CA2299202A1 - Translucent or opaque glass-ceramic containing .beta.-quartz solid solution as the predominant crystal phase, and the use thereof in a cooking hob - Google Patents

Abstract

A translucent or opaque glass-ceramic containing .beta.-quartz solid solution as the predominant crystal phase, having a composition (in % by weight) of Li2O 3-5, Na2O 0-1, K20 0-1, Na2O + K2O 0.2-2, MgO 0-1.8, BaO 0-3.5, SrO 0-1, CaO 0-1, BaO + SrO +
CaO
0.2-4, ZnO 0-2.8, Al2O3 17-26, SiO2 62-72, TiO2 0-2.5, ZrO2 0-3, TiO2 + ZrO2 1-<3.5, Sb2O3 0-2, As2O3 0-2, SnO 0-<1, and P2O5 0-8, an average coefficient of linear thermal expansion .alpha.20-700°C of <0.5~10 -6/K, an average crystal size of the .beta.-quartz solid solution of ~ 80 nm, and a transmission (sample thickness 4 mm) ~380-780 nm of < 30%. The glass-ceramic may be preferably used as a heatable plate for cooking and grilling, as a cooking utensil, as a stove window, and/or as a base plate for microwave ovens.

Description

TRANSLUCENT OR OPAQUE GLASS-CERAMIC CONTAINING
~3-QUARTZ SOLID SOLUTION AS THE PREDOMINANT CRYSTAL PHASE, AND
THE USE THEREOF
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The invention relates to a translucent or opaque glass-ceramic containing (3-quartz solid solution as the predominant crystal phase, and to the use thereof.

2. Background Information:
Glass-ceramics containing (3-quartz solid solutions as the predominant crystal phase are known.
Thus, United States Patent No. 4,461,839 describes transparent, translucent and opaque glass-ceramics comprising the Li20-A1203-SiOz system (so-called LAS
glass-ceramics) containing (3-quartz solid solution as the predominant crystal phase, where the glass-ceramics have inherent colors of from black via brown to red.
However, the optical appearance has been assessed by purely visual means.
Heatable plates of glass-ceramic intended for use as cooking hobs must withstand exposure to temperatures of significantly above 300°C, in some cases above 500°C, depending on the heating system used. For testing whether a glass-ceramic is suitable for use, for example, as a cooking hob, the determination of the coefficient of linear thermal 2o expansion for the temperature range of from 20°C to 700°C, a2o_~oo~c~ inter alia, has become established. Although glass-ceramics having a coefficient of expansion a2o-,oo~c of ~ 1 ~ 10-6/K
are in principle suitable as cooking hobs, today's standard of heating systems and temperatures in the region above 500°C in the vicinity of the cooking zones (alongside the areas close to room temperature) average that the requirement for low thermal expansion has risen to a coefficient of expansion a2o-,oo~c of < 0.5~ 10-6/K, ideally even a2o-~oo~c ~ 0.38-10-6/K, in order to achieve acceptable rates in the breakage failure probability.
Negative coefficients of thermal expansion are permissible to a greater extent than slightly positive ones since in this case a glass-ceramic is placed under compressive stress. It is generally known that this low expansion can be achieved using glass-ceramics comprising the Li20-A1z03-Si02 system, 3o which has been widespread in industry for decades in various areas, for example mirror carriers for telescopes, cooking utensils and cooking hobs.
In these glass-ceramics, a distinction can be made between the principal crystal phases (3-quartz solid solution ((3-QSS), also known as (3-eucryptite solid solution, and keatite solid solution (KSS), also known as (3-spodumene solid solution. Thus, the (3-QSS-LAS
glass-ceramics have a lower thermal expansion than KSS glass-ceramics, whose coefficients of linear thermal expansion are in the order of azo_,oo~c ~ 1 ~ 10-6/K.
Accordingly, the principal crystal phase, (3-quartz solid solution, has recently been preferred over keatite solid solution for applications which require very low expansion, for example, cooking hobs.
In other words, a (3-QSS ceramic may have a coefficient of linear thermal expansion azo-~oo~c of approximately 1 ~ 10-6/K.
Crystal nucleation may be usually carried out using TiOZ and/or Zr02.
Thus, European Patent No. EP 0 220 333 B 1, for example, discloses a transparent, colored glass-ceramic containing (3-quartz solid solution as the predominant crystal phase, where the transparency in the visible region is essentially established by adding the nucleation agents with a proportion of 1.5 - 5.0% by weight of Ti02 and 0 -3.0% by weight of ZrOz, and with a total amount of Ti02 and Zr02 of from 3.5 to 5.5% by weight.
German Patent No. DE-PS 43 21 373 C2 likewise discloses glass-ceramics containing (3-quartz solid solution as the predominant crystal phase. These are glass-ceramics having high transmission, in particular in the wavelength range from 2700 to 3300 nm, but also high transmission in the visible region. In order to reduce the high transmission in the visible region, which is particularly interfering on use of the glass-ceramic as a cooking hob, coloring components are added to the glass-ceramic. Glass-ceramics without coloring additives may have an essentially unchanged, high transmission in the visible region.
OBJECT OF THE INVENTION
One object of the invention may be to find a translucent or opaque glass-ceramic 2o containing (3-quartz solid solution as the predominant crystal phase and having essentially low thermal expansion, essentially low transmission in the visible region, even without addition of coloring components, and essentially high heat and thermal shock resistance.
Furthermore, the glass-ceramic should in addition be suitable for coloring and should be particularly suitable for use as, for example, a cooking hob, cooking utensil, or stove window.
SUMMARY OF THE INVENTION
One object of the present invention may be achieved by a glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition: Li20 3 - 5, Na20 0 - 1, KZO 0 - 1, NaZO + Kz0 0.2 - 2, Mg0 0-1.8, Ba0 0 -3.5, Sr0 0 - 1, Ca0 0 - 1, Ba0 + Sr0 + Ca0 0.2 - 4, Zn0 0 - 2.8, A1z03 17 -26, SiOz 62 - 72, 30 TiOz 0 - 2.5, ZrOZ 0 - 3, Ti02 + Zr02 1 - < 3.5, Sb203 0 - 2, As203 0 - 2, Sn0 0 - < l, and PZOS
0 - 8, an average coefficient of linear thermal expansion azo-,oo~c of < 0.5~
10-6/K, an average crystal size of the (3-quartz solid solution of >_ 80 nm and a transmission (sample thickness 4 mm) ~L380 - 780 nm of < 30%.
Overall, it may now be possible to obtain a translucent or opaque glass-ceramic containing (3-quartz solid solution as the predominant crystal phase which has an essentially advantageous low transmission in the visible region, the low transmission being achieved without addition of coloring components. In addition, the glass-ceramic may have an essentially advantageous, low thermal expansion.
The fact that the total content of Ti02 and Zr02 is restricted to the range from 1 to <
3.5% by weight means that, compared with known LAS glass-ceramics, only an essentially small amount of nucleating agents is made available. The low number of nucleating agents contributes to the fact that few, but large, (3-quartz solid solution crystals form during the ceramicization of the glass-ceramic. The solid solution crystals grow to an average size of greater than 80 nm. At a relatively high crystal nucleus density, many small crystals form, meaning that, owing to the resultant low crystal size, the glass-ceramic appears transparent.
In other words, (3-quartz solid solution glass ceramics may typically contain Ti02 as a nucleating agent. In another possible embodiment of the present invention, Zr02 may be partly or essentially wholly substituted for Ti02 as a nucleating agent in (3-quartz solid solution glass-ceramics.
In yet another possible embodiment of the present invention, the weight percent of TiOz and Zr02 in a glass-ceramic in the context of the present invention may be within the range of approximately 1 weight percent to approximately 3.5 weight percent.
This range may be essentially advantageous, compared with LAS glass-ceramics described in previous publications, because the relatively low total weight percent of possible nucleating agents, in a possible glass-ceramic related to the present invention, may result in the formation of relatively few, and relatively large, (3-quartz solid solution crystals during the ceramicization 2o of the glass-ceramic, thus possibly permitting the formation of an essentially opaque or essentially translucent glass-ceramic. In other words, there may be a low crystal density in the glass-ceramic possibly used in conjunction with at least one embodiment of the present invention, and the solid solution crystals may grow to an average size of approximately greater than 80 nanometers, thus essentially preventing transparency in at least one possible embodiment of the present invention.
The low nucleus density can be produced not only by a lower nucleating agent content, but also by process variations, in particular, for example, by shortening the nucleation time.
In other words, in at least one possible embodiment of the present invention, 3o crystallization or growth of nucleated crystals may be carried out by heating nucleated glass to a temperature within the range of approximately 750 degrees Celsius to 1200 degrees Celsius for a time period of approximately 30 seconds to approximately 8 hours.
In another possible embodiment of the present invention, crystallization or growth of nucleated crystals may be carried out by heating nucleated glass to a temperature within the range of approximately 900 degrees Celsius to 1100 degrees Celsius for a time period of approximately 60 seconds to approximately 2 hours or for a time period of approximately 1 minute to approximately 2 hours.

