The deposition of SnO 2 :Sb (ATO) and In 2 O 3 :Sn (ITO) transparent conducting coatings on glass substrate has been demonstrated by many techniques such as CVD, sputtering, vacuum deposition and sol-gel process. This paper presents an alternative process for the deposition of such coatings at room temperature by spin, dip and spray coating techniques using solutions prepared with crystalline nanoparticles fully redispersed in water (for ATO, ITO) or alcohol (for ITO) with solid contents up to 10±15 Vol.%, respectively. The deposited green coatings have been sintered at temperature as high as 9008C. In 2 O 3 :Sn coatings have a resistivity of 1.5 £ 10 22 V cm as sintered and 3.4 £ 10 23 V cm after annealing in nitrogen atmosphere. The resistivity of ATO single coatings shows a minimum r 1:7 £ 10 22 V cm after annealing at 5508C. SnO 2 :Sb coatings present long term stability but the resistivity of annealed ITO coatings steadily increases with time to a value three times higher. All coatings have a high optical quality with transmission in the visible range larger than 90%. q 1999 Elsevier Science S.A. All rights reserved.

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Inorganic membranes prepared by the sol-gel method are promising candidates for use as filters in separation processes. Conducting supported membranes and coatings have been produced from redispersable nanoscaled crystalline Sb-doped SnO 2 powders with Sb contents up to 10 mol%. The crystalline particles (ca. 4 nm) are fully redispersable in aqueous solution at pHÁ8 with a solid content up to 37 vol.% and are monosized. After thermal treatment at different temperatures and times, the pore size diameter of such a powder can be adjusted from 4-20 nm with a very narrow pore size distribution (ca. ±1 nm) and a total porosity of 63%, practically independent of the sintering parameters. Uniaxial compacted substrates (unsupported membranes) present similar characteristics but with a larger pore size distribution (±5 nm) and 80% total porosity. Their electrical resistance decreases with sintering temperature and time to 4 V (800°C, 8 h). Crack free transparent conducting coatings on glasses and ceramics have been obtained by spin-coating using fully dispersed aqueous solutions of the powder with volume content up to 7.8%. After thermal treatment (1 h at 550°C) single layers 200 nm thick are still porous and exhibit specific electrical resistivity as low as r=2.5×10−2 V cm with 90% transmission in the visible range. their redispersability is a particularly important aspect. In a

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