The effect of Bi3+ doping on the structural, magnetic, dielectric, optical, and photocatalytic efficiency of Mg-Ni ferrite nanoparticles

Ferrite nanoparticles with the general formula Mg0.7Ni0.3BixFe2-xO4 (MNB) (0 <= x <= 0.1, Delta x = 0.02) were prepared by the citrate combustion method. X-ray diffraction (XRD) results confirmed the spinel single-phase with crystallite size varied from 30.68 to 43.74 +/- 0.01 nm. Scanning electron microscopes with elemental mapping conformed to the nano-nature of the MNB samples with all the constituents present without secondary elements. The sample Mg0.7Ni0.3Bi0.02Fe1.98O4 has the highest saturation magnetization of 31.06 +/- 0.01 emu g(-1). The sample Mg0.7Ni0.3Bi0.08Fe1.92O4 has the lowest coercivity of 31.06 +/- 0.01 G. The high-frequency response of the MNB nanoferrites allows them to be used at frequencies around 6.48 +/- 0.01-6.87 +/- 0.01 GHz. The nanoferrite Mg0.7Ni0.3Bi0.1Fe1.9O4 has notable dielectric parameters at 300 K and 50 Hz: the highest dielectric constant (747.93 with enhancing ratio 371%) and the highest conductivity (26.14 mu(Omega.m)(-1) with enhancing ratio 288%). The Mg0.7Ni0.3Bi0.08Fe1.92O4 sample has a loss of 8.65 with an enhancing ratio of 56.79% compared to the loss of the pristine Mg0.7Ni0.3Fe2O4 sample of 15.23. Diffuse reflectance (DR) spectroscopy showed an irregular trend for the band gap values with increasing Bi3+ content, where the nanoferrite Mg0.7Ni0.3Bi0.1Fe1.9O4 had the lowest energy gap of 2 eV. The sample Mg0.7Ni0.3Bi0.1Fe1.9O4 exhibited the maximum photodegradation efficiency (96.16%) for rhodamine B (RhB) dye, with outstanding stability after five cycles (96.16, 95.92, 95.71, 95.56, and 95.23%, respectively). The current work has shown the capability to customize ferrite MNB for soft ferrite applications and to eliminate hazardous RhB from water.