Summary: Sensors and Actuators B 119 (2006) 384391
Fine-tuning of ceramic-based chemical sensors
via novel microstructural modification
I: Low level CO sensing by tungsten oxide, WO3
Abdul-Majeed Azad, Majed Hammoud
Department of Chemical and Environmental Engineering, The University of Toledo, 3052 Nitschke Hall, Toledo, OH 43606-3390, USA
Received 27 July 2005; received in revised form 12 December 2005; accepted 16 December 2005
Available online 24 January 2006
High selectivity, enhanced sensitivity, short response time and long shelf-life are some of the key features sought in the solid-state ceramic-based
chemical sensors. Since the sensing mechanism and catalytic activity are predominantly surface-dominated, benign surface features in terms
of small grain size, large surface area, and open and connected porosity, are required to realize a successful material. In order to incorporate
these morphological features, a technique based on rigorous thermodynamic consideration of the metal/metal oxide coexistence, is described.
By modulating the oxygen partial pressure across the equilibrium metal/metal oxide (M/MO) proximity line, formation and growth of new oxide
surface on an atomic/submolecular level under conditions of `oxygen deprivation', with exotic morphological features has been achieved in potential
sensor materials. This paper describes the methodology and discusses the results obtained in the case of tungsten oxide-based carbon monoxide
sensors (in the range of 14100 ppm CO) with enhanced sensing characteristics.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Microstructure; Chemical sensors; Semiconducting ceramic oxides; Redox reactions