TRANSPARENT BETA-QUARTZ GLASS CERAMICS WITH A LOW LITHIUM CONTENT

Abstract

The present applicationprovides transparent glass-ceramics of lithium aluminosilicate type, of β-quartz, the composition of which contains a low content of lithium, articles constituted at least in part by said glass-ceramics, precursor glasses for said glass-ceramics, and also a method of preparing said articles. Said glass-ceramics have a composition, expressed in percentages by weight of oxide, containing63% to 67.5% of SiO.sub.2; 18% to 21% of Al.sub.2O.sub.3; 2% to 2.9% of Li.sub.2O; 0 to 1.5% of MgO; 1% to 3.2% of ZnO; 0 to 4% of BaO; 0 to 4% of SrO; 0 to 2% of CaO; 2% to 5% of TiO.sub.2; 0 to 3% of ZrO.sub.2; 0 to 1% of Na.sub.2O; 0 to 1% of K.sub.2O; 0 to 5% of P.sub.2O.sub.5; with (0.74 MgO+0.19 BaO+0.29 SrO+0.53 CaO+0.48 Na.sub.2O+0.32 K.sub.2O)/Li.sub.2O<0.9; optionally up to 2% of at least one fining agent; and optionally up to 2% of at least one coloring agent.

Claims

1. A transparent glass-ceramic of lithium aluminosilicate type containing a solid solution of β-quartz as its main crystalline phase, the composition of which, expressed in percentages by weight of oxides, comprises: 63% to 67.5% of SiO.sub.2; 18% to 21% of Al.sub.2O.sub.3; 2% to 2.9% of Li.sub.2O; 0 to 1.5% of MgO; 1% to 3.2% of ZnO; 0 to 4% of BaO; 0 to 4% of SrO; 0 to 2% of CaO; 2% to 5% of TiO.sub.2; 0 to 3% of ZrO.sub.2; 0 to 1% of Na.sub.2O; 0 to 1% of K.sub.2O; 0 to 5% of P.sub.2O.sub.5; with (0.74 MgO+0.19 BaO+0.29 SrO+0.53 CaO+0.48 Na.sub.2O+0.32 K.sub.2O)/Li.sub.2O<0.9; 0 to 2% of at least one fining agent; and 0 to 2% of at least one coloring agent.

2. The glass-ceramic according to claim 1, wherein the composition comprises a content of Li20 that is less than or equal to 2.85%.

3. The glass-ceramic according to claim 1, wherein the composition comprises 1% to 3% of ZnO.

4. The glass-ceramic according to claim 1, wherein the composition comprises at least 0.5% of P.sub.2O.sub.5.

5. The glass-ceramic according to claim 1, wherein, except for inevitable traces, the composition does not contain any P.sub.2O.sub.5 and comprises 1% to 2.5% of ZnO.

6. The glass-ceramic according to claim 1, wherein, except for inevitable traces, the composition does not comprise any B.sub.2O.sub.3.

7. The glass-ceramic according to claim 1, wherein the composition, free from As.sub.2O.sub.3 and Sb.sub.2O.sub.3, except for inevitable traces, comprises SnO.sub.2 as the at least one fining agent.

8. The glass-ceramic according to claim 1, wherein the composition contains V.sub.2O.sub.5 as coloring agent, alone or mixed with at least one other coloring agent selected from CoO, Cr.sub.2O.sub.3, and Fe.sub.2O.sub.3.

9. The glass-ceramic according to claim 1, having a coefficient of thermal expansion: CTE.sub.(25-450° C.) lying in the range ±14×10.sup.−7K.sup.−1.

10. A cooktop comprising, at least in part, a glass-ceramic according to claim 1.

11. A lithium aluminosilicate glass, precursor for the glass-ceramic according to claim 1, comprising a composition that makes it possible to obtain the glass-ceramic according to claim 1.

12. The glass according to claim 11, having a liquidus temperature of less than 1400° C. and a viscosity at the liquidus of more than 200 Pa.s.

