Enhancement of microwave absorption properties of SrxFe12-yPr0.4o19-θ (x=0.6–1.3, y=0∼0.4) by tuning the calcination temperatures

Abstract

SrxFe12-yPr0.4O19-θ (x = 0.6–1.3, y = 0∼0.4) powders have been synthesized by the sol-gel auto-combustion method. The effect of iron and strontium ion content and calcination temperatures on the structure, magnetic properties and microwave absorption properties has been studied. The X-ray diffraction patterns of samples confirm the formation of M-type strontium ferrite and indicate that the secondary phases change with the increase of calcination temperature and strontium content, thereby affecting the structure and properties of the material. XPS and Raman spectrum analysis shows that some praseodymium ions are in the Pr4+ oxidation state, leading to the existence of Fe2+ ions and oxygen defects (Od), which can certainly affect the magnetic and dielectric properties of the materials. The VSM results show that the saturation magnetization first increases and then decreases with the increase of strontium content at different calcination temperatures and Sr0·8Fe11.8Pr0.4O19-θ has obtained the maximum saturation magnetization of 81.20 emu/g and the coercivity of 4100 Oe. Increase in strontium content not only promotes the reaction, but also generates a second phase FePrzSr1-zO3-δ, increasing the dielectric and magnetic losses of the materials. The maximum reflection loss reaches −66.77 dB and the maximum effective absorption bandwidth is 4.76 GHz. Therefore, on the one hand, the valence state changes of some praseodymium ions result in the generation of Fe2+ ions and oxygen vacancies, thereby increasing dielectric and magnetic losses. On the other hand, the change of the second phases also affects the absorption performance of the material. ɑ-Fe2O3 is not conducive to improving magnetic and absorption properties, and PrFeO3 may improve magnetic properties. Perovskite type PrzSr1-zFeO3-δ has a large number of ion valence state changes inside, leading to increased dielectric and magnetic losses, which is beneficial for improving the absorption performance of the materials.