Abstract: Alkali silicate glasses are described which, in view of their good chemical stability and their optical properties and processing properties, are particularly suitable as a coating or veneering material for ceramic dental frameworks and hence for the production of all-ceramic dental restorations such as crowns or bridges.

Abstract: The invention relates to a glass ceramic in which mica and ZrO.sub.2 are present in crystallized form, containing:K.sub.2 O: 0-9% by weightNa.sub.2 O: 0-9% by weight with the condition that Na.sub.2 O and K.sub.2 O together make up at least about 4% by weight,SiO.sub.2 : 35-60% by weightMgO: 10-25% by weightAl.sub.2 O.sub.3 : 7-30% by weightZrO2: 4-12% by weightF.sup.- : 2-10% by weight which is essentially free of lithium, calcium, strontium and barium, to a process for its production and to its use as a tooth replacement.

Abstract: The height of protrusions formed during laser texturing a glass-ceramic substrate is controlled by controlling the amount of the crystalline-phase of the substrate, to less than 70% by volume. In an embodiment, the amount of crystalline-phase is controlled by heating under controlled conditions to convert a glass substrate into the glass-ceramic substrate comprising a controlled amount of crystalline phase.

Abstract: A transparent class ceramic composition includes an oxide component, a rare earth component, a halide component, and a substantially pure rare earth-halide (e.g., REF.sub.3) crystal component. A method for making a transparent oxyfluoride glass includes preparing an oxyfluoride glass containing rare earth ions by a conventional melting method and subjecting the glass to a heat treatment thereby precipitating fluoride fine crystals containing a large amount of rare earth ions.

Abstract: The present invention relates to a transparent glass-ceramic article which includes a glass matrix and a crystalline phase of apatite crystals in the glass matrix. The present invention further relates to a method of producing the transparent glass-ceramic article.

Abstract: A glass-ceramic material that is doped with rare-earths and is especially suitable for lasers and optical amplifiers is disclosed. The glass-ceramic material is optically non-scattering, and the doping with rare earths is essentially in the microcrystalline phase. The glass-ceramic material is preferably made up from complexes of metals having a valency of three or greater and of halides of rare earth ions having a valency of three or greater. The rare-earth ions include an optically active rare-earth ion.

Abstract: A bioactive ceramic material for dental fillings and crowns on the basis of calcium phosphate compounds contains crystallites of sparingly water-soluble calcium phosphate compounds in an amorphous, vitreous or polycrystalline matrix of readily water-soluble calcium phosphate compounds, the Ca/P-atomic ratio of the calcium phosphate compounds being altogether <1.65.

Abstract: This invention is directed at the makings of glass-ceramic which is uniquely suited for use as a disc substrate for utilization in a magnetic memory storage device. The glass ceramic material exhibits a crystal phase assemblage comprised predominately of a mixture of lithium disilicate and tridymite which are uniformly interspersed with a residual glass phase and form an interlocked microstructure with the glass. The composition consists essentially, expressed in terms of weight percent on the oxide basis, of 75-95% SiO.sub.2, 3-15% Li.sub.2 O, 0-6% Al.sub.2 O.sub.3, and 0-6% K.sub.2 O. The nucleating agent for this glass-ceramic is selected from the group consisting of 0-0.1% Pd and 0-5% P.sub.2 O.sub.5 ; however if Pd is absent the P.sub.2 O.sub.5 amount is at least 0.5% and if P.sub.2 O.sub.5 is absent then the Pd amount is at least 0.005%. Additionally, up to 15% of optional ingredients may be added, including, B.sub.2 O.sub.3, Na.sub.2 O, ZnO, MgO, CaO, SrO, ZrO.sub.2, TiO.sub.2, F, Sb.sub.2 O.sub.3, As.

Abstract: The present invention is concerned with a process for the formation of dental restorations from glass-ceramic materials and the resulting dental restorations. In this invention, a dental restoration is prepared by placing a glass-ceramic material in a heat-pressure deformable crucible. Heat is then applied to the crucible in order to bring the glass-ceramic material to a working range at temperatures above its liquidus temperature. The crucible in which the glass-ceramic material is placed has heat-pressure deformation properties which are matched to the working temperature of the glass-ceramic material being heated. The heat deformation properties of the crucible must be such that when the glass-ceramic material in the crucible is in the working range the crucible is heat-pressure deformable without rupturing.