13. A method of preparing the cooktop according to claim 10, comprising in succession: melting a vitrifiable charge of raw materials, followed by fining the resulting molten glass; cooling the resulting refined molten glass and simultaneously shaping it to the shape desired for the cooktop; and applying ceramming heat treatment to the shaped glass; wherein the vitrifiable charge of raw materials has a composition that makes it possible to obtain the glass-ceramic of claim 1.

14. The method according to claim 13, characterized in that the vitrifiable charge of raw materials, free from As.sub.2O.sub.3 and of Sb.sub.2O.sub.3, except for inevitable traces, contains 0.05% to 0.6% SnO.sub.2 as fining agent.

15. The glass-ceramic according to claim 2, wherein the composition comprises a content of Li.sub.2O from 2.20% to 2.85%.

16. The glass-ceramic according to claim 4, wherein the composition comprises from 1% to 3% P.sub.2O.sub.5.

17. The glass-ceramic according to claim 7, wherein the composition comprises 0.05% to 0.6% SnO.sub.2.

18. The glass-ceramic according to claim 17, wherein the composition comprises 0.15% to 0.4% of SnO.sub.2.

19. The glass-ceramic according to claim 9, having a coefficient of thermal expansion: CTE.sub.(25-450° C.) lying in the range ±14×10.sup.−7K.sup.−1.

20. The glass according to claim 12, having a viscosity of 30 Pa.s at less than 1640° C. (T.sub.30 Pa.s<1640° C.).

Description

EXAMPLES

[0096] To produce batches of 1 kilogram (kg) of precursor glass, raw materials, in the proportions (proportions expressed by weight percentages of oxides) specified in the first portion of the tables below (table III and table IV, said tables III and IV spreading over several pages) were mixed together carefully.

[0097] The used raw material mixtures, for obtaining 1 kg of each one of the precursors glasses of examples 2, 13 and 23 of the following table III (taken for illustration), said glasses having the compositions (expressed in weight percentages) indicated in said table III, are hereafter specified in table II. The weight of each material is expressed in grams (g).

TABLE-US-00002 TABLEAU II Raw materials Example Example Example (weight (g)) 2 13 23 Quartz sand 399.7 416.2 420.6 Calcined alumina 90.8 94.2 94.1 Spodumene 342.6 316.7 316.6 Magnesium oxide 11.8 8.1 4.9 Zinc oxide 19.6 31.9 31.9 Barium nitrate 46.9 41.7 41.6 Dolomite 11.2 11.6 11.8 Rutile 30.6 27.5 29.3 Zirconium oxide 12.9 17.0 14.2 Feldspar 47.7 47.2 47.2 Tin oxide 3.0 3.0 3.0 Iron oxide 0.3 0.3 0.3 Vanadium oxide 0.1 0.2 0.2 Chromite 0.6 0.6 0.6

[0098] The mixtures were placed for melting in crucibles made of platinum. The crucibles containing said mixtures were then placed in a furnace preheated to 1550° C. The furnace was heated with MoSi electrodes. The crucibles were subjected therein to a melting cycle of the following type: [0099] hold at 1550° for 30 minutes (min); [0100] raise temperature from 1550° C. to 1650° C. in 1 hr; and [0101] hold at 1650° C. for 5 hr 30 min.

[0102] The crucibles were then extracted from the furnace and the molten glass was poured onto a preheated steel plate. It was rolled to have a thickness of 6 mm. Glass plates were thus obtained. They were annealed at 650° C. for 1 hr and subsequently cooled down slowly.

[0103] The properties of the resulting glasses are given in the second portion of the tables below.

[0104] Viscosities were measured using a rotational viscometer (Gero).

[0105] T.sub.30 Pa.s (° C.) corresponds to the temperature at which the viscosity of the glass was 30 Pa.s.

[0106] T.sub.liq (° C.) is the liquidus temperature. The liquidus temperature is given by a range of temperatures and associated viscosities: the highest temperature corresponds to the minimum temperature at which no crystal was observed, the lowest temperature corresponds to the maximum temperature at which crystals were observed. The experiments were carried out on precursor glass volumes of about 0.5 cubic centimeters (cm.sup.3) that were held for 17 h at the temperature of the test and the observations were performed by optical microscopy. The phase of the observed crystals is given in the tables below.

