Disclosed herein are glass-based articles having a first surface having an edge, wherein a maximum optical retardation of the first surface is at the edge and the maximum optical retardation is less than or equal to about 40 nm and wherein the optical retardation decreases from the edge toward a central region of the first surface, the central region having a boundary defined by a distance from the edge toward a center point of the first surface, wherein the distance is ½ of the shortest distance from the edge to the center point.

Disclosed herein are glass-based articles having a first surface having an edge, wherein a maximum optical retardation of the first surface is at the edge and the maximum optical retardation is less than or equal to about 40 nm and wherein the optical retardation decreases from the edge toward a central region of the first surface, the central region having a boundary defined by a distance from the edge toward a center point of the first surface, wherein the distance is ½ of the shortest distance from the edge to the center point.

Lithium silicate-diopside glass ceramics are described which are characterized by a controllable translucence and can be satisfactorily processed mechanically and therefore can be used in particular as restoration material in dentistry.

The disclosure relates to glass compositions with high coefficients of thermal expansion and low fracture toughness designed for thermal tempering. These glasses are ideally suited to produce a “dicing” pattern when thermally tempered, even when thin (<3 mm). Disclosed glasses have high thermal expansions at low and high temperatures to produce increased temper stresses once quenched, coupled with low fracture toughness which promotes crack bifurcation and enhanced frangibility. Methods of making such glasses are also provided.

The disclosure relates to glass compositions with high coefficients of thermal expansion and low fracture toughness designed for thermal tempering. These glasses are ideally suited to produce a “dicing” pattern when thermally tempered, even when thin (<3 mm). Disclosed glasses have high thermal expansions at low and high temperatures to produce increased temper stresses once quenched, coupled with low fracture toughness which promotes crack bifurcation and enhanced frangibility. Methods of making such glasses are also provided.

A transparent glass-ceramic composition including: of the formula Ta.sub.2-xAl.sub.xO.sub.5-x where x is less than 1; of the formula AlTaO.sub.4; of the formula AlPO.sub.4; a mixture of AlTaO.sub.4 and AlPO.sub.4; or a mixture of the formula Ta.sub.2-xAl.sub.xO.sub.5-x, AlTaO.sub.4, and AlPO.sub.4. Also disclosed are transparent glass-ceramic compositions including, for example, a dopant as defined herein, or a supplemental metal oxide or metalloid oxide of M.sub.xO.sub.y, M.sub.xM′.sub.xO.sub.y, or a mixture thereof such as oxides of Nb, Ti, W, B, or Ga, as defined herein. Also disclosed are methods of making the disclosed transparent glass-ceramic compositions, and optical articles, optical components, and optical apparatus thereof.

The present invention relates to a 3D printer printhead, a 3D printer using the same, a method for manufacturing a molded product by using the 3D printer, a method for manufacturing an artificial tooth by using the 3D printer, and a method for manufacturing a machinable glass ceramic molded product by using the 3D printer, the 3D printer printhead comprising: an inlet through which glass wire, which is a raw material, is introduced; a heating means for heating the glass wire introduced through the inlet; a melting furnace for providing a space in which the glass wire is fused; and a nozzle connected to the lower part of the melting furnace so as to temporarily store the fused glass or discharge a targeted amount of the fused glass, wherein the melting furnace includes an exterior frame made from a heat resistant material and an interior frame having a crucible shape, and the interior frame is made from platinum (Pt), a Pt alloy or graphite, which have a low contact angle, or a material having a surface coated with Pt or a diamond-like carbon (DLC) so as to prevent the fused glass from sticking thereto. According to the present invention, the molded product, the artificial tooth, and the machinable glass ceramic molded product can be manufactured with excellent mechanical properties, thermal durability, chemical durability and oxidation resistance and outstanding texture by using the glass wire as a raw material.

The invention provides a composition for glass, a glass, and a preparation method and application thereof. On an oxide basis, the composition for glass contains 45-64 wt % SiO.sub.2, 16-26 wt % Al.sub.2O.sub.3, 0.1-2 wt % MgO, 10-17 wt % Na.sub.2O, 0.5-15 wt % P.sub.2O.sub.5, and optionally 0-2 wt % TiO.sub.2. The glass prepared from the composition for glass has a higher chemical resistance, a higher strain point, and a higher compressive stress and depth of compressive stress layer formed on the glass surface, and the glass has a higher Young's modulus.

The invention provides a composition for glass, a glass, and a preparation method and application thereof. On an oxide basis, the composition for glass contains 45-64 wt % SiO.sub.2, 16-26 wt % Al.sub.2O.sub.3, 0.1-2 wt % MgO, 10-17 wt % Na.sub.2O, 0.5-15 wt % P.sub.2O.sub.5, and optionally 0-2 wt % TiO.sub.2. The glass prepared from the composition for glass has a higher chemical resistance, a higher strain point, and a higher compressive stress and depth of compressive stress layer formed on the glass surface, and the glass has a higher Young's modulus.

Glass-based articles are provided that exhibit improved fracture resistance. The relationships between properties attributable to the glass composition and stress profile of the glass-based articles are provided that indicate improved fracture resistance.