Chemical stability study of BaCe0.9Nd0.1O3-α high-temperature proton-conducting ceramic

BaCe0.9Nd0.1O3-alpha (BCN) ceramic is known to be an excellent high-temperature proton conductor, and is a candidate electrolyte for use in solid oxide fuel cells, hydrogen or steam sensors and steam electrolysers. The chemical stability of BCN was systematically studied by combining XRD and DTA-TG techniques to examine its processing compatibility and its feasibility in potential applications. It was found that above 1200 C, BCN reacted with Al2O3 or ZrO2, leading to the loss of Ba and an excess of Ce. In cold water, both sintered BCN discs and powder samples had very low solubility and did not hydrolyse, but were soluble in some mineral acids, especially HCl. In boiling water, BCN pellets dissolved readily, decomposing to CeO2 and Ba(OH)2. In 1 atm CO2, BCN decomposed to form CeO2 and BaCO3 below 1200 C during heating, but was stable above 1000 C during cooling, possibly because of the different crystal structures at low and high temperatures. At 600-1000 C, BCN showed a slight weight loss when exposed to a reducing atmosphere, and a slight gain in an oxidising atmosphere. XRD revealed that BCN was chemically and structurally stable in both reducing and oxidising atmospheres. 19 refs.