Abstract
New advanced fuel cell technologies are moving towards high-temperature proton conductors (HTPCs) to meet environmental issues. Their elaboration remains a challenge and micro-computed tomography (µCT) is an innovative way to control their quality. NiO-BZY anodic supports of a protonic ceramic electrochemical cell (PCEC), elaborated by co-tape casting and co-sintered at 1350 °C, were coated with a BZY20 electrolyte layer by DC magnetron sputtering. The µCT allowed to observe defects inside the volume of these PCEC half-cells and to show their evolution after an annealing treatment at 1000 °C and reduction under hydrogen. This technique consists in obtaining a 3D reconstruction of all the cross-sectional images of the whole sample, slice by slice. This allows seeing inside the sample at any desired depth. The resolution of 0.35 µm is perfectly adapted to this type of problem considering the thickness of the different layers of the sample and the size of the defects. Defects were detected, and their interpretation was possible thanks to the 3D view, such as the phenomenon of NiO grain enlargement explaining defects in the electrolyte, the effect of NiO reduction, and finally, some anomalies due to the shaping process. Ways to anticipate these defects were then proposed.
Highlights
Protonic ceramic electrical cells (PCEC) have an increasing research activity and show greater abilities for high performances and reversibility [1–3]
The starting powders of the substrate were provided by fuel cell materials (FCM, Cincinnati, OH, USA) for NiO (Ref: NiO-P, Lot#R5739, Item#312010, surface area 3.4 m2·g−1) and by Cerpotech (Cerpotech, Norway) for BZY20 (Lot#180120A, surface area 24 m2·g−1)
The anode-anode functional layer (AFL) assembly was prepared by co-tape casting as described elsewhere [36]
Summary
Protonic ceramic electrical cells (PCEC) have an increasing research activity and show greater abilities for high performances and reversibility [1–3]. Y-doped BaZrO3, called BZY, shows high chemical stability and an acceptable total conductivity at 600 ◦C, typically 10−3 S·cm−1 [12–16]. For these reasons, BZY is widely considered a promising electrolyte candidate for PCEC [17–19]. The elaboration of thin and highly textured BZY electrolyte by pulsed laser deposition or reactive DC sputtering has been developed in order to overcome the grain boundary resistance drawback [25–27]. Both techniques are highly sensitive to the substrate surface quality (flatness, roughness and densification) [28,29]. Three types of samples are studied: the raw half-cell, right after the deposition of the electrolyte on the anode with no added treatment, the annealed at 1000 ◦C half-cell and the reduced half-cell
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