FABRICATION OF DENSE, SHAPED BARIUM CERATE BY THE OXIDATION OF SOLID METAL-BEARING PRECURSORS

Some rare-earth-doped alkaline-earth cerates (e.g., Nd2O3-doped BaCeO3 ) are proton conductors that can act as solid-state electrolytes in hy drogen or steam sensors, hydrogen pumps, steam electrolyzers, and fuel cells. In the present study, dense tapes of neodymia-doped barium cer ate were produced by the oxidation of malleable Ba-CeH3-Nd2O3 precurso r tapes. Precursor tapes were produced by cold-rolling either blended or milled mixtures of Ba, CeH3, and Nd2O3 within a silver can. X-ray d iffraction, electron micro-probe analyses, and thermogravimetric analy ses were used to study the phase transformations resulting from heat t reatments conducted at 300 degrees to 900 degrees C in pure, flowing o xygen. Barium peroxide and cerium dioxide, produced during oxidation a t less than or equal to 300 degrees C, reacted at greater than or equa l to 500 degrees C to form barium cerate. The rate of formation of bar ium cerate depended on the degree of milling of the solid metal-bearin g precursor powder. Dense barium cerate tapes were obtained after heat treatment at 1080 degrees C.