Crystal structure of SrCo1-xMoxO3-d (0<= x <=1) perovskites obtained under oxidizing and reducing conditions with potential use as electrodes for intermediate-temperature symmetrical solid oxide fuel cells

OROZCO GIL, STEFANÍA; LARRALDE, ANA LAURA; LARRONDO, SUSANA; LAMAS, DIEGO GERMÁN

ACTA CRYSTALLOGRAPHICA A

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2021 vol. 77 p. 755 - 755

0108-7673

In this work, SrCo1-xMoxO3-δ (0 ≤ x ≤ 1) powders were synthesized by the gel-combustion method in order to explore two major aspects: the synthesis method and the crystal structure of these systems upon the variation of the Co/Mo relation. Sample SrCo0.95Mo0.05O3-δ, exhibiting a tetragonal phase (space group P4/mmm) at room temperature (RT) was used as the parent compound as it was reported to be a good cathode for intermediate-temperature solid-oxide fuel cells (IT-SOFCs) [1]. The amount of glycine used as fuel in the synthesis route was studied in order to obtain a single-phased material with high homogeneity and reproducibility. Afterward, the relationship between the Co/Mo ratio in the B site of the perovskite was also investigated with the aim of implementing these materials as potential electrodes for intermediate-temperature symmetrical solid-oxide fuel cells (IT-SSOFCs). Thus, both the crystal structure and the reducibility properties of the powders were investigated by X-ray powder diffraction (XPD) and temperatureprogrammed reduction under diluted H2 (H2-TPR) techniques respectively. Additionally, scanning electron microscopy (SEM) was performed for the SrCo0.95Mo0.05O3-δ sample in order to study its morphology. The SrCo0.95Mo0.05O3-δ sample synthesized by the addition of a non-stoichiometric amount of glycine, was able to stabilize the desired tetragonal phase as shown in Fig. 1. On the other hand, the undoped SrCoO3-δ sample showed the typical hexagonal structure corresponding to the R32 space group. Samples containing 0.1 ≤ x ≤ 1 Mo, prepared in air flow at RT, presented two additional tetragonal phases (space groups: I4/m and I41/a), which correspond to the Sr2CoMoO6- double perovskite and the SrMoO4 scheelite phase respectively, as depicted in Fig. 2. Recent research has shown that this double perovskite material can become a promising ceramic oxide for anode applications in IT-SOFC [2]. Samples calcinated in a 5 mol% H2 in Ar flow (50 cm3 (STP) min-1) during the H2-TPR experiments showed that, those with the lowest Mo content presented some reduction peaks at 275, 390 and 825 ºC; and the ones with the highest Mo content were partially reduced at 900 ºC. In the latter, a cubic phase was stabilized at RT (Pm-3m space group), which has been considered an ideal phase for its use as IT-SOFCs anode materials [3], meaning a big possibility to obtain other materials at intermediate Co/Mo compositions with optimal properties for IT-SSOFCs electrodes.