Highly sensitive humidity sensor based on the solid solution Zr0.2Ti0.8O2 nanofibers

The Zr x Ti 1−x O 2 (x = 0.0–0.5) nanofibers were synthesized by an electrospinning process. The influences of zirconium incorporation on the structure, phase composition, lattice parameters , morphology, specific surface area, and surface states were investigated in terms of XRD , SEM, BET, and XPS tests. The humidity sensing performances were also carried out in detail. It can be concluded that the replacement of Zr at Ti-site had significant impacts with regard to the phase structure: the anatase-rutile phase transformation was inhibited by Zr 4+ ion doping; Zr 4+ ion was successfully incorporated into the TiO 2 lattice through a substitutional mode resulting in the formation of solid solution Zr x Ti 1−x O 2 (x = 0.1–0.2) with anatase structure; when the Zr 4+ ion was saturated, excessive Zr 4+ ion formed new phase of Ti 2 ZrO 6 and ZrTiO 4 (nominal x ≥ 0.3); the lattice parameters and the cell volume increased as Zr 4+ ion incorporation. The solid solution Zr 0.2 Ti 0.8 O 2 nanofibers had the highest Ti 3+ abundance among the samples with x ≤ 0.2, accompanied by the highest oxygen vacancies . Moreover, the solid solution Zr 0.2 Ti 0.8 O 2 nanofibers exhibited the best humidity sensing properties: excellent sensitivity as proven by four orders of magnitude change to impedance at 11–95% relative humidity (RH), negligible hysteresis, rapid response and recovery speed as well as superior stability, which were induced by high concentration of oxygen vacancies combined with reactive Ti 3+ ions. A detailed study of the sensing mechanism was also performed in terms of complex impedance spectra.