Response to humidity of TiO2:WO3 sensors doped with V2O5: Influence of fabrication route

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 V 2 O 5 , 3, 5 and 7% in weight in sensors based on the T i O 2 : W O 3 pair sintered at 700 °C was investigated. Since V 2 O 5 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 T i O 2 : W O 3 pair, with 3, 5 and 7% in weight content of V 2 O 5 , 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 400 Hz–40 MHz, 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.