Energy band gap tuning of Ba-Ca hexagonal ferrite by Dy3+ ion substitution (0 ≤ x ≤ 0.2) to improve spectral, structural, dielectric and photocatalytic properties

Abstract

In the present study, Dy3+ substituted M-type Ba0.5Ca0.5DyxFe12-xO19 (0.00 ≤ x ≤ 0.20) hexagonal ferrites were synthesized using sol-gel auto-combustion method with lemon extract as a fuel. The single hexaferrite phase with space group P63/mmc is revealed by the X-ray powder diffraction (XRD) patterns. The Field emission scanning electron microscopy (FESEM) exhibits the agglomeration of nanoplates with vacancies at some places. Energy dispersive X-ray photoelectron spectroscopy (EDAX) mapping confirmed the presence of Ba, Ca, Fe, O, and Dy in the hexaferrite. Fourier Transform Infrared (FTIR) spectroscopy exhibits two characteristic bands at 579 and 429 cm−1 corresponding to tetrahedral and octahedral metal ions-oxygen stretching, revealing the occurrence of the ferrite phase. The optical energy band gap calculated using the Tauc plots was found to increase with the increase in dysprosium substitution to fall within the range of 2.8–3.5 eV. The Raman spectra confirmed the Raman vibration modes and M-type structures of hexagonal ferrites (HFs). The dielectric constant values drop rapidly with increasing frequency up to a few KHz and then gradually for the further higher frequencies. The occurrence of Ba and Ca with 2+, while Dy, and Fe with 3+ oxidation states is confirmed using X-ray photoelectron spectroscopy (XPS). The HFs exhibit remarkable efficiency by degrading the Reactive Brown dye to 99.3 % in just 15 min, equivalent to a high degradation reaction rate constant (k) value of up to 0.0396 min−1. Consequently, the catalyst shows promising potential for environmental remediation.