CHEMICAL-STABILITY STUDY OF BACE0.9ND0.1O3-ALPHA HIGH-TEMPERATURE PROTON-CONDUCTING CERAMIC

BaCe0.9Nd0.1O3-alpha (BCN) ceramic is known to be an excellent high-te mperature proton conductor and is a candidate electrolyte for use in s olid oxide fuel cells, hydrogen or steam sensors and steam electrolyse rs. In this work, the chemical stability of BCN was investigated syste matically by combining XRD and DTA-TG techniques to study its processi ng compatibility and its feasibility in potential applications. It was found that above 1200 degrees C, BCN reacted with alumina or zirconia , leading to the loss of barium and an excess of cerium. In cold water , both sintered BCN disks and powder samples had very low solubility a nd did not hydrolyse, but they were soluble in some mineral acids, esp ecially in HCl with the liberation of Cl-2. In boiling water, BCN pell ets dissolved readily with decomposition into CeO2 and Ba(OH)(2). In 1 atm CO2, BCN decomposed to form CeO2 and BaCO3 below 1200 degrees C d uring heating, but during cooling it was stable above 1000 degrees C, possibly because BCN has different crystal structures al low and high temperatures. At 600-1000 degrees C, BCN showed a slight mass loss whe n exposed to a reducing atmosphere, and a slight mass gain in an oxidi zing atmosphere. XRD results revealed that BCN demonstrated chemical a nd structural stability in both reducing and oxidizing atmospheres.