[0107] The resistivity of glass was measured while measuring viscosity. The table gives the resistivity measured at the temperature for which the viscosity was 30 Pa.s.

[0108] The ceramming cycle performed in a static furnace (in an atmosphere of ambient air) is set out below: [0109] rapid temperature rise up to 500° C.; [0110] temperature rise from 500° C. to 650° C. at a rate of 23° C./min; [0111] temperature rise from 650° C. to 820° C. at a rate of 6.7° C./min; [0112] temperature rise from 820° C. to 920° C. at a rate of 15° C./min; [0113] holding this temperature Tmax (=920° C.) for 7 min; [0114] cooling down to 850° C. at 35° C./min; [0115] cooling down to ambient temperature as a function of the inertia of the furnace.

[0116] The properties of the glass-ceramics obtained are given in the last portion of the tables below.

[0117] These glass-ceramics contain a solid solution of β-quartz as the main crystalline phase (as verified by X-ray diffraction).

[0118] The coefficients of thermal expansion (CTEs) (from 25° C. to 450° C.=CTE.sub.(25-450° C.) and also from 25° C. to 700° C.=CTE.sub.(25-700° C.)) were measured using a high-temperature dilatometer (DIL 420C, Netzsch) heating at a rate of 3° C./min, on bar-shaped glass-ceramic samples.

[0119] On polished samples having a thickness of 4 mm, total and diffuse transmission measurements were performed using a Varian spectrophotometer (model Cary 500 Scan), fitted with an integrating sphere. On the basis of these measurements, the integrated transmission (Y (%)) in the visible range (380 mm to 780 mm) and the level of haze (diffusion (%)) were calculated using the standard ASTM D 1003-13 (with D65 illuminant and 2° observer). A value of Y that is below 10% is recommended in order to hide the induction heating elements and other technical components arranged under the cooktop. A level of haze of less than 2% is recommend in order to ensure good visibility of the red light emitted by the LEDs that are generally arranged under the cooktop. Transmission values (at 625 nm (T.sub.625 nm) and at 950 nm (T.sub.950 nm)) are also specified in the tables.

Examples 1 to 26

(In Table III: IIIA to IIIG) Illustrate the Present Application

[0120] Examples 1 to 4 are preferred because of the particularly advantageous properties of the precursor glass: see the values given for high-temperature viscosity (T.sub.300 Pa.s<1630° C.) and for liquidus viscosity (>700 Pa.s).

[0121] Examples 4 and 11 show the advantage of having P.sub.2O.sub.5 present in the composition of the precursor glass. This presence leads to a reduction in the liquidus temperature (about −15° C.) and consequently to an increase in viscosity at the liquidus temperature (+200 Pa.s).

[0122] The precursor glasses of Examples 5 to 15 present preferred values for viscosity at high temperature (<1630° C.).

[0123] The precursor glasses of Examples 16 to 20 present preferred values for viscosity at the liquidus (>700 Pa.s).

[0124] Examples 24 to 26 show the use of SrO in complement to BaO.

[0125] Examples A to E (in Tables IVA and IVB) are comparative examples.

[0126] In comparative example A, the content of SiO.sub.2 is high (67.88%). The high-temperature viscosity is too high. It would be particularly difficult to manage melting and fining said precursor glass.

[0127] In comparative example B, the contents of SiO.sub.2 and of BaO are high (respectively 67.74% and 4.25%). The high-temperature viscosity is too high. It would be difficult to manage melting and fining said precursor glass.

[0128] In comparative example C, the content of MgO is too high (1.74%) and the ratio (0.74 MgO+0.19 BaO+0.29 SrO+0.53 CaO+0.48 Na.sub.2O+0.32 K.sub.2O)/Li.sub.2O is greater than 0.90. Consequently the CTE of the glass-ceramic is too high. Said glass-ceramic is therefore not suitable to be the material for making cooktops that are to be used with (conventional) induction heating elements.

