A glass-ceramic that includes a first crystal phase including (Mg.sub.xZn.sub.1-x)Al.sub.2O.sub.4, where x is ≤1, and a second crystal phase including tetragonal ZrO.sub.2. The glass-ceramic may be substantially free of arsenic, tin, antimony, and cesium, each of the arsenic, tin, antimony, and cesium present at less than 0.01% (by mole of oxide). Further, the glass-ceramic may include a transmittance of at least about 80% to light having a wavelength of 380 nm to 760 nm.

A glass ceramic for an optical filter and an optical filter are obtained that have both thermal expansion characteristics for preventing refractive index fluctuations at a usage temperature of a filter member and mechanical characteristics considering durability, and further have excellent workability.

An internal transmittance of the glass ceramic for an optical filter is 0.970 or more with respect to light having a wavelength of 1550 nm when a thickness of the glass ceramic is 1 mm. The glass ceramic includes, by mass % in terms of oxide, 40.0% to 70.0% of a SiO.sub.2 component, 11.0% to 25.0% of an Al.sub.2O.sub.3 component, 5.0% to 19.0% of a Na.sub.2O component, 0% to 9.0% of a K.sub.2O component, 1.0% to 18.0% of one or more components selected from a MgO component and a ZnO component, 0% to 3.0% of a CaO component, and 0.5% to 12.0% of a TiO.sub.2 component.

A glass ceramic for an optical filter and an optical filter are obtained that have both thermal expansion characteristics for preventing refractive index fluctuations at a usage temperature of a filter member and mechanical characteristics considering durability, and further have excellent workability.

An internal transmittance of the glass ceramic for an optical filter is 0.970 or more with respect to light having a wavelength of 1550 nm when a thickness of the glass ceramic is 1 mm. The glass ceramic includes, by mass % in terms of oxide, 40.0% to 70.0% of a SiO.sub.2 component, 11.0% to 25.0% of an Al.sub.2O.sub.3 component, 5.0% to 19.0% of a Na.sub.2O component, 0% to 9.0% of a K.sub.2O component, 1.0% to 18.0% of one or more components selected from a MgO component and a ZnO component, 0% to 3.0% of a CaO component, and 0.5% to 12.0% of a TiO.sub.2 component.

A glass-ceramic article includes from 60 mol % to 72 mol % SiO2; from 2.5 mol % to 8 mol % Al.sub.2O.sub.3; from 17 mol % to 26 mol % Li.sub.2O; from 0.2 mol % to 4 mol % ZrO.sub.2; and from 0.5 mol % to 2 mol % P.sub.2O.sub.5. The sum of alkaline earth oxides and transitional metal oxides in the glass-ceramic article may be from 0.1 mol % to 6 mol %, wherein alkaline earth oxides is the sum of CaO, MgO, SrO, and BaO and transition metal oxides is the sum of La.sub.2O.sub.3, Y.sub.2O.sub.3, Ta.sub.2O.sub.5, and GeO.sub.2. The sum of P.sub.2O.sub.5 and ZrO.sub.2 in the glass-ceramic article may be from 1 mol % to 6 mol %. The glass-ceramic article may comprise a crystalline phase comprising lithium disilicate and petalite. The total amount of lithium disilicate and petalite in the crystalline phase of the glass-ceramic article may be greater than 50 wt %, based on a total weight of the crystalline phase.

A glass-ceramic article includes a crystalline phase; a residual glass phase; greater than or equal to 52 mol % and less than or equal to 70 mol % SiO.sub.2, greater than or equal to 14 mol % and less than or equal to 35 mol % Li.sub.2O, greater than or equal to 0.1 mol % and less than or equal to 15 mol % CaO, greater than or equal to 0.5 mol % and less than or equal to 10 mol % ZrO.sub.2; and greater than or equal to 0.5 mol % and less than or equal to 5 mol % P.sub.2O.sub.5.

A glass-ceramic article includes a crystalline phase; a residual glass phase; greater than or equal to 52 mol % and less than or equal to 70 mol % SiO.sub.2, greater than or equal to 14 mol % and less than or equal to 35 mol % Li.sub.2O, greater than or equal to 0.1 mol % and less than or equal to 15 mol % CaO, greater than or equal to 0.5 mol % and less than or equal to 10 mol % ZrO.sub.2; and greater than or equal to 0.5 mol % and less than or equal to 5 mol % P.sub.2O.sub.5.

A dental bulk block for a CAD/CAM machining process. The dental bulk block is a glass-ceramic block having a crystalline phase embedded in an amorphous glass matrix. The crystalline phase includes lithium disilicate as a main crystalline phase, no sub-crystalline phase exists, and the crystalline phase has a mean grain size of 0.01 to 1.0 μm and a crystallinity degree of 25 to 45%. The dental bulk block can improve machinability during cutting such as CAD/CAM machining in the state of a high-strength workpiece with high flexural strength, thereby reducing a tool resistance and a wear rate, increasing a tool life span, and reducing edge chipping during a machining process. In addition, a dental restoration with desired translucency variations can be manufactured through a simple process of machining a block and altering post-heat treatment conditions, and thus can be realized with various shades.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

Dental composite composition including a glass ceramic and a curable organic material is described in which the glass ceramic includes a crystal phase having an average grain size of 50 to 400 nm, and the dental composite composition is provided as a dental prosthetic material exhibiting superior transparency and mechanical properties comparing to conventional composite products containing micro-sized crystal grains and also has excellent aesthetics and processability required for prosthetic materials for same-day dental prosthetic service.

A connected substrate of the present invention includes a plurality of element substrate regions partitioned by dividing grooves, wherein the connected substrate is a glass ceramic sintered body having precipitated therein an anorthite crystal.