A method for manufacturing a gas sensor element (100) including a solid electrolyte (110) and an electrode (130) formed on a surface (110a) of the solid electrolyte (110). The method includes: a slurry application step S3 of forming a first slurry layer (13) by applying a first slurry containing monoclinic zirconia and tetragonal/cubic zirconia to the surface (110a) of the solid electrolyte (110); a heat treatment step S4 of forming a base layer (14) by a heat treating the solid electrolyte (110) having the first slurry layer (13) formed thereon; and a plating step S5 of forming the electrode (130) by plating the base layer (14) using a plating solution containing a noble metal.

A maintenance method for a zirconia-type oxygen analyzer that uses a zirconia sensor to measure oxygen concentration of a gas to be measured includes storing in a memory, by the zirconia-type oxygen analyzer, an internal resistance of the zirconia sensor and/or a calibration coefficient for correcting, based on a measured value of a physical quantity measured by the zirconia sensor for a standard gas having a known oxygen concentration, a formula for converting a measured value of a physical quantity measured by the zirconia sensor into the oxygen concentration of the gas to be measured, determining, by an information processing apparatus, the timing for performing maintenance on the zirconia sensor based on a change over time in the internal resistance and/or calibration coefficient stored in the memory, and presenting, by the information processing apparatus, the timing for performing maintenance on the zirconia sensor.

The sensor element of a gas sensor includes an element body, a surface protective layer provided at the outermost surface position of a tip portion of the element body, in the longitudinal direction of the element body, and an internal protective layer provided between the surface protective layer and the element body. The internal protective layer has a lower thermal conductivity and a higher average porosity than the surface protective layer, and is disposed between the surface protective layer and the element body. In the internal protective layer, a first protective layer portion of the internal protective layer is located on a side that faces the heater, and at least the base position is positioned closer in the longitudinal direction to the tip end of the element body than is the maximum temperature position on the element body.

A preparation method of indium oxide with stable morphology includes: (1) mixing indium oxide powder and bismuth oxide powder according to a mass ratio of 1:0.1-0.5 to obtain a powder mixture; (2) putting the powder mixture into a ball mill for ball milling at room temperature to obtain a uniform powder mixture; (3) putting the obtained uniform powder mixture into a muffle furnace and calcining at 700-1000° C.; and (4) obtaining the indium oxide with cubic stable morphology after the muffle furnace naturally cools to room temperature. The method has advantages of simple synthesis process, short synthesis period, high sample yield, no need of complicated equipment, and morphology of the obtained indium oxide can be maintained after being heated at a high temperature within 1000° C. for 2 hours. An electrochemical sensor prepared by using the indium oxide obtained by the method has better selectivity to nonane.

A gas sensor includes: a laminate formed of a plurality of layers including at least one layer of a solid electrolyte; a reference gas chamber formed in the laminate and containing a reference gas; and a reference electrode partially exposed in the reference gas chamber. A portion which is not exposed in the reference gas chamber, of the reference electrode is sandwiched between, among the layers, a first layer and a second layer adjacent to the first layer. When an area of the portion sandwiched between the first layer and the second layer, of the reference electrode is defined as a first area, and an area of a portion exposed in the reference gas chamber, of the reference electrode is defined as a second area, a ratio of the first area to the second area is 0.3 or more.

Provided is a limiting current gas sensor including a first porous electrode including a main surface; a plurality of solid electrolyte islands provided on the main surface of the first porous electrode and separated from each other; and a second porous electrode provided on the plurality of solid electrolyte islands, in which the first porous electrode is provided across the plurality of solid electrolyte islands, the second porous electrode is provided across the plurality of solid electrolyte islands, and a maximum size of each of the plurality of solid electrolyte islands in plan view of the main surface is equal to or smaller than 50√2 μm.

A gas sensor that measures concentrations of a first target component and a second target component includes a first switch that controls driving of a first preliminary adjustment pump cell to be turned ON or OFF, a second switch that controls driving of a second preliminary adjustment pump cell to be turned ON or OFF, and a switching control device that controls switching between the first switch and the second switch.

A gas sensor includes: a metal tubular body including a through hole allowing a sensor element to penetrate in an axial direction; and a powder compact being filled between an inner surface of the tubular body constituting the through hole and the sensor element, and sealing between both end portion sides of the sensor element. At least a range of a through hole inner surface to come into contact with the powder compact filled between the inner surface and the sensor element is a stripe-like recessed and projecting region in which projecting portions and recessed portions are alternately arranged in the axial direction and those portions extend along an inner circumferential direction of the tubular body. An interval between the projecting portions in the axial direction is 50 μm to 150 μm. The following expressions are satisfied, 0.3 μm≤Rz1≤10 μm, and Rz1/Rz2≥2.0.

A limiting-current type gas sensor including a sensor element including a base part made of an oxygen-ion conductive solid electrolyte and measuring concentration of NOx in a measurement gas includes: a pump cell including a first electrode disposed to be capable of being in contact with a gas introduced into the element and a second electrode disposed so that a part made of the solid electrolyte is located between the first electrode and the second electrode; and a pumping diagnostic part to determine whether an inter-electrode electric field produced in the part made of the solid electrolyte through application of a predetermined pump voltage between the electrodes exceeds a first threshold, and, when the inter-electrode electric field exceeds the first threshold, the predetermined pump voltage is reduced so that the inter-electrode electric field falls below the first threshold.

Disclosed is a gas sensor element having: a solid electrolyte body containing oxygen-ion conductive ZrO.sub.2; a detection electrode disposed on the solid electrolyte body to be exposed to a gas under measurement; and a reference electrode disposed on the solid electrolyte body to be exposed to a reference gas. In the gas sensor element, the detection electrode contains Pt and ZrO.sub.2; the detection electrode has a thickness of 3 to 10 μm; the amount of ZrO.sub.2 contained relative to Pt in the detection electrode is 12 to 18 wt %; the detection electrode has a porosity of 5% or lower; and, in a particle size distribution graph of ZrO.sub.2 particles in the detection electrode, a cumulative value of peaks appearing in a range of 0.025 μm to 0.200 μm is 60 to 75%, and a cumulative value of peaks appearing in a range of 1.000 μm to 3.162 μm is 2 to 7%.