Bi 1.4 Er 0.6 Ru 2 O 7 –50 wt % δ-Bi 2 O 3 Oxygen-Permeable Membrane Material Prepared by Crystallization from Partially Molten State

A high-density ceramic composite Bi 1.4 Er 0.6 Ru 2 O 7 –50 wt % δ-Bi 2 O 3 , stable in the range 730–820°С was manufactured by reacting Bi 3 Ru 3 O 11 and Bi 1.6 Er 0.4 O 3 at 900°С followed by crystallization from a partially molten state. X-ray powder diffraction and dilatometric measurements were carried out. The microstructure and transport properties of the composite were studied. When the composite was cooled below 730°С, the metastable phase γ-Bi 2 O 3 was formed; it was stable up to room temperature and withstood thermal cycling cracking. The reasons behind this phenomenon were explained. The composite has ion–electron mixed conductivity and an oxygen permeability coefficient of about 1.8 × 10 –8 mol/(cm s) at 800°С, which makes it promising for use in ion-transport membranes for producing pure oxygen from air.