High-entropy effect is a novel design strategy to optimize properties and explore novel materials. In this work, (La1/5Nd1/5Sm1/5Ho1/5Y1/5)NbO4 (5RNO) high-entropy microwave dielectric ceramics were successfully prepared in the sintering temperature range of 1210-1290 ℃ via the solid-phase reaction route, and medium-entropy (3RNO and 4RNO) ceramics were compared. The effects of entropy on crystal structure, phase transition, and dielectric performances were evaluated. Entropy increase yields a significant increase in the phase transition temperature (from monoclinic fergusonite to tetragonal scheelite structure). Optimal microwave dielectric properties were achieved in the high-entropy ceramics (5RNO) at the sintering temperature of 1270 °C for 4 h with a relative density of 98.2%, and microwave dielectric properties of εr = 19.48, Q×f = 47,770 GHz, τf = -13.50 ppm/°C. This work opens an avenue for the exploration of novel microwave dielectric materials and property optimization via entropy engineering.
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