Influence of V2O5 as an effective dopant on the sintering behavior and magnetic properties of NiFe2O4 ferrite ceramics

Samples with small amounts of V2O5 (0, 0.5, 1.0, 2.0, 2.5 wt%, respectively) were prepared via ball-milling and two-step sintering from commercial powders (i.e., Fe2O3, NiO and V2O5). Micro-structural features, phase transformation, sintering behavior and magnetic properties of V2O5-doped NiFe2O4 composite ceramics have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal dilatometer and vibrating sample magnetometer (VSM), respectively. Morphology and the detecting result of thermal dilatometer show that V2O5 can promote sintering process, the temperature for 2.5 wt% V2O5-doped samples to reach the maximum shrinkage rate is 59 °C lower than that of un-doped samples. With an increase of V2O5 from 0 wt% to 2.5 wt%, the apparent activation energy decreased from 813.919 kJ/mol to 298.806 kJ/mol. The early-stage synthesis process of un-doped ceramic samples and 2.5 wt% V2O5-doped samples are mainly controlled by grain boundary diffusion and volume diffusion, respectively. Increasing V2O5 content, residual magnetization ratio (Mr/Ms) and coercivity (Hc) elevate, meanwhile, saturation magnetization decreases.