Dense inorganic membranes: studies on transport properties, defect chemistry and catalytic behaviour

Oxygen separation with dense oxide membranes may be an attractive method for the production of oxygen from air. Another possible application is the direct supply of oxygen in membrane reactors for the (partial) oxidation of hydrocarbons. The driving force for oxygen permeation through dense mixed ionic-electronic conducting membranes is an oxygen partial pressure gradient, which causes selective transport of O2- from the high to the low oxygen partial pressure side. The oxygen diffusion process is facilitated by a large concentration of vacant crystallographic sites in the oxygen sublattice of the oxide. Overall charge neutrality in the membrane is maintained by a counterbalancing flux of electrons or electron holes. This thesis describes a number of studies on the oxygen transport and catalytic properties of several dense inorganic membranes. The relationship with the defect chemistry of the metal oxide is investigated.