Ngk Insulators, Inc.

Ngk Insultators, Ltd.

Kei Sato

Tsutomu Nanataki

Morimichi Watanabe

Kiyoshi Matsushima

Nobuyuki Kobayashi

Yukihisa Takeuchi

Hirofumi Yamaguchi

Katsuhiro Imai

Jun Yoshikawa

Takashi Yoshino

Iwao Ohwada

Tomohiko Sugiyama

Yukinobu Yura

Toshikatsu Kashiwaya

Shohei Yokoyama

Shuichi Ozawa

Hiroshi Fukui

Takahiro Maeda

Yoshitaka Kuraoka

Tetsuya Hattori

Isao Shikata

An oriented ceramic sintered body production method includes (a) a step of preparing a ceramic compact before firing into an oriented ceramic sintered body; and (b) a step of obtaining an oriented ceramic sintered body by sandwiching the ceramic compact between a pair of releasing sheets, placing the ceramic compact and the releasing sheets in a hot press firing furnace, and hot press firing the ceramic compact while applying a pressure by a pair of punches through the pair of releasing sheets, wherein each of the releasing sheets is a releasing sheet such that, after the releasing sheet is sandwiched between PET films, is then placed and vacuum-packed on a stainless steel sheet, and is isostatically pressed at 200 kg/cm, a surface of the releasing sheet on the side opposite from the stainless steel sheet has a profile curve with a total profile height Pt of 0.8 μm or less.

Oriented ceramic sintered body production method and flat sheet

A method for producing an oriented sintered body according to the present invention includes the steps of: (a) preparing a multilayer body, the multilayer body including a layer including a fine raw-material powder and a layer including a plate-like raw-material powder which are alternately stacked each other, particles of the plate-like raw-material powder being arranged such that surfaces of the particles of the plate-like raw-material powder extend along a surface of the layer including a fine raw-material powder; and (b) sintering the multilayer body.

Method for producing oriented sintered body

A method for producing a transparent alumina sintered body according to the present invention includes (a) a step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more and a fine alumina powder having an average particle diameter smaller than that of the plate-like alumina powder so that, when a mixing ratio of the plate-like alumina powder to the fine alumina powder in terms of mass ratio is assumed to be T:(100&#x2212;T), T is 0.001 or more and less than 1, and so that a mass ratio R1 of F relative to Al in the alumina raw material powder is less than 15 ppm; (b) a step of forming a raw material for forming containing the alumina raw material powder into a compact; and (c) a step of sintering the compact so as to obtain a transparent alumina sintered body.

Method for producing transparent alumina sintered body

There is provided a self-supporting polycrystalline gallium nitride substrate having excellent characteristics such as high luminous efficiency and high conversion efficiency when used for devices, such as light emitting devices and solar cells. The self-supporting polycrystalline gallium nitride substrate is composed of gallium nitride-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate, and has a top surface and a bottom surface. The crystal orientations of individual gallium nitride-based single crystal grains as determined from inverse pole figure mapping by electron backscatter diffraction (EBSD) analysis on the top surface are distributed at various tilt angles from the specific crystal orientation, in which the average tilt angle thereof is 0.1&#xb0; or more and less than 1&#xb0; and the cross-sectional average diameter Dof the gallium nitride-based single crystal grains at the outermost surface exposed on the top surface is 10 &#x3bc;m or more.

Polycrystalline gallium nitride self-supported substrate and light emitting element using same

An oriented alumina substrate for epitaxial growth according to an embodiment of the present invention includes crystalline grains constituting a surface thereof, the crystalline grains having a tilt angle of 0.1&#xb0; or more and less than 1.0&#xb0; and an average sintered grain size of 10 &#x3bc;m or more.

Oriented alumina substrate for epitaxial growth

An oriented alumina substrate for epitaxial growth according to an embodiment of the present invention includes crystalline grains constituting a surface thereof, the crystalline grains having a tilt angle of 1&#xb0; or more and 3&#xb0; or less and an average sintered grain size of 20 &#x3bc;m or more.

An alumina sintered body of the present invention has a degree of c-plane orientation of 5% or more, which is determined by a Lotgering method using an X-ray diffraction profile in a range of 2&#x3b8;=20&#xb0; to 70&#xb0; obtained under X-ray irradiation, and an XRC half width of 15.0&#xb0; or less in rocking curve measurement, an F content of less than 0.99 mass ppm when measured by D-SIMS, a crystal grain diameter of 15 to 200 &#x3bc;m, and 25 or less pores having a diameter of 0.2 &#x3bc;m to 1.0 &#x3bc;m when a photograph of a viewing area 370.0 &#x3bc;m in a vertical direction and 372.0 &#x3bc;m in a horizontal direction taken at a magnification factor of 1000 is visually observed.

