Synthesis of Sodium Tungsten Bronze via Hydrothermal Method Assisted by Citric Acid

Abstract

Sodium tungsten bronze NaxWO3 powders have been prepared by hydrothermal method using sodium tungstate as raw material and citric acid as reducing agent, followed by annealing under the inert gas N2 atmosphere. The prepared powders were confirmed as tetragonal sodium tungsten bronze Na0.1WO3 by X-ray diffraction. The SEM observation showed that the as-prepared Na0.1WO3 particles exhibited rod-like morphology with about 20 μm in length and 5 μm in diameter. The influence of pH value of the precursor solution and annealing temperature on the synthesized powders were also investigated. The results indicated that sodium tungsten bronze NaXWO3 would not be obtained when the pH value of the precursor solution decreased to pH=1 or the annealing temperature was lower than 700°C by this hydrothermal method. Additionally, as the wavelength increasing, the transmittance of prepared NaxWO3 exhibited higher visible light transparency with reaching up to about 58% and a downward trend in near-infrared area, which indicates that the prepared Na0.1WO3 have potential application as near-infrared shielding material.

Rapid Synthesis of AxWO3 (A = H, Na, K) Tungsten Bronze Materials with Strong Near‐Infrared Absorption and Enhanced Photoelectric Anticorrosion Properties

“…And in the visible (380-780 nm) and NIR regions (780-2500 nm), the absorption values of HWO, NaWO, and KWO TBs were much higher than those of WO 3 sample, which implied that HWO, NaWO, and KWO TBs had potential as visible-NIR absorbing materials. [48] The NIR-absorption capability of TB could be attributed to the LSPR effect and small polariton transfer. [49] As seen in Figure 5c, the LSPR effect was caused by the free electrons in the conduction band.…”

Intermediate Phases and Reaction Kinetics of the Furnace-Assisted Synthesis of Sodium Tungsten Bronze Nanoparticles

“…Although many Na x WO 3 synthesis procedures have been reported, − furnace-assisted “solid-state” methods have been widely used ,− as they are capable of producing samples over the widest range of x . We have developed a furnace-assisted nanoparticle synthesis procedure based on the method of Straumanis, which uses the following chemical equation: Powdered reagents are mixed then heated in a furnace, though synthesis in a microwave oven has also been reported. , Reactions take place under an inert atmosphere or under vacuum, with temperatures ( T ) ranging from 500 to 1000 °C (typically T ≈ 850 °C) and hold times ( t ) ranging from 90 s to 500 h. − ,,− Similar techniques with long hold times can be used to produce large single-crystal samples. , …”