| 摘要 |
PURPOSE:To eliminate dependence of limiting current on temperature with a practical temperature range by holding the average pore diameter of a gas diffusion resistance layer provided on one of thin film electrodes provided on both of the surface and back of a solid electrolyte within the range of a specified value in a limiting current type oxygen concentration detector. CONSTITUTION:Porous thin-film-like electrodes 2 and 3 are respectively provided on the surface and back of solid electrolyte element 1 comprising an oxygen ion conductive metal oxide such as ZrO2-Y2O3. A material prepared by evenly mixing a powder of MgO.Al2O3 (spinel) with 1-4wt% of an SiO2 powder is plasma sprayed on one electrode 3 to form a gas diffusion resistance layer 4 at the thickness of 200-500mum. After the plasma spraying, the resistance layer 4 has the average pore diameter of 600-700Angstrom . Then, it is sintered for 2hr at 1,300-1,400 deg.C to change the average pore diameter 300-400Angstrom without impairing the continuity of the pores inside the layer 4. This makes the limiting current free from dependence on the temperature within the temperature range of 750+ or -100 deg.C enabling the use of the detector as element of an oxygen detector for internal combustion engines or the like requiring no temperature compensation within this tmperature range. |
