PREPARATION OF CERIA-GADOLINIA ELECTROLYTES BY THE TAPE ROLLING TECHNIQUE

The preparation of thin (ca. 200 mu m) Ce0.9Gd0.1O1.95 planar electrol ytes using the tape rolling technique is described. The processing and formation of these electrolytes involved several steps: (i) the produ ction of a processable ceramic paste, (ii) rolling and cutting, (iii) binder burnout, and (iv) sintering. The rheology of these ceramic past es is characterized by a hardness indentation test. The materials para meters which may be obtained from the hardness indentation test such a s the hardness (plastic flow stress), elastic modulus, and plasticity index are provided. The rheology, as characterized by the hardness met hod, 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 rheologica l properties. it is possible to produce uniform thin green tapes using a twin roll mill. The binder burnout characteristics of the ceramic p astes were studied by using a specially constructed thermal gravimetri c apparatus. It is shown that the heating rate and the ambient atmosph ere have strong influences upon the binder burnout kinetics of these g reen tapes. Finally, it is shown that sintered Ce0.9Gd0.1O1.9 electrol ytes, with a near theoretical density and with a uniform microstructur e as well as a chosen near net shape, may be prepared from the corresp onding tape rolled greens.