Two kinds of co-planar sensor cells based on Bi2TanV1 (-) O-n(5.5) (BITAVOX.n, where n corresponds to the substitution rate of V by Ta multiplied by 100) electrolytes were built by reactive magnetron sputtering. A sensor configuration exploited LASCO (La1 - x - yAgxSryCoO3-delta) and platinum electrodes (Pt/BITAVOX.16/LASCO). However, due to the activity of both of them with different response times, this sensor exhibited a complex behaviour under 723 K. The second cell, Pt/BITAVOX.08/Au, exhibits a response at 473 K, and its intensity increases up to 623 K. At 673 K, polarisation changes, and the absolute value of the response increases dramatically, which can be explained by the competition with catalytic reaction over the platinum electrode. (C) 2015 Elsevier B.V. All rights reserved.