A process for preparing roofing granules includes forming kaolin clay into green granules and sintering the green granules at a temperature of at least 900 degrees Celsius to cure the green granules until the crystalline content of the sintered granules is at least ten percent as determined by x-ray diffraction.

A composite ceramic with improved mechanical performance and a preparation method therefor. The composite ceramic comprises fluorescent powder, a ceramic matrix, and an optional sintering aid. The weight ratio of the fluorescent powder to the ceramic matrix is from 3:17 to 9:1, and the relative density of the composite ceramic is greater than 95%. The preparation method comprises using core shell-structured coated fluorescent powder as a raw material, and ball-milling and sintering the raw material to obtain the composite ceramic.

One aspect of the disclosure provides an optical wavelength conversion member including a polycrystalline ceramic sintered body containing, as main components, Al.sub.2O.sub.3 crystal grains and crystal grains represented by formula (Y,A).sub.3B.sub.5O.sub.12:Ce. In the optical wavelength conversion member, a (Y,A).sub.3B.sub.5O.sub.12:Ce crystal grain has a region wherein the A concentration of a peripheral portion of the (Y,A).sub.3B.sub.5O.sub.12:Ce crystal grain is higher than that of an interior portion of the (Y,A).sub.3B.sub.5O.sub.12:Ce crystal grain. Thus, the optical wavelength conversion member exhibits high fluorescence intensity (i.e., high emission intensity) and high heat resistance (i.e., low likelihood of temperature quenching). The optical wavelength conversion member has a structure wherein the element A concentration of a peripheral portion of a (Y,A).sub.3B.sub.5O.sub.12:Ce crystal grain differs from that in an interior portion of the crystal grain. This structure can achieve a ceramic fluorescent body exhibiting superior fluorescent characteristics and superior thermal characteristics with varied colors of emitted light.

Provided are a ceramic complex having high light emission intensity and a method for producing the same. Proposed is a ceramic complex, including a rare earth aluminate fluorescent material having a composition represented by the following formula (I) and an aluminum oxide, wherein the content of the aluminum oxide is 70% by mass or more, the content of Na is 7 ppm by mass or less, the content of Si is 5 ppm by mass or less, the content of Fe is 3 ppm by mass or less, and the content of Ga is 5 pm by mass or less, relative to the total amount of the rare earth aluminate fluorescent material having a composition represented by the following formula (I) and the aluminum oxide.
(Ln.sub.1-aCe.sub.a).sub.3Al.sub.5O.sub.12   (I) wherein Ln represents at least one element selected from the group consisting of Y, Gd, Lu, and Tb; and a satisfies 0<a≤0.022.

Various embodiments disclosed relate to an optical window including an infrared light transmissive optical material. The optical material includes a first ceramic phase including a first ceramic material and a first dopant distributed therein. The optical material further includes a second ceramic phase homogenously intermixed with the first ceramic phase and comprising a second ceramic material and a second dopant distributed therein. The first dopant increases the refractive index of the first ceramic material and the second dopant decreases the refractive index of the second ceramic material. The first dopant and the second dopant are present in an amount such that a difference in a refractive index of the first ceramic phase and of the second ceramic phase is in a range of from about 0.001 to about 0.2.

A thin film is provided that primarily comprises titanium oxide and includes Ti, Ag and O. The thin film contains 29.6 at % or more and 34.0 at % or less of Ti, 0.003 at % or more and 7.4 at % or less of Ag, and oxygen as the remainder thereof and has a ratio of oxygen to metals, O/(2Ti+0.5Ag), of 0.97 or more. The thin film has a high refractive index and a low extinction coefficient. In addition, the thin film has superior transmittance, minimally deteriorates in reflectance, and is useful as an interference film or a protective film for an optical information recording medium. The film may also be applied to a glass substrate to provide a heat reflective film, an antireflective film, or an interference filter. A method of producing the thin film is also disclosed.

Reaction mixtures, gel compositions that are a polymerized product of the reaction mixtures, shaped gel articles that are formed within a mold cavity and that retain the size and shape of the mold cavity upon removal from the mold cavity, and sintered articles prepared from the shaped gel articles are provided. The sintered article has a shape identical to the mold cavity (except in regions where the mold cavity was overfilled) and to the shaped articles but reduced in size proportional to the amount of isotropic shrinkage. Methods of forming the sintered articles also are provided.

The present disclosure relates to a phosphor ceramic comprising a plurality of luminescence conversion materials, wherein a luminescence conversion material serves as a matrix material for the others.

A substrate for mounting a light-emitting element according to the present disclosure contains a crystal particle of aluminum oxide and is composed of an alumina-based ceramic that contains 97% by mass or more of Al as a value of an Al.sub.2O.sub.3 equivalent among 100% by mass of all components thereof. An average value of an equivalent circle diameter of the crystal particle is 1.1 μm or greater and 1.8 μm or less and a standard deviation of an equivalent circle diameter thereof is 0.6 μm or greater and 1.4 μm or less.

The present invention provides a method for producing a powder containing zirconia particles and a fluorescent agent that enables easy production of a zirconia sintered body having both high translucency and high strength despite containing a fluorescent agent. The present invention relates to a method for producing a zirconia particle- and fluorescent agent-containing powder, comprising: a mixing step of mixing a zirconia particle-containing slurry and a liquid-state fluorescent agent; and a drying step of drying the slurry containing the zirconia particles and the fluorescent agent. Preferably, the fluorescent agent comprises a metallic element, and the powder comprises the fluorescent agent in an amount of 0.001 to 1 mass % in terms of an oxide of the metallic element relative to a mass of zirconia. Preferably, the zirconia particles have an average primary particle diameter of 30 nm or less. Preferably, the zirconia particles comprises 2.0 to 9.0 mol % yttria.