Investigation, for NH3 gas sensing applications, of the Nb2O5 semiconducting oxide in the presence of interferent species such as oxygen and humidity

Semiconducting oxides, like Nb2O5, can be used as sensitive materials in the manufacturing of gas sensors based on conductivity variation measurements. Since these materials are sensitive to many gases, precautions must be taken when they are operated. In the present paper, the sensitivity of Nb2O5 to NH3 is studied. NH3 behaves like an electron donor and induces an increase of the N-type semiconductor Nb2O5 conductivity. In presence of oxygen, the conductivity decreases and the sensitivity of the Nb2O5 oxide to the NH3 gas is much lower than in absence of oxygen. Humidity injects electronic carriers in the Nb2O5 material and acts like an electron donor. In presence of humidity, the conductivity of the Nb2O5 layer to NH3 is improved. Those results are interpreted by using a model where the sensor resistance is dominated by the grain boundary resistance. (C) 1997 Elsevier Science S.A.