High temperature humidity sensing ability of indium-doped barium cerate

Abstract

Acceptor-doped perovskites (ABO3 general formula) with large lattice constants (such as BaCeO3, SrCeO3, and BaZrO3) have been known as fast proton conductors. The ability to conduct protons at high temperatures makes them suitable for humidity sensors in a high-temperature environment. The presence of traces of humidity can play a key role in the functioning of certain industrial processes at higher temperatures. Electrical characteristics of BaCe0.75In0.25O3–δ (BCI25) sintered sample were analyzed in a dry and a wet argon atmosphere in the 250–700 °C temperature range. The water vapor sensing properties of BCI25 porous film and its response and recovery times were investigated under different conditions of temperature and water vapor concentration. A 30 μm thick film obtained from the powder calcined at 1050 °C exhibited sensitivity comparable to that of the sintered sample with significantly shorter response and recovery times. While the sensitivity of the film gradually decreased with a decrease in partial pressure of water vapor (p(H2O)), a noticeable sensitivity was still observed at p(H2O) of 200 Pa. Decrease in conductivity depended logarithmically on the partial pressure of water with the slope of 0.52 that is close to the theoretical value. After several cycles, the reusability test proved an almost unchanged ratio between the impedance value in the dry and the wet Ar atmosphere (p(H2O) = 2.34 kPa), which implied that BCI25, having good stability and sensitivity, is a promising high-temperature humidity sensor.