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Rola adsorpcji i katalizy w detekcji gazów przy użyciu półprzewodnikowych czujników gazowych. Cz.1 Mechanizm działania i preparatyka czujników rezystancyjnych

Kocemba I.

Wiadomości Chemiczne

1999

[Z] 53, 3-4

249-270

The development of semiconductor gas sensors for the detection of combustion and toxic gases has been in progress for several years. Ceramics gas sensors based on SnO2, TiO2, ZnO have been widely accepted as an important tool for detecting or monitoring gases and vapours like H2, CO, CH4, H2S, C2H5OH. The sensors are manufactured by means of different technologies. The most popular ones are resistant sensors based on SnO2, developed in Japan and currently produced on a large scale. Among these, TGS sensors (Tagushi Gas Sensors) from Japanese company Figaro are the most popular ones .The principle of the operation of this type of sensors consist in a comparison of electrical resistance of semiconducting oxide in air, and in the presence of the detected gas. The change in resistance is a function of the concentration of the gas. The gas sensing mechanism for a reducing gas such as carbon monoxide involves the reaction of CO with ionosorbed oxygen on the sensor surface leading to a decrease in resistance. (...) Because problem of catalysis in detection gases is very large, the review is divided into four parts: I. Sensing mechanism and preparation, II. The correlation between adsorption and detection, III. The correlation between catalytic activity and detection. In the last part of the paper (part IV) would like to show the role of adsorption and catalysis in other semiconductor gas sensors such as Pd-MISFET, SAW or Zirconia sensors. In this part of the paper, the mechanisms of detection and the influence of oxide-metal semiconductor preparation on properties of ceramics gas sensors is presented. The results of different works show that the sensing characteristic of semiconductor gas sensor can be improved by controlling fundamental factors which affect its receptor and transducer functions. The transducer function is related to the microstructure of the sintering specimen. This microstructure is characterised by the grain size and the depth of surface space-charge layer. On the other hand, the receptor function is modified by the introduction of foreign receptors on the surface of sensors. In the particular cases of Pt, Pb and Ag are promotors. These problems are presented in aspects of phenomenon of adsorption and catalysis and the role they play in detection of gases.