Synthesis of Ruddlesden-Popper LaSrFe1-Cr O4 phases (x = 0.0, 0.2, 0.4, 0.6) by glycine-nitrate combustion process: Effect of Cr doping on magnetic, optical and photocatalytic properties

Abstract

This work presents the study of new Ruddlesden-Popper phases, LaSrFe 1- x Cr x O 4 ( x = 0.0, 0.2, 0.4 and 0.6), synthesized by glycine-nitrate combustion method. In this research, we are for the first time reporting on a complete Ruddlesden-Popper series ( n = 1) for the photocatalytic degradation of a dye. The effect of Cr 3+ doping on the crystal structure, optical and magnetic properties of the LaSrFeO 4 phase has also been systematically explored via different characterization techniques. Rietveld refinement of PXRD data indicates the formation of single phase compounds with tetragonal symmetry in the space group I 4/ mmm . The results show a decrease in the lattice parameters a and c , as well as the unit cell volume V , with increase in Cr 3+ doping. The energy band gap ( E g ) values calculated using the DRS spectra decreases with increase in Cr concentration. The magnetic measurements revealed dominant anti-ferromagnetic (AFM) interactions in all the phases and the appearance of weak ferromagnetic (FM) interactions with Cr 3+ doping. The results are discussed by considering the increase in Fe 3+ ─O─Cr 3+ FM interaction in addition to the Fe 3+ ─O─Fe 3+ and Cr 3+ ─O─Cr 3+ AFM super-exchange interactions induced due to random distribution of Fe 3+ and Cr 3+ ions at the octahedral site. Rhodamine B, as a dye pollutant model, was used for evaluation of photocatalytic activity of the prepared phases. Enhanced photocatalytic activity was observed with the addition of Cr 3+ substitution. The results show ~99 % degradation for x = 0.6 while only ~76 % degradation is shown for x = 0.0 sample in 40 min under visible light irradiation. • New RP-type LaSrFe 1- x Cr x O 4 phases synthesized by glycine-nitrate combustion method. • E g values decreased with increase in Cr concentration. • Dominant AFM interactions in all the phases and the appearance of weak FM interactions with Cr doping. • Enhanced photocatalytic activity was observed by Cr doping.