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+delta 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+delta powder, with an average particle size of 0.2 mu m was used. The grain-size distribution of the resulting membranes varied from 0.015 mu m(2) for FAST/SPS sintered ceramic to 6.11 mu m(2) 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. (C) 2015 Elsevier Ltd. All rights reserved.