Preparation and properties of ferromagnetic Z-type hexaferrite from wet milled mixtures of intermediates

Almost pure Z-type phases of hexaferrites were synthesized by firing preliminarily milled M- and Y-type phases intermediates at 1250 °C. These phases were obtained by calcining the stoichiometric powder mixture precursors at 1080 °C, followed by wet milling in a planetary mill for 1 h and subsequent heating at 1250 °C that increased the fractional crystallization of the Z-phase up to 96%. Addition of 0.2 wt% SiO2 to the intermediates reduced the milling time necessary for the sintered density required for practical permeability measurement. Z-phase hexaferrite sintered at 1250 °C for 2 h exhibited fairly good high-frequency properties, i.e. an initial real permeability of up to 19.3 below 100 MHz and 8–10 at around 1 GHz.