Sensor element and gas sensor
A sensor element includes: an element body having a front end and a back end which are both ends in a longitudinal direction, a lateral face which is a face along the longitudinal direction, an outer lead section disposed on the lateral face; and a dense layer which covers part of the lateral face. The outer lead section has a first region which is covered at least in part by the dense layer. The first region contains zirconia. TM ratio is lower than 2, the TM ratio being a ratio Ht/Hm of a peak height Ht of T-phase to a peak height Hm of M-phase of zirconia in a Raman spectrum measured using Raman spectroscopy, and the dense layer has a thickness less than 11 μm.
1 . A sensor element for detecting a specific gas concentration in a measurement-object gas, the sensor element comprising:
an element body having a front end and a back end which are both ends along a longitudinal direction, and a lateral face which is a surface along the longitudinal direction, wherein a front-end side is to be exposed to the measurement-object gas;
an outer electrode disposed on the front-end side of the lateral face;
a connector electrode disposed on a back-end side of the lateral face to be electrically connected to an outside;
an outer lead section disposed on the lateral face to electrically connect the outer electrode and the connector electrode; and
a dense layer disposed closer to the front-end side than the connector electrode to cover part of the lateral face,
wherein the outer lead section has a first region which is covered at least in part by the dense layer,
the first region contains zirconia, TM ratio is lower than 2, the TM ratio being a ratio Ht/Hm of a peak height Ht of T-phase to a peak height Hm of M-phase of zirconia in a Raman spectrum measured using Raman spectroscopy, and
the dense layer has a thickness less than 11 μm.
2 . The sensor element according to claim 1 ,
wherein the first region has the TM ratio lower than or equal to 1.
3 . The sensor element according to claim 2 ,
wherein the first region has the TM ratio higher than or equal to 0.01.
4 . The sensor element according to claim 3 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
5 . The sensor element according to claim 2 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
6 . The sensor element according to claim 1 ,
wherein the first region has the TM ratio lower than or equal to 0.1.
7 . The sensor element according to claim 6 ,
wherein the first region has the TM ratio higher than or equal to 0.01.
8 . The sensor element according to claim 7 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
9 . The sensor element according to claim 6 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
10 . The sensor element according to claim 1 ,
wherein the first region has the TM ratio higher than or equal to 0.01.
11 . The sensor element according to claim 10 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
12 . The sensor element according to claim 1 ,
wherein the dense layer has a thickness less than or equal to 10 μm.
13 . The sensor element according to claim 1 ,
wherein the outer lead section has the first region and a second region, and
the dense layer covers only the first region between the first region and the second region over a length from the front-end side to the back-end side of the dense layer.
14 . A gas sensor comprising the sensor element according to claim 1 .