Abstract: Vitrified phosphor articles, intermediates, and methods for preparing the articles. In the methods, a combination of species are admixed. The combination of species are precursors for a glass-forming system. The glass-forming system includes precursors for a crystalline radiographic phosphor. The admixed combination of species are fired to form a melt having a single liquid. The product of the melt is molten-shaped.

Abstract: A high efficiency wavelength up-conversion transparent glass ceramics composition is provided containing a rare earth ion, which can be applied to short wavelength solid lasers, full color displays, infrared light detecting sensors, etc. The ceramic composition has the following chemical composition, in which fluoride fine crystals containing rare earth ions are preferentially precipitated:______________________________________ SiO.sub.2 10-60 mol % AlO.sub.1.5 0-40 mol % GaO.sub.1.5 0-40 mol % PbF.sub.2 5-60 mol % CdF.sub.2 0-60 mol % GeO.sub.2 0-30 mol % TiO.sub.2 0-10 mol % ZrO.sub.2 0-10 mol % ReF.sub.3 or ReO.sub.1.5 0.05-30 mol % (Re = Er, Tm, Ho, Yb, Pr, etc.

Abstract: An artificial nucleus made of a crystallized glass is provided for use in the production of a pearl. The crystallized glass has been produced using a batch having the following composition:SiO.sub.2 . . . 40-65 wt. %MgO . . . 3-16 wt. %MgF.sub.2 . . . 6.5-17 wt. %K.sub.2 O . . . 7.5-18 wt. %ZrO.sub.2 . . . 0.01-15 wt. %CaO . . . 0.1-20 wt. %P.sub.2 O.sub.5 . . . 0.1-20 wt. %BaO and/or SrO . . . 0.1-13 wt. %and has crystalline phases composed primarily of tetrasilicon fluormica and formed in a glass matrix phase.

Abstract: A color package is disclosed that provides a light ivory tint in potassium fluorrichterite glass-ceramic materials containing a cristobalite secondary crystal phase. The package includes Fe.sub.2 O.sub.3, NiO, Se and, optionally, cobalt oxide within limited ranges.

Abstract: A high efficiency wavelength up-conversion transparent glass ceramics composition is provided containing a rare earth ion, which can be applied to short wavelength solid lasers, full color displays, infrared light detecting sensors, etc. The ceramic composition has the following chemical composition, in which fluoride fine crystals containing rare earth ions are preferentially precipitated:______________________________________ SiO.sub.2 10-60 mol % AlO.sub.1.5 0-40 mol % GaO.sub.1.5 0-40 mol % PbF.sub.2 5-60 mol % CdF.sub.2 0-60 mol % GeO.sub.2 0-30 mol % TiO.sub.2 0-10 mol % ZrO.sub.2 0-10 mol % ReF.sub.3 or ReO.sub.1.5 0.05-30 mol % (Re = Er, Tm, Ho, Yb, Pr, etc.).

Abstract: This invention is directed to the formation of glass-ceramic articles which exhibit a yellow coloration in visible light and fluoresce with a yellow coloration while being exposed to ultraviolet radiation. The yellow coloration is produced through the incorporation of a color package comprising 0.05-0.5% V.sub.2 O.sub.5, 0.25-5% CeO.sub.2, and 0.1-1% Tb.sub.2 O.sub.3. When the glass-ceramic articles contain tetrasilicic fluormica as the predominant crystal phase, they are eminently suitable for use as dental prosthetic materials.

Abstract: A glass-ceramic biomaterial having high strength and toughness, a family of glasses from which the glass-ceramic biomaterial can be produced, and a method of production. The material has a primary crystal phase of F-canasite and a secondary crystal phase of F-apatite. The glass family is SiO.sub.2 --CaO--Na.sub.2 O--K.sub.2 O--P.sub.2 O.sub.5 --F. The method may be a single stage heat treatment, or a two stage involving an initial nucleation and a subsequent crystallization.

