Abstract: A NOx sensor for measuring NOx concentration including a main pumping cell and a detecting electrode, the main pumping cell-including an electrode having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used to control oxygen concentration in a measurement gas to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode. Accordingly, it is possible to suppress the oxidation of Rh and the reconversion into the metal contained in the detecting electrode, stabilize the impedance, and stabilize the sensitivity to NOx.

Abstract: A detecting electrode comprises a first cermet electrode layer formed directly on a solid electrolyte layer and a second cermet electrode layer formed on the first cermet electrode layer. The ratio between Pt and Rh in the first cermet electrode layer ranges from 100:0 to 25:75 by weight. The ratio between Pt and Rh in the second cermet electrode layer ranges from 25:75 to 0:100 by weight.

Abstract: A detecting electrode comprises a first cermet electrode layer formed directly on a solid electrolyte layer and a second cermet electrode layer formed on the first cermet electrode layer. A ratio between an alloy of Pt—Rh and ZrO2 in the first cermet electrode layer ranges from 20:80 to 50:50 by volume ratio. On the other hand, a ratio between an alloy of Pt—Rh and ZrO2 in the second cermet electrode layer ranges from 60:40 to 50:50 by volume ratio.

Abstract: A gas sensor for measuring an amount of a measurement gas component, including a solid electrolyte having an internal space, a gas-introducing port for introducing measurement gas from an external space into the internal space, diffusion rate-determining means between the internal space and the gas-introducing port, and inner and outer pumping electrodes for pumping-processing oxygen contained in the measurement gas. The diffusion rate-determining means includes slits each having, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, with at least one dimension of each slit being not more than 10 microns.

Abstract: A gas sensor for measuring an amount of a measurement gas component, including a solid electrolyte having an internal space, a gas-introducing port for introducing measurement gas from an external space into the internal space, diffusion rate-determining means between the internal space and the gas-introducing port, and inner and outer pumping electrodes for pumping-processing oxygen contained in the measurement gas. The diffusion rate-determining means includes slits each having, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, with at least one dimension of each slit being not more than 10 microns.

Abstract: A NOx sensor for measuring NOx concentration including a main pumping cell and a detecting electrode, the main pumping cell-including an electrode having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used to control oxygen concentration in a measurement gas to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode. Accordingly, it is possible to suppress the oxidation of Rh and the reconversion into the metal contained in the detecting electrode, stabilize the impedance, and stabilize the sensitivity to NOx.

Abstract: Disclosed is a NOx sensor for measuring a NOx concentration comprising a main pumping cell and a detecting electrode, the main pumping cell including an electrode (an inner pumping electrode and an outer pumping electrode) having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used so that an oxygen concentration in a measurement gas is controlled to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode.

Abstract: A gas sensor for measuring an amount of a measurement gas component, including a solid electrolyte having an internal space, a gas-introducing port for introducing measurement gas from an external space into the internal space, diffusion rate-determining means between the internal space and the gas-introducing port, and inner and outer pumping electrodes for pumping-processing oxygen contained in the measurement gas. The diffusion rate-determining means includes slits each having, when viewed in a plane substantially perpendicular to a longitudinal extension axis thereof, two dimensions, with at least one dimension of each slit being not more than 10 microns.

Abstract: Disclosed are a gas sensor and a nitrogen oxide sensor each comprising a first diffusion rate-determining section for giving a predetermined diffusion resistance to a measurement gas to be introduced into a first chamber, the first diffusion rate-determining section being formed with a slit having a laterally extending aperture formed at a front end portion of a second spacer layer to make contact with the lower surface of a second solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber, and a slit having a laterally extending aperture formed at a front end portion of the second spacer layer to make contact with the upper surface of a first solid electrolyte layer in which the aperture is formed to extend with an identical aperture width up to the first chamber.

Abstract: It is intended to avoid invasion of oxygen through any route except for an introducing port for a measurement gas so that the amount of oxide or inflammable gas contained in the measurement gas may be measured highly accurately. Insulative layers are provided for respective lead wires at positions corresponding to portions at which the temperature of the oxygen ion-conductive solid electrolyte is increased due to heat generation effected by a heater. Each of the insulative layers is formed to have a pattern in which one end is exposed to a first chamber or a second chamber, and the other end terminates at a position separated by a predetermined distance from a corresponding through-hole. At least the lead wires, which lead to an auxiliary pumping electrode and a detecting electrode, are densified. Preferably, the insulative layers for these lead wires are also densified.

