Structural, magnetic, low and high frequency dielectric properties of Al-substituted M-type SrCe hexaferrites synthesized in the presence of tecomastans (yellow bell) leaves extract

This paper represents a study of the effect of Al-substitutions on structural, magnetic, and dielectric properties of Sr0 & sdot;8Ce0 & sdot;2Fe12-xAlxO19 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) ferrites synthesized in presence of yellow bell leaves extract. All samples were synthesized using the sol-gel combustion technique with the influence of green synthesis by using leaves of Tecomastans (yellow bell) plant. These samples were preheated at 550 degrees C for 4 h and finally calcinated at 1150 degrees C for 6h. These samples were characterized using XRD, FTIR spectroscopy, SEM, VSM, LCR measurements, and VNA measurements. XRD analysis confirm the formation of a magnetoplumbite M-phase (hexagonal) with a minor impurity phase of CeO2 in all samples. Lattice parameters a and c are obtained from rietveld refinement, which are found in the range from 5.859 A to 5.883 A, and 22.96 A to 23.05 A respectively. FTIR spectra confirm the absence of organic compounds and the presence of an absorption band in the fingerprint region, which are linked to the stretching of the metal-oxygen bond at the octahedral and tetrahedral sites. The surface morphology of these samples is analyzed using SEM images. Grains with hexagonal plate shapes were observed in each sample. The average grain size varies in the range of 0.565 mu m-1.455 mu m. EDS data confirms the presence of desired elements in the respective sample. VSM analysis shows hard magnetic behavior in all samples. Magnetic parameters were found in the range, Ms: 36.281-43.397 emu/g, Mr: 12.297-19.841 emu/g, Hc: 2.0987-3.814 kOe. In low-frequency (20 Hz-2 MHz) dielectric measurements, the dielectric constant is high at low frequencies, which rapidly falls as frequency increases. Loss tangent curve shows a relaxation peak for each sample above 200 kHz. AC conductivity is very low in the order of 10-5 S/m in plateau region below 2 kHz, which increases as frequency increases. Cole-Cole plot suggests the effect of grain boundary contribution is higher in non-substituted sample compared to Al-substituted samples. In high-frequency (0.2 GHz-20 GHz) measurements, the dielectric constant remains almost constant. These values are found in the range 5-7.5. Low loss tangent of 0-0.16 were observed in every sample in this frequency domain, with AC conductivity of the order of 10- 2 S/m.