Effects of scandium doping concentration on the properties of strontium cobalt oxide membranes

• Published in: Brazilian journal of chemical engineering Vol. 26; no. 3; pp. 563 - 574
• Main Authors: Zeng, Pingying, Ran, Ran, Shao, Zongping, Yu, Hai, Liu, Shaomin
• Format: Journal Article
• Language: English
• Published: Brazilian Society of Chemical Engineering 01.09.2009
• Subjects: ENGINEERING, CHEMICAL; Perovskite; Mixed conduction; Rate limiting; Oxygen separation membrane
• ISSN: 0104-6632; 1678-4383; 0104-6632
• DOI: 10.1590/S0104-66322009000300012

Perovskite-type mixed conducting oxides of SrCo1-ySc yO3-δ (y=0.02-0.7) were synthesized by a combined EDTA-citrate complexing method. Different scandium doping concentrations in SrCo1-ySc yO3-δ have significant effects on the phase structure, electrical conductivity, surface properties and oxygen permeation behaviour of the resultant membranes. SrCoO3-δ without scandium incorporation displayed a 2H BaNiO3-type structure with almost zero oxygen flux at high temperatures. Small amounts of Sc2O3 doping (y<0.1) efficiently stabilized the oxide in a cubic perovskite structure, leading to a sharp increase in the permeation flux, with a maximum value of 3.1ml.cm-2.min-1 achieved at 900ºC for SrCo0.95Sc0.05O3-δ and SrCo0.9Sc0.1O3-δ membranes. The permeation process could be rate-limited by either the oxygen bulk diffusion, oxygen surface exchange, or a combination of both depending on the scandium doping level. Further increases of the Sc3+ doping concentration (y>0.1) were found to lower the membrane oxygen fluxes, with y³≥0.4 doped SrCo1-ySc yO3-δ ceramics no longer showing any oxygen permeation.