Low loss and temperature-stable Y <sub>3</sub>MgAl <sub>3</sub>GeO <sub>12</sub> microwave dielectric ceramics for X-band applications
Yanjun Liu, Guoqiang He, Wenjie Zhang, Yuan Nie, Fangyi Huang, Huanfu Zhou
Abstract
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 Y<sub>3</sub>MgAl<sub>3</sub>GeO<sub>12</sub> (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<sub>r</sub></em>) of 9.86, a quality factor (<em>Q×f</em>) of 89,000 GHz, and a temperature coefficient of resonant frequency (<em>τ<sub>f</sub></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><sub>L</sub> = 9.13 ppm/°C). To attain near-zero <em>τ<sub>f</sub></em>, we added TiO<sub>2</sub> as a positive <em>τ<sub>f</sub></em> compensation agent. This strategy effectively tuned the <em>τ<sub>f</sub></em> value to within |<em>τ<sub>f</sub></em>|<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-TiO<sub>2</sub> composite demonstrated excellent impedance matching (VSWR=1.02) and high radiation efficiency (>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.