Response to humidity of [formula omitted] sensors doped with [formula omitted]: Influence of fabrication route

Abstract

Nowadays, semiconducting metal oxides humidity sensors are applied in many areas: regarding Relative Humidity (RH) measurement, the electronic/ionic charge transfer reactions that take place at the semiconductor surface and inside the pores, for which the overall conduction mechanisms are highly influenced by the sensing material physical/chemical properties.In a previous paper, the influence of different contents of V2O5, 3, 5 and 7% in weight in sensors based on the TiO2:WO3 pair sintered at 700°C was investigated. Since V2O5 as a low melting point (∼690°C), authors decided to alter the fabrication procedure: mechanical alloying was applied to the as received starting powders, allowing the reduction of the sintering temperature to 500°C, and sensors based on the TiO2:WO3 pair, with 3, 5 and 7% in weight content of V2O5, were prepared. The present paper describes the influence that the change of fabrication steps had on the new sensors response to moisture: some of the sensors present a conduction type transition, and were investigated concerning microstructural characterization and their electrical response was measured in the range 400Hz–40MHz, at the operating temperature of 20°C and on the relative humidity (RH) range between 10 and 100%. Besides, a model of the sensors electrical behaviour is depicted, which permits to better comprehend the phenomena’s present in our sensors that contribute to the overall electrical response.