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.