Synthesis Of Rare Earth Aluminates From Pseudoboehmite And Oxides

During last decades considerable research efforts have been devoted in the quest of new materials for thermal barrier coatings; rare earth aluminates have emerged as candidates due to their good stability at high temperatures and high fracture toughness. Lanthanum aluminate (LAO) and gadolinium aluminate (GAO) perovskites have been synthetized through diverse and often expensive routes. This work is aimed to produce affordable LAO and GAO powders starting from pseudoboehmite as alumina precursor, which is a poorly crystallized alumina that exhibits certain convenient features like a nanometric size powder shown to be a readily produced low-cost aluminates precursor. The present chemical synthesis of the aluminates LAO and GAO, relies on the reverse precipitation on the pseudoboehmite particles. Synthesis of LAO used lanthanum nitrate as a precursor and a solution of gadolinium oxide was used as a reactant to synthesize GAO. Suspensions were subject to drying and calcination in order to obtain aluminates powders. X-ray characterization showed both LAO and GAO remain amorphous at 800 °C calcination temperature. At 1000 °C, perovskite structure sets in. SEM images show a platy, rounded particle morphology and normal size distribution in the nanometric range. TEM analysis corroborates that phases obtained present typical perovskite crystallographic planes.