A method for producing an oriented AlN sintered body includes a first step of preparing a formed body by forming a mixture obtained by mixing a sintering aid with an AlN raw-material powder containing a plate-like AlN powder whose plate surface is a c-plane and which has an aspect ratio of 3 or more and an average thickness of 0.05 to 1.8 m, wherein the mixture is formed such that the plate surface of the plate-like AlN powder is disposed along a surface of the formed body; and a second step of obtaining an oriented AlN sintered body by subjecting the formed body to hot-press sintering in a non-oxidizing atmosphere while applying a pressure to the surface of the formed body.

In a first step of a method for producing a transparent AlN sintered body, first, a formed body is prepared by forming a mixture obtained by mixing a sintering aid with an AlN raw-material powder containing a plate-like AlN powder whose plate surface is a c-plane and which has an aspect ratio of 3 or more. At this time, the mixture is formed such that the plate surface of the plate-like AlN powder is disposed along a surface of the formed body. In a second step, an oriented AlN sintered body is obtained by subjecting the formed body to hot-press sintering in a non-oxidizing atmosphere while applying a pressure to the surface of the formed body. In a third step, a transparent AlN sintered body is obtained by sintering the oriented AlN sintered body at normal pressure in a non-oxidizing atmosphere to remove a component derived from the sintering aid.

A cubic boron nitride-based sintered material includes cubic boron nitride particles of 70 to 95 vol %, in which in a structure of a cross-section of the sintered material, a binder phase with a width of 1 nm to 30 nm is present between the adjacent cubic boron nitride particles, the binder phase being made of a compound containing at least Al, B, and N and having a ratio of an oxygen content to an Al content of 0.1 or less in terms of atomic ratio.

When a large-sized silicon nitride substrate having high thermal conductivity is produced, a portion where the thermal conductivity is low is generated, which causes reduction in yield (pass rate). Provided is a silicon nitride substrate in which ?e/?c, which is a ratio of a thermal conductivity ?c at a center portion of the substrate to a thermal conductivity ?e at an end portion of the substrate, is 0.85 to 1.15. Preferably, the silicon nitride substrate has a size of 150 mm?150 mm or more. In the silicon nitride substrate, the ?c and the ?e each are preferably 100 W/m.Math.K or more.

A method for preparing nanometer MAX phase ceramic powder or slurry having a laminated structure by means of ball milling and regulating the oxygen content of the powder. Micron-sized MAX phase ceramic coarse powder is adopted as a raw material, during ball milling, a gas or a liquid-state gas having a special effect is introduced into a ball milling tank, and by means of multi-dimensional functions and regulation such as ball milling parameters and gas reaction, the nanometer laminated MAX phase ceramic powder or the slurry containing the component is obtained. The surface components and the activated state of the powder are regulated while the particle size adjustment control of the powder is realized.

A heater for a semiconductor manufacturing apparatus, the heater includes an AlN ceramic substrate and a heating element embedded inside the AlN ceramic substrate. The AlN ceramic substrate contains O, C, Ti, Ca, and Y as impurity elements, includes an yttrium aluminate phase as a crystal phase, and has a Ti/Ca mass ratio of 0.13 or more, and a TiN phase is not detected in an XRD profile measured with Cu K- radiation.

The present invention relates to a porous alpha-SiC-containing shaped body with a gas-permeable, open-pored pore structure comprising platelet-shaped crystallites which are connected to form an interconnected, continuous skeletal structure, wherein the skeletal structure consists of more than 80 wt.-% alpha-SiC, relative to the total weight of SiC, a process for producing same and its use as a filter component.

A silicon nitride substrate including silicon nitride crystal grains and a grain boundary phase and having a thermal conductivity of 50 W/m.Math.K or more, wherein, in a sectional structure of the silicon nitride substrate, a ratio (T2/T1) of a total length T2 of the grain boundary phase in a thickness direction with respect to a thickness T1 of the silicon nitride substrate is 0.01 to 0.30, and a variation from a dielectric strength mean value when measured by a four-terminal method in which electrodes are brought into contact with a front and a rear surfaces of the substrate is 20% or less. The dielectric strength mean value of the silicon nitride substrate can be 15 kV/mm or more. According to above structure, there can be obtained a silicon nitride substrate and a silicon nitride circuit board using the substrate in which variation in the dielectric strength is decreased.

A polycrystalline diamond comprising diamond particles, wherein: the content of the diamond particles is more than 99% by volume based on the total volume of the polycrystalline diamond; the median diameter d50 of the diamond particles is 10 nm or more and 200 nm or less; and the dislocation density of the diamond particles is 2.0?10.sup.15 m.sup.?2 or more and 4.0?10.sup.16 m.sup.?2 or less.

According to an embodiment, a highly thermally conductive silicon nitride sintered body includes silicon nitride crystal grains and a grain boundary phase. A thermal conductivity of the silicon nitride sintered body is not less than 80 W/(m.Math.K). An average value of solid solution oxygen amounts of the silicon nitride crystal grains existing in a 20 ?m?20 ?m unit area in any cross section is not more than 0.2 wt %. An average value of major diameters of the silicon nitride crystal grains existing in a 50 ?m?50 ?m unit area in any cross section is not less than 1 ?m and not more than 10 ?m. An average of aspect ratios of the silicon nitride crystal grains existing in the 50 ?m?50 ?m unit area is not less than 2 and not more than 10.