The invention relates to a process for the preparation of a dental restoration, in which an oxide ceramic material is (a) subjected to at least one heat treatment, and (b) cooled, wherein the cooling comprises (b1) a first cooling step with the cooling rate T1 and (b2) a second cooling step with the cooling rate T2 and wherein the absolute value of the cooling rate T2 is less than the absolute value of the cooling rate T1.

The present invention provides a high thermal conductive silicon nitride sintered body having a thermal conductivity of 50 W/m.Math.K or more and a three-point bending strength of 600 MPa or more, wherein when an arbitrary cross section of the silicon nitride sintered body is subjected to XRD analysis and highest peak intensities detected at diffraction angles of 29.3±0.2°, 29.7±0.2°, 27.0±0.2°, and 36.1±0.2° are expressed as I.sub.29.3°, I.sub.29.7°, I.sub.27.0°, and I.sub.36.1°, a peak ratio (I.sub.29.3°)/(I.sub.27.0°+I.sub.36.1°) satisfies a range of 0.01 to 0.08, and a peak ratio (I.sub.29.7°)/(I.sub.27.0°+I.sub.36.1°) satisfies a range of 0.02 to 0.16. Due to above configuration, there can be provided a silicon nitride sintered body having a high thermal conductivity of 50 W/m.Math.K or more, and excellence in insulating properties and strength.

To improve a TCT characteristic of a circuit substrate. The circuit substrate comprises a ceramic substrate including a first and second surfaces, and first and second metal plates respectively bonded to the first and second surfaces via first and second bonding layers. A three-point bending strength of the ceramic substrate is 500 MPa or more. At least one of L1/H1 of a first protruding portion of the first bonding layer and L2/H2 of a second protruding portion of the second bonding layer is 0.5 or more and 3.0 or less. At least one of an average value of first Vickers hardnesses of 10 places of the first protruding portion and an average value of second Vickers hardnesses of 10 places of the second protruding portion is 250 or less.

The invention relates to a method for preparing a material based on an aluminosilicate selected from barium aluminosilicate BAS, barium-strontium aluminosilicate BSAS, and strontium aluminosilicate SAS, said aluminosilicate consisting of aluminosilicate with a hexagonal structure, characterised in that it includes a single sintering step in which a mixture of powders of precursors of said aluminosilicate, including an aluminium hydroxide Al(OH).sub.3 powder, are sintered by a hot-sintering technique with a pulsed electric field SPS; whereby a material based on an aluminosilicate, said aluminosilicate consisting of an aluminosilicate with a hexagonal structure is obtained. The material based on an aluminosilicate prepared by said method can be used in a method for preparing a composite material consisting of an aluminosilicate matrix reinforced by reinforcements made of metalloid or metal oxide.

A wavelength converter 100 includes: a first phosphor 1 composed of an inorganic phosphor activated by Ce.sup.3+; and a second phosphor 2 composed of an inorganic phosphor activated by Ce.sup.3+ and different from the first phosphor. At least one of the first phosphor and the second phosphor is particulate. The first phosphor and the second phosphor are bonded to each other by at least one of a chemical reaction in a contact portion between the compound that constitutes the first phosphor and a compound that constitutes the second phosphor and of adhesion between the compound that constitutes the first phosphor and the compound that constitutes the second phosphor.

A method for manufacturing an electrostatic chuck with multiple chucking electrodes made of ceramic pieces using metallic aluminum as the joining. The aluminum may be placed between two pieces and the assembly may be heated in the range of 770 C to 1200 C. The joining atmosphere may be non-oxygenated. After joining the exclusions in the electrode pattern may be machined by also machining through one of the plate layers. The machined exclusion slots may then be filled with epoxy or other material. An electrostatic chuck or other structure manufactured according to such methods.

A sintered body includes a crystal grain containing silicon nitride, and a grain boundary phase. If dielectric losses of the sintered body are measured while applying an alternating voltage to the sintered body and continuously changing a frequency of the alternating voltage from 50 Hz to 1 MHz, an average value ε.sub.A of dielectric losses of the sintered body in a frequency band from 800 kHz to 1 MHz and an average value ε.sub.B of dielectric losses of the sintered body in a frequency band from 100 Hz to 200 Hz satisfy an expression |ε.sub.A−ε.sub.B|≤0.1.

Provided is a method for producing a β-sialon fluorescent material, comprising preparing a composition containing a silicon nitride that contains aluminium, oxygen, and europium; heat-treating the composition at a temperature in a range of 1300° C. or more and 1600° C. or less to obtain a heat-treated product; subjecting the heat-treated product to a temperature-decrease of from the heat treatment temperature to 1000° C. as a first temperature-decrease step; and subjecting the heat-treated product to a temperature-decrease of from 1000° C. to 400° C. as a second temperature-decrease step. The first temperature-decrease step has a temperature-decrease rate in a range of 1.5° C./min or more and 200° C./min or less, and the second temperature-decrease step has a temperature-decrease rate in a range of 1° C./min or more and 200° C./min or less.

Provided is a member for optical glass manufacturing apparatus. The member is used for optical glass manufacturing apparatus and exposed to a gas containing a halogen element in a high temperature environment of 1100° C. or higher. The member includes dense ceramics containing silicon nitride as a main component, and a porosity of a surface layer of the member is smaller than a porosity of the inside of the member.

The bonded ceramic assembly of the present disclosure includes a first substrate made of ceramic, a second substrate made of ceramic, and a bonding layer positioned between the first substrate and the second substrate. The bonding layer contains aluminum, at least one of calcium and magnesium, a rare earth element, silicon, and oxygen. Out of a total 100 mass % of all of the components making up the bonding layer, the bonding layer contains from 33 mass % to 65 mass % aluminum in terms of oxide, a total of from 27 mass % to 60 mass % calcium and magnesium in terms of oxide, and from 2 mass % to 12 mass % rare earth element in terms of oxide. The silicon content, in terms of oxide, of the surface of the bonding layer is greater than the silicon content, in terms of oxide, of the interior of the bonding layer.