The rapid advancement of 5G and emerging 6G communication technologies has placed unprecedented demands on the microwave dielectric ceramics that form the backbone of bandpass filters, dielectric resonator antennas, and low-loss substrates. These applications require an unusually difficult combination of properties: a low dielectric constant ( ε r ), an ultra-high quality factor ( Q×f ), and excellent temperature stability ( τ f ), ideally combined with compatibility with low-temperature co-fired ceramic (LTCC) technology. Unfortunately, these three parameters are locked in a delicate trade-off, making their simultaneous optimization one of the most formidable challenges in the field.
Among candidate material systems, vanadate-based zircon-type AVO 4 ceramics (A = trivalent rare-earth cation) are attractive because their distorted [AO 8 ] dodecahedra and rigid [VO 4 ] tetrahedra yield intrinsically low permittivity. However, conventional single-cation AVO 4 ceramics suffer from two critical drawbacks: large negative τ f values (< –30 ppm/°C) arising from strong dielectric anharmonicity, and modest Q×f values (< 50,000 GHz) caused by A-site lattice distortion and phonon damping. High-entropy strategies have recently pushed Q×f dramatically higher—the (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 )VO 4 host matrix used in this work reaches 107,200 GHz—but its τ f remains stuck at –32.7 ppm/°C.
Recently, a team led by Professor Huaicheng Xiang at Guilin University of Technology, China, has now combined configurational entropy engineering with targeted Bi 3+ doping to break this deadlock. Using a conventional solid-state reaction route, the researchers synthesized a compositional series (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 1– x Bi x VO 4 ( x = 0.05–0.9) in which Bi 3+ progressively replaces the five rare-earth cations at the A-site, driving the configurational entropy from the high-entropy regime (>1.61R) through the medium-entropy zone to a low-entropy state of only 0.49R.
The microwave dielectric properties validate this entropy engineering design. The relative permittivity rises steadily from 12.53 to 60.91 with increasing highly polarizable Bi 3+ content, while the Q×f decreases from 96,870 GHz ( x = 0.05) to 18,768 GHz ( x = 0.9), remaining far above pure scheelite BiVO₄ (~6,500 GHz) owing to entropy-stabilized lattice rigidity. Most strikingly, τ f varies non-monotonically—climbing from –11.9 ppm/°C ( x = 0.05) to a peak of +132.0 ppm/°C ( x = 0.7) before falling to –195.7 ppm/°C ( x = 0.9)—a behavior traced to competing thermal expansion, ionic polarizability, and dielectric anharmonicity effects. Consequently, two compositions achieve near-zero τ f : single-phase zircon LBV@0.1 (+8.5 ppm/°C, Q×f = 88,120 GHz) and zircon/scheelite composite LBV@0.8 (+10.7 ppm/°C), both outperforming previously reported AVO 4 -based ceramics and effectively breaking the long-standing trade-off between high Q×f and temperature stability.
The team published their work in Journal of Advanced Ceramics on October 12, 2026.
“The beauty of this strategy is that entropy reduction and Bi³⁺ doping act as two independent but synergistic knobs,” said Huaicheng Xiang, associate professor at College of Physics and Electronic Information Engineering, Guilin University of Technology. (China). “By tuning them together, we can steer the resonant-frequency temperature coefficient through zero twice within a single material family, while the high-entropy state preserves the lattice stability needed for ultra-low dielectric loss. This offers a tunable pathway to balance Q×f and temperature stability, rather than accepting the conventional compromise between them.”
“What excites us most is that the material does not force engineers to choose between low loss and temperature stability,” said Prof. Liang Fang, professor at College of Materials Science and Engineering, Guilin University of Technology (China), a senior expert whose research interests focus on the field of electronic functional ceramic materials. “With two independently tunable compositions—one single-phase zircon and one zircon/scheelite composite—both delivering near-zero τf alongside high Q×f , device designers can now select the optimum point for their specific frequency band and package architecture. That kind of compositional flexibility is exactly what industry has been asking for.”
Looking ahead, the entropy engineering paradigm demonstrated here is not limited to vanadate zircons. “The concept of steering phase evolution through a controlled entropy descent—from high-entropy stabilization to entropy-starved phase separation—provides a general materials design principle for microwave dielectrics and beyond,”Prof. Huaicheng Xiang added. The LBV@ x family, with its tunable ε r , exceptional Q×f , dual near-zero- τ f compositions, and proven LTCC and antenna compatibility, offers a promising materials platform for next-generation filters, antennas, and integrated RF modules in 5G/6G communication systems.
About Author
Dr. Huaicheng Xiang is an associate professor in the College of Physics and Electronic Information Engineering, Guilin University of Technology.
Dr. Liang Fang is a professor in the College of Materials Science and Engineering, Guilin University of Technology.
Funding
This work was supported by the National Natural Science Foundation of China (No. 52462016) and the Natural Science Foundation of Guangxi Zhuang Autonomous Region (Nos. 2025GXNSFAA069448 and 2023GXNSFBA026076).
DOI LINK: 10.26599/JAC.2026.9221395
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 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
Journal of Advanced Ceramics
Tailoring configurational entropy and phase evolution in (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)1–xBixVO4 ceramics for high-performance C-band dielectric resonator antennas
12-Oct-2026