EFFECT OF Al3+ DOPING ON MAGNETIC AND DIELECTRIC PROPERTIES OF Ni–Zn FERRITES BY "ONE-STEP SYNTHESIS"

Al 3+-doped Ni – Zn ferrites with composition of Ni 0.5 Zn 0.5( Fe 1-x Al x)2 O 4 (where x = 0, 0.012, 0.023, 0.035 and 0.045) were prepared by a method named "one-step synthesis." The magnetic and dielectric properties of the as-prepared Ni – Zn ferrites were investigated. X-ray diffraction data indicated that all the ferrite samples had a single-phase spinel structure. The addition of Al 3+ resulted in a reduction of the grain size, lattice constant, density, shrinkage and saturation magnetization of the as-prepared samples. The Curie temperatures, however, raised first and reduced later with increasing contents of Al 3+ in the samples, but still kept high values. Both the real and imaginary parts of permeability of ferrites decreased with increasing amount of Al 3+ doped before they reached peak value. As the applied frequency increased to higher than about 10 MHz, the real part of permeability of non-doped ferrite had already become lower than those of ferrites doped with Al 3+. Moreover, the doping of Al 3+ made their utility of magnetic permeability move to much higher frequency. The observed decreases in dielectric constants and dielectric loss tangent could be attributed to the decreased electron conductivity by substituting Fe 3+ with Al 3+ in the samples. The as-prepared high-performance soft magnetic materials prepared using such a simple and low-cost method will be much promising in high-frequency applications and industrialization.