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.

High-performance dielectric antennas have pursued a high quality factor (Q×f) for microwave ceramics. Nevertheless, the cross-laboratory inconsistency in reported Q×f would confuse the invention of materials systems, owing to divergent preparation and measurement protocols. Herein, based on a self-consistent dataset, an interpretable machine learning framework is proposed to unveil the structure–property relationship and consequently guide the compositional design of candidate microwave ceramic Li₄SrCaSi₂O₈. Through feature engineering, nine critical features are identified, in which the Si/Li atomic mass ratio (Si/Li-AW), Si/Sr ionic radius ratio (Si/Sr-IR), and total electronegativity of cations (TEC) are found to be predominant. Interpretability technologies further reveal that a higher Si/Li-AW coupled with lower Si/Sr-IR and TEC is conducive to the increase in the Q×f value for the chosen decision tree (DT) model. Guided by these insights, Sn⁴⁺-doped microwave ceramic Li₄SrCaSi_1.98Sn_0.02O₈ is created with a Q×f value up to 83,526 GHz, the origin of which is elucidated by P–V–L theory combined with first-principles calculations and infrared spectroscopy. Such an optimized material is ultimately verified by a microstrip patch antenna with a high radiation efficiency of 81.12% and a gain of 5.94 dB in the C-band.

Pb(Zr,Ti)O₃-based ceramics are the mainstream materials for commercial multilayer piezoelectric ceramic actuators, but to date, large strains at low electric fields have not been well solved. Herein, 0.95Pb(Zr_0.56Ti_0.44)O₃–0.05(Bi_0.5Na_0.5)TiO₃–xBaZrO₃ (PZT–BNT–xBZ) ceramics with efficient ferroelectric domain wall motion were designed and realized by reducing lattice distortion and changing the domain structure. It is found that the introduction of BaZrO₃ (BZ) weakens the tetragonal phase distortion of PZT, contributing to a reduction in the mechanical stress that impedes the migration of domain walls. Moreover, the domain structures could be modified by adjusting the BZ content, where short and broad striped domains are constructed with high amplitude characteristics to enhance the domain wall motion. A large strain of 0.39% is accordingly achieved at an electric field as low as 40 kV/cm for the sample with x = 0.03, accompanied by excellent temperature stability over the temperature range of 30–210 °C. This study delves into the synergistic effects of reducing lattice distortion and changing domain structure on domain wall motion and provides an effective strategy to improve the strain of PZT-based piezoelectric ceramics.

In this study, tri-rutile type Mg_0.5Ti_0.5TaO₄ ceramics were synthesized, where the structure–property relationship, especially the structural configuration and intrinsic dielectric origin of Mg_0.5Ti_0.5TaO₄ ceramics, and the low-firing characteristics were studied. It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis, the selected area electron diffraction (SAED), and the high-resolution transmission electron microscopy (HRTEM) along the [110] zone axis. With the increase in sintering temperature, the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_0.5Ti_0.5TaO₄ ceramics. Intrinsically, theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values, indicating the importance of structural features to dielectric properties. Furthermore, a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_0.5Ti_0.5TaO₄ ceramics, where 2–4 wt% Li₂O–MgO–ZnO–B₂O₃–SiO₂ (LMZBS) glass frit was adopted to reduce the suitable temperature from 1275 to 1050 ℃ without significantly deteriorating the microwave dielectric characteristics. Specifically, Mg_0.5Ti_0.5TaO₄ ceramics containing 2 wt% glass addition sintered at 1050 ℃ for 4 h possess excellent microwave dielectric properties: dielectric constant (ε_r) = 44.3, quality factor multiplied by resonant frequency (Q×f) = 23,820 GHz (f = 6.2 GHz), and the temperature coefficient of resonant frequency (τ_f) = 123.2 ppm/℃.