Carbon dioxide gas sensing properties of ordered oxygen deficient perovskite LnBaCo2O5+ı(Ln = La, Eu)

Abstract

Polycrystalline samples of layered cobaltites LnBaCo2O5+ı(Ln = La, Eu) were synthesized by standardsolid state reaction. Structural, magnetic and carbon dioxide gas sensing properties of the samples werecarefully investigated. The polycrystalline LnBaCo2O5+ısamples showed typical sequences of magnetictransitions according to the nonstoichiometric oxygen (ı) content. Well-defined hysteresis loops wereobserved at different temperatures (270 K for EuBaCo2O5+ı), which supports the existence of a ferro-magnetic order in the samples. Thick films were prepared with the as-prepared powders for the gassensing evaluation. Considerable response to CO2gas was measured for the first time on sensors basedon LnBaCo2O5+ıpowders. The resistance of the sensors increases with an increase of CO2concentration,with dry air as base gas. The gas sensing response of the sensors is fast and shows good reproducibility.The EuBaCo2O5+ı, and LaBaCo2O5+ıcobaltites show distinct behavior upon increase in the CO2concen-tration, which might be associated with the value of ı for each system. The probable carbon dioxide gassensing mechanism of the studied cobaltites is discussed.