Structure analysis and magnetic properties of nano-sized Nb(x)Ni(y)Zn1-x-yFe2O4 powders formed by combustion synthesis and mechanical milling

Nano-sized Nb(x)Ni(y)Zn1-x-yFe2O4 ferrites with average particle size of less than 100 nm were prepared by using self-propagating high-temperature synthesis and mechanical ball milling. Average ferrites size of the SHS products were less than about 100 nm after 20 minutes mechanical milling. The average combustion temperatures and the combustion propagating rates were in the ranges of 1145 to 1543 K and 4.1 to 7.2 mm/s, respectively. Rietveld refinement of the pattern converged to good agreement (chi2 = 4.87). Final product of SHS was Nb0.13Ni0.41Zn0.46Fe2O4 with Fd3m structure and the lattice parameter of 0.83623 nm. Maximum magnetization (Ms), residual magnetization (Mr), coercive force (iHc) and susceptibility of the Nb0.013Ni0.41Zn0.46Fe2O4 ferrites formed at the oxygen pressure of 0.25 MPa were 12.30 Wb/m2 Kg, 1.57 Wb/m2 Kg, 6321 A/m, and 0.02 m3/Kg, respectively. Niobium addition to nickel-zinc ferrites resulted in increasing Ms, Mr and iMc about 59%, 78% and 387%, respectively. Neutron diffractometry revealed that the variation of magnetic properties was related to non-stoichiometric number and oxygen position of the niobium-nickel-zinc ferrites due to the competitive reduction reaction among niobium, nickel and zinc oxides.