Camber Evolution and Stress Development of Porous Ceramic Bilayers During Co‐Firing

Abstract

Camber evolution and stress development during co‐firing of asymmetric bilayer laminates, consisting of porous Ce0.9Gd0.1O1.95 gadolinium‐doped cerium oxide (CGO) and La0.85Sr0.15MnO3 lanthanum strontium manganate (LSM)‐CGO were investigated. Individual layer shrinkage was measured by optical dilatometer, and the uniaxial viscosities were determined as a function of layer density using a vertical sintering approach. The camber evolution in the bilayer laminates was recorded in situ during co‐firing and it was found to correspond well with the one predicted by the theoretical model. The estimated sintering mismatch stress in co‐fired CGO‐LSM/CGO bilayer laminates was significantly lower than general sintering stresses expected for free sintering conditions. As a result, no co‐firing defects were observed in the bilayer laminates, illustrating an acceptable sintering compatibility of the ceramic layers.

Fabrication and performance of a tubular ceria based oxygen transport membrane on a low cost MgO support

“…In the present work the shrinkage, final density and potential distortion of ceramic multilayer systems during the co-sintering process have been measured using optical dilatometry [23][24][25]. The densification and strain rate development of single green layers of a MgO extrusion mass and a dip-coating composition (after de-bindering) as function of sintering temperature are shown in Fig.…”

Design and processing parameters of La2NiO4+δ-based cathode for anode-supported planar solid oxide fuel cells (SOFCs)

“…3, the single-phase LNO starts shrinking at~1000 C, indicating that the sintering temperature should be at least higher than 1000 C to initiate the consolidation of particles at the interface. The LNOeGDC composite with coarse GDC powder (specific surface area of 15 m 2 g À1 ) exhibits inferior sintering behavior compared to the single phase LNO, and the onset sintering temperature was found to be above 1100 C. The sintering behavior of the ceramic composite is quite complex compared to the single-phase materials and is strongly influenced by the secondary phase inclusions [67,68]. Retardation of densification of the LNO-coarse GDC composite compared to the LNO single phase could be explained by the hydrostatic tensile stress countering the natural sintering stress and geometrical constraints imposed by the large GDC particles [69,70].…”

Design and optimization of porous ceramic supports for asymmetric ceria-based oxygen transport membranes

“…Considering the importance of the co-firing process of asymmetric porous/dense ceramic bilayers, first asymmetric CGO bi-layers with different combinations of support and membrane layers were produced by lamination. These bi-layers were then co-sintered at a defined isothermal sintering cycle at a final temperature of 1050° C. Previous work described the cofiring as a major challenge in the preparation of defect free asymmetric porous/dense CGO bilayers [6], [18]. The experiments demonstrated that defect free bi-layers could be produced by combination of individual layers of porous CGO supports (high graphite supports (HG-CGO) and low graphite (LG-CGO)) and membrane layers (Co-CGO and Fe-CGO) at an isothermal sintering temperature of 1050 °C and an holding time of 4hrs.…”

“…Alternatively, porosity may be introduced in the support structure by inhibiting the sintering activity of the ceramic by using a relatively coarse-grained powder (with particle size in the micron range). However, this can introduce a differential sintering shrinkage between the (coarse-grained) porous support and the fine-grained membrane layer which will result in stresses that cause defects in the bi-layer structure during the subsequent co-firing [18]. It is also a requirement that the support structure has sufficient porosity to ensure the infiltration of catalyst material into the region close to the support/membrane interface.…”

“…Considering our experiences with the challenges of co-firing defect-free, flat and planar asymmetric porous/dense CGO structures [18], [20], [23], we start with a brief description of optical dilatometry studies on the different CGO layers with Fe 2 O 3 and Co 3 O 4 as sintering additives for isothermal co-sintering at low temperature (chapter 3.1). The dilatometer measurements of shrinkage and densification (rates) of different layers give us a guide to predict stresses and distortion (camber) for different combination of layers and sintering temperatures.…”