Low‐temperature synthesis of single‐domain Sr‐hexaferrite particles by solid‐state reaction route

Abstract

Sr‐hexaferrite particles have been synthesized by conventional solid‐state reaction route at low temperatures by boron addition that is used as an inhibitor for crystal growth. The effect of boron concentration on the structural, magnetic and electrical properties of Sr‐hexaferrite particles are investigated by X‐ray crystallography, scanning electron microscopy, magnetization and conductivity measurements. Saturation magnetization of Sr‐hexaferrite increases up to 1 wt% boron addition, while coercivity becomes maximum with a boron amount of 2 wt%. Then, both magnetic parameters start to decrease with higher boron concentrations. Single‐domain and single‐phase powders have been obtained in the sample containing 1 wt% of boron that is sintered at 1050 °C. Impedance spectroscopies reveal that the dc conductivity increases tremendously with boron addition, while the ac conductivity increases with elevated temperature. The ac conductivity obeys roughly the power law of angular frequency in which tendencies change with temperature at low and medium temperature. Furthermore, higher contents of the dopant over approximately 2.0 wt% cause its temperature independency at higher frequencies. These are due to the grain size and secondary phase of hexaferrites that increases with the increase in boron amount.

Hopkinson effect and temperature‐dependent dielectric properties of single domain SrFe12O19 particles

“…The observed ferrimagnetism is only due to the Fe 3þ ions arranged in five non-equivalent crystallographic sites with different coordination and spin orientations [3]. [13] and comparable to the values obtained using other chemical methods [1,11,23]. But these values are low compared to the reports on milling and subsequent sintering process [15][16][17].…”

“…In these methods, fine particles were obtained by the mixing of precursors in a liquid medium on ionic level, followed by heat treatment. The reports on the use of solid state method for the preparation of strontium hexagonal ferrite describe its formation at high temperature (1473 K) [13], which leads to the growth of bigger particles. In some reports [14], the sintered sample was subjected to milling process in order to reduce its particle size.…”

The Conductivity and Dielectric Properties of Neobium Substituted Sr-Hexaferrites

“…V-shape curves for the rest become expanded when the substitution ratio is 0.01 and 0.06. Thus, this can be attributed to any influential dipoles oriented by the alternative electric field as discussed in the literature [32,33,34].…”

Effect of Mechanical Load on Defects Level in Soft Ferrite Ceramics

“…The second stage is characterized by the Hopkinson peak, which is a sharp increase with the pass of an acute maximum and a sharp fall in the values of the initial permeability near the Curie point. This behavior is associated with the domains transition to a superparamagnetic state, which is inherent in the singledomain state in the case when the domain size and the average grain size coincide, for example, in the case of a nanoparticle [9][10][11].…”