Ultralow-loss and temperature-stable microwave ceramics for C-band dielectric resonator antennas

La-substituted CaZrO3 microwave dielectric ceramics were designed to improve the balance between Q×f and τ f . Ca1–1.5 x La x ZrO3 ceramics were prepared by a solid-state reaction method and sintered in air at 1500 – 1600 °C. The optimized Ca0.925La0.05ZrO3 ceramic achieved ε r = 28.3, Q×f = 46,500 GHz, and τ f = − 3.2 ppm/°C, corresponding to a 59% Q×f increases over undoped CaZrO3 while retaining near-zero τ f . Structural and spectroscopic analyses indicate that moderate La substitution promotes densification and induces local lattice distortion associated with A-site vacancy formation. The designed dielectric resonator antenna exhibited good impedance matching at 5.203 GHz, with a radiation efficiency of 84.3%. Furthermore, the effective ionic polarizabilities were re-evaluated, yielding αCa = 1.66 Å3, αLa = 3.05 Å3 and αZr = 6.23 Å3. These results demonstrate that La substitution is an effective route for developing low-loss and temperature-stable microwave dielectric ceramics toward next-generation microwave devices.

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