Utilisation of methylcellulose as a shaping agent in the fabrication of Ba0.95Ca0.05Ce0.9Y0.1O3 proton-conducting ceramic membranes via the gelcasting method

The gelcasting method was used to form gastight Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 samples proposed for use as proton-conducting electrolytes in solid oxide fuel cells. Methylcellulose was used as an environmentally friendly shaping agent for Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 powder in an ethanol solution. Samples of Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 were also prepared from the same powder via traditional isostatic pressing, as a reference for cast samples, and sintered in the same conditions. Comparative studies of the physicochemical properties of Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 electrolytes, formed by means of these two methods and then sintered at 1550 °C for 2.5 h, were presented and discussed. Using the X-ray diffraction method, only the pure orthorhombic phase of BaCe 0.9 Y 0.1 O 3 was detected in the Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 powder, as well as in the Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 sintered pellets formed via both gelcasting (A) and isostatic pressing (B). Thermal effects occurring during heating of methylcellulose, as well as ceramic Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 powder, dried cast samples obtained from the prepared slurry, and sintered Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 samples, were examined by differential scanning calorimetry, differential thermal analysis, thermogravimetric analysis, and evolved gas analysis of volatile products using a quadrupole mass spectrometer. The measurements were performed within the temperature range of 20–1200 °C in air. Based on dilatometric tests, it was found that the Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 cast samples exhibited slightly higher degree of sinterability than the 5CBCY samples obtained by isostatic pressing. In comparison with pressed pellets, higher values of total electrical conductivity in air or in a gas mixture of 5% H 2 in Ar were also attained for Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 cast samples. The Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 samples were used to construct oxygen–hydrogen electrolytes for solid oxide fuel cells. The results of the electrochemical performance of solid oxide fuel cells with Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 electrolytes were comparable to the data in the literature on BaCe 0.9 Y 0.1 O 3 electrolytes. An electrochemical study of a Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ |Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 interface was also performed. Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ appears to be a suitable cathode material for a Ba 0.95 Ca 0.05 Ce 0.9 Y 0.1 O 3 electrolyte.