Influence of Ca-La and Cr-addition on the structure and magnetic characteristics of nanocrystalline Sr-hexaferrite powder

摘要

AbstractSr–Ca hexaferrite nanopowders with a nominal chemical composition of Sr1−xCaxFe12O19, Sr1−xCaxFe11.5Cr0.5O19and Sr0.85−xCaxLa0.15Fe11.5Cr0.5O19,with x = 0, 0.1, 0.3, and 0.5, were synthesized via sol–gel auto combustion method. Structural and phase formation of the samples were evaluated through X-ray diffraction (XRD). The XRD results indicated the Sr–Ca hexaferrites formation with the presence of α-Fe2O3as second phase, after subsequent heat treatment of the synthesized samples at 1030 °C for 2.5 h. By increasing the amount of Ca from x = 0 to x = 0.5, the intensity of second phase (α-Fe2O3) increased. Furthermore, the hexaferrite lattice constant “c” decreased while the “a” remained almost constant. Field emission scanning electron microscopy results indicated that the grains shape becomes more needle and spherical like with increasing the X content. By doping Cr3+at x = 0.5, the grains would vary from needle-like shape to platelet hexagonal. The magnetic behavior of the Sr–Ca hexaferrite samples with and without adding La3+and Cr3+ions were studied. The best result was achieved for the nanopowders with a chemical composition of Sr0.35Ca0.5La0.15Fe11.5Cr0.5O19with coercivity (HcJ) = 5474.28 Oe, saturation magnetization (Ms) = 61.16 emu/g and remnant magnetization (Mr) = 42.57 emu/g.