A further advantage of this invention is the relatively low Ti02 content. It is known from the specialist literature that a Ti-Fe complex has a slightly coloring action. If this slight coloration is undesired, for example, in transparent, white translucent, or white opaque glass-ceramics, use of pure, in particular low-Fe raw materials may be necessary. If the component Ti02 is present in small amounts in the glass-ceramic, the expensive low-Fe raw materials can be omitted.
If the ZrOz content is selected to be greater than 3% by weight, problems may occur during melting.
For fining of the glass, conventional fining agents, such as, for example, Asz03, Sbz03, Sn02, Ce02, fluorides, and chlorides, are used.
In other words, for freeing the molten glass of bubbles, conventional agents for freeing molten glass of bubbles, such as, for example, As20~, Sbz03, SnOz, Ce02, fluorides, and chlorides, may be used.
The H20 content can be set in the range 0.01 - 0.05 mol/1 via the choice of raw materials and the mode of operation of the production unit (see German Patent No. DE-PS 43 21 373 C2).
In other words, the Hz0 content of the glass or glass-ceramic may be within the range of approximately 0.01 moles per liter to approximately 0.05 moles per liter.
The glass-ceramic according to the invention preferably has a lightness value L* in 2o the L*a*b* color system (CIELAB system) of > 85. The glass-ceramic thus has predominantly light white shades.
In other words, the CIELAB system or L*a*b* color system may be essentially a color coordinates system for describing color or defining a color in a rectangular coordinate system having 3 axes, where, in one possible embodiment of the present invention, the symbol L* may equal the parameter on the lightness scale, ranging from 0 (black) to 100 (white); the symbol a* may equal the parameter on the red-green scale, with positive values for red and negative values for green; and the symbol b* may equal the parameter on the yellow-blue contrast scale, with positive values for yellow and negative values for blue. In the CIELAB or L*a*b* color system, the L* values may not be a measure of transparency of 30 a material, but may refer only to the lightness of a material. In another possible embodiment of the present invention, the symbol L* may denote lightness or metric lightness; C*ab may denote brightness, chroma, or metric chroma; and the symbol H degree, or the symbol H°, may denote a color angle or a metric hue angle.
An essentially full description of the CIELAB system may be found in the following CIE (Commission Internationale de 1'Eclairage, or International Commission on Illumination) publications: CIE Publication No. 15.2-1986, entitled "Colorimetry, 2nd Edition" and Supplement No. 2 to CIE Publication No. 15 ((E-1.3.1)1971)/(TC-1.3) 1978.

These CIE publications may be available from the CIE National Committee of USA, Mr.
Thomas Lemons, TLA - Lighting Consultants Inc., 7 Pond Street, Salem, MA 01970 or from The CIE Central Bureau, Kegelgasse 27, A-1030 Vienna, Austria.
Some further examples of descriptions of the CIELAB system or the L*a*b*
system, the CIE system, or the Standard Valence System defined in DIN 5033 and methods and apparatus for measurement related thereto may be found in the following U.S.
patents and other publications: U.S. Patent No. 5,994,249, issued to inventors Graber et al. on November 30, 1999; U.S. Patent No. 5,958,126, issued to inventors Adel et al. on September 28, 1999;
U.S. Patent No. 5,754,448, issued to inventors Edge et al. on May 19, 1998;
U.S. Patent No.

