Multilayered air-fuel ratio sensing element

摘要

A multilayered air-fuel ratio sensing element has a zirconic solid electrolytic body (11) and a heat-generating portion (13, 16, 22) including an alumina substrate located adjacent to the zirconic solid electrolytic body (11). The zirconic solid electrolytic body (11) is made of a partially stabilized zirconia containing 5 SIMILAR 7 mol% yttria and having a mixed phase structure including a cubic phase, a monoclinic phase and a tetragonal phase. The zirconic solid electrolytic body (11) has a relative density of 94 SIMILAR 100% with a mean sintered grain size (RZR) of 0.5 SIMILAR 3.0 mu m. The alumina substrate has a relative density of 95 SIMILAR 100% with a mean sintered grain size (RAL) of 0.5 SIMILAR 4.0 mu m. And, the partially stabilized zirconia has an M/C ratio in a range from 0.05 to 0.25. <IMAGE> <IMAGE>