Effects of Lanthanum Substitution and Annealing on Structural, Morphologic, and Photocatalytic Properties of Nickel Ferrite

Abstract

Nanoparticles of NiLaxFe2−xO4 ferrite spinel incorporated in a SiO2 matrix were synthesized via a sol-gel method, followed by annealing at 200, 500, and 800 °C. The resulting materials were characterized via XRD, AFM, and BET techniques and evaluated for photocatalytic activity. The XRD diffractograms validate the formation of a single-phase cubic spinel structure at all temperatures, without any evidence of secondary peaks. The size of crystallites exhibited a decrease from 37 to 26 nm with the substitution of Fe3+ with La3+ ions. The lattice parameters and crystallite sizes were found to increase with the rise in La3+ content and annealing temperature. Isotherms were employed to calculate the rate constants for the decomposition of malonate precursors to ferrites and the activation energy for each ferrite. All nanocomposites have pores within the mesoporous range, with a narrow dispersion of pore sizes. The impact of La content on sonophotocatalytic activity was evaluated by studying Rhodamine B degradation under visible light irradiation. The results indicate that the introduction of La enhances nanocomposite performance. The prepared Ni-La ferrites may have potential application for water decontamination.

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“…The impact of La 3+ doping and annealing on the structure, morphology, and photocatalytic properties of Ni ferrite was also reported by Dippong et al [32]. The XRD validated the formation of a single-phase cubic spinel structure at all annealing temperatures.…”

“…The XRD validated the formation of a single-phase cubic spinel structure at all annealing temperatures. The particle and crystallite sizes decreased from 37 to 26 nm by substituting Fe 3+ with La 3+ ions, while the lattice constants increased with an increase in La 3+ content and annealing temperature, owing to the different La 3+ and Fe 3+ ionic radii [ 32 ]. The specific surface area varied with the La 3+ content, and decreased with the increase in the treatment temperature, possibly due to the larger particle size and higher crystallinity at higher temperatures [ 32 ].…”

“…The particle and crystallite sizes decreased from 37 to 26 nm by substituting Fe 3+ with La 3+ ions, while the lattice constants increased with an increase in La 3+ content and annealing temperature, owing to the different La 3+ and Fe 3+ ionic radii [ 32 ]. The specific surface area varied with the La 3+ content, and decreased with the increase in the treatment temperature, possibly due to the larger particle size and higher crystallinity at higher temperatures [ 32 ]. The excellent sonophotocatalytic performance was reported for NiLa 0.3 Fe 1.7 O 4 /SiO 2 , most likely due to the La 3+ content inserted in the band gap of Ni ferrite [ 32 ].…”

“…The specific surface area varied with the La 3+ content, and decreased with the increase in the treatment temperature, possibly due to the larger particle size and higher crystallinity at higher temperatures [ 32 ]. The excellent sonophotocatalytic performance was reported for NiLa 0.3 Fe 1.7 O 4 /SiO 2 , most likely due to the La 3+ content inserted in the band gap of Ni ferrite [ 32 ].…”