The invention relates to glass ceramics and glasses with cerium and tin content, which comprise the following components: TABLE-US-00001 Component wt.-% SiO.sub.2 42.0 to 80.0 Al.sub.2O.sub.3 0.1 to 42.0 Cerium, calculated as CeO.sub.2 0.5 to 10.0 Tin, calculated as SnO 0.1 to 4.0
and which are suitable in particular for the preparation of dental restorations, the fluorescence properties of which largely correspond to those of natural teeth.

To provide an inorganic composition article containing at least one kind selected from α-cristobalite and α-cristobalite solid solution as a main crystal phase, in which by mass % in terms of oxide, a content of a SiO.sub.2 component is 50.0% to 75.0%, a content of a Li.sub.2O component is 3.0% to 10.0%, a content of an Al.sub.2O.sub.3 component is 5.0% or more and less than 15.0%, and a total content of the Al.sub.2O.sub.3 component and a ZrO.sub.2 component is 10.0% or more, and a surface compressive stress value is 600 MPa or more.

Lithium silicate-low quartz glass ceramics are described which are characterized by a combination of very good mechanical and optical properties and can therefore be used in particular as restoration material in dentistry.

The present invention relates to a process for producing a workpiece made of glass ceramics, and to the workpiece obtainable by the process according to the invention. Further, the invention relates to the use of the workpiece obtained as a dental restoration, and to a process allowing the translucency of a workpiece to be controlled.

In embodiments, a precursor glass comprising from about 55 wt. % to about 80 wt. % SiO.sub.2; from about 5 wt. % to about 20 wt. % Al.sub.2O.sub.3; from about 5 wt. % to about 20 wt. % Li.sub.2O; from about 2 wt. % to about 4 wt. % P.sub.2O.sub.5; and from about 0.2 wt. % to about 15 wt. % ZrO.sub.2.

Embodiments of a glass-based article including a first surface and a second surface opposing the first surface defining a thickness (t) of about 3 millimeters or less (e.g., about 1 millimeter or less), and a stress profile, wherein all points of the stress profile between a thickness range from about 0.Math.t up to 0.3.Math.t and from greater than about 0.7.Math.t up to t, comprise a tangent with a slope having an absolute value greater than about 0.1 MPa/micrometer, are disclosed. In some embodiments, the glass-based article includes a non-zero metal oxide concentration that varies along at least a portion of the thickness (e.g., 0.Math.t to about 0.3.Math.t) and a maximum central tension in the range from about 80 MPa to about 100 MPa. In some embodiments, the concentration of metal oxide or alkali metal oxide decreases from the first surface to a value at a point between the first surface and the second surface and increases from the value to the second surface. The concentration of the metal oxide may be about 0.05 mol % or greater or about 0.5 mol % or greater throughout the thickness. Methods for forming such glass-based articles are also disclosed.

A glass-ceramic includes a silicate-containing glass and crystals within the silicate-containing glass. The crystals include non-stoichiometric tungsten and/or molybdenum sub-oxides, and the crystals are intercalated with dopant cations.

The present application relates to glass-ceramics that are white, opalescent or opaque, of the lithium aluminosilicate (LAS) type, containing a solid solution of β-spodumene as the main crystalline phase. The application also provides articles that are constituted, at least in part, of said glass-ceramics, precursor glasses for said glass-ceramics, and a method of preparing said article. Said glass-ceramics have a composition that is free from arsenic oxide and antimony oxide, with the exception of inevitable traces, and that contains the following, expressed as percentages by weight of oxides: 60% to 70% of SiO.sub.2, 18% to 23% of Al.sub.2O.sub.3, 3.0% to 4.3% of Li.sub.2O, 0 to 2% of MgO, 1 to 4% of ZnO, 0 to 4% of BaO, 0 to 4% of SrO, 0 to 2% of CaO, 1.3% to 1.75% of TiO.sub.2, 1% to 2% of ZrO.sub.2, 0.05% to 0.6% of SnO.sub.2, 0 to 2% of Na.sub.2O, 0 to 2% of K.sub.2O, 0 to 2% of P.sub.2O.sub.5, 0 to 2% of B.sub.2O.sub.3, with Na.sub.2O+K.sub.2O+BaO+SrO+CaO≤6% and Na.sub.2O+K.sub.2O≤2%, and a maximum of 500 ppm of Fe.sub.2O.sub.3.

The present invention discloses a microcrystalline glass, a microcrystalline glass product, and a manufacturing method therefor. The main crystal phase of the microcrystalline glass comprises lithium silicate and a quartz crystal phase. The haze of the microcrystalline glass of the thickness of 0.55 mm is below 0.6%. The microcrystalline glass comprises the following components in percentage by weight: SiO.sub.2: 65-85%; Al.sub.2O.sub.3: 1-15%; Li.sub.2O: 5-15%; ZrO.sub.2: 0.1-10%; P.sub.2O.sub.5: 0.1-10%; K.sub.2O: 0-10%; MgO: 0-10%; ZnO: 0-10%. A four-point bending strength of the microcrystalline glass product is more than 600 Mpa.

Glass-ceramic articles are manufactured by an ion exchange process that results in glass-based articles having improved stress profiles. A knee may be located at a depth of 3 microns or deeper. A compressive stress at a surface may be 200 MPa or more and at a knee may be 20 MPa or more. A non-sodium oxide may have a non-zero concentration that varies from the first surface to a depth and a depth of compression (DOC) may be located at 0.10.Math.t, or even at 0.17.Math.t or deeper. A two-step ion exchange (DIOX) includes, for example, a potassium bath in a first treatment to form a spike in a spike region of the stress profile, followed by a second treatment which includes, for example, a potassium and sodium mixed bath to maintain the spike and form a tail region of the stress profile. The glass-ceramic articles may thereby avoid developing a vitreous surface layer, which facilitates repeatable and reliable measurement of waveguide modes and determination of compressive stress in the surface (CS) and depth of the spike.