Abstract: A sensor element includes an element body that contains a measurement-object gas flow section and a heat generation portion. The measurement-object gas flow section includes a main pump chamber, an auxiliary pump chamber, and a measurement chamber. A distance X1 in a left-right direction between a part of a first inner linear portion and a part of a second inner linear portion of the heat generation portion that overlap a main pump chamber projection region is equal to or more than ? of a width Wp of the main pump chamber projection region in the left-right direction. A distance X2 in the left-right direction between a part of the first inner linear portion and a part of the second inner linear portion that overlap an auxiliary pump chamber projection region is equal to or more than 0.4 times the width Wp.

Abstract: A sensor element comprises an element body and a porous protective layer covering a surface of the element body. In this sensor element, the porous protective layer comprises a first layer exposed on a surface of the sensor element and a second layer disposed between the element body and the first layer. The first layer contains ceramic particles and anisotropic ceramics having an aspect ratio of 5 or more and 100 or less, and a part of the first layer is in contact with the element body. Further, a porosity of the second layer is 95 vol % or more.

Abstract: The gas sensor is configured to measure a concentration of a predetermined gas component. The gas sensor includes a sensor element. An internal cavity configured to introduce the measurement target gas from an external space is formed inside the sensor element. The sensor element has a long side and a short side in a plan view. In the sensor element, a proportion of a length in the short side direction of a portion that is shortest in the short side direction, out of portions in which the internal cavity is not formed, to the length of the short side is 0.22 or more. The sensor element has an upper face and a lower face. A proportion of a length from the end portion of the internal cavity near the lower face to the lower face, to a thickness of the sensor element, is 0.50 or more and 0.65 or less.

Abstract: A heater part of a planar sensor element includes: a Pt heater element; and an insulating layer including 90-99.9 wt % of an insulating material having a different coefficient of thermal expansion from a solid electrolyte forming a base part of the element. The heater part other than a heater electrode is buried in the base part. The heater element has a thickness of 10-50 ?m and is covered with the insulating layer. The insulating layer has a porosity of 4% or less and a thickness of 50-150 ?m. The distances of the insulating layer from an end portion of the element, from a main surface on which the heater electrode is located, and from a side surface of the element are respectively 0.25-0.75 mm, 0.20-0.60 mm, and 0.20-0.60 mm. The total length of the element is 80.0 mm or less.

Abstract: A heater part of a planar sensor element includes: a heater element containing Pt; an insulating layer covering the heater element; and a heater electrode located on a main surface of the sensor element to be exposed. A portion of the heater part other than the heater electrode is buried in a base part formed of a solid electrolyte. The insulating layer at least contains MgO, MgAl2O4, and Mg4Nb2O9 in a weight percentage of 97 wt % to 100 wt % in total. MgO, MgAl2O4, and Mg4Nb2O9 are contained in weight percentages of 30 wt % to 60 wt %, 30 wt % to 60 wt %, and 0.5 wt % to 15 wt %, respectively. The insulating layer has a porosity of 4% or less.

Abstract: A heater part of a planar sensor element includes: a Pt heater element; and an insulating layer including 90-99.9 wt % of an insulating material having a different coefficient of thermal expansion from a solid electrolyte forming a base part of the element. The heater part other than a heater electrode is buried in the base part. The insulating layer includes: a porous portion having a porosity of 20-40%; and a dense portion having a porosity of 4% or less. The heater element is covered with the dense portion. A laminated portion in which the porous portion and the dense portion are laminated has a total thickness of 25-100 ?m. The dense portion has a thickness of 5 ?m or more. A thickness ratio of the dense portion to the porous portion is 0.05 to 2.0.

Abstract: A heater part of a planar sensor element includes: a Pt heater element; and an insulating layer including 90-99.9 wt % of an insulating material having a different coefficient of thermal expansion from a solid electrolyte forming a base part of the element. The heater part other than a heater electrode is buried in the base part. The insulating layer includes: a porous portion having a porosity of 20-40%; and a dense portion having a porosity of 4% or less. The heater element is covered with the dense portion. A laminated portion in which the porous portion and the dense portion are laminated has a total thickness of 25-100 ?m. The dense portion has a thickness of 5 ?m or more. A thickness ratio of the dense portion to the porous portion is 0.05 to 2.0.

Abstract: A heater part of a planar sensor element includes: a Pt heater element; and an insulating layer including 90-99.9 wt % of an insulating material having a different coefficient of thermal expansion from a solid electrolyte forming a base part of the element. The heater part other than a heater electrode is buried in the base part. The heater element has a thickness of 10-50 ?m and is covered with the insulating layer. The insulating layer has a porosity of 4% or less and a thickness of 50-150 ?m. The distances of the insulating layer from an end portion of the element, from a main surface on which the heater electrode is located, and from a side surface of the element are respectively 0.25-0.75 mm, 0.20-0.60 mm, and 0.20-0.60 mm. The total length of the element is 80.0 mm or less.

Abstract: A heater part of a planar sensor element includes: a heater element containing Pt; an insulating layer covering the heater element; and a heater electrode located on a main surface of the sensor element to be exposed. A portion of the heater part other than the heater electrode is buried in a base part formed of a solid electrolyte. The insulating layer at least contains MgO, MgAl2O4, and Mg4Nb2O9 in a weight percentage of 97 wt % to 100 wt % in total. MgO, MgAl2O4, and Mg4Nb2O9 are contained in weight percentages of 30 wt % to 60 wt %, 30 wt % to 60 wt %, and 0.5 wt % to 15 wt %, respectively. The insulating layer has a porosity of 4% or less.