A Cr:YAG sintered body including Al, Y, Cr, Ca, Mg, Si, and O, and component contents in the sintered body satisfying conditional expressions of 1) to 3) below, provided in the Conditional expression, each chemical symbol represents a component content (atppm).
|(Y+Ca)/(Al+Cr+Si+Mg)−0.6|<0.001;  1)
0≤(Ca+Mg)−(Cr+Si)≤50 atppm; and  2)
50≤Si≤500 atppm  3) The embodiment of the present invention is to provide a Cr:YAG sintered body which exhibits high transparency and has a high Cr.sup.4+ conversion ratio, and its production method.

A thermoelectric conversion material made of a sintered body containing a magnesium silicide as a major component includes: a magnesium silicide phase; and a magnesium oxide layer formed on a surface layer of the magnesium silicide phase, in which an aluminum concentrated layer having an Al concentration higher than an aluminum concentration in an inside of the magnesium silicide phase is formed between the magnesium oxide layer and the magnesium silicide phase, and the aluminum concentrated layer has a metallic aluminum phase including aluminum or an aluminum alloy.

A sputtering target configured from a magnesium oxide sintered body, wherein a ratio of crystal grains of the magnesium oxide sintered body in which a number of pinholes in a single crystal grain is 20 or more is 50% or less. The present invention is a sputtering target configured from a magnesium oxide sintered body in which the generation of particles during sputtering is less.

The present invention provides a gallium nitride sintered body and a gallium nitride molded article which have high density and low oxygen content without using a special apparatus. According to the first embodiment, a gallium nitride sintered body, which is characterized by having density of 2.5 g/cm.sup.3 to less than 5.0 g/cm.sup.3 and an intensity ratio of the gallium oxide peak of the (002) plane to the gallium nitride peak of the (002) plane of less than 3%, which is determined by X-ray diffraction analysis, can be obtained. According to the second embodiment, a metal gallium-impregnated gallium nitride molded article, which is characterized by comprising a gallium nitride phase and a metal gallium phase that exist as separate phases and having a molar ratio, Ga/(Ga+N), of 55% to 80%, can be obtained.

A process for preparing a sintered silicon carbide body including sintering a sample including silicon carbide particles to form a shaped sintered silicon carbide body, the particles containing a silicon carbide core and a surface layer containing carbon and oxygen, the sample having at least 90 weight % being C or Si and having a carbon to silicon molar ratio molC/molSi higher than 1 and a carbon in excess to oxygen molar ratio Cex/molO which is higher than 0.5 and lower than 5.3.

A slurry or slip composed of a dispersion medium and a dispersoid including sinterable raw material powder containing a complex oxide powder represented by the following formula (1):
(Tb.sub.1-x-yR.sub.xSc.sub.y).sub.3(Al.sub.1-zSc.sub.z).sub.5O.sub.12  (1)
wherein R is yttrium and/or lutetium, 0.05≤x<0.45, 0<y<0.1, 0.5<1-x-y<0.95, and 0.004<z<0.2 is prepared; the slurry or slip is subsequently enclosed in a mold container to be subjected to solid-liquid separation by centrifugal casting to mold a cast compact; the cast compact is dried thereafter; a dried compact is degreased; a degreased compact is sintered thereafter; and a sintered body is further subjected to a hot isostatic pressing treatment to obtain the transparent ceramic material composed of the sintered body of garnet-type rare earth complex oxide represented by the formula (1).

A paramagnetic garnet-type transparent ceramic that exhibits a high laser damage threshold, said ceramic being a sintered body of a Tb-containing rare earth-aluminum garnet represented by formula (1), and being characterized in that the average sintered grain size is 10-40 μm, and the insertion loss at a wavelength of 1,064 nm in the optically effective region along the length direction of a 20 mm-long sample is 0.05 dB or less.

(Tb.sub.1-x-yY.sub.xSc.sub.y).sub.3(Al.sub.1-zSc.sub.z).sub.5O.sub.12  Formula (1)

(In the formula, 0≤x<0.45, 0≤y<0.08, 0≤z<0.2, and 0.001<y+z<0.20.)

The present invention relates to a method for producing a metal-ceramic substrate (1) comprising: —providing a ceramic element (30) and at least one metal layer (10), wherein the ceramic element (30) and the at least one metal layer (10) extend along a main extension plane (HSE), —joining the ceramic element (30) to the at least one metal layer (10) to form a metal-ceramic substrate (1), in particular by means of a direct metal joining method, a hot isostatic pressing method and/or a soldering method, and —machining the at least one metal layer (10) by means of a machine tool (40) and/or laser light in order to define a geometry, at least in some portions, of a side face (15) of the at least one metal layer (10) not running parallel to the main extension plane (HSE).

The invention relates to a process for producing a metal-ceramic substrate (1), comprising: —providing a ceramic element (10), a metal ply (40) and at least one metal layer (30), —forming an ensemble (18) of the ceramic element (10), the metal ply (40) and the at least one metal layer (30), —forming a gas-tight container (30) surrounding the ceramic element (10), wherein the at least one metal layer (30) is arranged between the ceramic element (10) and the metal ply (40) in the container, and—forming the metal-ceramic substrate (1) by hot isostatic pressing.

A method for the assembly of a metal part and a ceramic part, including the following steps: supplying a solid ceramic part of the alumina type; supplying a solid metal part, the metal being selected from platinum and tantalum, or an alloy including a majority of one of these metals; depositing at least one layer, called interface layer, on at least one of the solid parts, the interface layer containing magnesium oxide; bringing into contact the solid metal part and the solid ceramic part such that the interface layer is located between the solid parts; and hot densification under pressure of the solid parts brought into contact, to create a close bond between the solid parts and form a spinel from the interface layer. An electrical device, such as a capacitive sensor having a sensitive part produced according to the present method, is also provided.