Dielectric properties of M-type barium hexaferrite prepared by co-precipitation

摘要

Highly stoichiometric and phase pure barium hexaferrite has been synthesized by co-precipitation as well as a solid-state preparative method using high purity nitrates, oxides and carbonates of iron(III), barium(II) and ammonium hydroxide. The isochronal and isothermally measured complex permittivity and dielectric loss tangents over 1 MHz-1 GHz in frequency remained relatively stable until a sintering temperature between 1100 and 1300 deg C. A high value of relative permittivity of 32 and low loss tangent of 0.0329 indicate suitable high frequency characteristics for barium hexaferrite. The measured apparent densities before and after each firing cycle showed a monotonic increase. The crystal structure determined from X-ray diffraction studies confirmed the presence of single phase belonging to the theoretical space group P63/mmc with calculated cell parameters of a = b = 5.895 A and c = 23.199 A. In addition the DTA hexaferrite formation temperature was found to be 1050 deg C.