Abstract: Disclosed is a process for preparing Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 ceramic sintered bodies. Lithium fluoride powder is added to a calcined Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 powder prepared by sol-gel process as sintering agent. The resulting powder mixture is compressed into a molded article and sintered at a temperature of 950.degree.-1250.degree. C. to obtain the sintered bodies of the invention. The sintered bodies according to the present invention have a relative density of 97.9% and a thermal expansion coefficient of 10.sup.-7 /.degree.C. magnitude.

Abstract: The invention relates to an apatite glass ceramic which can be used as a material in medicine and as an inorganic component of a glass ionomer cement. The apatite glass ceramic comprises in wt-%) 15-40% SiO.sub.2, 15-35% Al.sub.2 O.sub.3, 12-30% CaO, 6-25% P.sub.2 O.sub.5, 2.5-15% F.sup.-, 0-18% R.sub.2 O, wherein R.sub.2 O is an alkali oxide. The apatite glass ceramic comprises a crystal phase which contains apatite.

Abstract: This invention is directed to the fabrication of magnetic memory storage devices which consist essentially of a head pad and a rigid information disc, that disc consisting essentially of a rigid substrate having a layer of magnetic media joined to the surface of said substrate through an underlayer. The invention is particularly drawn to the substrate for the information disc which is composed of a glass-based material containing 0.05-2% by weight total of cobalt oxide and/or iron oxide and/or nickel oxide. The most preferred glass-based material comprises a glass-ceramic wherein canasite constitutes the predominant crystal phase.

Abstract: An orthodontic bracket made of a partially crystallized amorphous glass material and method for making same. The orthodontic bracket has a thin compressive outer crystalline layer.

Abstract: A glass-ceramic which is excellent in mechanical strength, cutting processability and chemical durability and suitable for the production of an artificial dental crown and a mold, the glass-ceramic containing, by weight percentage, 2 to 17% of CaO, 0 to 5% of K.sub.2 O, 0 to 4% of Na.sub.2 O, the total content of K.sub.2 O and Na.sub.2 O being 0.5-7%, 15 to 35% of MgO, 30 to 49% of SiO.sub.2, 2 to 15% of ZrO.sub.2 and not more than 14% (calculated as F) of fluorine, and having a zirconia crystal and a mica crystal precipitated.

Abstract: Glass or crystal particles of nanocrystalline size having a minor dimension of 0.1 to 100 Angstrom units. They may be prepared by controlled thermal separation of phase-separable glasses. Preferred crystal forms are zinc pyrophosphate and lithium disilicate. A crystallizable glass is combined with phyllosilicate particles and sintered to form an oriented composite body. During slow sintering, the crystal grows epitaxially on the phyllosilicate.

Abstract: Ceramic matrix composite articles of improved high temperature oxidation resistance are provided, the articles comprising reinforcing fibers disposed within a ceramic matrix, the matrix further comprising a minor matrix addition consisting of a dispersion of fluormica crystallites in a proportion effective to improve the oxidation resistance of the article and ranging up to about 20% by weight of the matrix.

Abstract: A method for synthesizing alkaline earth metal-containing ceramic materials by sol-gel processing is described, wherein a sol containing alkoxides or other soluble precursors for a selected ceramic composition, and additionally containing one or more dissolved alkaline earth metal/crown either complexes, is gelled, dried and fired to convert the precursors and complexes to a polycrystalline ceramic product. The crown ether complexes improve alkaline earth metal solubility and the homogeneous incorporation of these metals into the precursor gels and final crystalline products.

Abstract: A method is disclosed for preparing an improved bioreactive material of the glass or partially crystallized glass type for bone prostheses or dental implants, which can be welded to bone tissue by chemical bonding. The material consisting essentially of, by weight, 5 to 14% Na.sub.2 O, 0 to 12% P.sub.2 O.sub.5, 49 to 57% SiO.sub.2, and balance, no more than 33% CaO+CaF.sub.2, the material containing 0.5 to 7% CaF.sub.2, and is prepared by a method comprising the steps of preparing a mixture of powders constituting a precursor of the material made of carbonates, phosphates, silica, oxides and fluorides, melting, homogenizing, casting and cooling the mixture to obtain an intermediate, non-crystallized glass, optionally annealing, and then grinding, either pressing the non-crystallized ground glass obtained cold to shape it, then sintering naturally or under a load after degassing, or sintering under a load directly after degassing, then cooling and optionally polishing or machining.