4,698,100, issued to inventors Burow et al. on October 6, 1987; U.S. Patent No. 4,620,879, issued to inventors Burow et al. on November 4, 1986; U.S. Patent No.
4,546,045, issued to inventor Elias on October 8, 1985; U.S. Patent No. 4,448,608, issued to inventors Jenkins et al. on May 15, 1984; U.S. Patent No. 4,404,254, issued to inventors Franz et al. on September 13, 1983; U.S. Patent No. 4,394,470, issued to inventors Werner et al. on July 19, 1983; U.S.
Patent No. 4,378,252, issued to inventors Kiemle et al. on March 29, 1983;
U.S. Patent No.
4,370,270, issued to inventors Bock et al. on January 25, 1983; U.S. Patent No. 4,363,888, issued to inventors Willison et al. on December 14, 1982; U.S. Patent No.
4,067,850, issued to inventors Kohler et al. on January 10, 1978; the book entitled Coloring ofPlastics, having the editor T. G. Webber, published by Wiley-Interscience of New York in 1979;
and 2o Ullmann's "Enzyklopedie der technischen Chemie", 4th edition, Vol. 18, Weinheim 1979.
The desired translucency or opacity, the essentially low transmission in the visible region, and the essentially high lightness value - besides the composition -can be adjusted and regulated essentially via the content of nucleating agents, i.e., Zr02 and TiOz, and via the average size of the (3-quartz solid solution crystals.
In order to ensure essentially adequate meltability, at least 0.2% by weight of the non-crystal-forming alkali metal oxides Na20 and/or KZO may be present. In order to obtain a residual glass content in the glass-ceramic in which ceramicization stresses can be relaxed, at least 0.2% by weight of the non-crystal-forming alkaline earth metal oxides BaO, SrO, and/or Ca0 may be present. The total amount of the non-crystal-forming alkali metal oxides and 3o alkaline earth metal oxides may be limited to 2% and 4% by weight respectively, since the residual glass phase may be responsible for the increase in the coefficient of thermal expansion of the glass-ceramic product.
In other words, in order to ensure essentially adequate meltability in at least one possible embodiment of the present invention, at least 0.2% by weight of the non-crystal-forming alkali metal oxides Na20 and/or Kz0 are present. In order to obtain a residual glass content in the glass-ceramic in which ceramicization stresses can be relaxed, at least 0.2% by weight of the non-crystal-forming alkaline earth metal oxides BaO, SrO, and/or Ca0 are present in another possible embodiment of the present invention. The total amount of the non-crystal-forming alkali metal oxides and alkaline earth metal oxides is limited to 2% and 4% by weight respectively in at least one possible embodiment of the present invention, since the residual glass phase is responsible for the increase in the coefficient of thermal expansion of the glass-ceramic product.
The components Li20, A1203, SiOz and, in smaller amounts, Mg0 and ZnO, form the (3-quartz solid solution.
An Li20 content of greater than 5% by weight may result in undesired, premature crystallization during the production process.
A similar effect is exhibited by high Mg0 contents. In other words, the Mg0 content of the glass-ceramic may be within the range of approximately 0 weight percent to approximately 1.8 weight percent because a greater Mg0 content in this glass-ceramic may result in undesired premature crystallization or nucleation during the production process of the glass-ceramic.
In order to essentially avoid increased coefficients of expansion of the glass-ceramic, the Mg0 content may be restricted to approximately 1.8% by weight or less, and the Zn0 content may be restricted to approximately 2.8% by weight or less.
A1z03 contents of greater than 25% by weight may increase the viscosity of the glass considerably and increase the tendency toward undesired mullite crystallization. SiOz 2o contents of greater than 72% by weight may increase the requisite melting temperatures impermissibly.
The glass-ceramic according to the invention preferably has a composition of the following components by weight percent, based on the total weight of the composition: LizO
3.2-4.8,Naz00- l,Kz00- l,Na20+K200.2-2,Mg00.1 - 1.S,Ba00-3.0, Sr00- 1, Ca0 0 - 1, Ba0 + Sr0 + Ca0 0.2 - 4, Zn0 0.2 - 2, A1203 18 - 24, Si02 63 - 70, Ti02 0 - < 2, Zr02 0 - 2.5, TiOz + ZrOz 1 - 3.3, Sbz03 0 - 2, As203 0 - 2, Sn0 0 - < l, and P205 0 - 8, an average coefficient of linear thermal expansion a,2o-~oo~c of < 0.4~ 10-6/K, an average crystal size of the (3-quartz solid solution of >_ 85 nm, and a transmission (sample thickness 4 mm) i38o-,so nm of < 30%.
3o The glass-ceramic according to the invention particularly preferably has a composition of the following components by weight percent, based on the total weight of the composition: Li20 3.5 - 4.5, Na20 0 - 1, KZO 0 - l, NazO + K20 0.2 - 2, Mg0 0.1 - 1.5, Ba0 0-<3, Sr00- 1, Ca00-l,BaO+Sr0+Ca00.2-4,Zn00.2-<2,A1z03 18-22, Si0264 68, TiOZ 0 - < 1.8, Zr02 0 - 2.2, TiOz + Zr02 1 - 3.2, Sb203 0 - 2, Asz03 0 -2, and Sn0 0 - <
1, an average coefficient of linear thermal expansion of < 0.38 10 -6/K, an average crystal size of the (3-quartz solid solution of >_ 90 nm, and a transmission (sample thickness 4 mm) i3go-730 nm ~f < 3~%.

