Low loss and temperature-stable Y ₃MgAl ₃GeO ₁₂ microwave dielectric ceramics for X-band applications

With the rapid deployment of 5G and the emergence of 6G technologies, the demand for high-performance microwave dielectric ceramics (MWDCs) has surged. This study developed Y₃MgAl₃GeO₁₂ (YMAG) garnet ceramics to meet 5G/6G requirements for low signal delay, low loss, and high-temperature stability. Synthesized via solid-state reaction, YMAG ceramics were characterized for phase composition, crystal structure, microstructure, and microwave dielectric properties. The results revealed that YMAG ceramics exhibited excellent microwave performance: a permittivity (<em>ε_r</em>) of 9.86, a quality factor (<em>Q×f</em>) of 89,000 GHz, and a temperature coefficient of resonant frequency (<em>τ_f</em>) of -40 ppm/°C. Far-infrared and terahertz spectroscopic analyses verified the low intrinsic dielectric loss and frequency-stable dielectric characteristics of the material in high-frequency ranges. Temperature-dependent dielectric measurements coupled with thermal expansion studies revealed outstanding stability in this material, as evidenced by its low coefficient of thermal expansion (<em>α</em>_L = 9.13 ppm/°C). To attain near-zero <em>τ_f</em>, we added TiO₂ as a positive <em>τ_f</em> compensation agent. This strategy effectively tuned the <em>τ_f</em> value to within |<em>τ_f</em>|&lt;10 ppm/°C while preserving excellent microwave dielectric performance (<em>Q×f </em>~ 43,000 GHz). Furthermore, a rectangular dielectric resonator antenna (DRA) designed with the optimized YMAG-TiO₂ composite demonstrated excellent impedance matching (VSWR=1.02) and high radiation efficiency (&gt;90%) in the X-band (10.21 GHz), validating its potential for 5G/6G applications. This work provides a novel approach to developing high-performance MWDCs for next-generation communication technologies, and emphasizes the critical role of material design and optimization in achieving superior microwave properties.