Dependence of oxygen desorption kinetics on processing methods of SrCoO2.5

Abstract

The effect of processing methods on oxygen storage and exchange kinetics of brownmillerite (BM) SrCoO2.5 is compared in terms of their reversible oxygen incorporation and desorption kinetics. BM SrCoO2.5 was synthesized through two different methods; solid-state synthesis and the nitrate–citrate gel method, both followed by Al foil pad quenching. Oxygen storage characteristics of synthesized samples were analysed using a home-built volumetric set-up. The maximum oxygenation achievable for BM SrCoO2.5 under prevailing conditions of O2 partial pressure (16 bar O2), temperature (673 K) and time (1 h) was unaltered, regardless of the synthesis method. Oxygen exchange kinetics of desorption was faster in the nitrate–citrate synthesized sample than in the solid-state synthesized sample. The kinetics of desorption correlated with the crystallite and particle sizes of the samples. The mechanism of desorption follows nucleation and growth model for nitrate–citrate synthesized sample, while it follows contracting sphere model for solid-state synthesized sample.