Optical and structural characterization of lanthanum orthoferrites doped with chromium and aluminum

Abstract

This work aimed to synthesize oxides with the perovskite structure of LaFeO₃, LaFe_0.8Al_0.2O₃ and LaFe_0.8Cr_0.2O₃ by proteic sol-gel, in order to use as a ceramic pigment. The resulting powders from the synthesis process were calcined at 600 and 800 °C and then characterized by X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy, and CIE-L*a*b* colorimetry. According to the XRD patterns, all calcined powders were single-phase with orthorhombic perovskite structure. The SEM and TEM images revealed that the powders were porous and nanometric. The pure lanthanum ferrites presented pastel colors, being lighter in aluminum-doped powders. The chromium-doped ferrite presented a light brown color. The colors were more intense with increasing calcination temperature.

Keywords:
pigment; gelatin; perovskite; ferrite