Hydrothermal synthesis of SrFe₁₂O₁₉ nanoparticles: effect of the choice of base and base concentration

Abstract Platelet shaped strontium hexaferrite (SrFe 12 O 19 ) crystallites were hydrothermally synthesized in an autoclave to study the effect of (a) Fe/Sr molar ratio, (b) choice base NaOH/KOH and (c) concentration. The influence these parameters on final product is evaluated with regards phase composition, structure magnetic properties. Rietveld refinements performed powder x-ray diffraction (PXRD) data determine structural changes, crystallite sizes, preferred orientation, while properties measured using a vibrating sample magnetometer. When NaOH used as base, samples consist mostly (>95 wt.%) SrFe up same ratio = 8, independent concentration base. In contrast, when KOH, composition depends both KOH. High concentrations Sr 2+ OH ? (Fe/Sr 1 /NO 3 4) result growth wide (>400 nm). thickness are all cases around 40 nm causing have anisotropic shape, which can align without applying external field. case KOH instead NaOH, expansion unit cell observed, be attributed K + substituting structure. This corroborated by increasing microstrain KOH/NO ratio. Variations observed coercivity may substitution . present illustrates that meticulous control reaction analysis crystal key for preparing understanding hard-magnetic