| 摘要 |
An electrochemical sensor for measuring the oxygen content of gases, in particular exhaust gases from internal combustion engines, comprises a solid electrolyte of zirconium dioxide and/or other oxides which conduct oxygen ions and at least one electrode arranged on the side of the solid electrolyte exposed to the gas to be measured. The electrode(s) may contain a ceramic supporting skeleton and the electrode(s) exposed to the gas to be measured is (are) covered with a porous ceramic protective coating of an Al2O3- and/or Mg spinel (MgO.Al2O3) matrix in which preferably metastable ZrO2 particles are embedded. The use of a mixed oxide system of Al2O3/ZrO2, which may contain a stabilizer for the ZrO2, and which is preferably obtained by coprecipitation or by combination of suspensions of separately precipitated components or by spray calcination of a common solution of salts of the components, makes it possible in a surprising way to obtain a sintered adhesive protective layer with a relatively narrow pore size distribution which allows the optimal passage of gas to the outer electrode of the sensor. The use of the Al2O3/ZrO2 mixed oxide powder also makes it possible to compensate to a very large extent for the previously observed disproportion between the mechanical stresses and the adhesive strength of the layer and to obtain the desired porosity and regulating position of the sensor.
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