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Some rare‐earth‐doped alkaline‐earth cerates (e.g., Nd2O3‐doped BaCeO3) are proton conductors that can act as solid state electrolytes in hydrogen or steam sensors, hydrogen pumps, steam electrolyzers, and fuel cells. In the present study, dense tapes of neodymia‐doped barium cerate were produced by the oxidation of malleable Ba‐CeH3‐Nd2O3precursor tapes. Precursor tapes were produced by cold‐rolling either blended or milled mixtures of Ba, CeH3, and Nd2O3 within a silver can. X‐ray diffraction, electron microprobe analyses, and thermogravimetric analyses were used to study the phase transformations resulting from heat treatments conducted at 300° to 900°C in pure, flowing oxygen. Barium peroxide and cerium dioxide, produced during oxidation at ≤300°C, reacted at ≤500°C to form barium cerate. The rate of formation of barium cerate depended on the degree of milling of the solid metal‐bearing precursor powder. Dense barium cerate tapes were obtained after heat treatment at 1080°C.

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Multilayer capacitors with thin, dielectric BaTiO, layers can possess a relatively high capacitance per unit volume. A solid metallic precursor method has recently been developed for preparing thin BaTiOJnoble metal laminates. In the present paper, the phase and microstructural evolution of Ba-Ti metallic precursors were examined after oxidation at 300" to 900°C in pure oxygen at 1 atm pressure. Barium peroxide, BaO,, formed rapidly during oxidation at 300"C, with titanium largely remaining as unoxidized particles in the peroxide matrix. Between 375" and 500"C, the solidstate reaction of barium peroxide with metallic titanium yielded barium orthotitanate, Ba,TiO,. Further exposure to temperatures between 500" and 900°C resulted in the oxidation of residual metallic titanium. The oxidized titanium then reacted with the orthotitanate matrix to form barium metatitanate, BaTiO,. The rate of formation of BaTiO, was found to be strongly dependent on the degree of milling of the Ba-Ti precursors and on the heating rate between 300" and 500°C.