Rietveld refinement, electrical properties and magnetic characteristics of Ca-Sr substituted barium hexaferrites

M-type Ca-Sr substituted barium hexaferrites having compositions BaFe12O19, Ba0.5Ca0.5Fe12O19 and Ba0.5Ca0.25Sr0.25Fe12O19 have been synthesized by commercial solid state reaction method. The effects of doping on structural, dielectric and magnetic properties were systematically investigated. The Rietveld refinement of X-ray powder diffraction data revealed that the samples possess single hexagonal phase with space group P63/mmc, with two molecules in the unit cell (Z = 2). However, in Ba0.5Ca0.5Fe12O19 sample, a secondary phase (Fe2O3) is also present with space group R3c with six molecules in the unit cell (Z = 6). SEM results show a heterogeneous distribution of grain sizes within the samples. The dc electrical resistivity (rho) has been measured as a function of temperature. The variation of dielectric constant (epsilon') and dielectric loss (tan delta) with temperature and frequency were analyzed on the basis of Maxwell-Wagner and Koops' models. Lower saturation magnetization and increased coercivity is observed in substituted samples. (C) 2011 Elsevier B. V. All rights reserved.