The glass-ceramic may additionally contain at least one coloring component, in particular, at least one of CoO, CrzO~, Ce02, CuO, Fe20,, MnO, NiO, and VZOS, and, if desired, further coloring compounds. Owing to the said properties of the glass-ceramic, in particular the essentially high lightness value L*, particularly pure hues may be obtained through addition of coloring components.
The glass-ceramic may be preferably ceramicized at below approximately 950°C.
Above approximately 950°C, the formation or conversion into a glass-ceramic containing keatite solid solution as the predominant crystal phase takes place, this being associated with an undesired increase in the thermal expansion.
1 o The conversion of the glassy starting material into a glass-ceramic should likewise take place at below 950°C for economic reasons.
In other words, in at least one possible embodiment of the present invention, the glass-ceramic is preferably ceramicized at below 950°C. Above 950°C, the formation or conversion into a glass-ceramic containing keatite solid solution as the predominant crystal phase takes place, this being associated with an undesired increase in the thermal expansion.
In at least one possible embodiment of the present invention, the conversion of the glassy starting material into a glass-ceramic should likewise take place at below 950°C for economic reasons.
The glass-ceramic according to the invention may be used preferably as at least one of 2o a treatable plate for cooking and grilling, as a cooking utensil, as a stove window, and as a base plate for microwave ovens.
The above-discussed embodiments of the present invention will be described further hereinbelow with reference to the accompanying table and examples. When the word "invention" is used in this specification, the word "invention" includes "inventions, that is, the plural of "invention". By stating "invention", the Applicants do not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention. The Applicants maintain that this application may include more than one patentably and non-obviously distinct invention. The Applicants hereby assert that the disclosure of this application may include more than one invention and that these inventions 3o may be patentable and non-obvious one with respect to the other.
One aspect of the invention resides broadly in a translucent or opaque glass-ceramic containing (3-quartz solid solution as the predominant crystal phase, said glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition:
Component Weight Percent Li20 3 - 5 NazO 0 - 1 Kz0 0 -NazO + K20 0.2 -Mg0 0 -1.8 Ba0 0 -3.5 Sr0 0 -Ca0 0 -Ba0+Sr0+Ca0 0.2-4 Zn0 0 -2.8 -Si02 62 -Ti02 0 -2.5 Zr02 0 -TiOz + Zr02 1 - <
3.5 Sbz03 0 - 2 As203 0 - 2 Sn0 0-<1 Pz~s 0 - 8 100%
said glass-ceramic further having an average coefficient of linear thermal expansion a2o-,oo~c of < 0.5~ 10-6/K, an average crystal size of the (3-quartz solid solution of >_ 80 nm, and a transmission (sample thickness 4 mm) i38o _,go nm of < 30%.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following examples illustrate the invention.
Table 1 shows compositions and some properties of glass-ceramics, Examples 1 and 2 relating to a glass-ceramic according to the invention and Example 3 relating to a glass-ceramic whose Ti02 content and total content of the nucleating agents Ti02 and Zr02 lie outside at least one possible embodiment of the present invention.
Table 1 also shows the chroma C* (C* = the square root of ((a*)Z + (b*) 2)) in the L*C*h* color system. The chroma of the glass-ceramics according to at least one possible 3o embodiment of the present invention is preferably C* < 5.
In other words, the CIELAB system or L*a*b* color system may be essentially a color coordinate system for describing color or defining a color in a rectangular coordinate system having 3 axes, where, in one possible embodiment of the present invention, the symbol L* may equal the parameter on the lightness scale, ranging from 0 (black) to 100 (white); the symbol a* may equal the parameter on the red-green scale, with positive values for red and negative values for green; and the symbol b* may equal the parameter on the yellow-blue contrast scale, with positive values for yellow and negative values for blue. In the CIELAB or L*a*b* color system, the L* values may not be a measure of transparency of a material, but instead may refer only to the lightness of a material. In another possible embodiment of the present invention, the symbol L* may denote lightness or metric lightness; C*ab may denote brightness, chroma, or metric chroma; and the symbol H degree, or the symbol H°, may denote a color angle or a metric hue angle.
An essentially full description of the CIELAB system may be found in the following CIE (Commission Internationale de 1'Eclairage, or International Commission on Illumination) publications: CIE Publication No. 15.2-1986, entitled "Colorimetry, 2nd Edition" and Supplement No. 2 to CIE Publication No. 15 ((E-1.3.1)1971)/(TC-1.3) 1978.
These CIE publications may be available from the CIE National Committee of USA, Mr.
Thomas Lemons, TLA - Lighting Consultants Inc., 7 Pond Street, Salem, MA 01970 or from The CIE Central Bureau, Kegelgasse 27, A-1030 Vienna, Austria.
Some further examples of descriptions of the CIELAB system or the L*a*b*
system, the CIE system, or the Standard Valence System defined in DIN 5033 and methods and apparatus for measurement related thereto may be found in the following U.S.
patents and other publications: U.S. Patent No. 5,994,249, issued to inventors Graber et al. on November 30, 1999; U.S. Patent No. 5,958,126, issued to inventors Adel et al. on September 28, 1999;
U.S. Patent No. 5,754,448, issued to inventors Edge et al. on May 19, 1998;
U.S. Patent No.
4,698,100, issued to inventors Burow et al. on October 6, 1987; U.S. Patent No. 4,620,879, 2o issued to inventors Burow et al. on November 4, 1986; U.S. Patent No.
4,546,045, issued to inventor Elias on October 8, 1985; U.S. Patent No. 4,448,608, issued to inventors Jenkins et al. on May 15, 1984; U.S. Patent No. 4,404,254, issued to inventors Franz et al. on September 13, 1983; U.S. Patent No. 4,394,470, issued to inventors Werner et al. on July 19, 1983; U.S.
Patent No. 4,378,252, issued to inventors Kiemle et al. on March 29, 1983;
U.S. Patent No.
4,370,270, issued to inventors Bock et al. on January 25, 1983; U.S. Patent No. 4,363,888, issued to inventors Willison et al. on December 14, 1982; U.S. Patent No.
4,067,850, issued to issued to inventors Kohler et al. on January 10, 1978; the book entitled Coloring of Plastics, having the editor T. G. Webber, published by Wiley-Interscience of New York in 1979; and Ullmann's "Enzyklopedie der technischen Chemie", 4th edition, Vol.
18, 3 o Weinheim 1979.
The precursor glasses were melted at temperatures of about 1620°C
using raw materials which are conventional in the glass industry, and fined or essentially freed of bubbles. The shaping was carried out by conventional methods, for example, casting or rolling. Castings measuring about 140 x 140 x 20 mm were cooled to room temperature in a cooling oven starting at about 660°C.
For conversion (la) into a glass-ceramic, the glass-ceramic precursor glasses were heated to 740°C at about 5 K/min, held at this temperature for 1 hour, then heated to 890°C at about 2.5 K/min and held at this temperature for about % hour. The cooling was carried out by switching off the oven heating.
Depending on the selected composition, the temperature/time profile of the conversion program must be adjusted. In total, the conversion process takes significantly less than 18 hours.
In conversion 1 b, the nucleation time was shortened to about '/ hour. This conversion program required less than 6 hours.
The fact that the residual glass phase remained or remains in the range 5-15%
ensures stress relaxation in the sample essentially prevented or prevents rejects during ceramicization.
After conversion la, Example 3, with 2.6% by weight of Ti02, which reflects a typical composition of conventional, transparent ~3-QSS glass-ceramics, exhibits essentially high transparency. In order to produce the desired translucency, a second conversion (2) is necessary, carried out in this example at 940°C with a hold time of 2 hours (conversion 2).
This sample is then already converted into a KSS glass-ceramic which has a thermal expansion azo-,oo~c of significantly greater than 0.5~ 10-6/K.
The thermal expansion, inter alia, of the ceramicized sample was measured on the rods with a length of 100 mm and their transmission was measured on samples with a thickness of 4 mm which were polished on both sides. The sample was positioned directly at the inlet of a 60 mm integration ball. The degree of light i~,s (380-780 nm) is given in 2o accordance with DIN 5033.
In other words, the light reflection and/or color stimulus specification was determined according to German Industrial Standard DIN 5033.
Some descriptions of German Industrial Standard DIN 5033 may be found in the following U.S. patents and publications: German Industrial Standard DIN 5033, Sheet 1 of July 1962, German Industrial Standard DIN 5033, Sheet 3 of April 1954, German Industrial Standard DIN 5033, Sheet 6 of September 1964, and German Industrial Standard DIN 5033, Sheet 7 of October 1966; U.S. Patent No. 4,211,619, issued to inventor Usbeck on July 8, 1980; U.S. Patent No. 4,082,711, issued to inventors Andrascheck et al. on April 4, 1978; and No. 4,006,031, issued to inventors Ferch et al. on February 1, 1977.
3o The principal crystal phase and the average crystallite size were determined by X-ray diffraction diffractometry.

