RESUMO
Hexagonal cesium tungsten bronze (Cs0.33WO3) nanoparticles (NPs) have attracted attention for their potential applications in near-infrared (NIR) absorbing materials. However, the insufficient Cs doping in Cs0.33WO3 NPs has limited their NIR absorbing capabilities and practical stability. In this study, we demonstrate the transition pathway from intermediate W-defective Cs0.33WO3 NPs synthesized by flame spray pyrolysis to cationic (Cs, W)-disordered Cs0.33WO3 NPs prepared through appropriate heat treatments. Direct atomic observations reveal the basal shear and prismatic (Cs, W)-defective planes, which contributed to the disorder of full Cs doping in Cs0.33WO3 NPs. The obtained Cs0.33WO3 NPs with cationic disorder exhibited enhanced practical performance compared with conventional Cs0.33WO3 NPs. Therefore, the developed approach that regulates cationic disorder enables the rational design of defective metal oxides for a variety of applications, including NIR absorbing materials.
RESUMO
Cesium tungsten bronzes (Cs0.32WO3) have attracted much attention as a near-infrared absorbing material. We report the successful synthesis of highly crystalline and high purity Cs0.32WO3 nanoparticles through a spray pyrolysis route. Careful analyses disclosed the presence of cationic defects, that is, a tungsten deficiency and insufficient Cs doping in the Cs0.32WO3 nanoparticles. These cationic defects can be controlled by facile heat treatment in a mildly reducing atmosphere. In particular, we clarify that the tungsten deficiency is a key factor among the cationic defects to obtain high near-infrared absorption properties. Furthermore, this study clearly demonstrates the precise tunability of the optical properties by means of the lattice constants of the Cs0.32WO3 crystal. The realized range of lattice constants is significantly wider than those previously reported. These findings should contribute to the engineering of Cs0.32WO3 structure and properties.