A gas sensor element including a solid electrolyte body, a sensor electrode, and a reference electrode is provided. The solid electrolyte body has oxygen ion conductivity and includes a measurement gas surface to be exposed to a measurement gas introduced from the exterior and a reference gas surface to be exposed to a reference gas introduced from the exterior. The sensor electrode is provided on the measurement gas surface of the solid electrolyte body. The reference electrode is provided on the reference gas surface of the solid electrolyte body. The sensor electrode includes a porous body containing a solid electrolyte having oxygen ion conductivity and a precious metal, the peak pore size of the sensor electrode being 0.03 μm to 0.3 μm.

The present invention provides a gas sensor capable of suppressing a variation of a sensor output by a sensor cell to be small. A sensor element of a gas sensor comprises a first solid electrolyte body and a second solid electrolyte body having oxygen ion conductivity, a measured gas chamber into which the measured gas is introduced, a first reference gas chamber and a second reference gas chamber into which reference gas is introduced, a first pump cell, a second pump cell, a sensor cell, and a heater. A value obtained by dividing a first average cross-sectional area of the first reference gas chamber by the first length is larger than the value obtained by dividing the second average cross-sectional area of the second reference gas chamber by the second length.

A sensor element 101 includes an element main body 101a that includes oxygen ion-conductive solid electrolyte layers (1 to 6), and a porous protective layer 90 that covers at least part of the element main body 101a. The porous protective layer 90 includes a porous inner protective layer 92 and a porous outer protective layer 91 disposed on the outer side of the inner protective layer 92 and having a smaller average pore diameter than the inner protective layer 92.

A leading-end protective layer of a sensor element includes: an inner layer covering a leading end surface and four side surfaces of an element base; and an outer layer covering the inner layer and having a lower porosity than the inner layer, and a film thickness variation degree, defined as a ratio of a difference between a maximum and a minimum value of total thicknesses of the leading-end protective layer at following positions with respect to an average value of the total thicknesses when the value is based at 100, is 20 or less: two positions to intersect with the protective layer, on planes passing through line intersections of an imaginary plane containing the end surface and imaginary planes containing main surfaces of the element base, and forming an angle of 45° with the former imaginary plane, and an intermediate position in an element thickness direction on the end surface.

A sensor element includes a porous leading-end protective layer disposed around an outer periphery of an element base in a predetermined range from an end portion on a side where a sensing part is disposed, wherein the protective layer includes: a first layer disposed on two main surfaces of the element base; a second layer disposed to cover the end portion and four side surfaces of the element base including the two main surfaces on which the first layer is disposed; and a third layer disposed to cover the second layer, and having a lower porosity than the second layer, the first layer has a porosity of 40% or more, and L1≥L2 and L1≥L3 where L1, L2, and L3 are extension lengths of the first layer, the second layer, and the third layer, respectively, from an end surface of the element base in a longitudinal direction of the element base.

A sensor element includes a porous leading-end protective layer disposed around an outer periphery of an element base in a predetermined range from an end portion on a side where a sensing part is disposed, the protective layer includes: a first layer disposed on two main surfaces of the element base; a second layer disposed to cover the end portion and four side surfaces of the element base including the two main surfaces on which the first layer is disposed; and a layer disposed to cover the second layer, the second layer has a porosity of 30% to 70% and a thickness of 6 to 30 times a thickness of the first layer, and the third layer has a porosity of 10% to 40% and a thickness of 2 to 15 times the thickness of the first layer.

A gas sensor includes a solid electrolyte body with oxygen ion conductivity, a gas flow portion (ranging from a gas inlet port to a second inner cavity), a particular gas detector (including a main pump cell, a measurement pump cell, an auxiliary pump cell, etc.), and a control device. Prior to startup of the gas sensor, the control device sets electric power supplied to a heater such that a temperature difference between a temperature of the heater and a preset target temperature becomes zero, and determines, on the basis of the set electric power, whether temperature raising control of supplying the set electric power to the heater is to be executed.

A gas sensor element includes: an element base being a ceramic structure including a sensing part; and a leading-end protective layer being a porous layer disposed around an outer periphery of the element base in a predetermined range on a side of the sensing part. The leading-end protective layer includes: a first layer disposed at least on two main surfaces of the element base; a second layer disposed to cover the end portion and four side surfaces of the element base including the two main surfaces; and a third layer disposed to cover the second layer. The second layer has a porosity of 30% to 80%, and has a thickness of 30 to 50 times thickness of the first layer, and the third layer has a porosity of 15% to 30%, and has a thickness of 5 to 10 times the thickness of the first layer.

A gas sensor element capable of preventing a decrease in responsiveness despite a protective layer covering a gas introduction opening is provided. A gas sensor element according to an aspect of the present invention includes an element base having a surface in which a gas introduction opening is open, a protective layer, a buffer layer, and a gas introduction layer that is disposed between the element base and the buffer layer. The gas introduction layer covers the gas introduction opening, is in contact with the protective layer, and has a porosity that is 30% or more and is higher by 5% or more than the porosity of the buffer layer.

Provided is a sensor including a substrate that includes a major surface, a sensor part that includes a gas flow path formed of a porous material, and at least one of a heater or a temperature sensor. The heater is capable of heating the sensor part, the temperature sensor is capable of measuring temperature of the sensor part, the sensor part and the at least one of the heater or the temperature sensor are stacked over the major surface, the at least one of the heater or the temperature sensor is an interconnect having forward tapered side surfaces, and the at least one of the heater or the temperature sensor includes a metal interconnect layer, and the forward tapered side surfaces of the interconnect overlap with the gas flow path in plan view of the major surface.