Table 1 Composition and properties of glass-ceramics according to the invention (Examples 1 and 2) and of a comparative glass-ceramic (Example 3) Oxides (lo y xamp a xamp a ' xamp a wt.

~IVZ b /.j 65.45 2 3 G1.0 lU.j 1? .
_ a .

a g .

n ~ .

~,. ~z , , sz 3 ~onvers~on is _ was L ~oJ, '+
mm .
." ,.~, azo-zooc rmc~pa crysta p ase Average crystal about nm a out nm size ysG not measure not measure ~.onvers~on m zv~s o , mm -/K~ .
azo-zoo~c l'~

Prmcipa crysta p ase -Average crystal about a out nm size nm not measured . not measure onverston omitte om~tte ims [%], 4 mm - _ /KJ
azo-zooc [~'1U

Yrmcipa crysta p ase One feature of the invention resides broadly in the translucent or opaque glass-ceramic containing (3-quartz solid solution as the predominant crystal phase, having a composition of the following components by weight percent, based on the total weight of the composition:
Component Weight Percent Li20 3 - 5 NazO 0 - 1 Na20 + Kz0 0.2 - 2 ~ o Mg0 0 - 1.8 Ba0 0 - 3.5 Sr0 0 - 1 Ca0 0 - 1 Ba0+Sr0+Ca0 0.2-4 Zn0 0 - 2.8 Si02 62 - 72 TiOZ 0 - 2.5 ZrOz 0 - 3 2 o Ti02 + Zr02 1 - < 3.5 Sb20~ 0 - 2 As20~ 0 - 2 Sn0 0-<1 P_ZOS 0 - 8 100%

said glass-ceramic having an average coefficient of linear thermal expansion a2o_,oo~c of < 0.5~ 10-6/K, an average crystal~3-quartz solid solution of >_ size of the 80 nm and a transmission (sample thickness _ ~g0 nm of < 30%.
4 mm) i;8o Another feature of the invention resides broadly in the glass-ceramic having a 3o composition of the following by weight percent, based on the components total weight of the composition:

Component Weight Percent LizO 3.2 - 4.8 NazO 0 - 1 Na20 + K20 0.2 - 2 Mg0 0.1 - 1.8 Ba0 0 - 3.0 Sr0 0 - 1 Ca0 0 - 1 Ba0+Sr0+Ca0 0.2-4 Zn0 0.2 - 2 SiOZ 63 - 70 TiOz 0 - < 2 ZrOz 0 - 2.5 TiOz + ZrOz 1.0 - 3.3 Sbz03 0 - 2 Asz03 0 - 2 Sn0 0-< 1 P_ZOS 0 - 8 100%

said glass-ceramic having an average coefficient of linear thermal expansion a,ZO-,oo~c of < 0.4~ 10-6/K, an average crystal(3-quartz solid solution of >_ size of the 85 nm, and a transmission (sample thickness -780nm of < 30%.
4 mm) i3go Yet another feature of the invention resides broadly in the glass-ceramic having a 2o composition of the following by weight percent, based on the components total weight of the composition:

Component Weight Percent LiZO 3.5 - 4.5 Na20 0 - 1 Na20 + KZp 0.2 - 2 Mg0 0.1 - 1.5 Ba0 0-<3 Sr0 0 - 1 3o Ca0 0-1 Ba0+Sr0+Ca0 0.2-4 Zn0 0.2-<2 A1z03 18 - 22 Si02 64 - 68 TiOz 0 - < 1.8 ZrOz 0 - 2.2 Ti02 + Zr02 1.0 - 3.2 Sbz03 0 - 2 Asz03 0 - 2 Sn0 0 - < 1 100%
said glass-ceramic having an average coefficient of linear thermal expansion azo_,oo~c of < 0.38 10-6/x, an average crystal size of the (3-quartz solid solution of >_ 90 nm, and a transmission (sample thickness 4 mm) i~8o _ ,8o nm of < 30%.
Still another feature of the invention resides broadly in the glass-ceramic having a lightness value L* in the L*a*b* color system (CIELAB system) of > 85.
A further feature of the invention resides broadly in the glass-ceramic containing at least one coloring component.
Another feature of the invention resides broadly in the glass-ceramic containing at least one of the metal oxides selected from the group consisting of CoO, Crz03, CeOz, CuO, Fez03, MnO, NiO, and V205.
Yet another feature of the invention resides broadly in the glass-ceramic ceramicized at a temperature below 950°C.
Still another feature of the invention resides broadly in the glass-ceramic formed into at least one of heatable plates for cooking and grilling, cooking utensils, stove windows, and base plates for microwave ovens.
2 o One feature of the invention resides broadly in the translucent or opaque glass-ceramic containing (3-quartz solid solution as the predominant crystal phase, having a composition of the following components (in percent by weight) of:
LizO 3 - S
NazO 0 - 1 Kz0 0 _ 1 NazO+Kz0 0.2-2 Mg0 0 - 1.8 Ba0 0 - 3.5 Sr0 0 - 1 3o Ca0 0 - 1 Ba0+Sr0+Ca0 0.2-4 Zn0 0 - 2.8 A1z03 17 - 26 SiOz 62 - 72 TiOz 0 - 2.5 ZrOz 0 - 3 TiOz + ZrOz1 - <
3.5 Sbz03 0 - 2 AszO~ 0 - 2 Sn0 0-<1 Pz~s 0 - 8 and an average coefficient of linear thermal expansion azo-~oo~c of < 0.5~ 10-6/K, an average crystal size of the (3-quartz solid solution of >_ 80 nm and a transmission sample thickness 4 mm T3g0 - 780 nm of < 30%.
Another feature of the invention resides broadly in the glass-ceramic characterized by a composition of the following components (in percent by weight) o~
LizO 3.2 - 4.8 NazO 0 - 1 K20 0 _ 1 NazO+KZO 0.2-2 Mg0 0.1 - 1.8 Ba0 0 - 3.0 Sr0 0 - 1 Ca0 0 - 1 Ba0+Sr0+Ca0 0.2-4 Zn0 0.2 - 2 2o A1z03 18 - 24 SiOz 63 - 70 TiOz 0-<2 ZrOz 0 - 2.5 TiOz + ZrOz 1.0 - 3.3 Sbz03 0 - 2 AszO~ 0 - 2 Sn0 0-< 1 pz~s 0 - 8 and an average coefficient of linear thermal expansion azo_~oo~c of < 0.4~ 10-6/K, an average 3o crystal size of the (3-quartz solid solution of >_ 85 nm, and a transmission (sample thickness 4 mm) T3g0 - 780 nm of < 30%.
Yet another feature of the invention resides broadly in the glass-ceramic characterized by a composition of the following components (in percent by weight) of:
LizO 3.5 - 4.5 NazO 0 - 1 Kz0 0 _ 1 NazO+K20 0.2-2 Mg0 0.1 - 1.5 Ba0 0-<3 Sr0 0 -Ca0 0-1 Ba0+Sr0+Ca0 0.2-4 Zn0 0.2-<2 Si02 64 -TiOz 0 -< 1.8 Zr02 0 -2.2 TiOz + Zr02 1.0 - 3.2 Sb20, 0 -As203 0 -Sn0 0-<

