Fabrication Of Ag/WO₃ Composite Films Via Sol-Gel Method And Its Discoloration Performance

In the paper,WO3 thin film was prepared by spin-coating through Sol-Gel Method using W powder and H2O2 as raw material. Ag/WO3 and PEG/WO3 composite films were synthesized via adding AgNO3 solution and PEG to the WO3 sol, respectively. The microstructure morphologies, photochromic properties and related mechanism of the composite films has been studied. The main contents are as follows:(1) WO3 thin film was prepared through spin-coating method with W powder and H2O2 as raw material that the proportion is 1g: 4ml. After heat treatment in the air at 450℃, the morphologies of WO3 film are smooth and crack-free, and there are two forms’ grains that include columnar and granular. When the atmosphere conditions of heat treatment was changed from air to N2 or NH3 into the tube furnace, the surface morphologies of WO3 film became maze structure; when atmosphere into the tube furnace is O2, WO3 film become river-like surface. The band gap of all WO3 thin films are about 3.3eV.(2) WO3/PEG film was synthesized by mixing WO3 sol and PEG under the volume ratio of 5:0.2, 5:0.5, 5:1, respectively. After heat treatment at 450℃, the surface of film obtained the volume ratio of 5:0.2 is smooth and crack-free and has columnar grains and dendrite structure; With the volume ratio of 5:0.5, the surface of film has crack-free and uniform distribution of grains with size of 1-2μm. The WO3/PEG film will fall off from glass substrate when volume ratio is 5:1, but the film showed good photochromic properties after dried at 130℃, with a xenon lamp as the light source. The WO3/PEG film has the same photochromic phenomenon when the light source is daylight.(3) Ag/WO3 composite film was prepared via incorporating AgNO3 solution into the WO3 sol taking the W: Ag atomic number ratio of 100: 1, 100: 5, 100: 10, respectively. Experiment results indicate that the incorporation of Ag can change the band gap of WO3 thin films, The band gap of Ag/WO3 composite films are 3.2eV and 2.9e V with the ratio of 100: 5 and 100: 10, respectively.(4) WO3/Ag/PEG composite film was prepared throuhg putting AgNO3 solution and PEG into WO3 sol, which the volume ratio was 5:0.2 and the W: Ag atomic number ratio was 100:1. The morphologies of the film are formed by a large number of nano-rods and nano-sheets. The morphologies increase contact area between film and light. Meantime, the photochromic properties of the film has also been improved.