Preparation of mixed oxide MoO3-WO3 thin films by spray pyrolysis technique and their characterisation

Mixed oxide MoO3-WO3 thin films have been deposited onto the amorphous and fluorine doped tin oxide (FTO) coated glass substrates at 300 degreesC by using a simple and inexpensive spray pyrolysis technique. Equimolar ammonium tungstate and ammonium molybdate solutions were mixed together in volume proportions and used as precursors for spraying. The samples were annealed at 400 degreesC for 1 h. They were approximately 0.6 mum thick. The structural, electrical and optical properties were studied and values of room temperature electrical resistivity, its activation energy and band gap energy were estimated. The crystallinity of the samples improved with increase in Mo content in the samples. The sample with 2% Mo-oxide in the W-oxide sample exhibited more pronounced electrochromism than other samples including WO3. The existence of two peaks in the cyclic voltammogram, unlike WO3, suggests that there are two kinds of oxidation states corresponding to WO3 and MoO3. The response times were also improved when Mo oxide is added into the WO3. The stability of these samples were tested by repeating colour/bleach cycles several times in H2SO4 electrolyte. (C) 2001 Elsevier Science B.V. All rights reserved.