Abstract: In a mold material for use in molding a titanium cast to be mounted into the mouth as a dental prosthesis, magnesia and phosphate are added as a binder to its main ingredient composed of alumina and zirconia.

Abstract: The present invention concerns synthetic mica powder containing from 75 to 99% of the stoichiometrical composition of fluorine and/or having a shape in which the end face of particle is laminated, process for producing such synthetic mica powder, as well as cosmetics having synthetic mica powder blended therewith, in which the synthetic mica powder shows no leaching of fluorine ions and/or improved hold of oils due to lamination at the surface of powder. Accordingly, in this invention, cosmetics excellent in extensibility, gloss, adherence and modability, having appearance of high chroma and of high stability and safety can be obtained.

Abstract: The instant invention is directed to the production of opaque glass-ceramic articles containing canasite crystals as the predominate crystal phase exhibiting strong bright colors. The desired color is obtained through the addition of a colorant system to the precursor glass composition utilized for the production the canasite glass-ceramic.Opaque glass ceramic articles exhibiting bright colors ranging from purple-to-blue-to-green are obtained through the addition of a colorant system consisting essentially, expressed in weight percent, of about 0.02%-1.5% total of at least one member selected from the group consisting of Cr.sub.2 O.sub.3 and Co.sub.3 O.sub.4, with the maximum amount of either member being about 1.0%.Another embodiment is directed towards the production of opaque glass-ceramic articles exhibiting strong bright colors yellow-to-orange-to-red-to-brown colors.

Abstract: A color package is disclosed that provides a light beige tint in potassium fluorrichterite glass-ceramic materials containing a cristobalite secondary crystal phase. The package includes Fe.sub.2 O.sub.3, NiO, Se and, optionally, cobalt oxide within limited ranges.

Abstract: Disclosed is glass-ceramics produced by and a method of producing the glass-ceramics comprising the step of precipitating a calcium-potassium mica crystal consisting of Ca-K-Mg-Al-Si-O-F and at least one crystal selected from the group consisting of an enstatite crystal, an akermanite crystal and a diopside crystal, from glass containing components, in percent by weight, 2 to 17% of CaO, 0.5 to 5% of K.sub.2 O, 20 to 35% of MgO, 30 to 50% of SiO.sub.2, 5 to 30% of Al.sub.2 O.sub.3, and 1.5 to 14% of Fluorine (Calculated as F); or precipitating a calcium-potassium-sodium mica crystal consisting of Ca-K-Na-Mg-Al-Si-O-F and at least one crystal selected from the group consisting of an enstatite crystal, an akermanite crystal, a diopside crystal, an anorthite crystal and a richterite crystal, from glass containing components, in percent by weight, 2 to 17% of CaO, 0.5 to 5% of K.sub.x O, 0.1 to 4% of Na.sub.2 O, 15 to 35% of MgO, 30 to 49% of SiO.sub.2, 5 to 30% of Al.sub.2 O.sub.3, and 1.

Abstract: This invention is directed to the production of transparent glass-ceramic articles demonstrating linear coefficients of thermal expansion of less than 10.times.10.sup.-7 /.degree.C. and exhibiting a blue or gray coloration. The articles are prepared by heat treating reducing precursor glass articles consisting essentially, in weight percent as calculated from the batch, of 2.5-3.5% Li.sub.2 O, 1.5-2.5% MgO, 17.75-20% Al.sub.2 O.sub.3, 64-70% SiO.sub.2, 2-4.5% TiO.sub.2, 1-2% ZrO.sub.2, 0-2% BaO, and 0.2-0.5% Cl, wherein alkali metals other than Li.sub.2 O, alkaline earth oxides other than MgO and BaO, ZnO, and B.sub.2 O.sub.3 are essentially absent therefrom.

