Electrical Properties of Porous Titania Ceramic Humidity Sensors

Abstract

Ceramic humidity sensors made with pure TiO 2 powder as the starting material are investigated. The sensor can be reversibly operated without repeated high‐temperature thermal desorption, and the conductance versus relative humidity (rh) sensitivity of the sensor is more than 4 orders of magnitude in the range ∼15% to 95% rh at 400 Hz and 25°C. The sensor can be polarized similar to electrolytes in the charging process, and the degree of polarization is enhanced with increasing rh. The conduction carriers of the sensor in the humid atmosphere are ions and electrons, and ions are the dominant conduction carrier. The relative dielectric dispersion k′(ω) is almost proportional to ω −1.84 for rh ∼50% to 95% at low frequencies, where ω is the angular frequency. An inductive effect is also observed in a low‐humidity atmosphere, which implies desorption of water vapor with the regeneration of the adsorption sites.