Synthesis of barium hexaferrite nano-particles via mechano-combustion route

Abstract

Nano-size particles of barium hexaferrite have been synthesized by what is termed mechano-combustion after milling of intermediate products obtained in the sol–gel combustion process using nitrate–citrate gels prepared from metal nitrates and citric acid. The effects of precursor milling conditions on the phase evolution, crystallite size and annealing behavior of the products were investigated using XRD technique. The XRD results indicate the presence of γ-Fe 2O 3 as a major phase and BaCO 3 as a minor phase in as-burnt powder. Analysis of the XRD patterns also confirms the transformation of γ- to α-Fe 2O 3 via mechanical milling; the rate of this transformation is strongly affected by milling conditions. Barium hexaferrite starts to form at 700 °C and fully formed at 1000 °C for milled sample under the optimum milling conditions. XRD and DTA/TGA results showed that an intermediate precursor milling accelerates the formation of magnetic phase. SEM micrograph of the sample milled for 120 h and then annealed at 1000 °C exhibited nano-size particles of BaFe 12O 19 with mean particle size of around 100 nm.