Preparation of Protonic Conductor BaZr0.5Ce0.3Ln0.2O3-δ (Ln=Y, Sm, Gd, Dy) by using a Solid State Reactive Sintering Method

Protonic conductors of BaZr0.5Ce0.3Ln0.2O3-δ (BZCLn532, Ln=Y, Sm, Gd, Dy) were successfully synthesized by using a cost-effective solid state reactive sintering (SSRS) method with 1 wt.% NiO as a sintering aid. The pellets of the BZCLn532 were obtained at sintering temperatures between 1300 1600 °C. The results show that the morphologies and the final relative densities of the obtained BZCLn532 pellets are influenced significantly when different sintering temperatures were applied. Dense pellets of the BZCLn532 can be obtained at sintering temperatures of 1600 °C for BaZr0.5Ce0.3Y0.2O3-δ and 1400 °C for BaZr0.5Ce0.3Sm0.2O3-δ, BaZr0.5Ce0.3Gd0.2O3-δ and BaZr0.5Ce0.3Dy0.2O3-δ. The ionic conductivity results show that the BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) and BaZr0.5Ce0.3Dy0.2O3-δ (BZCD532) ceramics are demonstrated to be good candidates of oxygen ion conductor and proton conductor materials for intermediate temperature solid oxide fuel cells (ITSOFCs) applications. Introduction Protonic conductor based electrolytes are good candidates for solid oxide fuel cells (SOFCs) applications, due to their promising protonic conductivity at lower operating temperatures. Since Iwahara et al. [1, 2] first reported the proton conduction phenomenon in the ABO3 perovskite compounds of doped strontium cerates and doped barium cerates, many doped perovskite-type cerates and zirconates compounds have been investigated intensively, especially during the recent years [319]. However, high sintering temperatures (normally higher than 1600 °C) and long sintering times (more than 24 h) are always needed for BaCeO3and BaZrO3-based ceramic materials to obtain dense bulk materials. But this will lead to very large grain sizes, and eventually result in a low mechanical strength. Thus, this will limit their application for electrolyte-support cell structure designs. Therefore, many wet chemistry methods have been introduced to prepare high quality nanocrystalline powders to decrease the sintering temperatures and sintering times of Barium zirconate and Barium cerate based materials [20]. In addition, various transition metal oxides, such as NiO, CoO, MnO, FeO, ZnO [8, 9, 16-18, 20-26], have been added into the pre-synthesized powder, to improve the sintering behaviour and to achieve a reduced sintering temperature. Among these alternative methods, the solid state reactive sintering (SSRS) method was improve by Tong et al. [23-25] for BaZr0.8Y0.2O3-δ, by Coors et al.[26] for BaZr0.6Ce0.2Y0.2O3-δ and by Ricote et al. [18] for BaCexZr0.9-xY0.1O3-δ by using NiO as a sintering aid. Therefore, the normal two separate steps solid-state reaction method for synthesize the powder and the sintering of pellets can be combined into one cost-effective single sintering step. Also, as one of the most promising protonic conductor candidates, BaCe0.5Zr0.3Y0.2O3-δ have attracted more and more attention during the recent years [27, 28]. This is due to that it can maintain a good chemical and mechanical stability as well as that it possesses a very good electrical conductivity. Thus, dense ceramic pellets of lanthanides doped barium zirconate-cerate with the formula of BaCe0.5Zr0.3Ln0.2O3-δ (BZCLn532, Ln=Y, Sm, Gd, Dy) were prepared by the solid state reactive sintering method in this study. The obtained pellets were characterized by XRD and SEM. In addition, the relative densities of the BZCLn532 pellets, which were sintered at different sintering temperatures, were also studied. Advances in Science and Technology Vol. 87 (2014) pp 1-5 Online available since 2014/Oct/31 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AST.87.1 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 130.237.66.205-19/01/15,10:32:36)