Effect of Pr 3+ doping on magnetic and dielectric properties of Ni-Zn ferrites by "one-step synthesis"

Pr ³⁺-doped Ni-Zn ferrites with a nominal composition of Ni _0.5Zn _0.5Pr _xFe _{2- x}O ₄ (where x=0-0.08) were prepared by a one-step synthesis. The magnetic and dielectric properties of the as-prepared Ni-Zn ferrites were investigated. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase in combination of a small amount of a foreign PrFeO ₃ phase. The lattice constants of the ferrites initially increased after Pr ³⁺ doping, but then became smaller with additional Pr ³⁺ doping. The addition of Pr ³⁺ resulted in a reduction of grain size and an increase of density and densification of the as-prepared samples. Magnetic measurement revealed that the saturation magnetization of the as-prepared ferrites, M_s, decreased, while the coercivity, H_c, increased with increasing substitution level, x, and the Curie temperature, T_c, kept a rather high value, fluctuating between 308 and 320 °C. Both the real and imaginary parts of permeability of the ferrites decreased slightly after Pr ³⁺ doping. However, the natural resonance frequency shifted towards higher frequency from 13.07 to 36.17 MHz after the addition of Pr ³⁺, driving the magnetic permeability to much higher frequency, reaching the highest value (36.17 MHz) when x=0.04. Introduction of Pr ³⁺ ions into the Ni-Zn ferrite reduced the values of the dielectric loss tangent, especially in the frequency range of 1-400 MHz. However, the magnitude of dielectric loss of the samples doped with different amounts of Pr ³⁺ raised little.