Microstructural analysis and electrical conductivity of hexagonal WO₃ thin films during annealing

Abstract

1 Introduction Tungsten trioxide (WO 3 ) thin films have interesting physicochemical properties for many applications such as catalysts in oxidation and reduction reactions, electro-chromic devices and gas sensors [1][2][3][4][5]. Tungsten trioxide-based gas sensors are efficient for detecting numerous gases; more significant are NO 2 , H 2 S and NH 3 [3-7]. In this field various studies were devoted to two important effects. First: these devices are also capable of detecting many other compounds present in vapor states within the atmosphere. Thus, in order to be able to use these devices for characterizing various pollutants in the atmosphere, it is necessary to first understand their behavior when placed in contact with WO 3 -based gas sensors. Second: the physicochemical properties of WO 3 thin films similar to other transition-metal oxides depend mainly on the structure and morphology, which are strongly dependent on the conditions of preparation [7][8][9]. In the case of the WO 3 thin films, the degree of structural order depends on the methods of preparation and annealing treatments. As-deposited WO 3 thin films are usually either polycrystalline with short-range order or amorphous. However, for applications such as gas sensors, thin films have to be an-

Synthesis, Separation and Electrical Properties of WO3-xNanopowders via Partial Pressure High Energy Ball-Milling

“…The broadening was very rapid during the first milling time, but was quite marginal after that. The size variation of milled NPs was quantitatively calculated using the Scherrer formula [13,17] and also observed by TEM [18]. Both methods showed consistent results, as presented in Fig.…”

“…Besides these methods, the high-energy ball milling or mechanical alloying has proven to be a very effective route in preparing nanosized solid solution for gas sensing applications [13][14][15][16]. The alloying process can be carried out using different apparatus, namely, planetary mills, horizontal ball mills or vibration mills.…”

“…Non-stoichiometric tungsten oxides (WO 3−x where 0 ≤ x ≤ 3) as thin films or nanopowders (NPs) have been studied because of their potential applications in MOS gas sensor devices [10][11][12][13][14] such as electrochromic devices (ECDs) solar panel arrays and smart windows. Generally, the majority of the WO 3 sensing properties are connected with: (1) the WO 3 structural model is perovskite--type ABO 3 lattice with A site, which remains an unoccupied site; (2) the WO 3 is considered as oxygen-deficient or non-stoichiometrical oxide represented by WO 3−x , where x depends on the sample treatments.…”

Integrated procedure for recycling and valorization of useful components from secondary raw materials based on hard metals

“…The reduction process of tungsten oxide, because of the low reaction temperature and a high degree of purity of the obtained products, is the subject of many researches [31][32][33][34]. The results of researches point to the fact that the properties of the synthesized powder of tungsten depends, above all, of the characteristics of the starting powder, and the parameters of the technological processes, respectively of a manner performing of the reduction process.…”

Highly Ordered Good Crystalline ZnO-Doped WO3 Thin Films Suitable for Optoelectronic Applications

“…The structural and morphological properties of WO3 thin films (at sub-micrometric scale) have profound effects on its physiochemical properties, which strongly depends on its preparation methods and conditions [8]. WO3 thin films have been prepared by many groups through different techniques like chemical vapour deposition [9], RF magnetron sputtering [10], solvothermal process [11], electrodeposition [12], sol-gel process [13], hydrothermal techniques [14], atomic layer deposition [15], pulsed laser deposition technique [16][17], etc.…”