This work presents an attempt to apply the undoped n-type semiconductor CeO
2 in the detection of gases - acetone and NO - in an oxygen containing envi
ronment. However, in such gas mixture chemical reactions may take place at
and near the hot sensor surface, changing the composition of the gas enviro
nment. The effect of CeO2 - its catalytic activity - was studied in the oxi
dation of acetone and NO during their detection. For this purpose, a partic
ular experimental set-up was planned and built: a special, flow type quartz
microreactor connected to a mass spectrometer, offering the possibility fo
r simultaneous resistance measurement and analysis of the near sensor gas c
omposition. The sensor was operated both in self- and oven-heated mode betw
een 20-900 degreesC. The maximum sensitivity of CeO2 was found between 350-
450 degreesC for both gases. While acetone causes a well measurable resista
nce change, the signal due to NO is quite small. The CeO2 surface proved to
be catalytically active in the oxidation of acetone resulting in the forma
tion of CO2. Surprisingly, the same surface led to the reduction of NO. (C)
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