Synthesis of sodium tungsten oxide nano-thick plates

In this letter a simple procedure to synthesize sodium tungsten oxide nano-thick plates from WO3 films has been reported. WO3 films were grown by pulsed-laser deposition method and then heat treated at temperatures up to 560 degrees C and times up to 120 min. Slide glass was used as both substrate and sodium source simultaneously. XRD analysis revealed presence of an amorphous structure for as-deposited WO3 films. On the other hand. XRD showed formation of a monoclinic WO3 structure with annealing in lower temperatures and a triclinic Na0.5WO3.25 structure with annealing at higher temperatures. Intensity of the triclinic phase peaks enhanced drastically by rising annealing temperature and time. SEM results depicted presence of Na0.5WO3.25 nano-thick plates with thickness of about 160 nm and width of about 3 mu m. Finally. XPS analysis revealed that heat treatment temperature does not affect tungsten valence state. (C) 2012 Elsevier B.V. All rights reserved.