Fine Strontium Ferrite Powders from an Ethanol‐Based Microemulsion

Abstract

A fine strontium ferrite powder with high coercivity was successfully prepared by forming hydroxide precursor particles in the continuous ethanol‐based phase of a microemulsion consisting of iso‐octane, NP9, and an ethanol solution containing Sr2+ and Fe3+ cations at a molar ratio of 1:12. The microemulsion‐derived hydroxide precursor was calcined at various temperatures, ranging from 600° to 1100°C, to develop the hexagonal strontium ferrite phase. X‐ray diffractometry and infrared characterizations revealed that the formation mechanisms of strontium ferrite in the microemulsion‐derived precursor differed from those of the precursor derived by conventional coprecipitation. The microemulsion resulted in a strontium ferrite of finer particle size and better magnetic properties than those of the conventionally coprecipitated strontium ferrite. The microemulsion‐derived strontium ferrite exhibited an intrinsic coercivity of 6195 Oe and a saturation magnetization of 58.28 emu/g when calcined at 900oC. The saturation magnetization increased further, to 69.75 emu/g, when the microemulsion‐derived precursor was calcined at 1100oC.

Study of SrFe12O19 synthesized by the sol–gel method

“…2 shows the XRD patterns of samples obtained. It is seen that the sample calcined at 500 • C shows only ␥-Fe 2 O 3 (maghemite) [12], this phase has been observed as an intermediate phase before formation of the crystalline ferrite in other chemistry-derived precursors [13]. When the calcining temperature was raised to 600 • C, ␣-Fe 2 O 3 (hematite) [14] and SrFe 12 O 19 [15] appear as new phases.…”

Synthesis and magnetic properties of strontium hexaferrite from celestite ore

“…Strontium hexaferrite SrFe 12 O 19 is a hard magnetic material due to their high coercivities (6.64 kOe) which originates from its high magnetocrystalline anisotropy and it is strongly dependent on the size and the shape of the particles. Moreover, the Curie temperature of SrFe 12 O 19 is around 470 • C and the saturation magnetization between 74.3 and 92.6 emu/g [5][6][7][8][9][10]. For the preparation of hexaferrite, the solid state reaction method is commonly employed that involves firing of a stoichiometric mixture of strontium carbonate and iron oxide at high temperature (∼1200 • C) but the obtaining fine, high chemical homogeneity and monodispersed particles may not be easy.…”

Synthesis and Characterization of PEG-Sr Hexaferrite by Sol–Gel Conversion

“…Large number of synthetic techniques have been developed to control the particle size, shape and the properties of the materials [4][5][6][7][8][9]. It is difficult to obtain ultrafine and monodispersed particles by the commercial ceramic method (solid-state reaction) which involves the firing of stoichiometric mixture of barium carbonate and iron oxide at high temperatures (about 1200 • C) followed by milling to break up the aggregates [10].…”