Tailoring configurational entropy and phase evolution in (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 1 – x Bi x VO 4 ceramics for high-performance C-band dielectric resonator antennas

Abstract

Abstract Achieving a near-zero temperature coefficient of resonant frequency (τf) while maintaining an ultra-high quality factor (Q×f) remains a critical challenge for microwave dielectric ceramics in next-generation 5G/6G communication systems. Herein, we report a configurational entropy engineering strategy that tailors the phase evolution and dielectric properties of (La0.2Ce0.2Nd0.2Sm0.2Eu0.2)1–xBixVO4 (LBV@x, x = 0.05-0.9) ceramics through controlled Bi3+ substitution. By systematically decreasing the configurational entropy from the high-entropy regime (>1.61 R) to the low-entropy regime (0.49 R), we trigger a phase transition from tetragonal zircon (I41/amd) to monoclinic scheelite (I2/b) at x > 0.7, driven by the combined effects of large ionic radius mismatch and entropy reduction. The high-entropy ceramic LBV@0.05 exhibits an exceptional Q×f of 96,870 GHz and a τf of –11.9 ppm/°C, whereas near-zero τf values of +8.5 and +10.7 ppm/°C are achieved in the single-phase zircon LBV@0.1 and the zircon-scheelite composite LBV@0.8, respectively, thereby effectively mitigating the conventional trade-off between high Q×f and temperature stability and offering a tunable pathway to balance these two critical parameters. The τf exhibits a non-monotonic dependence on Bi3+ content, transitioning from –11.9 ppm/°C (x = 0.05) to +132.0 ppm/°C (x = 0.7) and then to –195.7 ppm/°C (x = 0.9), attributed to the competing effects of linear expansion coefficient, ionic polarizability, and dielectric anharmonicity. Furthermore, a C-band dielectric resonator antenna fabricated from LBV@0.1 demonstrates a peak gain of 6.88 dBi, a simulated radiation efficiency of 95.25%, and a bandwidth of 269 MHz at 5.449 GHz, validating the practical viability of these materials.