Ceramic applications in gas and humidity sensors

In this paper chemical sensors which employ ceramic materials are reviewed in general terms; the sensing technologies are outlined, construction materials and fabrication methods are noted, advantages and disadvantages discussed and commercial applications described. The paper is not comprehensive in scope but instead highlights significant features and focuses on those ceramic sensors which are the most successful commercially. Recent developments in microsensors and recent research activities are also covered. Much work on semiconducting oxides, particularly on tin oxide, has been identified. Tin oxide is probably the material of choice for the greater growth of gas sensor applications. Zirconium oxide based oxygen sensors are routinely employed in the automotive industry while titanium oxide materials are finding increasing application. Humidity sensors are now used in a variety of consumer products such as microwave ovens and video tape recorders. There is also an increase in the use of sensors at the consumer level to detect combustible house gases and related toxic gases such as carbon monoxide. Smart materials and structures are advanced technologies which rely heavily on chemical sensors.