Abstract: Disclosed is a NOx sensor for measuring a NOx concentration comprising a main pumping cell and a detecting electrode, the main pumping cell including an electrode (an inner pumping electrode and an outer pumping electrode) having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used so that an oxygen concentration in a measurement gas is controlled to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode.

Abstract: Disclosed is a NOx concentration-measuring apparatus for measuring a NOx concentration by using a main pumping cell including an electrode (inner pumping electrode and outer pumping electrode) having no or low decomposing/reducing ability with respect to NOx to control an oxygen concentration in a measurement gas to have a predetermined value which substantially does not affect measurement of NOx component, and using a detecting electrode having certain or high decomposing/reducing ability with respect to NOx to decompose NOx so that an amount of oxygen produced during this process is measured, wherein the detecting electrode is a cermet electrode composed of an alloy of Pt—Rh and a ceramic component, and Pt and Rh are contained in a weight ratio of Pt:Rh=20:80 to 1:99.

Abstract: It is intended to avoid invasion of oxygen through any route except for an introducing port for a measurement gas so that the amount of oxide or inflammable gas contained in the measurement gas may be measured highly accurately. Insulative layers are provided for respective lead wires at positions corresponding to portions at which the temperature of the oxygen ion-conductive solid electrolyte is increased due to heat generation effected by a heater. Each of the insulative layers is formed to have a pattern in which one end is exposed to a first chamber or a second chamber, and the other end terminates at a position separated by a predetermined distance from a corresponding through-hole. At least the lead wires, which lead to an auxiliary pumping electrode and a detecting electrode, are densified. Preferably, the insulative layers for these lead wires are also densified.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: A method for producing a NOx sensor comprises the steps of forming electrodes on ceramic green sheets, and stacking and integrating the ceramic green sheets into one unit followed by sintering to prepare a substrate, wherein an oxygen concentration is controlled to be not more than 0.5% in a sintering atmosphere after removal of a binder in the step of sintering the substrate. Specifically, the sintering is performed in an atmospheric atmosphere in Interval 1 in which the temperature in a furnace is changed from room temperature to about 1000.degree. C., and the sintering is performed in a nitrogen atmosphere (oxygen concentration in the atmosphere in the furnace is controlled to be about 400 ppm) in Interval 2 in which the temperature is changed from 1000.degree. C. to a maximum temperature followed by spontaneous radiational cooling.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: Disclosed is a gas sensor comprising a first internal space for making communication with the external space via a first diffusion rate-determining section, a first electrochemical pumping cell for controlling the oxygen concentration in the atmosphere in the first internal space to have a predetermined value, a second internal space for making communication with the first internal space via a second diffusion rate-determining section, a second electrochemical pumping cell for finely adjusting the oxygen concentration in the atmosphere in the second internal space to have a predetermined value, a third internal space for making communication with the second internal space via a third diffusion rate-determining section, a third electrochemical pumping cell for pumping out oxygen produced by reduction or decomposition of a component having bound oxygen in the measurement gas in the third internal space, and an ammeter Ip for detecting a pumping current which is allowed to flow in accordance with the pumping ope

Abstract: Disclosed is an oxide sensor in which O.sub.2 contained in a measurement gas introduced into a first chamber through a first diffusion rate-determining section is removed by the aid of a pumping voltage applied between pumping electrodes, and then the measurement gas is introduced into a second chamber through a second diffusion rate-determining section to remove excessive O.sub.2 by the aid of auxiliary pumping electrodes. A detecting electrode is arranged to satisfy d.gtoreq.t provided that d represents a distance from an end of the auxiliary pumping electrodes on the side of the second diffusion rate-determining section to an end of the detecting electrode on the side of the second diffusion rate-determining section, and t represents a height of the second chamber. A predetermined pumping voltage is applied to the detecting electrode to decompose oxides contained in the measurement gas by the aid of the detecting electrode or a catalyst.

Abstract: Disclosed is an oxide sensor in which a measuring electrode is arranged at a distance d to satisfy -3t.ltoreq.d.ltoreq.3t for a downstream end of an inner pumping electrode for a first chamber, i.e., the end located on a side of a second diffusion rate-determining section, provided that d represents a distance between the measuring electrode and the downstream end in a positive direction directed from the first chamber to a second chamber, and t represents a height of the first chamber. A partial pressure of oxygen in the first chamber is measured by using the measuring electrode. A main pumping cell is subjected to feedback control on the basis of a measured value so that the partial pressure of oxygen in the first chamber is controlled. After that, a measurement gas is introduced into the second chamber. Oxides contained in the measurement gas are decomposed by the aid of a detecting electrode or a catalyst.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.