Sol-gel processed TiO2-based thin films as innovative humidity sensors

Giampiero Montesperelli*, Antonio Pumo, Enrico Traversa, Gusmano, Andrea Bearzotti, Angelo Montenero, Guglielmina Gnappi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Active elements for humidity sensors based on alkali-doped and undoped TiO2 films have been prepared by the sol--gel technique. TiO2-based films are deposited onto Al2O3 substrates with comb-type Au electrodes by dip-coating, from the appropriate solutions, to obtain four different compositions of 1, 3, 6, and 10 at.% Li and K, with respect to the alkali metal/Ti system. The humidity-sensing electrical properties of the films are evaluated using d.c. and a.c. measurements. The electrical characterization of TiO2 films doped with 10 at.% K shows that this material has some unique properties. Resistence versus relative humidity(rh) values show variations as high as seven orders of magnitude in the humidity range tested. Very high humidity sensitivity is also observed at the lowest rh values (4-10% rh), at 40°C, when the resistence is measured at frequencies lower than 1 Hz. The results also show great stability over time. The possibility of modifying the rh sensitivity of TiO2, films doped with 10 at.% K by varying the frequency at which the resistance is measured is a characteristic that allows this material to be described as smart.

Original languageEnglish (US)
Pages (from-to)705-709
Number of pages5
JournalSensors and Actuators: B. Chemical
Issue number1-3
StatePublished - Jan 1 1995


  • Alkali
  • Humidity sensors
  • Sol-gel process
  • Thin films
  • Titania

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry


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