Controlling structural and magnetic properties of SrFe12O19 nanoplatelets by synthesis route and calcination time

Abstract

Nanocrystalline platelets of Sr hexaferrite, SrFe12O19, were prepared by four techniques (two hydrothermal and two sol-gel techniques) and calcined at 1000 degrees C for 1, 2, 4, 8 and 16 h. The microstructure of these samples was analyzed using Rietveld refinements of high-resolution synchrotron powder x-ray diffraction data, and the obtained results were correlated with the magnetic properties obtained from vibrating sample magnetometer measurements. The calcination treatment causes the crystallites to preferentially grow along thec-axis, leading to more isotropic crystallites. Moreover, the microstructural changes induced by calcination alter the magnetic properties, yielding a higher saturation magnetization in all samples. The attained coercivity is correlated with the crystallite size along the width of the platelets. Despite the pronounced changes of the microstructure and the magnetic properties after calcination, the calcination duration has a minor effect on the properties, i.e. in most cases the steady state is obtained after 1 h. The starting material has a profound impact on the microstructural change during calcination, despite the high calcination temperature.