Gas Selectivity of Polycrystalline Thick Films of SrPb 1−x Bi x O 3−δ

Polycrystalline samples of the perovskites: SrPb1-xBixO3-δ (x = 0, 0.1) were prepared from the dissolution of stoichiometric amounts of Sr(NO3), Pb(NO3)2 and Bi(NO3)3 in aqueous media. The solutions were heat-dried at 75°C obtaining powder precursors. To determine the temperature of formation of these phases, thermal analyses were made on them. Calcination at 650°C for 6 h produced pure samples, which were characterized by X-ray powder diffraction. The surface microstructure of powders was analyzed by scanning electron microscopy, and showed that this preparation procedure yield micron-sized particles, which formed agglomerations. To evaluate their gas sensing behavior, the resulting powders were finely ground and mixed with acetone to form thick-films. The electrical conductivity vs. temperature of films was measured in dry air, O2 and CO2, and resulted that SrPb0.9Bi0.1O3-δ has a better sensitivity to O2 compared to SrPbO3-δ, caused by the partial substitution of lead by bismuth.