A composition includes 30 mol % to 60 mol % SiO.sub.2; 15 mol % to 40 mol % Al.sub.2O.sub.3; 5 mol % to 25 mol % Y.sub.2O.sub.3; 5 mol % to 15 mol % TiO.sub.2; and 0.1 mol % to 15 mol % RO, such that RO is a sum of MgO, CaO, SrO, and BaO.

A composition includes 30 mol % to 60 mol % SiO.sub.2; 15 mol % to 40 mol % Al.sub.2O.sub.3; 5 mol % to 25 mol % Y.sub.2O.sub.3; 5 mol % to 15 mol % TiO.sub.2; and 0.1 mol % to 15 mol % RO, such that RO is a sum of MgO, CaO, SrO, and BaO.

A tubular member for an exhaust gas treatment device according to at least one embodiment of the present invention includes: a tubular main body made of a metal; and an insulating layer formed at least on an inner peripheral surface of the tubular main body. The insulating layer contains glass containing a crystalline substance, and the glass contains silicon, boron, and magnesium.

To provide a crystallized glass substrate including a surface with a compressive stress layer, in which a stress depth DOL.sub.zero of the compressive stress layer, at which the compressive stress is 0 MPa, is 45 to 200 μm, a compressive stress CS on an outermost surface of the compressive stress layer is 400 to 1400 MPa, and CS×DOL.sub.zero, which is a product of the compressive stress CS on the outermost surface and the stress depth DOL.sub.zero (μm), is 4.8×10.sup.4 or more.

Provided is a Li.sub.2O-Al.sub.2O.sub.3-SiO.sub.2-based crystallized glass that has a high permeability to light in a ultraviolet to infrared range and is less likely to be broken. A Li.sub.2O-Al.sub.2O.sub.3-SiO.sub.2-based crystallized glass contains, in terms of % by mass, 40 to 90% Si.sub.O2, 5 to 30% Al.sub.2O.sub.3, 1 to 10% Li.sub.2O, 0 to 20% SnO.sub.2, 0 to 5% ZrO.sub.2, 0 to 10% MgO, 0 to 10% P.sub.2O.sub.5, and 0 to 4% TiO.sub.2 and a mass ratio of Li.sub.2O/(MgO+CaO+SrO+BaO+Na.sub.2O+K.sub.2O) is 3 or less.

An optical diffuser can comprise an amorphous phase and a crystalline phase comprising lithium disilicate and one or more of ß-spodumene or ß-quartz comprising a median grain size ranging from about 500 nanometers to about 1,000 nanometers. The crystalline phase can be dispersed throughout a volume of the optical diffuser. The optical diffuser can comprise, on an oxide basis in mol %, SiO.sub.2: 60-75; Al.sub.2O.sub.3: 2-9; Li.sub.2O: 17-25; and Na.sub.2O+K.sub.2O: 0.5-6. Methods of making an optical diffuser can comprise forming a mixture by melting together, on an oxide basis in mol %, SiO.sub.2: 60-75; Al.sub.2O.sub.3: 2-9; Li.sub.2O: 17-25; and Na.sub.2O+K.sub.2O: 0.5-6. Methods can comprise forming a ribbon from the mixture. Methods can comprise heating the ribbon about 850° C. to about 900° C. for about 0.5 hours to about 6 hours.

The present invention relates to a chemically strengthened glass ceramic including a crystalline phase, having two main surfaces opposed to each other, and including an amorphized region in a surface layer of at least one of the main surfaces and a crystallized region inside the glass, in which the amorphized region has a crystallinity of 10 vol % or less at a depth of 100 nm from an outermost surface of the glass.

A glass ceramic includes feldspar crystal phases, non-crystalline glass phases, Al.sub.2O.sub.3 phases, and SiO.sub.2 phases. At least one pair of the Al.sub.2O.sub.3 phases is bonded via at least one of the feldspar crystal phases.

The present invention relates to compositions in the form of precursor glass powders, pastes and preforms comprising said precursor glass powders and glass-ceramics produced from the precursor glass powders, pastes or preforms. The present invention also relates to a method of forming a seal between a first and second material with a glass-ceramic, and a joint comprising a first material, a second material and a glass-ceramic sealing material joining the first and second materials together.

A glass-ceramic component is provided that has a low average coefficient of thermal expansion (CTE) and a high CTE homogeneity. The use of such a component and a process for producing such a component are also provided.