Effect of annealing temperature on the electromagnetic properties of La0.8Sr0.2MnO3 prepared by sol–gel process

La0.8Sr0.2MnO3 (LSMO) powder was prepared using the sol–gel method and treated at different annealing temperatures (AT), and the effects of AT on the crystal structure, oxygen vacancies, magnetic, electromagnetic, and microwave absorption properties of LSMO were investigated. Our results showed that with increased AT, the lattice constant and average grain size increased while the density of oxygen vacancies gradually decreased. The bond angle of Mn–O–Mn and saturation magnetization also increased gradually when AT ≤ 1373 K, and decreased slightly when AT = 1473 K. The increase of mole ratio of Mn4+ and grain size growth also contributed to the significant improvement in electrical conductivity of LSMO, while the decreases polarization of the material weakened its dielectric properties. When the frequency range was 2–18 GHz, and AT = 1173 K, LSMO exhibited the maximum effective bandwidth, which was 4.7 GHz (13.1–17.8 GHz) when the thickness was 1.62 mm. A minimum reflection loss (RL) of − 21.4 dB was reached at 15.8 GHz. Furthermore, when T = 973 K, LSMO exhibited excellent low-frequency absorption properties. When the thickness was 2.2 mm, the effective bandwidth in the X-band was 3.2 GHz (8.65–11.85 GHz) and RL was − 46.3 dB at 10.4 GHz. This indicated that the annealing temperature was the key parameter for determine the effective working frequency band of LSMO. As a result, this work provides a reference for regulating the electromagnetic properties of LSMO, which is necessary to meet the microwave absorption requirements in different occasions.