Response to environmental gases of BaCoO3 nanowires prepared by a microwave-assisted colloidal method

BaCoO3 is a pseudo perovskite-type oxide, characterized by having linear chains of CoO6 octahedra, held together by Ba2+ ions. This oxide has been studied for their unique magnetic and electric properties, as well as its crystal structure. However, the gas sensing properties of this material are practically unknown. On the other hand, BaCoO3 has been mainly synthesized at high oxygen pressure, whereas BaCoO3 − δ can be obtained at atmospheric pressure. In this work, BaCoO3 nanowires were prepared by a microwave-assisted colloidal method, using cobalt nitrate, barium nitrate, polyvinylpyrrolidone and formic acid. At low calcination temperatures, fibers composed by Ba(NO3)2 and Co3O4 were obtained; whereas at 600 °C, BaCoO3 nanowires were produced. The diameter of the latter was in the range 70-100 nm, and their length between 5 and 70 μm. The gas sensing characterization was performed on thick films prepared with the as-prepared BaCoO3 nanowires. At 400 °C and f = 100 kHz, an outstanding performance for detecting CO was observed. It was characterized by a large variation of the magnitude of impedance (Δ|Z|). For CO2 and an oxygen-rich atmosphere, Δ|Z| was significantly smaller; however, a reproducible and reliable detection was noticed. Another relevant result was the quantitative detection of the test gases. The overall gas sensing behavior of BaCoO3 corresponded to a p-type semiconductor material.