Microwave dielectric ceramics (MWDCs) are pivotal to modern wireless communication systems, with their performance governed by three key parameters: relative dielectric constant (ε_r), Q×f value (product of quality factor Q (reciprocal dielectric loss) and frequency f), and temperature coefficient of resonant frequency (τ_f). This review systematically summarizes the recent research progress of MWDCs from five interrelated aspects. In terms of performance characterization, standardized resonant methods achieve ε_r measurement errors below 1% and a tanδ detection limit as low as 10^-5. Theoretically, frameworks from complex crystal chemistry to the recently elucidated cation rattling effect enable quantitative interpretation of dielectric behavior. In processing, the cold sintering process achieves ceramic densification below 300 °C, reducing energy consumption by over 97% in comparison with conventional sintering. For applications, these materials have been widely deployed in high-performance substrates, resonators, and filters for 5G/6G communications, with device insertion loss maintained below 1 dB. Additionally, data-driven approaches, particularly machine learning, can accurately predict key dielectric properties with a coefficient of determination (R²) higher than 0.9, accelerating the exploration and development of novel MWDCs. By integrating these perspectives, this review offers a systematic insight into the state-of-the-art progress and future development directions of MWDCs research.

Zircon ceramics have potential applications in next-generation wireless communication because of their low permittivity and adjustable temperature coefficient at microwave frequencies. However, the vast challenge of realizing ultralow dielectric loss still exists. Here, we propose a high-entropy strategy to enhance the bonding of the A-site dodecahedron in zircon and design (Nd_0.2Eu_0.2Y_0.2Ho_0.2Yb_0.2)VO₄ ceramics with a high quality factor (high Q × f, that is, low dielectric loss). The (Nd_0.2Eu_0.2Y_0.2Ho_0.2Yb_0.2)VO₄ high-entropy ceramics, which belong to the tetragonal zircon structure with the I4₁/amd space group, exhibit a low relative permittivity (ε_r = 11.55), a negative temperature coefficient of resonant frequency (τ_f = −37.3 ppm/°C), and a high Q × f of 76,400 GHz (at 12.31 GHz). The high Q × f value can be attributed to the high chemical bond strength and structural stability. Furthermore, the relationship between the crystal structure and the microwave dielectric properties of (Nd_0.2Eu_0.2Y_0.2Ho_0.2Yb_0.2)VO₄ high-entropy ceramics was analyzed through high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, far-infrared reflection spectroscopy, and chemical bond theory. This work provides an effective avenue for designing microwave dielectric materials with low loss to meet the demands of passive components.