Sintering process optimization for multi-layer CGO membranes by in situ techniques

The sintering of asymmetric CGO bi-layers (thin dense membrane on a porous support; Ce0.9Gd0.1O1.95−δ = CGO) with Co3O4 as sintering additive has been optimized by combination of two in situ techniques. Optical dilatometry revealed that bi-layer shape and microstructure are dramatically changing in a narrow temperature range of less than 100 °C. Below 1030 °C, a higher densification rate in the dense membrane layer than in the porous support leads to concave shape, whereas the densification rate of the support is dominant above 1030 °C, leading to convex shape. A flat bi-layer could be prepared at 1030 °C, when shrinkage rates were similar. In situ van der Pauw measurements on tape cast layers during sintering allowed following the conductivity during sintering. A strong increase in conductivity and in activation energy Ea for conduction was observed between 900 and 1030 °C indicating an activation of the reactive sintering process and phase transformation of cobalt oxide.