In-situ X-ray diffraction (XRD) and micro-Raman scattering have been used to study the thermal stability of lithium fluoride (LiF)-added (7% weight ratio) Ba(Zr0.8-xCexY0.2)O-2.9 (BZCY: x = 0.1 and 0.2) proton-conducting ceramic powders as a function of temperature in 1 atm of flowing CO2. This work reveals that LiF-addition can reduce the thermal stability of Ba(Zr0.8-xCexY0.2)O-2.9 in CO2 and cause decomposition to BaCO3, and possibly Ba3Ce2(CO3)(5)F-2 (or CeCO3F), and Y2O3-like compound after exposure to CO2 from high temperatures. LiF-related compounds can be removed after calcining (or sintering) in air above 1200 degrees C, but a minor amount of a Y2O3-like compound could remain after calcining at 1400 degrees C in air. (C) 2010 Elsevier B.V. All rights reserved.