and an average coefficient of linear thermal expansion a2o_,oo~c of < 0.3810-6/K, an average crystal size of the (3-quartz solid solution of >_ 90 nm, and a transmission (sample thickness 4 mm) 'L3g0 - 780 nm of < 30%.
Still another feature of the invention resides broadly in the glass-ceramic characterized in that the glass-ceramic has a lightness value L* in the L*a*b* color system (CIELAB
2o system) of > 85.
A further feature of the invention resides broadly in the glass-ceramic characterized in that the glass-ceramic contains at least one coloring component.
Another feature of the invention resides broadly in the glass-ceramic characterized in that the glass-ceramic contains CoO, Cr203, CeOz, CuO, Fez03, MnO, NiO, andlor V205.
Yet another feature of the invention resides broadly in the glass-ceramic characterized in that its ceramicization is carried out at below 950°C.
Still another feature of the invention resides broadly in the use of a glass-ceramic as a heatable plate for cooking and grilling, as a cooking utensil, as a stove window, or as a base plate for microwave ovens.
3o In other words, in at least one possible embodiment of the present invention, the composition of the glass-ceramic may be expressed in percent by weight, or by weight percent, on an oxide basis.
Some examples of beta-quartz solid solutions or beta-spodumene solid solutions that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S. patents: No. 5,591,682, issued to inventor Goto on January 7, 1997; No. 5,512,520, issued to inventor Pfitzenmaier on April 30, 1996; No.
5,070,045, issued to inventors Comte et al. on December 3 1991; No. 3,157,522, issued to inventor Stookey ; No. 5,173,453, issued to inventors Beall et al. on December 22, 1992; and No. 5,010,041, issued to inventors Koyama et al. on April 23, 1991.
Some examples of apparatus, procedures, and materials for nucleation, nucleating agents, and nucleation sites that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S.
patents: No.
5,792,270, issued to inventor Saxena on August 1 l, 1998; No. 5,591,682, issued to inventor Goto on January 7, 1997; No. 5,486,495, issued to inventors Jewell et al. on January 23, 1996; No. 5,512,520, issued to inventor Pfitzenmaier on April 30, 1996; No.
5,446,008, issued to inventors Krolla et al. on August 29, 1995; and No. 5,173,453, issued to inventors 1 o Beall et al. on December 22, 1992.
Some examples of processes, apparatus, procedures, or materials for melting raw materials to form glass, forming glass, cooling glass, crystallizing, ceraming, or ceramicization that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S. patents: No. 5,486,495, issued to inventors Jewell et al. on January 23, 1996; No. 5,658,835, issued to inventors Onitani et al.
on August 19, 1997; No. 5,591,682, issued to inventor Goto on January 7, 1997;
No.
5,512,520, issued to inventor Pfitzenmaier on April 30, 1996; No. 5,446,008, issued to inventors Krolla et al. on August 29, 1995; No. 5,173,453, issued to inventors Beall et al. on December 22, 1992; No. 5,010,041, issued to inventors Koyama et al. on April 23, 1991; No.
20 4,536,203, issued to inventor Kramer on August 20, 1985; No. 4,438,210, issued to inventor Rittler on March 20, 1984; No. 4,360,567, issued to inventor Guillevic on November 23, 1982; and No. 3,941,117, issued to inventors Pei et al. on March 2, 1976.
Some examples of coloring additives, coloring component, or colorants and processes for their production that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S. patents and patent application:
U.S. Patent Application Serial No. 09/364,479, entitled "Lead-Free and Cadmium-Free Glass Composition for Glazing, Enamelling and Decorating Glasses or Glass-Ceramics, and Process for the Production of a Glass-Ceramic Coated Therewith", filed on July 30, 1999, having inventors Ina Mitra, Dr. Friedrich Siebers, Dr. Jutta Reichert, Dr.
Cora Krause, Dr.
3o Otmar Becker, and Dr. Michael Bug, and having assignee Schott Glas, which assignee has the address Hattenbergstral3e 10, D-55122 Mainz, Federal Republic of Germany; and U.S.
Patents No. 5,512,520, issued to inventor Pfitzenmaier on April 30, 1996; No.
5,256,602, issued to inventors Danielson et al. on October 26, 1993; No. 5,446,008, issued to inventors Krolla et al. on August 29, 1995; No. 5,250,112, issued to inventors Wussow et al. on October 5, 1993; No. 5,010,041, issued to inventors Koyama et al. on April 23, 1991; No.
4,698,100, issued to inventors Burow et al. on October 6, 1987; No. 4,620,879, issued to inventors Burow et al. on November 4, 1986; and No. 5,421,878, issued to inventors Lerch et al. on June 6, 1995.
U.S. Patent Application Serial No. 09/364,479, entitled "Lead-Free and Cadmium-Free Glass Composition for Glazing, Enamelling and Decorating Glasses or Glass-Ceramics, and Process for the Production of a Glass-Ceramic Coated Therewith", filed on July 30, 1999, having inventors Ina Mitra, Dr. Friedrich Siebers, Dr. Jutta Reichert, Dr.
Cora Krause, Dr.
Otmar Becker, and Dr. Michael Bug, and having assignee Schott Glas, which assignee has the address Hattenbergstral3e 10, D-55122 Mainz, Federal Republic of Germany; and the corresponding foreign patent applications, namely, Federal Republic of Germany Patent Application No. 198 34 801.0-45, filed on August 1, 1998, entitled "Blei- and cadmiumfreie 1 o Glaszusammensetzung zum Glasieren, Emailieren and Dekorieren von Glasern oder Glaskeramiken Bowie Verfahren zur Herstellung einer damit beschichteten Glaskeramik", having inventors Dr. Ina Mitra, Dr. Friedrich Siebers, Dr. Jutta Reichert, Dr.
Cora Krause, Dr.
Otmar Becker, and Dr. Michael Bug, and having assignee Schott Glas, which assignee has the address Hattenbergstral3e 10, D-55122 Mainz, Federal Republic of Germany; and 34 801.0-45 and DE-PS 198 34 801.0-45, as well as their published equivalents, and other equivalents or corresponding applications, if any, in corresponding cases in the Federal Republic of Germany and elsewhere, and the references cited in any of the documents cited herein, are hereby incorporated by reference as if set forth in their entirety herein.
Throughout the specification and claims to U.S. Patent Application Serial No.