[0129] In comparative example D, the ZnO content is too high. Consequently, the viscosity at the liquidus of the precursor glass is too low.

[0130] In comparative example E the ratio (0.74 MgO+0.19 BaO+0.29 SrO+0.53 CaO+0.48 Na.sub.2O+0.32 K.sub.2O)/Li.sub.2O is greater than 0.90. Consequently the CTE of the glass-ceramic is too high.

TABLE-US-00003 TABLE IIIA Examples (wt %) 1 2 3 4 SiO.sub.2 66.98 66.98 65.75 65.06 P.sub.2O.sub.5 0.04 0.04 1.14 2.11 Al.sub.2O.sub.3 18.92 18.86 19.64 18.81 Li.sub.2O 2.53 2.48 2.82 2.66 MgO 1.34 1.34 0.30 0.33 ZnO 1.85 1.80 2.27 2.96 BaO 2.48 2.76 2.09 2.42 CaO 0.45 0.46 0.33 0.47 TiO.sub.2 2.73 2.89 2.93 2.79 ZrO.sub.2 1.44 1.18 1.19 1.12 Na.sub.2O 0.61 0.60 0.88 0.66 K.sub.2O 0.17 0.17 0.17 0.15 SnO.sub.2 0.28 0.29 0.30 0.28 Fe.sub.2O.sub.3 0.13 0.10 0.12 0.12 V.sub.2O.sub.5 0.03 0.03 0.04 0.04 Cr.sub.2O.sub.3 0.02 0.02 0.03 0.02 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.81 0.85 0.45 0.50 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1623 1627 1628 1624 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 5.2 5.2 3.5 4.1 T.sub.liq (° C.) 1309-1334 1311-1328 1326-1339 1322-1339 Viscosity at T.sub.liq (Pa .Math. s) 810-1170 900-1170 740-900 750-970 Crystalline phase devitrifying at T.sub.liq spinel + spinel spinel Spinel zircon Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 12.0 13.1 5.6 3.3 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 11.7 12.9 4.9 3.1 Y (%) 5.6 2.4 1.5 0.9 Diffusion (%) 0.5 0.4 0.6 1.0 T.sub.625nm (%) 14.0 6.6 4.7 2.9 T.sub.950nm (%) 67 66 65 60

TABLE-US-00004 TABLE IIIB Examples (wt %) 5 6 7 8 SiO.sub.2 66.60 66.92 65.07 66.67 P.sub.2O.sub.5 0.05 0.05 2.12 0.05 Al.sub.2O.sub.3 19.95 18.83 18.69 18.53 Li.sub.2O 2.89 2.59 2.61 2.75 MgO 0.95 0.45 0.45 0.44 ZnO 2.23 3.05 2.95 2.11 BaO 1.83 2.42 2.38 3.89 CaO 0.49 0.47 0.47 0.48 TiO.sub.2 2.70 2.67 2.66 2.61 ZrO.sub.2 1.46 1.26 1.29 1.25 Na.sub.2O 0.23 0.65 0.66 0.60 K.sub.2O 0.14 0.15 0.17 0.17 SnO.sub.2 0.29 0.28 0.29 0.29 Fe.sub.2O.sub.3 0.12 0.15 0.13 0.10 V.sub.2O.sub.5 0.04 0.04 0.04 0.04 Cr.sub.2O.sub.3 0.03 0.02 0.02 0.02 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.51 0.54 0.54 0.60 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1621 1629 1625 1620 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 4.1 5 4.7 4.2 T.sub.liq (° C.) 1328-1353 13474363 1345-1361 1330-1346 Viscosity at T.sub.liq (Pa .Math. s) 590-860 540-690 520-660 630-800 Crystalline phase devitrifying at T.sub.liq mullite + spinel spinel zircon spinel Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 4.9 4.7 3.7 7.2 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 3.2 4.0 3.4 6.2 Y (%) — 5.3 1.2 — Diffusion (%) — 0.3 0.7 — T.sub.625nm (%) — 13.8 3.9 — T.sub.950nm (%) — 64 61 —

