A Ceramic Thick Film Humidity Sensor Based on MnZn Ferrite

Abstract

A ceramic thick film humidity sensor, produced from MnZn ferrite, is presented. The proposed sensing mechanism is a combination of proton hopping, hydronium diffusion, and vacancy donor traps releasing electrons into the conduction band. The sensor structure comprises a two-layer device; the first layer is an interdigitated conductor and the second layer is a 30μm thick sensing layer. The effects of sintering the sensing pastes in air and vacuum have been reported. The air-fired sample exhibits the highest humidity sensitivity (1.54%/RH%) and the lowest temperature sensitivity (0.37%/^oC). The vacuum-fired sample has the lowest humidity sensitivity (0.043%/RH) and the highest temperature sensitivity (0.77%/^oC). The sensitivity results indicate that the air-fired sample has the best potential for use in humidity sensing applications.