Influence of different sintering techniques on microstructure and phase composition of oxygen-transporting ceramic

The membrane microstructure and phase composition of Ruddlesden–Popper-type La2NiO4+δ ceramics, which were prepared by field-assisted sintering technique/spark plasma sintering (FAST/SPS) process or by conventional pressing and pressureless sintering were investigated. As starting material, a La2NiO4+δ powder, with an average particle size of 0.2 μm was used. The grain-size distribution of the resulting membranes varied from 0.015 μm2 for FAST/SPS sintered ceramic to 6.11 μm2 for pressureless sintered membrane. The microstructure analysis of membranes was performed by transmission and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. Phase transition from orthorhombic to tetragonal crystallographic structure in FAST/SPS material was investigated by temperature-dependent X-ray powder diffraction. The effect of sintering technique and grain size on the oxygen permeation performance of the membranes is discussed with respect to impurities in the material.