BaFe_(1-x)Ta_xO_(3-δ) - A material for temperature independent resistive oxygen sensors

摘要

The sensing properties for resistive oxygen sensors of BaFe_(1-x)Ta_xO_(3-δ) (BFT) were investigated as a function of the Tantalum content x (0.2 ≤ x ≤ 0.7). Bulk samples were produced by using the mixed-oxide route. X-ray diffraction pattern showed that the perovskite structure was obtained and no second phases were found up to x = 0.5. The electrical conductivity of sintered samples was determined in an oxygen concentration between 1% and 100% in a wide temperature range between 400 and 900 C. Samples between x = 0.2 and 0.4 are p-type conducting perovskite oxides with almost zero thermal activation. The range, at which the temperature dependency is absolutely zero, shifts with x from 450 C for x = 0.2 to about 800 to 900℃ for x=0.4. Specimens of BaFe_(0.7)Ta_(0.3)O_(3-δ) revealed the lowest overall temperature dependency in the entire temperature range. All samples up to x = 0.4 responded fast and reversibly to oxygen concentration changes, even at 400℃.