A study of Ca-doped hexaferrite Sr1−xCaxFe12O19 (x = 0.0, 0.05, 0.1, 0.15, and 0.2) synthesized by sol-gel combustion method

Abstract

Ca-doped Hexaferrites of composition Sr1−xCaxFe12O19 (x = 0.0, 0.05, 0.1, 0.15, and 0.2) were synthesized by the sol-gel combustion method and sintered at the two temperatures of 900 and 1100 °C. X-ray powder diffraction (XRPD) measurements with Rietveld refinement analysis confirmed the formation of pure M-type hexaferrite phase for all samples, except for the x = 0.1 and 0.15 samples, sintered at 1100 °C, which also contained 2% and 0.7% hematite phase. The images obtained from field emission scanning electron microscope indicated all the prepared hexaferrite samples were composed of agglomerated nanoparticles and plate shape morphology for samples sintered at 1100 °C. FT-IR measurements also confirmed the formation of the hexaferrite structure. Hysteresis loops (M–H) of the samples were measured by a vibration sample magnetometer at room temperature, and the results obtained revealed decreasing saturation magnetization with increasing Ca content. Coercivity for the samples sintered at 900 °C was increased with increasing Ca content, while for the samples sintered at 1100 °C, it decreased due to the particle size effect. The optical band gaps of the prepared samples were in a range suitable for photovoltaic application. Dielectric constant (ε) and dielectric loss (tanδ) were measured for all samples, and the values for ε and tanδ for the samples sintered at 900 °C were less than those for the samples sintered at 1100 °C.