Effect of lanthanum substitution and annealing temperature on the structural and morphological properties of M-type calcium hexaferrite

Abstract

To investigate the influence of annealing temperature and lanthanum substitution on the structural properties of M-type calcium hexaferrite, we prepared unsubstituted and lanthanum-substituted Ca1-xLaxFe12O19 (x = 0.3, 0.4 and 0.5) powders by mean of sol–gel auto-combustion procedure, annealed between 800 °C and 1350 °C during 5 h in a rate of 180 °C per hour. XRD analysis showed that the M-type phase does not appear in the unsubstituted samples even with annealing at 1200 °C. The XRD patterns of the substituted samples contained peaks of the M-type phase with the presence of α-Fe2O3 as a secondary phase, the intensity of α-Fe2O3 decreased with increasing annealing temperature between 1200 °C and 1350 °C, and also as a function of lanthanum substitution concentration, which shows that the best lanthanum substitution concentration was x = 0.5. Lattice parameters of synthesized Ca0.5La0.5Fe12O19 align with literature results of various M-type hexaferrite. SEM micrographs of the Ca0.5La0.5Fe12O19 annealed at 1350 °C revealed that the mean and median crystallite size values were calculated to be 4.37 μm and 4.32 μm respectively.