UltrahighQ Sr1+xY2O4+x (x = 0–0.04) microwave dielectric ceramics for temperature-stable millimeter-wave dielectric resonator antennas

Abstract

Microwave dielectric ceramics should be improved to advance mobile communication technologies further. In this study, we prepared Sr1+xY2O4+x (x = 0–0.04) ceramics with nonstoichiometric Sr2+ ratios based on our previously reported SrY2O4 microwave dielectric ceramic, which has a low dielectric constant and an ultrahigh quality factor (Q value). The ceramic exhibited a 33.6% higher Q-by-frequency (Q×f) value (Q ≈ 12,500) at x = 0.02 than SrY2O4. All Sr1+xY2O4+x (x = 0–0.04) ceramics exhibited pure phase structures, although variations in crystal-plane spacings were observed. The ceramics are mainly composed of Sr–O, Y1–O, and Y2–O octahedra, with the temperature coefficient of the resonant frequency (τf) of the ceramic increasing with Y2–O octahedral distortion. The ceramic comprises uniform grains with a homogeneous elemental distribution, clear grain boundaries, and no obvious cavities at x = 0.02. The Sr1+xY2O4+x (x = 0–0.04) ceramics exhibited good microwave dielectric properties, with optimal performance observed at x = 0.02 (dielectric constant (εr) = 15.41, Q×f = 112,375 GHz, and τf = −17.44 ppm/℃). The τf value was reduced to meet the temperature-stability requirements of 5G/6G communication systems by adding CaTiO3, with Sr1.02Y2O4.02+2wt%CaTiO3 exhibiting εr = 16.14, Q×f = 51,004 GHz, and τf = 0 ppm/℃. A dielectric resonator antenna prepared using Sr1.02Y2O4.02+2wt%CaTiO3 exhibited a central frequency of 26.6 GHz, with a corresponding gain and efficiency of 3.66 dBi and 83.14%, respectively. Consequently, Sr1.02Y2O4.02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band (24.5–27.5 GHz) applications.

Keywords

• millimeter wave
• microwave dielectric ceramics
• dielectric resonator antenna
• nonstoichiometric ratio