Abstract: This invention is directed to the formation of blue-to-black transparent glass-ceramic articles containing .beta.-quartz solid solution as essentially the sole crystal phase present therein. The articles are prepared by heat treating reduced precursor glass articles consisting essentially, in weight percent, of 2.5-5% Li.sub.2 O, 1-2% MgO, 18-30% Al.sub.2 O.sub.3, 2-4% TiO.sub.2, 1-4% ZrO.sub.2, 48-70% SiO.sub.2, 1-12% P.sub.2 O.sub.5, and 0-2% ZnO. The precursor glass articles are placed in a reduced state through the inclusion of a sufficient amount of a hydrogen-containing phosphate and/or chloride and/or Ti.sub.2 O.sub.3 to obtain about 0.2-6% of the total titanium content in the form of Ti.sup.+3 ions.

Abstract: A method of manufacturing readily machinable high strength glass ceramics includes the steps of: preparing a powder mixture by mixing glass powders 1 and 2, each having a predetermined composition, with each other; and producing a calcined product by granulating, molding, and heating the powder mixture. This method makes it possible to obtain readily machinable high strength glass ceramics of a novel composition, which exhibit a heat resistance of not less than 1000.degree. C., which excel in mechanical strength and electrical insulation performance, and which allow precision machined parts and large-sized products to be produced with ease.

Abstract: A high-mechanical strength biocompatible crystallized glass essentially comprises both crystallines consisting of tetrasilicic fluorine mica series and calcium phosphate series. The crystallized glass has substantially non-sodium oxide and useful in a dental medical care, as repairing material of tooth.

Abstract: This invention is directed to the production of organic-inorganic composite bodies demonstrating electrical insulating characteristics consisting essentially of lithium and/or sodium water-swelling crystals selected from the group of fluorhectorite, hydroxyl hectorite, boron fluorphlogopite, hydroxyl boron phlogopite, and solid solutions among those and between those and other structurally-compatible species selected from the group of talc, fluortalc, polylithionite, fluorpolylithionite, phlogopite, and fluorphlogopite, wherein the Li.sup.30 and/or Na.sup.+ ions from the interlayer of said lithium and/or sodium water-swelling mica crystals have been exchanged with an organic polycation, the galleries of said crystals containing an organic polymer exhibiting very low permittivity resulting from the transformation of the organic polycation. The preferred organic polycation is a poly(p-xylene-.alpha.

Abstract: This invention is principally directed to the production of an organic-inorganic composite body demonstrating electrical insulating behavior consisting essentially of lithium and/or sodium water-swelling mica crystals selected from the group of fluorhectorite, hydroxyl hectorite, boron fluorphlogopite, hydroxyl boron phlogopite, and solid solutions among those and between those and other structurally-compatible species selected from the group of talc, fluortalc, polyithionite, fluorpolylithionite, phlogopite, and fluorphlogopite, wherein the Li.sup.+ and/or Na.sup.+ ions from the interlayer of said lithium and/or sodium water-swelling mica crystals have been exchanged with ions of a transition metal having multiple oxidation states, the galleries of said crystals containing an organic polymer exhibiting very low permittivity. The preferred organic polymer exhibiting very low permittivity is the emeraldine base form of polyaniline.

Abstract: Machinable ceramics with 30-60 vol. % of fine crystals of fluorophlogopite, a synthetic mica, evenly dispersed in a vitreous matrix is produced using as principal raw materials kaolin and activated clay, which are natural minerals, other than metal oxides themselves. According to the production process, a mixture of fine particulate raw materials is calcined under first heat treatment conditions in which a maximum temperature is in the range of 1,000.degree.-1,100.degree. C. The raw materials include kaolin and activated clay as principal raw materials, Mg-containing, K-containing and F-containing compounds as auxiliary raw materials and B.sub.2 O.sub.3 as a sintering aid. The resulting calcined mass is ground into fine particles, followed by the formation of a green body of a desired shape. The green body is then sintered into a fired body under second heat treatment conditions in which a maximum temperature is in the range of 1,100.degree.-1,250.degree. C.

