Effect of calcination temperature on microstructure, dielectric, magnetic and optical properties of Ba0.7Lao.3Fen11.7Co0.3O19 hexaferrites

M-type barium hexalerrite Ba0.7La0.3Fe11.7Co0.3O19 (BaLCM) powder, synthesized using sol gel auto combustion method, heat treated at 700, 900,1100 and 1200 degrees C. X ray diffraction (XRD) powder pattems of heat treated samples show the formation of pure phase of M-type hexaferrite after 700 degrees C. Thermo gravimetric analysis (TGA) reveals that the weight loss of BaLCM becomes constant after 680 degrees C. The presence of two prominent peaks, at 432 cm(-1) and 586 cm(-1) in Fourier Transforin Infrared Spectroscopy (FT-IR) spectra, gives the idea of formation of M-type hexaferrites. The M-H curve obtained from Vibrating Sample Magnetometer (VSM) were used to calculate saturation magnetization (M-s), retentivity (M-r), squareness ration (SR) and coercivity (H-c). The maximum value of coercivity (5602 Oe) is found at 900 degrees C. The band gap dependency on temperature was studied using UV-vis NIR spectroscopy. The dielectric constant has been found to be high at low frequency but it decreases with increase in frequency. Such kind of dielectric behavior is explained on the basis of Koop's phenomenological theory and Maxwell Wagner theory. (C) 2014 Elsevier B.V. All rights reserved.