Influence of sintering additives of transition metals on the properties of gadolinium-doped barium cerate
Introduction
Gadolinium doped barium cerates (Gd-doped BaCeO3 — BCG) are solid electrolytic materials of special interest for their application in electrochemical devices, due to the fact that they exhibit high protonic conductivity in hydrogen and/or water containing atmospheres at the temperature range of 600–900 °С [1]. However, there is a series of problems related to the preparation method of these materials [2], [3], [4], [5], [6], [7], including the high synthesis temperature and the insufficient density of the sintered samples. Towards the solution of the latter, the introduction of sintering additives is considered as one of the most effective and simple methods. In the present work, the influence of various transition metals' (Cu, Ni, Zn, Fe, Ti, Co) addition on the sintering behavior and electrical properties of BCG is investigated.
Section snippets
Experimental
Both the BaCe0.9Gd0.1O3 − δ and the BaCe0.89Gd0.1M0.01O3 − δ, (M = Cu, Ni, Zn, Fe, Co, Ti) solid solutions were prepared according to the conventional solid state reaction method. The starting materials were BaCO3, CeO2, Gd2O3 and oxides of Cu, Ni, Zn, Fe, Ti, Co. The mixed powders were initially calcined at 1400 °С in the case of BaCe0.9Gd0.1O3 − δ and at 1150 °С in the case of Cu, Ni, Zn, Fe, Ti and Co-containing samples, for 2 h. Thereafter, the powders were ground and pressed into pellets, which
Results and discussion
The results of the XRD analyses indicated that all samples are characterized by single phase, orthorhombic perovskite-type structure (Fig. 1). The XRD patterns show only the peaks of BaCeO3 with orthorhombic perovskite-type structure, without the impurities phase. The corresponding lattice parameters, unit cell volume and relative densities are presented in Table 1, where it is obvious that the introduction of the sintering additives results in the increase of the samples' relative density.
Conclusions
In the present work the effect of MOx (where M = Cu, Ni, Zn, Fe, Co, Ti) addition on the sintering and electrical behavior of gadolinium-doped barium cerate was investigated. It was found that the BCG doping by small amounts of transition metals allows the decrease of both calcination and sintering temperature by 250 °С and 150 °С, respectively. Moreover, the introduction of 1% Zn, Fe, or Ti increases the samples' density by 6–7%, while in the case of Co, Ni and Cu by 10–13%. Finally, the
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