A glass ceramic contains the following components by wt %: 60 to 80% of SiO.sub.2; 4 to 20% of Al.sub.2O.sub.3; 0 to 15% of Li.sub.2O; more than 0 but less than or equal to 12% of Na.sub.2O; 0 to 5% of K.sub.2O; more than 0 but less than or equal to 5% of ZrO.sub.2; 0 to 5% of P.sub.2O.sub.5; and 0 to 10% of TiO.sub.2. A crystalline phase contains at least one of R.sub.2SiO.sub.3, R.sub.2Si.sub.2O.sub.5, R.sub.2TiO.sub.3, R.sub.4Ti.sub.5O.sub.12, R.sub.3PO.sub.3, RAlSi.sub.2O.sub.6, RAlSiO.sub.4O.sub.10, R.sub.2Al.sub.2Si.sub.2O.sub.8, R.sub.4Al.sub.4Si.sub.5O.sub.18, quartz and quartz solid solution. With a liquidus temperature below 1,450° C., a thermal conductivity above 2 w/m.Math.k, and a Vickers hardness above 600 kgf/mm2, the glass ceramic is applicable to portable electronic devices and optical devices.

A method of manufacturing glass ceramic articles such as glass ceramic plates for cooktops or fireplace windows is provided. The method facilitates the adjustment of a specific hue or a specific absorptivity of the glass ceramic in the visible spectral range. The method is based on the finding that the absorption of light by coloring agents which are appropriate for or present in glass ceramics can be attenuated during the ceramization process by adding substances that have a decoloring effect.

Disclosed herein are glass-ceramics having crystalline phases including β-spodumene ss and either (i) pseudobrookite or (ii) vanadium or vanadium containing compounds so as to be colored and opaque glass-ceramics having coordinates, determined from total reflectance—specular included—measurements, in the CIELAB color space of the following ranges: L*=from about 20 to about 45; a*=from about −2 to about +2; and b*=from about −12 to about +1. Such CIELAB color space coordinates can be substantially uniform throughout the glass-ceramics. In each of the proceeding, β-quartz ss can be substantially absent from the crystalline phases. If present, β-quartz ss can be less than about 20 wt % or, alternatively, less than about 15 wt % of the crystalline phases. Also Further crystalline phases might include spinel ss (e.g., hercynite and/or gahnite-hercynite ss), rutile, magnesium zinc phosphate, or spinel ss (e.g., hercynite and/or gahnite-hercynite ss) and rutile.

A black β-spodumene glass ceramic is provided. The glass ceramic includes β-spodumene as a primary crystal phase and gahnite as a minor crystal phase. The glass ceramic is characterized by the color coordinates: L*: 20.0 to 40.0, a*: −1.0 to 0.5, and b*: −5.0 to 1.0. The glass ceramic may be ion exchanged. Methods for producing the glass ceramic are also provided.

Transparent, dyed cook top or hob with improved color display capability, consisting of a glass ceramic with high quartz mixed crystals as predominant crystal phase, whereby the glass-ceramic contains none of the chemical refining agents arsenic oxide and/or antimony, with transmission values of greater than 0.1% in the range of the visible light within the entire wavelength range greater than 450 nm, a light transmission in the visible of 0.8-2.5% and a transmission in the infrared at 1600 nm of 45-85%.

A chemically strengthened bioactive glass-ceramic composition as defined herein. Also disclosed are methods of making and using the disclosed compositions.

A transparent coloured lithium aluminium silicate glass ceramic and method of producing are provided. The glass ceramic has a brightness Y of 0.1% to 80% at thickness 4 mm. The glass ceramic has a D65 standard illuminant light, after passing through the glass ceramic with thickness 4 mm, with a colour locus in a white region W1 determined by coordinates in a chromaticity diagram CIExyY-2°: TABLE-US-00001 White region W1 x y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29.

A transparent colored glass ceramic, in particular an LAS glass ceramic, suitable for use as a cooking surface is provided. The transparent colored glass ceramic includes high-quartz solid solution (HQ s.s.) as a main crystal phase and exhibits thermal expansion of −1 to +1 ppm/K in the range from 20° C. to 700° C. The glass ceramic has from 3.0 to 3.6 percent by weight of lithium oxide (Li.sub.2O) as constituents and either is colored with 0.003 to 0.05 percent by weight of vanadium oxide (V.sub.2O.sub.5) or is colored with 0.003 to 0.25 percent by weight of molybdenum oxide (MoO.sub.3).

A sightglass for a stove is provided that has a substrate made of transparent coloured lithium aluminium silicate glass ceramic. The sightglass has a light transmittance of 0.1% to 50%. Standard illuminant D65 light, after passing through the glass ceramic, at a thickness of 4 mm, has a colour locus in the white region W1 determined by the following coordinates in the chromaticity diagram CIExyY-2: TABLE-US-00001 White region W1 x y 0.27 0.21 0.22 0.25 0.32 0.37 0.45 0.45 0.47 0.34 0.36 0.29.

A chemically strengthened bioactive glass-ceramic composition as defined herein. Also disclosed are methods of making and using the disclosed compositions.