New synthesis of nanopowders of proton conducting materials. A route to densified proton ceramics Zohreh Khani a , Me ´lanie Taillades-Jacquin a , Gilles Taillades a , Mathieu Marrony b , Deborah J. Jones a,Ã , Jacques Rozie ` re a a Institut Charles Gerhardt Montpellier, UMR 5253, Laboratoire des Agre ´gats, Interfaces et Mate´riaux pour l’Energie, Universite´ Montpellier II, 34095 Montpellier, France b European Institute for Energy Research, Emmy-Noether Strasse 11, 76131 Karlsruhe, Germany article info Article history: Received 23 October 2008 Received in revised form 17 December 2008 Accepted 23 December 2008 Available online 6 January 2009 Keywords: Barium yttrium cerate Barium yttrium zirconate Nanopowders Reverse micelles Acrylate hydrogelation High density ceramic membrane Proton conductivity Proton ceramic fuel cell abstract Low temperature routes have been developed for the preparation of BaCe 0.9 Y 0.1 O 2.95 (BCY10) and BaZr 0.9 Y 0.1 O 2.95 (BZY10) in the form of nanoparticulate powders for use after densification as ceramic membranes for a proton ceramic fuel cell. These methods make use on the one hand of the chelation of metal (II), (III) and (IV) ions by acrylates (hydrogelation route) and on the other of the destabilisation and precipitation of micro-emulsions. Both routes lead to single phase yttrium doped barium cerate or zirconate perovskites, as observed by X-ray diffraction, after thermal treatment at 900 1C for 4h for BCY10 and 800 1C for BZY10. These temperatures, lower than those usually used for preparation of barium cerate or zirconate, lead to oxide nanoparticles of size o40 nm. Dense ceramics (X95%) are obtained by sintering BCY10 pellets at 1350 1C and BZY10 pellets at 1500 1C for 10 h. The water uptake of compacted samples at 500 1C is 0.14wt% for BCY10 and 0.26wt% for BZY10. Total conductivities in the range 300–600 1C were determined using impedance spectroscopy in a humidified nitrogen atmo- sphere. The total conductivity was 1.8  10 2 S/cm for BCY10 and 2  10 3 S/cm for BZY10 at 600 1C. The smallest perovskite nanoparticles and highest conductivities were obtained by hydrogelation of precursor barium, zirconium, cerium and yttrium acrylates. & 2008 Elsevier Inc. All rights reserved. 1. Introduction Proton conduction of perovskite-type oxides was described by Iwahara [1] in 1981 and since then aliovalent metal ion doped barium cerate and barium zirconate perovskites have been widely studied. Rare earth doped barium cerate exhibits higher proton conductivity than doped barium zirconate in the same conditions, but is less chemically inert in air, since carbonate formation tends to occur by reaction with carbon dioxide [2]. The literature provides some variation in the conductivity values of rare earth doped barium cerates and zirconates, depending on the pre- parative method used for the material, its capacity for water uptake, and the experimental conditions used in conductivity determination. Thus the conductivity of 10% yttrium doped barium cerate has been variously reported in the range between 10 4 and 10 2 S/cm at temperatures of 300–600 1C [3–6], while that of yttrium–barium zirconate has been described in an even broader range of 10 6 –10 3 S/cm at the same temperatures [6–11]. The higher value range of these conductivity values is sufficient for energy conversion applications, and these materials hold promise for use as solid electrolytes in proton ceramic fuel cells (PCFC) operating in the temperature range between that of proton exchange membrane and solid oxide fuel cells (PEMFC, SOFC), in particular between 400 and 600 1C. At this intermediate temperature, non-precious metal catalysts and oxide-type catalyst supports and electrode materials can be used, while the problem of thermal ageing of SOFC components is avoided to some extent. Perovskite rare earth doped barium cerate and zirconate are conventionally prepared by solid state reaction from carbonate or oxide precursors. In addition, a large variety of wet chemistry methods have been employed such as co-precipitation [12–15] modifications of the Pechini method [16,17], glycine–nitrate combustion [18–20], sol–gel synthesis [21,22], polyacrylamide gel process [23], use of molten salts [24,25] and hydrothermal syntheses [26,27]. All these methods present their advantages and disadvantages. Drawbacks include difficulty in controlling the rate of hydrolysis of different metal alkoxides in the sol–gel process, a non-homogeneous compositional distribution and agglomeration of particles prepared by co-precipitation, the thermodynamic instability of barium cerate in the molten salt reaction medium [28] and inhomogeneous particle size and irregular morphology in hydrothermal methods. On the other hand, a single phase material can be obtained at high synthesis temperatures (41000 1C) which will result in a large particle size (4100 nm). ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jssc Journal of Solid State Chemistry 0022-4596/$ - see front matter & 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.jssc.2008.12.020 Ã Corresponding author. Fax: +33 467143304. E-mail address: Deborah.Jones@univ-montp2.fr (D.J. Jones). Journal of Solid State Chemistry 182 (2009) 790–798