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.

Low-perittivity (1–x)Ca₃(BO₃)₂–xTiO₂ (CBTO, x = 0–0.25) ceramics were fabricated via cold sintering. Phase composition was confirmed by XRD. The effects of TiO₂ doping on the dielectric properties and temperature stability (τ_f) were systematically investigated. Guided by lattice dynamics, phonon characteristics were probed using Raman and FTIR spectroscopy. Eight Raman-active and ten infrared-active modes were identified. A four-parameter semi-quantum model successfully extracted the intrinsic dielectric parameters, revealing that vibrations related to Ca²⁺ (Mode 4) contributed most significantly (21.89% to ε_r, 32% to loss). TiO₂ addition effectively tuned τ_f from −39.89 × 10⁻⁶ ℃⁻¹ towards zero. This comprehensive phonon analysis established a clear structure–property relationship. The optimal composition (x = 0.20) exhibited a balanced performance: ε_r = 10.56, Q × f = 10,896 GHz, and τ_f = −6.58 × 10⁻⁶ ℃⁻¹. To demonstrate practical utility, a 5G microstrip patch antenna was designed using this ceramic. The antenna resonated at 9.97 GHz with excellent impedance matching (S₁₁ = −49.56 dB) and a peak gain of 6.39 dBi. These results confirm CBTO ceramics as a promising candidate for temperature-stable, high-frequency applications.