Abstract: A gas sensor includes an internal space, diffusion control part, pumping cell, and measuring cell. The diffusion control part communicates with the internal space and has a slit-like shape with a smaller thickness than that of the internal space. The pumping cell pumps out oxygen from the internal space when voltage is applied between a first electrode formed on a surface of the internal space and a second electrode formed outside the internal space. The measuring cell measures a current flowing between a third and fourth electrodes when a voltage is applied between the third and fourth electrodes. The third electrode is formed in the diffusion control part, and can reduce an oxide gas component in a predetermined gas component to which a predetermined diffusion resistance has been applied by the diffusion control part. The fourth electrode is formed in a part different from the diffusion control part.

Abstract: A gas sensor having a sensor element that includes an inner space for introducing a measurement gas therein from an external space and a pump cell which has a first electrode formed on a surface of the inner space and a second electrode formed in a space different from the inner space and is provided to pump oxygen out of the inner space by applying a predetermined voltage between the first electrode and the second electrode. Assuming that the length of the inner space in a short-side direction of the sensor element as viewed from the front end portion side thereof is x1 and the length of the inner space in a longitudinal direction of the sensor element as viewed from the front end portion side thereof is x2, the following inequality is satisfied: 0.05?x1/x2?0.25.

Abstract: A gas sensor including a pump electrode and a method for manufacturing a conductive paste for forming the pump electrode. When the pump electrode constituting an electrochemical pump cell for adjusting an oxygen partial pressure inside a gas sensor to measure a concentration of a gas component in a measurement gas by a current-limiting method is formed of a cermet of a noble metal and an oxide having oxygen ion conductivity, the noble metal contains a first noble metal having a catalytic activity, and a second noble metal having a catalytic activity suppressing ability to suppress the catalytic activity of the first noble metal with respect to an oxide gas except for oxygen, and an abundance ratio of the second noble metal with respect to the first noble metal in a particle surface of the first noble metal existing in the pump electrode is to be 0.01 to 0.3.

Abstract: A gas sensor for specifying a concentration of a predetermined gas component in a measurement gas on the basis of a current flowing in an electrolyte by decomposition of the predetermined gas component, includes an internal space; a reference gas space; a pumping cell capable of pumping out oxygen in the internal space by applying a predetermined voltage between a first electrode and a second electrode; and a measuring cell including a third electrode and a fourth electrode and measuring a current flowing between the third electrode and the fourth electrode when a voltage is applied between the third electrode and the fourth electrode; wherein the first electrode is formed of porous cermet consisted of noble metal containing gold of greater than or equal to 0.01 wt % and less than or equal to 0.95 wt %.

Abstract: A sensor for specifying a concentration of a predetermined gas component in a measurement gas on the basis of a current flowing in an electrolyte by decomposition of the predetermined gas component, includes an internal space; a reference gas space; a pumping cell capable of pumping out oxygen in the internal space by applying a predetermined voltage between a first electrode and a second electrode; and a measuring cell including third and fourth electrodes and measuring a current flowing when a voltage is applied between the third electrode and the fourth electrode; wherein the first electrode is formed of porous cermet consisted of a noble metal and an oxygen ion conductive solid electrolyte, and the porosity of the first electrode is greater than or equal to 10% and less than or equal to 50%.