Binary and ternary eutectic composites of the CaO – ZrO2 – MgO system for porous ceramic supports

We recently reported on the use of c -ZrO 2 -MgO eutectic composites produced by directional solidification as supports for CO 2 -selective membranes based on molten carbonates. Here, we explore other compositions, particularly within the CaO – ZrO 2 – MgO system, with the ultimate goal of improving the membrane permeation by either increasing the support’s ionic conductivity or reducing its tortuosity. The three eutectic-like composites studied display MgO fibres embedded in single-phase or two-phase matrices. The composite with 8.5CaO/48.5ZrO 2 /43MgO mol% composition consists of MgO fibres in an oxide-ion conducting c -ZrO 2 matrix containing both Ca and Mg. A binary CaZrO 3 – MgO eutectic-like composite forms at ∼33CaO/35ZrO 2 /32MgO mol% with MgO fibres in a Ca-poor, Mg-doped CaZrO 3 matrix displaying mixed oxide-ion and hole conductivity. For 22CaO/45ZrO 2 /33MgO mol% composition, a ternary eutectic forms with MgO fibres at the interfaces of CaZrO 3 and c -ZrO 2 phases. Acid etching tests were conducted to verify the feasibility of fabricating a porous support.