Ni doped Sm0.95Ce0.05FeO3−δ perovskite based sensors for hydrogen detection

In the recent series of perovskites with formula Sm0.95Ce0.05Fe1−xNixO3−δ (0 ≤ x ≤ 0.10), materials with low Ni content (x = 0–0.05) show n-type conducting behaviour while those of high Ni content (x = 0.07–0.10) show p-type conductivity. We tested the x = 0–0.05 materials for hydrogen detection at 300 °C. The bulk sensors were rectangular pellets which were reduced at 1000 °C in 5% (v/v) H2/N2 for 1 h. This treatment has been shown to improve electrical conductivity due to formation of surface nanoparticles consisting of Sm2O3 and iron species. A four probe DC method was used to determine the electrical conductivity of the sensors under air and mixtures of H2 and N2 (1–5%, v/v, H2/N2). The results showed that all these sensors have a linear response as a function of H2 concentration. The effect of Ni concentration is more complex, for example the sensitivity for x = 0.01 was highest in the series but with a very slow response (2 h). The optimal electrical conductivity with shortest response time towards 1, 3 and 5% (v/v) H2/N2 was shown by the x = 0.03 material. Since all the materials showed complete response recovery, the sensing process appears to be reversible.