of high-frequency wireless communication, microwave dielectric ceramics should possess a low dielectric constant (εr < 15) to reduce signal transmission delay, a high quality factor (Q×f > 50,000 GHz) to achieve low dielectric loss and enhance frequency selection characteristics, and a near-zero resonant frequency temperature coefficient (τf ≈ 0 ppm/°C) to ensure the frequency stability of the device over a broad temperature range. The collaborative optimization of these properties is crucial for advancing the next generation of communications equipment, enabling high performance and reliability. High-frequency, low dielectric constant, and low-loss olivine microwave dielectric ceramics (A2BO4) have attracted significant attention due to their tunable structural and performance characteristics. However, their negative temperature coefficient of resonant frequency poses a limitation on their practical applications.
Recently, Professor Huaicheng Xiang's research team from Guilin University of Technology in China focused on the olivine-structured ceramic CaYGaO4 as the subject of their study. By incorporating the design principle that variations in bond length can enhance ion polarization, they successfully improved the τf value through controlled structural transformation from an ordered orthorhombic olivine phase to a disordered tetragonal K2NiF4-type structure. This work clarifies how ion polarization and ordered influence τf and Q×f, while also investigating the potential of CaYGaO4 as a new C-band antenna for 5G communications.
The team published their work in Journal of Advanced Ceramics on August 1, 2025.
“Studies indicate that in CaLnGaO4, a larger radius difference between Ca2+ and Ln3+ promotes A-site ordering, and high temperatures can induce a transition from the orthorhombic olivine structure to the tetragonal K2NiF4-type structure (I4/mmm). In the K2NiF4 structure, substituting Ga3+ with Al3+ forms stable CaLnAlO4 microwave dielectric ceramics with slightly higher dielectric constants (εr = 17.9–18.9) and τf values shifting from -12 to +6 ppm/°C, a rare occurrence in olivine systems. Leveraging the structural characteristics of olivine and K2NiF4 ceramics, compositional and phase structure modulation in the A2BO4 system offers the potential to achieve low εr, high Q×f, and near-zero τf .” said Huaicheng Xiang, professor at College of Physics and Electronic Information Engineering at Guilin University of Technology (China), a senior expert whose research interests focus on the field of microwave dielectric ceramic materials.
“Our team utilized XRD, HRTEM, Raman spectroscopy, dielectric temperature spectra, Rietveld refinement, and lattice energy calculations to confirm that the significant changes in dielectric properties of the CaYGa1-xAlxO4 ceramic system are primarily driven by secondary phases, ionic polarization, ion order/disorder, and chemical bond variations induced by structural evolution. Additionally, a cylindrical dielectric resonator antenna (CDRA) designed using CaYGaO4 exhibited high gain (5.36–6.15 dBi) and efficiency (>90%) in the 5.065–5.747 GHz band, offering an innovative strategy for high-performance microwave dielectric ceramics and antenna design in high-frequency 5G communications.” said Ying Tang, professor at at College of Physics and Electronic Information Engineering at Guilin University of Technology (China).
“The structural evolution is effectively applied to olivine and K2NiF4 ceramics, achieving near-zero τf. However, it is crucial to further increase their Q×f values and to lower the sintering temperature.” said Huaicheng Xiang. Exploring low-temperature sintering technology to reduce costs and adopting advanced characterization methods to deepen the understanding of phase transformation mechanisms will broaden the application of olivine ceramics in high-frequency communications for 5G and 6G technology.
Other contributors include Yang Zhou, Ning Zhang, Xiaoyu Wu, and Ying Tang from Guilin University of Technology, China; Junqi Chen from Guilin University of Aerospace Technology, China.
This work was supported by the National Natural Science Foundation of China (52462016), the Natural Science Foundation of Guangxi Zhuang Autonomous Region (2025GXNSFAA069448 and 2023GXNSFBA026076), and the Guangxi BaGui Young Scholars Funding.
About Author
Huaicheng Xiang is an associate professor in the College of Physics and Electronic Information Engineering, Guilin University of Technology. He obtained his Ph.D. in Materials Science and Engineering from Guilin University of Technology in 2019, during which time he was jointly trained at the University of Oulu in Finland for one year. From 2019 to 2021, he conducted postdoctoral research at Shenzhen University. His research work covers the fields of low-dielectric microwave dielectric ceramics, electronic information functional materials, high-entropy ceramics, and solid-state electrolytes. He has hosted one project funded by the National Natural Science Foundation of China, two by the Natural Science Foundation of Guangxi, and one by the Natural Science Foundation of Shenzhen. He has published over 100 academic papers, including more than 40 as the first or corresponding author in journals such as Journal of Advanced Ceramics, Applied Materials Today, ACS Sustainable Chemistry & Engineering, Journal of Materials Science & Technology, and Journal of the European Ceramics Society. He holds 7 authorized national invention patents.
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen. JAC’s 2024 IF is 16.6, ranking in Top 1 (1/33, Q1) among all journals in “Materials Science, Ceramics” category, and its 2024 CiteScore is 25.9 (5/130) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
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