Abstract
The work addresses the problem of long- term stability of metal oxide materials gas sensor performance and deals with Nb(V) doped nanocrystalline TiO2 which is characterized by reasonable response values for practical application alongside with the absence of response decay during continuous operation. The TiO2 nanomaterials containing up to 4 at% Nb were synthesized using flame spray pyrolysis. Materials are investigated by XRD and EPR methods. The sensor properties were studied by in situ electrical conductivity measurements. Nb(V) reduces the electrical resistance of TiO2 due to the formation of oxygen vacancies and increase in conduction electron concentration, but this effect is limited by the appearance of a significant number of charge traps. Pure TiO2 tended to transform into rutile phase during annealing in the analyte gas mixture, while Nb stabilized the anatase phase. Both pure and doped TiO2 demonstrate stable sensor performance in long-term, however slow growth of baseline resistance and sensor response are observed which is, according to EPR data, connected with slow processes of defect annealing and intergrain contact formation.
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