Abstract
Ceramic coatings obtained by sol-gel routes are more and more attractive for protective purposes. Improved resistance against wet corrosion of steels can be obtained by doping the covering layer with elements like for instance transition ones. It is of major importance to have a clear-cut knowledge of the oxidation state of the doping element, especially after different heat treatments which usually follow the deposition process. Here we report about the oxidation states of 5 wt.% iron doped TiO2, SiO2 and mixed sol powders obtained by the sol-gel method with alkoxide precursors added with FeSO4, 7 H2O in organic medium. The evolution of the Fe oxidation state versus various heat treatments is followed by 57Fe Mössbauer spectrometry supplemented by XRD data. As-dried samples are amorphous and contain ferric Fe cations, with a local distorted oxygen environment. After heating at 500°C during 3 min, ferrous and ferric oxides are evidenced together solely for silica and mixed silica-titania powders, in marked contrast with titania powders where only ferric species exist. The complete ferric state is restored for all samples after annealing at 900°C for one hour.
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References
M. Guglielmi, Journal of Sol-Gel Science and Technology 8, 443 (1997).
P. Innocenzi, G. Brusatin, A. Martucci, and K. Urabe, Thin Solid Films 279, 28 (1996).
M. Fallet, H. Mahdjoub, B. Gautier, and J.-P. Bauer, Journal of Non-Crystalline Solids, 293–295, 527 (2001).
R.A. Brand (Normosdist).
P. Gütlich, R. Link, and A. Trautwein, Mössbauer Spectroscopy and Transition Metal Chemistry (Springer-Verlag, Berlin, 1978), p. 57.
G. Concas, F. Congiou, C. Muntoni, and G. Pinna, Journal of Phys. Chem. Solids 57, 887 (1995).
W. Kündig and J.A. Cape, Journal of Applied Physics 38, 947 (1967).
O.C. Kistner and A.W. Sunyar, Physics Review Letters 4, 412 (1960).
C. Cannas, G. Concas, A. Musinu, G. Piccaluga, and G. Spano, Z. Naturforsch 54a, 513 (1999).
C. Cannas, G. Concas, A. Falqui, A. Musino, G. Spano, and G. Piccaluga, Journal of Non-Crystalline Solids 286, 64 (2001).
B. Pal, M. Sharon, and G. Nogami, Mat. Chem. Phys. 59, 254 (1999).
G.M. Bancroft, A.G. Maddock and R.G. Burns, Geochimica Acta 31, 2219 (1967).
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Fallet, M., Gschwind, R. & Bauer, P. Oxidation States of Iron in Doped TiO2-SiO2 Sol-Gel Powders: A 57Fe Mössbauer Study. Journal of Sol-Gel Science and Technology 27, 167–173 (2003). https://doi.org/10.1023/A:1023750517779
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DOI: https://doi.org/10.1023/A:1023750517779