Effect of nonequivalent doping on dielectric and microwave absorbing properties of LaFeO3-based ceramics

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Development of microwave absorption materials (MAMs) with thin thickness, high oxidation resistance and tunable effective absorbing bandwidth (EAB) is particularly urgent for practical applications but remains a great challenge. In this work, a series of novel MAMs, (La1-xSrx)FeO3/Al2O3 pseudo-binary composites were synthesized, and their electromagnetic parameters, microwave absorbing capacity and related mechanisms were revealed systematically. Attributed to appropriate attenuation coefficients and superior impedance matching, the equilibrium phase in (La0.3Sr0.7)FeO3/Al2O3 pseudo-binary composite presents the best electromagnetic wave absorption property, in which RLmin = −38dB, effective absorption bandwidth (EAB: RL＜-10 dB) is up to 2.78 GHz with a thickness of 1.5 mm and its tunable EAB is 13.22 GHz when thickness ranged from 1 mm to 3 mm, indicating its is a superior MAM. The excellent microwave absorbing properties of (La0.3Sr0.7)FeO3/Al2O3 pseudo-binary composite is derived from space charge polarization caused by plenty of heterogeneous interfaces, dipole polarization introduced by doping, and conductive loss originating from directional movement of charge carriers.