Rare-earth-chromium oxides powders RECrO3 (RE: La, Yb, Gd, Pr) “perovskite type”: Synthesis and characterization via citrate gel process

Abstract

Recently, there has been increasing interest in the synthesis and use of refractory oxide ceramics as a high-temperature electrode and also thermo-electric materials. These materials, such as perovskite type oxides, particularly, compounds like lanthanum chromite LaCrO3, usually exhibit hopping-type electrical conductivities approaching 30(Ω.cm)-1. The present work aims to synthesize and characterize rare-earth chromite oxides RECrO3 (RE: La, Yb, Gd, Pr), which have the orthorhombic perovskite structure that is apparently stable at 1000 °C calcination temperature. The synthesis of RECrO3 (RE: La, Yb, Gd, Pr) compounds was made by a citrate gel process, using rare-earth-nitrate salts as cation precursors, and followed by a heat-treatment at various temperatures (400 °C, 600 °C, 800 °C, and 1000 °C) for 4 h. The obtained powders were characterized by X-Ray diffraction (XRD), and scanning electron microscopy (SEM). Results show that all the products, especially calcined at 1000 °C have a high purity degree and good crystallinity and that this latter increases with the calcination temperature increasing which has “in contrast” a great effect on the agglomeration of the powders as is shown in the SEM’s micrographs.