Structure and humidity sensing properties of La1−xKxCo0.3Fe0.7O3−δ perovskite

The effects of K-substitution at La-site of La1−xKxCo0.3Fe0.7O3-δ perovskite on its structure and humidity sensing properties were studied in detail. The XRD, SEM-EDS, N2 adsorption–desorption measurements (BET), ICP-AES and XPS were used to characterize the microstructure of La1−xKxCo0.3Fe0.7O3−δ perovskite. The results show that the partial substitution of K at La-site has no obvious effect on the crystal phase, morphology and surface area of samples, but leads to the increased oxygen vacancies and surface enriched K+. The sensitivity of humidity sensor based on all samples was evaluated by measuring the impedance response to the humidity changes. The partial substitution of K at La-site significantly enhanced the humidity sensitivity of La1−xKxCo0.3Fe0.7O3−δ perovskite at low relative humidity (RH). By correlating the structure of material with its sensing properties, the probable reasons that lead to the remarkable sensitivity enhancement of the K-substitution samples compared with the unsubstituted sample (LaCo0.3Fe0.7O3−δ) were given; moreover, the sensing mechanism was also discussed by the complex impedance spectra in detail.