Structural, magnetic, and dielectric properties of solution combustion synthesized LaFeO3, LaFe0.9Mn0.1O3, and LaMnO3 perovskites

Abstract

Nanocrystalline LaFeO₃, LaFe_0.9Mn_0.1O₃, and LaMnO₃ perovskites have been synthesized by a novel solution combustion route, in which oxalyl dihydrazide (ODH) has been used as a fuel. These materials have been characterized using several physicochemical techniques. LaFeO₃ and LaFe_0.9Mn_0.1O₃ adopt an orthorhombic structure and LaMnO₃ crystallizes in a rhombohedral structure as demonstrated by X-ray diffraction (XRD) patterns. The microporous character of the materials due to huge gas evolution during preparation has been revealed by field emission scanning electron microscopy (FESEM) images. Corresponding elements are present in stoichiometric amounts in all perovskites as revealed by energy dispersive X-ray spectroscopy (EDXS) analyses. X-ray photoelectron spectroscopy (XPS) studies demonstrate the presence of La³⁺, Fe²⁺, Fe³⁺, Mn³⁺, and Mn⁴⁺ species in the respective materials. Absorption bands in the frequency range of 500–600 cm⁻¹ related to Fe–O/Mn–O bonds in FeO₆/MnO₆ octahedra are observed in Fourier transform infrared (FTIR) spectra. Raman spectroscopy depicts symmetric modes related to metal–oxygen bonds in orthorhombic and rhombohedral structures. Weak ferromagnetism has been observed in LaFeO₃ and LaFe_0.9Mn_0.1O₃ which is due to superexchange interaction between the magnetic cations. However, LaMnO₃ shows paramagnetic behavior. The electrical characteristics exhibit the lowest dielectric loss for magnetic LaFeO₃ among the LaFeO₃, LaFe_0.9Mn_0.1O₃, and LaMnO₃ perovskites studied here.