Structural properties of disordered macroporous La₂O₂CO₃/ZnO materials prepared by a solution combusion method

Abstract

Disordered macroporous La₂O₂CO₃/ZnO materials were prepared by a solution combustion method, and then their microstructures and La₂O₂CO₃ phases were investigated as functions of La/Zn ratios and calcination temperatures. All of the materials prepared by the solution combustion method clearly showed disordered macroporous morphology whose framework was composed of ZnO and La₂O₂CO₃ nanoparticles. A monoclinic La₂O₂CO₃ structure was mainly formed in the disordered macroporous materials at La/Zn=1 and 2. In contrast, the conventional coprecipitation of La₂O₂CO₃/ZnO materials dominantly formed a hexagonal La₂O₂CO₃ phase with aggregating morphology of ZnO and La₂O₂CO₃ nanoparticles. However, nanocrystalline sizes of ZnO (7–10 nm) and monoclinic La₂O₂CO₃ (12–14 nm) in the disordered macroporous structure were much smaller than those (29–36 nm for ZnO and 44–58 nm for hexagonal La₂O₂CO₃) by conventional co-precipitation. In addition, the high temperature calcination at 700 °C increased the ZnO nanocrystallite size (24 nm) in the disordered macroporous framework, with transforming La₂O₂CO₃ into La₂O₃. This result implies that the interaction between monoclinic La₂O₂CO₃ and ZnO in the disordered macroporous structure inhibited ZnO nanoparticle agglomeration.