Textured La2NiO4+δ membrane with enhanced oxygen permeability

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Mixed ionic-electronic conducting (MIEC) ceramic-based membranes gained considerable attention, concerning their oxygen-transporting rates. Perovskite-based materials often tend to form carbonates in carbon dioxide atmospheres. The Ruddlesden-Popper type oxide La2NiO4+δ has the advantage of high chemical stability in carbon dioxide atmosphere at working conditions, thus membranes made of it would be favorable. However, compared to perovskite materials, the oxygen flux is poor. Therefore, the synthesis of La2NiO4+δ membranes with high oxygen permeation rates is a topic of interest in modern research. This project deals with the synthesis of textured La2NiO4+δ membranes with enhanced oxygen permeation. To enhance the oxygen permeation properties, a templated grain growth method by tape casting is proposed. Due to the anisotropy of the oxygen flux of the material, the particle arrangement of polycrystalline La2NiO4+δ membranes needs to be controlled. The templated grain growth method is described for several anisotropic materials in the literature and shows material properties, comparable to single crystals. For this method large anisotropic template particles are dispersed in a matrix of fine-grained, equiaxial particles. The equiaxial particles are synthesized via a sol-gel route and the anisotropic template particles are synthesized via a molten-salt flux method. After the production of the slurry, textured plates are obtained. These textured plates are stacked and laminated before sintering. Through heat treatment the growth of the anisotropic particles is favored over the small matrix particles. The particles are calcined until they impinge on one another and an anisotropic material is obtained. Finally, oxygen permeability, oxygen surface exchange coefficient and oxygen diffusion coefficient of the manufactured, textured La2NiO4+δ membranes are estimated.