Crystallinity and magnetic properties dependence on sintering temperature and soaking time of mechanically alloyed nanometer-grain Ni0.5Zn0.5Fe2O4

Abstract

The separate influences of sintering temperature and soaking time on mechanically alloyed ferrites' crystallity degree and properties are reported. To understand the two influences in the case of a ferrite with the composition Ni0.5Zn0.5Fe2O4, toroids of this composition were separated into three groups for investigation of three respective and different sintering parameters. The first parameter was the sintering temperature of 500°C to 1400°C with a 100°C increment. The second parameter was the sintering temperature from 800°C to 1000°C with a 25°C increment which were believed the temperature range of magnetic phase transition. All toroidal samples were sintered for 10 hours in an ambient air atmosphere. The soaking time was the third parameter employed with prolonged soaking from 1 to 96 hours and a fixed sintering temperature of 800°C. The X-ray diffraction (XRD) results of the three parameters show that the first appearance of a single phase occurred at as low as 600°C and the intensity peaks increased as the sintering temperature and soaking time increased, yielding for the entire sintering sequence three distinct families of magnetic hysteresis loops. The density results against temperatures show almost a linear increase until 1200°C and remain relatively unchanged for 1300°C and 1400°C. The increase of XRD intensity with the sintering temperature indicates higher crystallinity and possible higher values of magnetization. From the differential scanning calorimetry (DSC) result, maximum exothermic peak appear at 960°C and the nanometer starting powders could be speculated to give high reactivity due to a high surface area. The Curie temperatures were all found to be the same i.e. 232°C.