Characterisation by EPR and other techniques of La1-xCexCoO3+δ perovskite-like catalysts for methane flameless combustion

Two differently prepared series of La1-xCexCoO3 (x=0, 0.05, 0.1, 0.2), indicated by A and C, have been analysed by EPR at temperature ranging between 95 and 295 K, both before and after their use as catalysts for methane flameless combustion. At progressively lowering temperature, some samples showed a narrowing Lorentzian-shaped pattern. This has been attributed to the formation of ordered layer-like systems. A different behaviour has been noticed with the x=0.1 samples of both series. The formation of spin bags and of spin glass has been hypothesised with these samples. A correlation between EPR spectra and catalytic performance has been highlighted. (C) 2001 Elsevier Science B.V. All rights reserved.