Chromium Titanium Oxide-Based Ammonia Sensors

  • K. Schmitt
  • C. Peter
  • J. WöllensteinEmail author
Part of the Springer Series on Chemical Sensors and Biosensors book series (SSSENSORS, volume 11)


Chromium titanium oxide (Cr2–x Ti x O3+z , CTO) is a solid solution with the corundum crystal structure of the pure chromium oxide if x is in the range of 0.01–0.45. When heated to temperatures above 300°C, CTO shows a very strong and fast resistivity response to the presence of ammonia in air. The conductivity of CTO is primarily determined by chromium imperfections. In gas measurements, CTO shows a p-type semiconductor behavior. At even higher temperatures (>400°C), CTO is an excellent material for ammonia (NH3) detection with a reduced cross sensitivity to humidity. This has been the key to the successful development of ammonia sensors based on CTO.

We investigated CTO as a sensitive material for NH3 sensors operating at room and slightly elevated temperatures. It is based on the change of work function of Cr1.8Ti0.2O3 upon gas exposure. CTO exhibits fast response and relaxation, no baseline drift induced by exposure and little influence of changing ambient humidity. The cross sensitivity to other gases is low, in particular to NO2.


Ammonia Chromium titanium oxide Gas sensor Inkjet printing Work function 



This work is partly funded by the European Commission (Glassgas project) by the US National Science Foundation (NSF, DMR-9701699) and by the German BMBF (MISSY-project). The authors wish to thank Dr. M. Burgmair and Prof. Dr. I. Eisle, Universität der Bundeswehr München for the Kelvin probe and HSGFET measurements. We also like to thank very much Dr. Graham A. Shaw and Dr. Peter Smith, University College London for the support of the work.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  1. 1.Fraunhofer Institute for Physical MeasurementFreiburgGermany
  2. 2.Department of Microsystems EngineeringUniversity of FreiburgFreiburgGermany

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