Journal of Power Sources 169 (2007) 53–58 Short communication Chemical and electrical properties of BaPr 0.7 Gd 0.3 O 3-δ  A. Magras ´ o a,∗ , F. Espiell a , M. Segarra a , J.T.S. Irvine b a DIOPMA Center, Departament of Materials Science and Metallurgical Engineering, Faculty of Chemistry, University of Barcelona, Mart´ ı i Franqu` es 1, E-08028 Barcelona, Spain b School of Chemistry, Purdie Building, University of St. Andrews, Fife KY16 9ST, Scotland, UK Available online 30 January 2007 Abstract Doped perovskites have a growing interest as electrolytes for IT-SOFCs. In the search for proton conducting electrolytes, Gd-doped BaPrO 3 was studied. The present work reports the chemical stability and electrical conductivity of BaPr 0.7 Gd 0.3 O 3-δ powders. This system is found to be highly reactive under water, CO 2 and hydrogen containing atmospheres. Comparison of the conduction behaviour measured at different atmospheres indicates that the system behaves as a p-type electronic conductor. The total conductivity is about 1 × 10 -3 S cm -1 at 300 ◦ C, in dry O 2 . The resistance of the system seems to be dominated by the grain boundary contribution. However, structure investigation reveals there is a gadolinia segregation, which may act as a resistive barrier. The material is not suitable for SOFC applications due to its low stability. © 2007 Elsevier B.V. All rights reserved. Keywords: BaPrO 3 ; p-Type conductivity; Proton conductivity; Electrolyte; Electrode; Perovskite 1. Introduction There is a growing interest on finding new materials suscep- tible to be used as electrolytes in IT-SOFC, which can reduce the operating temperature to the range under 600 ◦ C. Therefore, energetic costs, chemical degradation and mechanical stress can be reduced. In that direction, Fukui et al. [1] reported a new perovskite material supposed to be used as proton conducting electrolyte in high temperature proton conducting fuel cells. That material, BaPr 1-x Gd x O 3-δ , is very interesting because of its high conduc- tivity (0.1 S cm -1 at 500 ◦ C for x = 0.3). However, there are still some contradictory results about its nature of conduction. The same author pointed out that the dominant conduction species for the compound x = 0.4 used as electrolyte were mainly holes [2]. However, it was later said [3] that compound was not single phase for the mentioned composition and reported a conductivity of 5 × 10 -3 S cm -1 , t H+ = 0.85 at 200 ◦ C for x = 0.3. In terms of chemical stability, BaPrO 3 -based compounds seem to be chemically unstable under CO 2 [3] and under reduc-  This paper is presented at the 2nd National Congress on Fuel Cells, CONAP- PICE 2006. ∗ Corresponding author. Tel.: +34 93 4021316; fax: +34 93 4035438. E-mail address: amagraso@ub.edu (A. Magras´ o). ing conditions [4]. It has been recently pointed out that BaPrO 3 may be also partially reduced under humid conditions [5]. Due to the fact that there is few and contradictory bibli- ography about BaPrO 3 based compounds, in this paper we report a study on the chemical stability of the compound BaPr 0.7 Gd 0.3 O 3-δ and the AC impedance studies under various atmospheres. 2. Experimental work 2.1. Sintering studies and morphological characterization The synthesis of BaPr 0.7 G 0.3 O 3-δ was done using the acry- lamide combustion synthesis described elsewhere (Magras´ o et al. [6]). The sintered bodies were obtained by uniaxial pressing at 3t, for 13 mm diameter discs. A study of the sintering properties of this powder was carried out. The sintering temperature varies from 1250 to 1500 ◦ C and time from 5 up to 30 h. Ramp rate was maintained constant at 3 ◦ C min -1 from room temperature. Because BaPrO 3 based compounds react with alumina at high temperatures [3] an old sintered pellet of the same com- position was used between the alumina boat and the pellet in order to avoid undesired reactions and consequent stoichiometry losses. 0378-7753/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2007.01.041