Role of intermediate milling in the processing of nano-size particles of barium hexaferrite via co-precipitation method

Nano-crystalline particles of barium hexaferrite (BaFe12O19) have been prepared by a co-precipitation/mechanical milling technique using aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11 and subsequent mechanical milling with a high energy planetary mill. The thermal properties, phase composition and morphology of the products were studied. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium hexaferrite occurs at relatively low temperature of 634 °C in co-precipitated/40 h milled sample. The XRD results also showed that intermediate phase of BaO·Fe2O3 does not form in milled samples. Nano-size particles of barium hexaferrite with a diameter of 50–100 nm could be observed in the SEM micrograph of co-precipitated/40 h milled sample after calcination at 800 °C for 1 h. SEM micrographs of the samples calcined at 1100 °C for 1 h exhibits hexagonal plate-like particles of barium hexaferrite; an intermediate milling resulted in decreasing of mean particle size from 1.3 μm to 750 nm.