20 09/364,479, described above and incorporated by reference herein, the term "mean" is more preferably stated as the term "average".
In addition, throughout the specification and claims to U.S. Patent Application Serial No. 09/364,479, described above and incorporated by reference herein, the term "in % by weight", "in percent by weight", or "in weight percent" is more preferably stated as the term "by weight percent, based on the total weight of the composition".
An essentially full description of the CIELAB system may be found in the following CIE (Commission Internationale de 1'Eclairage, or International Commission on Illumination) publications: CIE Publication No. 15.2-1986, entitled "Colorimetry, 2nd Edition" and Supplement No. 2 to CIE Publication No. 15 ((E-1.3.1)1971)/(TC-1.3) 1978.
3o These CIE publications may be available from the CIE National Committee of USA, Mr.
Thomas Lemons, TLA - Lighting Consultants Inc., 7 Pond Street, Salem, MA 01970 or from The CIE Central Bureau, Kegelgasse 27, A-1030 Vienna, Austria.
Some further examples of descriptions of the CIELAB system or the L*a*b*
system, the CIE system, the Standard Valence System defined in DIN 5033, and other color systems and chromaticity systems and methods and apparatus for measurement related thereto may be found in the following U.S. patents and other publications: U.S. Patent No.
5,994,249, issued to inventors Graber et al. on November 30, 1999; U.S. Patent No. 5,958,126, issued to inventors Adel et al. on September 28, 1999; U.S. Patent No. 5,754,448, issued to inventors Edge et al. on May 19, 1998; No. 5,512,520, issued to inventor Pfitzenmaier on April 30, 1996; U.S. Patent No. 4,698,100, issued to inventors Burow et al. on October 6, 1987; U.S.
Patent No. 4,620,879, issued to inventors Burow et al. on November 4, 1986;
U.S. Patent No.
4,546,045, issued to inventor Elias on October 8, 1985; U.S. Patent No.
4,448,608, issued to inventors Jenkins et al. on May 15, 1984; U.S. Patent No. 4,404,254, issued to inventors Franz et al. on September 13, 1983; U.S. Patent No. 4,394,470, issued to inventors Werner et al. on July 19, 1983; U.S. Patent No. 4,378,252, issued to inventors Kiemle et al. on March 29, 1983; U.S. Patent No. 4,370,270, issued to inventors Bock et al. on January 25, 1983;
U.S. Patent No. 4,363,888, issued to inventors Willison et al. on December 14, 1982; U.S.
Patent No. 4,067,850, issued to inventors Kohler et al. on January 10, 1978;
the book entitled Coloring ofPlastics, having the editor T. G. Webber, published by Wiley-Interscience of New York in 1979; and Ullmann's "Enzyklopedie der technischen Chemie", 4th edition, Vol.
18, Weinheim 1979.
Some examples of stoves, stove windows, utensils, cooking hobs or apparatus, or microwave ovens, or base plates for microwave ovens that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S.
patents: No. 5,679,273, issued on October 21, 1997; No. 5,406,932, issued on April 18, 1995;
No. 5,422,460, issued on June 6, 1995; No. 5,424,512, issued on June 13, 1995;
No.
20 5,425,353, issued on June 20, 1995; No. 5,429,114, issued on July 4, 1995;
No. 5,448,036, issued on September 5, 1995; No. 5,213,091, issued on May 25, 1993; No.
D336,210, issued on June 8, 1993; No. 5,280,152, issued on January 18, 1994; No. 5,400, 765, issued on March 28, 1995; No. 5,437,262, issued on August 1, 1995; No. 4,997,302, issued to inventors Merigaud et al. on December 1 l, 1990; No. 4,597,374, issued to inventor Igarashi on July l, 1986; No. 4,438,210, issued to inventor Rittler on March 20, 1984; No.
4,360,567, issued to inventor Guillevic on November 23, 1982; No. 4,351,998, issued to inventors Keppel et al. on September 28, 1982; No. 4,320,275, issued to inventor Reiss on March 16, 1982;
No.
4,163,141, issued to inventors Tanaka et al. on July 31, 1979; and No.
3,941,117, issued to inventors Pei et al. on March 2, 1976.
3o Some examples of methods or apparatus for X-ray diffraction measurement and X-ray diffractometry that may be used or adapted for use in at least one possible embodiment of the present invention may be found in the following U.S. patents: No. 5,663,327, issued to inventors Tambo et al. on September 2, 1997; No. 5,416,207, issued to inventors Imai et al.
on May 16, 1995; No. 4,770,593, issued to inventor Anderson on September 13, 1988; No.
4,658,41 l, issued to inventors Argoud et al. on April 14, 1987; and No.
4,644,761, issued to inventors Chatzipetros et al. on February 24, 1987.
The components disclosed in the various publications, disclosed or incorporated by reference herein, may be used in the embodiments of the present invention, as well as equivalents thereof.
The drawings are incorporated in their entirety by reference into this specification.
All, or substantially all, of the components and methods of the various embodiments may be used with at least one embodiment or all of the embodiments, if more than one embodiment is described herein.
The corresponding foreign patent publication applications, namely, Federal Republic of Germany Patent Application No. 199 07 038.5, filed on February 19, 1999, entitled " Transluzente oder opake Glaskeramik mit Hochquarz-Mischkristallen als vorherrschender Kristallphase and deren Verwendung'; having inventors Dipl.-Ing. Ina Mitra, Dr. Friedrich Siebers, Dipl.-Geol. Klaus Schonberger, Dr. Bernd Riidinger and Dipl.-Phys.
Bernd Schultheis,and having assignee Schott Glas, which assignee has the address Hattenbergstral3e 10, D-55122 Mainz, Federal Republic of Germany, and DE-OS 199 07 038.5 and DE-07 038.5, as well as their published equivalents, and other equivalents or corresponding applications, if any, in corresponding cases in the Federal Republic of Germany and elsewhere, and the references cited in any of the documents cited herein, are hereby incorporated by reference as if set forth in their entirety herein.
Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.
The invention as described hereinabove in the context of the preferred embodiments is not to be taken as limited to all of the provided details thereof, since modifications and variations thereof may be made without departing from the spirit and scope of the invention.

