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

Disordered macroporous La 2 O 2 CO 3 /ZnO materials were prepared by a solution combustion method, and then their microstructures and La 2 O 2 CO 3 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 La 2 O 2 CO 3 nanoparticles. A monoclinic La 2 O 2 CO 3 structure was mainly formed in the disordered macroporous materials at La/Zn=1 and 2. In contrast, the conventional coprecipitation of La 2 O 2 CO 3 /ZnO materials dominantly formed a hexagonal La 2 O 2 CO 3 phase with aggregating morphology of ZnO and La 2 O 2 CO 3 nanoparticles. However, nanocrystalline sizes of ZnO (7–10 nm) and monoclinic La 2 O 2 CO 3 (12–14 nm) in the disordered macroporous structure were much smaller than those (29–36 nm for ZnO and 44–58 nm for hexagonal La 2 O 2 CO 3 ) 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 La 2 O 2 CO 3 into La 2 O 3 . This result implies that the interaction between monoclinic La 2 O 2 CO 3 and ZnO in the disordered macroporous structure inhibited ZnO nanoparticle agglomeration.