TABLE-US-00005 TABLE IIIC Examples (wt %) 9 10 11 12 SiO.sub.2 66.77 66.92 66.88 65.67 P.sub.2O.sub.5 0.05 0.04 0.05 1.12 Al.sub.2O.sub.3 18.43 18.44 18.93 19.62 Li.sub.2O 2.77 2.30 2.62 2.83 MgO 0.53 1.15 0.34 0.33 ZnO 2.03 2.95 2.99 2.17 BaO 3.84 2.45 2.45 2.47 CaO 0.47 0.47 0.49 0.49 TiO.sub.2 2.62 2.80 2.84 2.89 ZrO.sub.2 1.26 1.21 1.13 1.16 Na.sub.2O 0.61 0.66 0.66 0.61 K.sub.2O 0.17 0.17 0.16 0.16 SnO.sub.2 0.29 0.28 0.29 0.29 Fe.sub.2O.sub.3 0.10 0.11 0.11 0.12 V.sub.2O.sub.5 0.04 0.03 0.04 0.04 Cr.sub.2O.sub.3 0.02 0.02 0.02 0.03 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.62 0.84 0.51 0.47 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1627 1620 1626 1621 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 4.4 4.7 4.2 3.6 T.sub.liq (° C.) 1330-1346 13464365 1339-1353 1325-1342 Viscosity at T.sub.liq (Pa .Math. s) 640-820 470-620 590-720 680-880 Crystalline phase devitrifying at T.sub.liq zircon spinel spinel spinel Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 7.3 10.3 4.3 4.5 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 6.4 10.1 3.5 3.5 Y (%) — — 2.8 1.7 Diffusion (%) — — 0.4 0.4 T.sub.625nm (%) — — 7.9 5.2 T.sub.950nm (%) — — 66 64

TABLE-US-00006 TABLE IIID Examples (wt %) 13 14 15 16 SiO.sub.2 67.04 66.72 65.40 67.08 P.sub.2O.sub.5 0.04 0.04 1.12 0.05 Al.sub.2O.sub.3 18.48 19.54 20.54 19.15 Li.sub.2O 2.33 2.46 2.88 2.44 MgO 0.98 1.21 0.39 1.19 ZnO 2.99 1.79 2.59 1.78 BaO 2.42 2.45 0.01 2.49 CaO 0.46 0.47 1.49 0.47 TiO.sub.2 2.57 2.91 2.93 2.95 ZrO.sub.2 1.42 1.20 1.34 1.19 Na.sub.2O 0.65 0.60 0.63 0.59 K.sub.2O 0.16 0.17 0.16 0.18 SnO.sub.2 0.29 0.28 0.30 0.28 Fe.sub.2O.sub.3 0.12 0.11 0.15 0.11 V.sub.2O.sub.5 0.03 0.03 0.04 0.03 Cr.sub.2O.sub.3 0.02 0.02 0.03 0.02 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.77 0.79 0.50 0.80 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1620 1622 1612 1640 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 5.6 4.7 3.6 4.3 T.sub.liq (° C.) 1339-1353 1334-1346 1326-1342 1330-1352 Viscosity at T.sub.liq (Pa .Math. s) 570-670 670-790 600-760 730-1010 Crystalline phase devitrifying at T.sub.liq spinel + mullite spinel spinel + zircon mullite Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 9.2 13.2 2.9 12.6 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 8.8 12.9 2.4 12.6 Y (%) 5.5 4.6 1.2 3.8 Diffusion (%) 0.4 0.6 1.2 0.6 T.sub.625nm (%) 14.4 11.2 3.8 9.7 T.sub.950nm (%) 65 68 62 67

