Ngk Insulators, Inc.

Kei Kosaka

Yusuke Vincent Fujii

Yuki Nakayama

Shota Kageyama

Takayuki Sekiya

Tomohiko Shibata

Shigeaki Sumiya

Shodai Hirata

Iwao Ohwada

Takayoshi Akao

Shuichi Ozawa

Sang Jae Lee

Masao Takahashi

Michiaki Isoda

Yosuke Noritake

Keita Kayano

A sensor element includes an element body, an upper connector electrode disposed on a first surface of the element body, and a protective layer that covers at least a front end-side part of the first surface. The protective layer includes a first specific protective layer having a thickness Tof 10 μm or less. The ratio T/Tof the thickness Tto the thickness Tof a front-side portion of the protective layer which faces the front end of the first specific protective layer is 1.0 or less.

Sensor element and gas sensor

A gas sensor includes a sensor element and one or more hollow columnar dense bodies. The sensor element includes an element main body having a side surface, a porous layer and a water-penetration reduction portion that cover at least a front end-side part of the side surface. The water-penetration reduction portion disposed on the side surface so as to divide the porous layer or to be located closer to the rear end than the porous layer, an overlap length W that is the length of a continuous overlap between a range in which the water-penetration reduction portion is present in a longitudinal direction and a range in which inner peripheral surfaces of the one or more dense bodies are present in the longitudinal direction being 0.5 mm or more, and having a dense layer covers the side surface, the water-penetration reduction portion reduces the capillarity of water.

Gas sensor

A sensor element includes element main body including side surfaces, a detection unit, connector electrodes disposed on the rear end-side part of the side surfaces, a porous layer that covers at least front end-side part of the side surface, the porous layer having a porosity of 10% or more, and a water-penetration reduction portion. The water-penetration reduction portion is disposed on the side surface so as to divide the porous layer or to be located closer to the rear end than the porous layer. The length L of the water-penetration reduction portion is 0.5 mm or more. The water-penetration reduction portion includes, among a dense layer covering the side surface and having a porosity of less than 10% and a gap region in which the porous layer is absent, at least the dense layer. The water-penetration reduction portion reduces the capillarity of water.

A gas sensor includes a sensor element and one or more hollow columnar dense bodies. The sensor element includes an element main body having a side surface, a porous layer and a water-penetration reduction portion that cover at least a front end-side part of the side surface. The water-penetration reduction portion disposed on the side surface so as to divide the porous layer an overlap length W that is the length of a continuous overlap between a range in which the water-penetration reduction portion is present in the longitudinal direction and a range in which inner peripheral surfaces of the one or more dense bodies are present in the longitudinal direction being 0.5 mm or more, the water-penetration reduction portion being a gap region in which the porous layer is absent, the water-penetration reduction portion reduces the capillarity of water.

The sensor element, which can detect the concentration of a specified gas, is held with a housing with a front end thereof exposed. A protective cover includes an inner cover and an outer cover, and secured to the housing. A ratio &#x3c6;1/&#x3c6;2 is set to a range from 0.6 to 0.9, where &#x3c6;1 represents an outer diameter of a portion where an inner gas aperture is formed in the inner cover, and &#x3c6;2 represents an inner diameter of a portion where an outer gas aperture is formed in the outer cover.

Gas concentration detection sensor

First outer gas aperturesare arranged in a first cornersuch that the outer opening plane of each first outer gas apertureforms an angle of 45 degrees with a bottom face of a step elementand the outer opening plane forms an angle of 90 degrees with an inner circumferential face of the first outer gas aperture. Second outer gas apertures are arranged in a second corner 146such that the outer opening plane of each second outer gas apertureforms an angle of 45 degrees with a bottom face of an edge sectionand the outer opening plane forms an angle of 90 degrees with an inner circumferential face of the second outer gas aperture. This structure prevents water from adhering to a sensor elementand thereby enhances the response of a gas sensor

A flow path from outer gas introduction aperturesto inner gas introduction apertureshas a narrower-width flow passage formed by an inner wall member. This structure effectively lowers the probability that a liquid, such as water, entering from the outer gas introduction aperturespasses through a gas inflow chamberand reaches a sensor element, compared with a structure without the inner wall member. The inner wall memberis formed as a solid member that is capable of storing the surrounding heat. Even if there is a certain event that has the potential of causing a temperature decrease of the sensor element, for example, an abrupt change in flow rate of an object gas, the heat stored in the inner wall membereffectively prevents a temperature decrease of the sensor element. This structure prevents the occurrence of cracking in the sensor element, compared with a conventional sensor structure having a double-layered protective cover.

A gas sensor, that represses a manufacturing cost, obtains high responsiveness and can effectively reduce adhesion of water to a sensor element and intrusion of water into the sensor element, is provided. In the gas sensor that has the sensor element mainly containing a solid electrolyte with oxygen ion conductivity and a protective cover arranged to surround the sensor element and detects a predetermined gas component in a measurement gas, the protective cover includes an inner protective cover that is formed into a bottomed cylindrical shape, has a plurality of inner gas distributing holes formed in two rows on its side surface in a longitudinal direction of the sensor element and surrounds one front end of the sensor element, and an outer protective cover that is formed into a bottomed cylindrical shape, has a plurality of outer gas distributing holes on its side surface and surrounds the inner protective cover.

A method for preparing an AlGaN crystal layer with good surface flatness is provided. A surface layer of AlN is epitaxially formed on a c-plane sapphire single crystal base material by MOCVD method, and the resulting laminated body is then heated at a temperature of 1300&#xb0; C. or higher so that a template substrate applying in-plane compressive stress and having a surface layer flat at a substantially atomic level is obtained. An AlGaN layer is formed on the template substrate at a deposition temperature higher than 1000&#xb0; C. by an MOCVD method that includes depositing alternating layers of a first unit layer including a Group III nitride represented by the composition formula AlGaN (0&#x2266;x&#x2266;1) and a second unit layer including a Group III nitride represented by the composition formula AlGaN (0&#x2266;y&#x2266;1 and y&#x2260;x) such that the AlGaN layer has a superlattice structure.

Method for forming AlGaN crystal layer

An electron-emitting device includes an emitter section composed of a dielectric material, a lower electrode disposed on the lower side of the emitter section, and an upper electrode disposed on the upper side of the emitter section so as to be opposed to the lower electrode with the emitter section therebetween, electrons being emitted from the emitter section through the upper electrode by the application of a drive voltage between the lower electrode and the upper electrode, wherein the upper electrode is provided with a plurality of through-holes which expose the emitter section and which have an average diameter of 10 nm or more and less than 100 nm, and a peripheral portion of each through-hole facing the emitter section is separated at a predetermined distance from the emitter section.

Electron-emitting device and method for manufacturing same

There is provided a method for preparing an AlGaN crystal layer having an excellent surface flatness. A buffer layer effective in stress relaxation is formed on a template substrate having a surface layer that is flat at a substantially atomic level and to which in-plane compressive stress is applied, and an AlGaN layer is formed on the buffer layer, so that an AlGaN layer can be formed that is flat at a substantially atomic level. Particularly when the surface layer of the template substrate includes a first AlN layer, a second AlN layer may be formed thereon at a temperature of 600&#xb0; C. or lower, while a mixed gas of TMA and TMG is supplied in a TMG/TMA mixing ratio of 3/17 or more to 6/17 or less, so that a buffer layer effective in stress relaxation the can be formed in a preferred manner.

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Nagoya, Japan

Kei Kosaka