Effects of impurity Na ions on the structural and magnetic properties of Ni-Zn-Cu ferrite powders: An improvement for chemical coprecipitation method

Ni-Zn-Cu ferrite powders with nominal composition Ni_0.4−xZn_0.6Cu_xFe₂O₄ (x=0.00-0.20) were prepared via chemical coprecipitation method. X-ray diffractometer, vibrating sample magnetometer, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry and energy dispersive spectrum were used to study the effects of impurity Na⁺ ions on the structural and magnetic properties. As a result, it was found that the impurity Na⁺ ions affect the crystalline structures and magnetic properties greatly. Moreover, the heterogeneous distribution of impurity Na⁺ ions and the formation of Na compounds retard the phase formation and the grain growth of specimens. Our study also reveals that for the chemical coprecipitation method, a second washing process introduced after drying can eliminate the impurity Na⁺ ions effectually and thus helps in the formation of single-phase structure and the growth of grains, which is very important for the improvement of magnetic properties and the preparation of ferrites via chemical coprecipitation method.