Preparation of ceria-gadolinia electrolytes by the tape rolling technique

The preparation of thin (ca. 200 mu m) Ce0.9Gd0.1O1.95 planar electrolytes using the tape rolling technique is described. The processing and formation of these electrolytes involved several steps: (i) the production of a processable ceramic paste, (ii) rolling and cutting, (iii) binder burnout, and (iv) sintering. The rheology of these ceramic pastes is characterized by a hardness indentation test. The materials parameters which may be obtained from the hardness indentation test such as the hardness (plastic flow stress), elastic modulus, and plasticity index are provided. The rheology, as characterized by the hardness method, of the pastes is shown to be influenced by the nature and extent of processing aids and also the mixing and milling times. Further, it is shown that by using a paste formulation with appropriate rheological properties. it is possible to produce uniform thin green tapes using a twin roll mill. The binder burnout characteristics of the ceramic pastes were studied by using a specially constructed thermal gravimetric apparatus. It is shown that the heating rate and the ambient atmosphere have strong influences upon the binder burnout kinetics of these green tapes. Finally, it is shown that sintered Ce0.9Gd0.1O1.9 electrolytes, with a near theoretical density and with a uniform microstructure as well as a chosen near net shape, may be prepared from the corresponding tape rolled greens.