Density and Ionic Conductivity of Sintered (CeO ₂ ) _0.82 (GdO _1.5 ) _o.18

Abstract

A study is presented on sintering of the mixed oxide (CeO 2 ) 0.82 (GdO 1.5 ) 0.18 where the density of the green samples, the density of the sintered samples, and the ionic conductivity of O 2 ‐ ions in the sintered samples were measured. The dependence of these three parameters on the method of preparation of the powder and on the pressure in pressing of the green samples was determined. The pressures used varied from 25 to 1200 MPa. The different preparation methods used resulted in powders of different degree of mixing of the two oxides, which then determined the compositional homogeneity of the samples when sintered. An apparent relation exists between compositional homogeneity and ionic conductivity as well as density. However, when high pressures (∼1000 MPa) were applied, densities up to 98 % of theoretical value were obtained. A temperature dependence of the activation energy in seemingly homogeneous samples is attributed to a higher dopant concentration in the grain boundary than in the grain bulk.