Abstract: Glass having ultrafine particles of CuCl and/or CuBr precipitated therein, which consists essentially of:from 10 to 70 mol % of SiO.sub.2,from 30 to 90 mol % of B.sub.2 O.sub.3,from 0.1 to 50 mol % of Li.sub.2 O+Na.sub.2 O+K.sub.2 O, andfrom 0.01 to 10 mol % of CuCl+CuBr.The glass may further contain from 0.01 to 40 mol % of Al.sub.2 O.sub.3.

Abstract: The present invention is related to the fabrication of a magnetic memory storage device consisting essentially of a head pad and a rigid information disk, which disk consists essentially of a rigid substrate having a coating of magnetic media on the surface thereof facing the head pad. More particularly, this invention is directed to a substrate for use in the disk. The substrate is selected from two different groups of glass-ceramics: the first group contains a sheet silicate as the predominant crystal phase; and the second group contains a chain silicate as the predominant crystal phase.

Abstract: The inorganic biomaterial of the present invention comprises a ceramic-crystallized glass composite wherein a zirconia ceramic, an alumina ceramic or a zirconia-alumina ceramic is dispersed in a crystallized glass composed mainly of CaO, P.sub.2 O.sub.5, MgO and Al.sub.2 O.sub.3. This inorganic biomaterial, having biocompatibility and a high strength, is useful as an implant material for artificial bones and dental implants.

Abstract: Ceramic matrix composite articles comprising a ceramic, glass-ceramic or glass matrix and a fiber reinforcement phase disposed within the matrix consisting of amorphous or crystalline inorganic fibers, wherein there is provided, on or in close proximity to the surfaces of the inorganic fibers, a layer of sheet silicate crystals constituting a sheet silicate interface between the inorganic fibers and the ceramic, glass, or glass-ceramic matrix. Optionally, the composition of the matrix may be the same as the sheet silicate interface so that the matrix provides the sheet silicate layer.

Abstract: The present invention is directed to a method for synthesizing fluorine-containing, aluminosilicate crystals having a stoichiometry approximating that of topaz. The method comprises three basic steps:(1) vapors of a readily-oxidizable compound of silicon and of a readily-oxidizable compound of aluminum and fluorine are passed to a flame oxidation burner;(2) amorphous fluorine-containing, aluminosilicate particles resulting from the combustion of those gases are collected; and(3) the collected particles are sintered into an integral body at a temperature between about 650.degree.-925.degree. C.

Abstract: Ceramic matrix composite articles comprising a ceramic, glass-ceramic or glass matrix and a fiber reinforcement phase disposed within the matrix consisting of amorphous or cyrstalline inorganic fibers, wherein there is provided, on or in close proximity to the surfaces of the inorganic fibers, a layer of sheet silicate crystals constituting a sheet silicate interface between the inorganic fibers and the ceramic, glass, or glass-ceramic matrix. Optionally, the composition of the matrix may be the same as the sheet silicate interface so that the matrix provides the sheet silicate layer.

Abstract: A complex oxide comprising zirconium oxide and an oxide of at least one metal selected from the group consisting of an alkali metals, alkaline earth metals, silicon and lead is mixed with pottery stone, magnesium fluoride, a compound capable of forming magnesium oxide, a compound capable of forming potassium oxide and a compound capable of forming boron oxide to obtain a composition in which the contents of elements in 100 parts by weight of the total amount exclusive of the ignition loss are 16 to 25 parts of silicon, 6 to 9 parts of aluminum, 5.5 to 12 parts of potassium, 4.7 to 15 parts of magnesium, 0.7 to 5.0 parts of zirconium, 0.7 to 3.2 parts of boron, 3.0 to 9.3 parts of fluorine, up to 7.0 parts of metals other than the foregoing elements, and the balance being oxygen. This composition is heat-melted and then cooled from a temperature higher at least 50.degree. C. than the glass transition temperature of a vitreous body to be formed to a temperature lower by at least 70.degree. C.

Abstract: A colored frit prepared by fusing by heating a material composition comprising a devitrifying substance, a coloring agent and glass, and a method for manufacturing an artificial stone made by utilizing the colored frit. In the method of manufacturing artificial stones, the colored frits alone or a mixture of at least one kind of the colored frits and at least one kind of the colored frits and at least one kind of frits containing fluormicas are sintered, so that the colored frits are devitrified and the colors of the devitrified colored frits become distinctly visible to a viewer. This produces artificial stones having a wide variety of distinct colors and patterns.