TABLE-US-00007 TABLE IIIE Examples (wt %) 17 18 19 20 SiO.sub.2 67.29 65.22 65.04 64.87 P.sub.2O.sub.5 0.04 2.13 2.17 2.13 Al.sub.2O.sub.3 18.98 19.52 19.36 19.45 Li.sub.2O 2.45 2.80 2.78 2.80 MgO 1.20 0.32 0.32 0.33 ZnO 1.79 1.79 2.11 2.16 BaO 2.45 2.46 2.44 2.46 CaO 0.47 0.48 0.50 0.50 TiO.sub.2 2.92 2.87 2.88 2.89 ZrO.sub.2 1.20 1.18 1.15 1.15 Na.sub.2O 0.60 0.60 0.61 0.62 K.sub.2O 0.17 0.17 0.16 0.17 SnO.sub.2 0.28 0.29 0.29 0.30 Fe.sub.2O.sub.3 0.11 0.11 0.13 0.11 V.sub.2O.sub.5 0.03 0.04 0.04 0.04 Cr.sub.2O.sub.3 0.02 0.02 0.02 0.02 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.79 0.46 0.47 0.47 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1638 1640 1635 1631 Resistivity at 30 Pa .Math. s (Ω .Math. cm) — 3.9 4.2 4.2 T.sub.liq (° C.) 1330-1350 1294-1320 13094335 1311-1327 Viscosity at T.sub.liq (Pa .Math. s) 740-1000 1170-1770 860-1270 920-1180 Crystalline phase devitrifying at T.sub.liq spinel spinel spinel spinel Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 12.3 4.8 4.2 4.1 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 12.3 4.3 3.7 3.6 Y (%) 3.2 1.3 1.0 Diffusion (%) 0.6 0.8 0.7 T.sub.625nm (%) 8.4 4.0 3.2 — T.sub.950nm (%) 64 64 61 —

TABLE-US-00008 TABLE IIIF Examples (wt %) 21 22 23 SiO.sub.2 67.01 66.72 67.27 P.sub.2O.sub.5 0.05 0.05 0.04 Al.sub.2O.sub.3 18.88 18.40 18.50 Li.sub.2O 2.68 2.60 2.30 MgO 0.31 0.46 0.71 ZnO 2.93 2.94 3.01 BaO 2.42 2.96 2.45 CaO 0.48 0.71 0.48 TiO.sub.2 2.69 2.65 2.77 ZrO.sub.2 1.29 1.25 1.19 Na.sub.2O 0.64 0.65 0.67 K.sub.2O 0.15 0.15 0.17 SnO.sub.2 0.28 0.28 0.28 Fe.sub.2O.sub.3 0.13 0.12 0.11 V.sub.2O.sub.5 0.04 0.04 0.03 Cr.sub.2O.sub.3 0.02 0.02 0.02 (0.74 MgO + 0.19 BaO + 0.48 0.63 0.70 0.29 SrO + 0.53 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1637 1635 1640 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 3.9 3.6 5.4 T.sub.liq (° C.) 1347-1364 1346-1363 1339-1357 Viscosity at T.sub.liq (Pa .Math. s) 590-750 570-730 660-850 Crystalline phase devitrifying at T.sub.liq spinel spinel spinel Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 3.4 5.6 8.1 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 2.6 4.8 7.8 Y (%) 4.6 2.1 — Diffusion (%) 0.7 0.7 — T.sub.625nm (%) 12.3 6.4 — T.sub.950nm (%) 66 63 —

TABLE-US-00009 TABLE IIIG Examples (wt %) 24 25 26 SiO.sub.2 66.66 66.24 64.88 P.sub.2O.sub.5 0.04 0.04 2.10 Al.sub.2O.sub.3 19.31 19.66 19.11 Li.sub.2O 2.50 2.56 2.67 MgO 1.37 1.41 0.35 ZnO 1.88 2.04 3.06 BaO 1.40 0.004 1.25 SrO 0.89 1.89 0.73 CaO 0.45 0.46 0.47 TiO.sub.2 2.94 2.97 2.82 ZrO.sub.2 1.32 1.48 1.24 Na.sub.2O 0.61 0.62 0.67 K.sub.2O 0.17 0.17 0.17 SnO.sub.2 0.29 0.28 0.29 Fe.sub.2O.sub.3 0.11 0.13 0.12 V.sub.2O.sub.5 0.03 0.02 0.04 Cr.sub.2O.sub.3 0.03 0.03 0.03 (0.74 MgO + 0.19 BaO + 0.85 0.85 0.50 0.29 SrO + 0.53 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1631 1625 1635 Resistivity at 30 Pa .Math. s (Ω .Math. cm) — 4.1 3.6 T.sub.liq (° C.) 1317-1335 1313-1332 1330-1344 Viscosity at T.sub.liq (Pa .Math. s) 840-1100 840-1120 780-960 Crystalline phase devitrifying at T.sub.liq spinel spinel spinel Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 12.7 12.3 3.5 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 12.5 12.1 3.2 Y (%) 2.4 2.3 0.9 Diffusion (%) 0.2 0.1 0.1 T.sub.625nm (%) 6.7 6.4 3.0 T.sub.950nm (%) 66 65 62