Claims (20)

1. A translucent or opaque glass-ceramic containing .beta.-quartz solid solution as the predominant crystal phase, said glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition:

Component ~~Weight Percent Li2O ~~~3 - 5 Na2O ~~~0 - 1 K2O ~~~0 - 1 Na2O + K2O ~~0.2 - 2 MgO ~~~0 - 1.8 BaO ~~~0 - 3.5 SrO ~~~0 - 1 CaO ~~~0 - 1 BaO + SrO + CaO ~0.2-4 ZnO ~~~0 - 2.8 Al2O3 ~~17 - 26 SiO2 ~~~62 - 72 TiO2 ~~~0 - 2.5 ZrO2 ~~~0 - 3 TiO2 + ZrO2 ~~1 - < 3.5 Sb2O3 ~~0 - 2 As2O3 ~~0 - 2 SnO ~~~0 - < 1 P2O5 ~~~0 - 8 100%
said glass-ceramic further having an average coefficient of linear thermal expansion .alpha.20-700°C
of <0.5~10 -6/K, an average crystal size of the .beta.-quartz solid solution of ~ 80 nm, and a transmission (sample thickness 4 mm) ~380 - 780 nm of <30%.

2. The glass-ceramic according to Claim 1, said glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition:
Component ~~Weight Percent Li2O ~~~3.2 - 4.8 Na2O ~~~0 - 1 K2O ~~~0 - 1 Na2O + K2O ~~0.2-2 MgO 0.1 - 1.8 BaO 0 - 3.0 SrO 0 - 1 CaO 0 - 1 BaO + SrO + CaO 0.2-4 ZnO 0.2 - 2 Al2O3 18 - 24 SiO2 63 - 70 TiO2 0 - < 2 ZrO2 0 - 2.5 TiO2 + ZrO2 1.0 - 3.3 Sb2O3 0 - 2 As2O3 0 - 2 SnO 0- < 1 100%

said glass-ceramic further having an average coefficient of linear thermal expansion .alpha.20-700°C of < 0.4~10 -6/K, an average crystal size of the .beta.-quartz solid solution of ~ 85 nm, and a transmission (sample thickness 4 mm)~380 - 780 nm of < 30%.

3. The glass-ceramic according to Claim 1, said glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition:
Component Weight Percent Li2O 3.5 - 4.5 Na2O 0 - 1 Na2O + K2O 0.2-2 MgO 0.1 - 1.5 BaO 0 - < 3 SrO 0 - 1 CaO 0 - 1 BaO + SrO + CaO 0.2-4 ZnO 0.2 - < 2 Al2O3 18 - 22 SiO2 64 - 68 TiO2 0 - < 1.8 ZrO2 0 - 2.2 TiO2 + ZrO2 ~~1.0 - 3.2 Sb2O3 ~~0 - 2 As2O3 ~~0 - 2 SnO ~~~0 - < 1 100%
said glass-ceramic further having an average coefficient of linear thermal expansion .alpha.20-700°C of < 0.38~10 -6/K, an average crystal size of the .beta.-quartz solid solution of ~ 90 nm, and a transmission (sample thickness 4 mm) ~380 - 780 nm of < 30%.

4. The glass-ceramic according to Claim 2, said glass-ceramic having a composition of the following components by weight percent, based on the total weight of the composition:
Component Weight Percent Li2O 3.5 - 4.5 Na2O 0 - 1 Na2O + K2O 0.2 - 2 MgO 0.1 - 1.5 BaO 0 - < 3 SrO 0 - 1 CaO 0 - 1 BaO + SrO + CaO 0.2-4 ZnO 0.2 - < 2 Al2O3 18 - 22 SiO2 64 - 68 TiO2 0 - < 1.8 ZrO2 0 - 2.2 TiO2 + ZrO2 ~~ 1.0 - 3.2 Sb2O3 ~~ 0 - 2 As2O3 ~~ 0 - 2 SnO ~~~ 0 - < 1 100%
said glass-ceramic further having an average coefficient of linear thermal expansion .alpha.20-700° of < 0.38~10 -6/K, an average crystal size of the .beta.-quartz solid solution of ~ 90 nm, and a transmission (sample thickness 4 mm) ~380 - 780 mn of < 30%.

5. The glass-ceramic according to Claim 1, said glass-ceramic having a lightness value L* in the L*a*b* color system (CIELAB system) of > 85.

6. The glass-ceramic according to Claim 4, said glass-ceramic having a lightness value L* in the L*a*b* color system (CIELAB system) of > 85.

7. The glass-ceramic according to Claim 1, said glass-ceramic containing at least one coloring component.

8. The glass-ceramic according to Claim 6, said glass-ceramic containing at least one coloring component.

9. The glass-ceramic according to Claim 7, said glass-ceramic containing at least one of (i), (ii), (iii), (iv), (v), (vi), (vii), and (viii), where (i), (ii), (iii), (iv), (v), (vi), (vii), and (viii) are the following:
(i) CoO;
(ii) Cr2O3;
(iii) CeO2;
(iv) CuO;
(v) Fe2O3;
(vi) MnO;
(vii) NiO; and (viii) V2O5.

10. The glass-ceramic according to Claim 8, said glass-ceramic containing at least one of (i), (ii), (iii), (iv), (v), (vi), (vii), and (viii), where (i), (ii), (iii), (iv), (v), (vi), (vii), and (viii) are the following:
(i) CoO;
(ii) Cr2O3;
(iii) CeO2;
(iv) CuO;
(v) Fe2O3;
(vi) MnO;
(vii) NiO; and (viii) V2O5.

11. The glass-ceramic according to Claim 1, said glass-ceramic being ceramicized at a temperature below 950°C.

12. The glass-ceramic according to Claim 9, said glass-ceramic being ceramicized at a temperature below 950°C.

13. The glass-ceramic according to Claim 10, said glass-ceramic being ceramicized at a temperature below 950°C.

14. The glass-ceramic according to Claim 1, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

15. The glass-ceramic according to Claim 2, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

16. The glass-ceramic according to Claim 3, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

17. The glass-ceramic according to Claim 9, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

18. The glass-ceramic according to Claim 10, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;

(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

19. The glass-ceramic according to Claim 11, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.

20. The glass-ceramic according to Claim 13, formed into at least one of (a), (b), (c), and (d), where (a), (b), (c), and (d) are the following:
(a) a heatable plate for cooking and grilling;
(b) a utensil for cooking;
(c) a stove window; and (d) a base plate for a microwave oven.