| abstract |
A sensor is proposed for detecting nitrogen oxides (NO, NO 2 , N 2 O 4 ) in a test gas, having a semiconducting metal oxide layer (3) which is deposited on a ceramic substrate (10) and whose electrical resistance provides information about the concentration of nitrogen oxides (NO, NO 2 , N 2 O 4 ) in the test gas. The main components of the sensor are a converter layer (4) which is deposited on the metal oxide layer (3) and is made of a material which causes the oxidation of combustible components of the test gas and converts the nitrogen monoxide (NO) contained in the test gas into nitrogen dioxide (NO 2 ) or dinitrogen tetroxide (N 2 O 4 ), which then reaches the metal oxide layer (3), as well as a heating device (5) which heats the metal oxide layer (3) and the converter layer (4). The converter layer is suitably constituted of titanium oxide (TiO 2 ) and/or zirconium oxide (ZrO 2 ) and/or silicon oxide (SiO 2 ) and/or aluminum oxide (Al 2 O 3 ) and has a platinum content of from 0.01 to 20 weight percent. |