Abstract: A dental crown is prepared from a dental crown material including 7 to 11% by weight of Li.sub.2 CO.sub.3, 18 to 28% by weight of MgO, 9 to 15% by weight of Al.sub.2 O.sub.3, 38 to 48% by weight of SiO.sub.2 and 10 to 15% by weight of Na.sub.2 SiF.sub.6. The dental crown material is melted and the molten material is molded in a lost wax mold. The molded material is crystallized to form the dental crown.

Abstract: Micaceous-cordierite-glass ceramic particularly suitable for stomatological, head surgery and neck surgery applicatiosn has a fracture toughness K.sub.IC of up to 2.0 MPa m.sup.1/2, a hardness HV.sub.0.07 of 300-1000, a compressive strength of up to 450 N/mm.sup.2, a linear thermal expansion coefficient of 75-125.times.10.sup.-7 K.sup.-1, good chemical stability and excellent machinability as well as a high resistance to wear and comprises a composition in weight percentages of______________________________________ SiO.sub.2 43-50 Al.sub.2 O.sub.3 26-30 MgO 11-15 R.sub.2 O 7-10.5 F.sup.- 3.3-4.8 Cl.sup.- 0.01-0.6 CaO 0.1-3 P.sub.2 O.sub.5 0.1-5 ______________________________________wherein R.sub.2 O is the sum of 3 to 5.5 wt. % Na.sub.2 O and 4 to 6 wt. % K.sub.2 O, a first crystal phase of mica, and a second crystal phase of 5 to 30 volume % cordierite, wherein relatively large mica crystals of 10 to 200 .mu.m are embedded in the glass and cordierite crystals of 0.5 to 5 .mu.m are arranged in the glass.

Abstract: This invention relates to the preparation of glass-ceramic articles in which potassium fluorrichterite and/or a related fluormica constitutes the predominant crystal phase(s). The precursor glasses can be crystallized in situ very rapidly and exhibit very little thermal deformation during the crystallization heat treatment. The base glasses are essentially free of Li.sub.2 O and consist essentially, expressed in terms of weight percent on the oxide basis, of:______________________________________ SiO.sub.2 61-70 Na.sub.2 O 0.5-3 BaO 0-3.5 Al.sub.2 O.sub.3 2.75-7 K.sub.2 O 2.5-5.5 P.sub.2 O.sub.5 0-2.5 MgO 11-16 Na.sub.2 O + K.sub.2 O <6.8 CaO 4.75-9 F 2-3.

Abstract: A biocompatible glass ceramic comprises, by weight, 7-16% MgO, 20-45% CaO, 41-50% SiO.sub.2, 8-30% P.sub.2 O.sub.5, 0-5% B.sub.2 O.sub.3, 0-5% F.sub.2, and 0-10% Al.sub.2 O.sub.3, and has a crystal structure where a number of fine crystals of apatite, wollastonite, and diopside are densely dispersed and interlace with one another in a glass phase. The glass ceramic is non-porous and has an increased mechanical strength of 2,000 Kg f/cm.sup.2 without degradation of the chemical bonding with the bone of the living body. The glass ceramic contains no alkali and is chemically stable in the living body. The glass ceramic is useful for replacement materials of tooth roots and crowns as well as bones.

Abstract: Disclosed is a glass-ceramic product having a chemical composition, as expressed in terms of oxides with the exception of F, in the weight range of 35 to 60% SiO.sub.2, 10 to 20% Al.sub.2 O.sub.3, 12 to 25% MgO, 5 to 15% K.sub.2 O and 4 to 15% F, containing no B.sub.2 O.sub.3, and containing 40 to 70% by weight of fluorophlogopite microcrystals. This glass-ceramic product has a flexural strength of not less than 1500 kgf/cm.sup.2, a heat resistance of about 1100.degree. C., excellent dielectric properties and good machinability, and is a material capable of extending the range of use of high performance ceramics.