A new Ruddlesden-Popper oxide LaSr3Mn1.5Fe1.5O9.71 as photocatalyst for degrading highly toxic dyes in waste water: Structural, magnetic and transport properties

Abstract

This paper presents the magnetic, transport, and photo-catalytic properties of a new Sr4Ti3O10-type oxygen deficient Ruddlesden-Popper oxide LaSr3Mn1.5Fe1.5O9.71. The Rietveld refinement analysis of the PXRD data confirms the formation of the compound which crystallizes in tetragonal symmetry and adopts space group I4/mmm, tI34. The phase is found to be oxygen deficient as determined from the results of iodometric titrations. The energy band gap (Eg) obtained from the DRS study shows that the phase is semiconducting in nature at room temperature. The magnetic studies revealed that the oxygen deficient phase exhibits dominant anti-ferromagnetic (AFM) ordering with Néel temperature, TN ​= ​71 ​K owing to Fe3+―O―Fe3+, Mn4+―O―Mn4+ super-exchange interactions. The divergence between the zero field cooled (ZFC) and field cooled (FC) molar magnetic susceptibility curves at low temperatures implies that the phase shows a spin-glass transition. The temperature-dependent resistivity measurements indicate that the material exhibits insulating behavior with decreasing temperature. The conduction mechanism is discussed by fitting the resistivity data in different transport mechanism models. It has been found that the conduction mechanism is dominated by Mott’s variable range hopping model. The photo-oxidative degradation of different dye pollutants using LaSr3Mn1.5Fe1.5O9.71 as a photocatalyst was carried out under visible irradiation. The results indicate that Methylene Blue (MB) shows 99.1% degradation in 45 ​min while Rhodamine B (RhB) and Methyl Orange (MO) dyes show 99.3% and 98.6% degradation respectively in 20 ​min.