TABLE-US-00010 TABLE IV A Comparative examples (wt %) A B C D SiO.sub.2 67.88 67.74 66.74 66.02 P.sub.2O.sub.5 0.04 0.06 0.03 0.06 Al.sub.2O.sub.3 19.00 18.46 19.08 19.40 Li.sub.2O 2.27 2.47 2.32 2.80 MgO 0.90 0.24 1.74 0.31 ZnO 1.83 1.23 1.83 3.30 BaO 2.44 4.25 2.47 2.42 CaO 0.47 0.45 0.45 0.48 TiO.sub.2 2.73 2.80 2.91 2.83 ZrO.sub.2 1.26 1.11 1.21 1.04 Na.sub.2O 0.59 0.57 0.60 0.68 K.sub.2O 0.17 0.21 0.17 0.15 SnO.sub.2 0.27 0.27 0.29 0.29 Fe.sub.2O.sub.3 0.10 0.07 0.11 0.15 V.sub.2O.sub.5 0.03 0.05 0.03 0.04 Cr.sub.2O.sub.3 0.02 0.02 0.02 0.03 (0.74 MgO + 0.19 BaO + 0.29 SrO + 0.53 0.76 0.63 1.01 0.46 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1656 1681 1619 1600 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 5.5 5.4 5.6 4.4 T.sub.liq (° C.) 1361-1372 1296-1325 1328-1346 1362-1372 Viscosity at T.sub.liq (Pa .Math. s) 750-880 1700-2700 660-870 360-420 Crystalline phase devitrifying at T.sub.liq mullite zircon + spinel + spinel mullite mullite Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 11.1 — 14.6 2.7 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 10.8 — 14.4 1.3 Y (%) 7.9 — 1.9 0.9 Diffusion (%) 2.3 — 0.7 1.0 T.sub.625nm (%) 17.4 — 5.3 2.8 T.sub.950nm (%) 69 — 64 59

TABLE-US-00011 TABLE IV B Comparative examples (wt %) E SiO.sub.2 66.44 P.sub.2O.sub.5 0.03 Al.sub.2O.sub.3 18.73 Li.sub.2O 2.19 MgO 1.31 ZnO 1.65 BaO 3.46 CaO 1.07 TiO.sub.2 2.79 ZrO.sub.2 1.12 Na.sub.2O 0.60 K.sub.2O 0.17 SnO.sub.2 0.29 Fe.sub.2O.sub.3 0.10 V.sub.2O.sub.5 0.03 Cr.sub.2O.sub.3 0.02 (0.74 MgO + 0.19 BaO + 0.29 SrO + 1.16 0.53 CaO + 0.48 Na.sub.2O + 0.32 K.sub.2O)/Li.sub.2O Precursor glass properties T.sub.(30Pa.Math.s) (° C.) 1615 Resistivity at 30 Pa .Math. s (Ω .Math. cm) 5.7 Glass-ceramic properties CTE.sub.(25-700°C.) (×10.sup.−7 K.sup.−1) 18.1 CTE.sub.(25-450°C.) (×10.sup.−7 K.sup.−1) 17.5 Y (%) 2.4 Diffusion (%) 0.7 T.sub.625nm (%) 6.5 T.sub.950nm (%) 65