Alumina sintered body and base substrate for optical device

96 parts by mass of a &#x3b3;-alumina powder, 4 parts by mass of a an AlFpowder, and 0.17 parts by mass of an &#x3b1;-alumina powder as a seed crystal were mixed by a pot mill. The purities of each raw material were evaluated, and it was found that the mass ratio of each impurity element other than Al, O, F, H, C, and S was 10 ppm or less. In a high-purity alumina-made sagger having a purity of 99.9 percent by mass, 300 g of the obtained mixed powder was received, and after a high-purity alumina-made lid having a purity of 99.9 percent by mass was placed on the sagger, a heat treatment was perforated at 900&#xb0; C. for 3 hours in an electric furnace in an air flow atmosphere, so that an alumina powder was obtained. The value of AlFmass/container volume was 0.016 g/cm.

Method for manufacturing plate-like alumina powder and plate-like alumina powder

An alumina sintered body according to the present invention includes a surface having a degree of c-plane orientation of 5% or more, the degree of c-plane orientation being determined by a Lotgering method using an X-ray diffraction profile obtained through X-ray irradiation at 2&#x3b8;=20&#xb0; to 70&#xb0;. The alumina sintered body contains Mg and F, a Mg/F mass ratio is 0.05 to 3500, and a Mg content is 30 to 3500 ppm by mass. The alumina sintered body has a crystal grain size of 15 to 200 &#x3bc;m. When a field of view of 370.0 &#x3bc;m long&#xd7;372.0 &#x3bc;m wide is photographed with a 1000-fold magnification and the photograph is visually observed, a number of pores having a diameter of 0.2 to 0.6 &#x3bc;m is 250 or less.

A method for producing a transparent alumina sintered body includes (a) the step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more so that the mass ratio R1 of F to Al in the alumina raw material powder is 5 ppm or more, and forming a compaction raw material containing the alumina raw material powder into a compact, and (b) the step of pressure-sintering the compact at a temperature at which F evaporate to yield a transparent alumina sintered body.

A plate-like alumina powder production method of the present invention comprises placing a transition alumina and a fluoride in a container such that the transition alumina and the fluoride do not come into contact with each other and then performing heat treatment to obtain a plate-like &#x3b1;-alumina powder. The transition alumina is preferably at least one selected from the group consisting of gibbsite, boehmite, and &#x3b3;-alumina. It is preferable that the amount of the fluoride used is set such that the percentage ration of F in the fluoride to the transition alumina is 0.17% by mass or more. The container preferably has a volume such that a value obtained by dividing the mass of F in the fluoride by the volume of the container is 6.5&#xd7;10g/cmor more. The heat treatment is preferably performed at the temperature of 750 to 1,650&#xb0; C.

Method for producing a plate-like alumina power

An alumina sintered body according to the present invention has a degree of c-plane orientation of 90% or more as determined by Lotgering's method from an X-ray diffraction profile obtained by irradiating a plate surface with X-rays in a range of 2&#x3b8;=20&#xb0; to 70&#xb0;. The alumina sintered body has no pores when a cross-sectional surface formed in a direction perpendicular to the plate surface is polished using an Arion beam and a mask and is examined under a scanning electron microscope at a magnification of 5,000 times. The alumina sintered body has a total mass fraction of impurity elements other than Mg and C of 100 ppm or less. This alumina sintered body has a high degree of orientation, high density, and high purity and thus has a higher optical translucency than those known in the art.

There is provided a positive electrode active material capable of achieving a high volume energy density and yet superior rate characteristics when configured as a positive electrode for lithium secondary batteries. This positive electrode active material comprises a plurality of secondary particles each comprising primary particles composed of a lithium-nickel based complex oxide having a layered rock-salt structure. The plurality of secondary particles have a volume-based average particle diameter D50 of 5 to 100 &#x3bc;m, and at least part of the plurality of secondary particles are coarse secondary particles having a particle diameter of 9 &#x3bc;m or greater. The coarse secondary particles have a voidage of 5 to 25%, and the ratio of through holes among all voids in the coarse secondary particles is 70% or greater.

Positive electrode active material for lithium secondary battery and positive electrode including same

Provided is a light emitting device composite substrate suitable for manufacturing large-area light emitting devices at low cost. The light emitting device composite substrate comprises a substrate composed of an oriented polycrystalline alumina sintered body, and a light emitting functional layer formed on the substrate and having two or more layers composed of semiconductor single crystal grains, wherein each of the two or more layers has a single crystal structure in a direction approximately normal to the substrate.

Composite substrate for light-emitting element and production method therefor

Provided is a self-supporting gallium nitride substrate useful as an alternative material for a gallium nitride single crystal substrate, which is inexpensive and also suitable for having a large area. This substrate is composed of a plate composed of gallium nitride-based single crystal grains, wherein the plate has a single crystal structure in the approximately normal direction. This substrate can be manufactured by a method comprising providing an oriented polycrystalline sintered body; forming a seed crystal layer composed of gallium nitride on the sintered body so that the seed crystal layer has crystal orientation mostly in conformity with the crystal orientation of the sintered body; forming a layer with a thickness of 20 &#x3bc;m or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer; and removing the sintered body.

Growing community of inventors

Tokai, Japan

Kei Sato