DE1596855C - Compositions for the production of opaque glass ceramics with specifically adjustable coefficients of expansion between 9 and 75.10 to the power of 7 / degrees C. - Google Patents

Description

The invention relates to compositions for the production of opaque glass-ceramic, often also referred to as glass-crystal mixed bodies, which are obtained through a heat treatment of the glass objects melted from the compositions above the transformation temperature (toughness // <10 ¹³⁵ poise) by controlled crystallization , and which coefficients of thermal expansion between 75 and 9 · 10 ~ ⁷ / ° C in the temperature range from 20 to 300 ⁰ C have. These glass ceramics are made from glasses made of SiO ₂ , B ₂ O ₃ , Li ₂ O, CaO, BaO, MgO, ZnO, P ₂ O ₅ , TiO ₂ , ZrO ₂ and As ₂ O ₃ . P ₂ O ₅ , TiO ₂ and ZrO ₂ act as nucleating agents and serve to initiate and thus promote crystallization. As ₂ O ₃ is used to refine the glass melt. The other components determine, through the respective mixing ratio, the crystal phases that separate out during the ceramization process and thus the properties of the glass-ceramics created in this way.

Such glass ceramics are generally characterized by a higher mechanical strength, by higher Usage temperatures and by higher or lower coefficients of thermal expansion than the original glasses and are described, for example, in the German patent 1 045 056 (transparent and opaque glass ceramics), German patent specification 1 159 142 (transparente Glass ceramic), German Auslegeschrift 1 090 397 (transparent glass ceramic), French Patent 1,300,614 (transparent and opaque glass-ceramics) and U.S. Patent 3 241 985 (transparent glass ceramic).

Both high melting and processing temperatures were required for the production of these known glass ceramics necessary. In addition, the transition temperatures were also very high.

The object of the present invention are compositions for the production of opaque glass ceramics containing, in addition to beta-eucryptite mixed crystals as further crystal phases, at least zinc spinel and / or Celsian and / or ZrO ₂ seed phase with selectively adjustable between 9 and 75 · 10 -7 ° C (20 to 300 ⁰ C) lying coefficients of expansion by a heat treatment between 720 and 820 ° C of the glass objects melted from the compositions.

According to the invention, this object is achieved by the following composition range in percent by weight :

SiO ₂ 54.0 to 62.0,

B ₂ O ₃ 0 to 6.4,

Al ₂ O ₃ .
Li ₂ O.
CaO ..
BaO ..

at least one of the oxides

MgO

ZnO.

P ₂ O ₅

TiO ₂

ZrO ₂

14.5 until 22.0, 1.5 until 2.8, O until 1.9, O until 7.0, O until 7.5 and O until 12.0 as well as O until 8.0, 0.6 until 1.8, 1.8 until 4.0, 0.15 until 0.30,

As ₂ O ₃ 0.15 to

whereby the following sums are to be observed

CaO + BaO + MgO + ZnO

= 7.5 to 19 percent by weight,
P ₂ O ₅ + TiO ₂ + ZrO ₂

= 3.6 to 11.6 percent by weight.

The glass ceramics according to the invention differ from the known glass ceramics in that they are used other compositions with a significantly higher content of the divalent metal oxides CaO, BaO, MgO, ZnO and by a low

Li ₂ O and SiO ₂ content. The glasses are off. Therefore, and can be melted in good quality between 1560 and 158O ⁰ C, in contrast to the known glass ceramics at lower temperatures to process because they are less tough in the molten state. Another difference is the crystalline phase content after conversion (ceramization). While the previous Li ₂ O-containing opaque glass-ceramics were predominantly lithium minerals / S-eucryptite (Li ₂ O Al ₂ O ₃ :

SiO ₂ = 1: 1: 2) and h-spodumene (Li ₂ O: Al ₂ O ₃ : SiO ₂ = 1: 1: 4) contain as crystalline phase, in addition to / S-eucryptite mixed crystals, zinc spinel ( ZnO · Al ₂ O ₃ ) and / or celsian (BaO-Al ₂ O ₃ · 2SiO ₂ ) and / or ZrO ₂ seed phase present as crystal phases. Finally, the low transformation temperature between 720 and 820 ° C should be mentioned as a particular advantage, which prevents deformation of the shaped bodies during ceramization. According to the prior art, temperatures of up to 1300 ° C. had to be used for this, the final stage of the conversion being above 1000 ° C. for all products known on the market.
To further explain the invention, the compositions of 16 glass ceramic base glasses are listed in Table 1. Table 2 contains various property values of the glasses and the corresponding ceramized products together with the crystalline phase contents.

Table 1
Weight percent compositions of the glass ceramic base glasses 1 to 16

No. SiO ₂ B ₂ O ₃ AI ₂ O ₃ Li ₂ O BaO CaO MgO ZnO TiO ₂ ZrO ₂ P ₂ O ₅ As ₂ O ₃ 1 54.0 6.4 17.0 2.8 4.2 12.0 1.8 1.8 0.15 2 54.0 0.6 17.0 2.0 4.0 3.0 12.0 0.6 4.0 2.8 0.30 3 54.0 0.6 17.0 2.8 7.0 12.0 1.0 3.6 2.0 0.30 4th 54.7 1.1 22.0 Z, ö 7.5 1.8 1.8 8.0 0.30 5 54.7 22.0 2.0 7.5 1.9 1.8 1.8 8.0 0.30 6th ■ 60.5 14.5 2.0 3.0 12.0 1.0 2.8 4.2 0.30

continuation

No. SiO, B, O, Λ UO, Li, o BnO Ca O MgO ZnO TiO, ZrO, P, O ₅ /\so., 7th 54.7
22.0 2.8 7.5 1.1 1.8 1.8 8.0 0.30 8th 62.0 14.5 1.5 3.0 12.0 1.0 1.8 4.2 0.30 9 61.5 14.5 2.0 3.0 12.0 1.0 1.8 4.2 0.30 10 54.0 3.6 17.0 2.8 7.0 12.0 1.0 2.6 0.15 11th 61.0 16.0 2.5 1.90 3.0 12.0 1.8 1.8 0.30 12th 55.6 17.0 2.8 7.0 12.0 1.0 2.6 2.0 0.15 13th 56.9 17.0 1.5 7.0 12.0 1.0 2.6 2.0 0.15 14th 54.0 0.6 17.0 2.0 7.0 12.0 0.6 4.0 2.8 0.30 15th 61.0 16.0 2.5 3.0 12.0 1.0 1.8 2.7 0.30 16 54.0 17.0 2.8 7.0 12.0 1.0 2.6 3.6 0.15

Table 2

7 Properties of the composition examples 1 to 16 of Table 1 in the vitreous and ceramized state. after a heat treatment of 2 hours 72o C ⁰ + 3 hours 820 ⁰ C.

Out Glass Density" Out density Ceramized product * crystalline phases elongation (g / ccm) elongation (g / ccm) No. coefficient coefficient percentage a ■) 0 ^η T ₉ ( ⁰ C) 2.67 α · 10 ⁷ 2.88 density ß-eucryptite solid solution, (20 to 300 ° C) /; ~ 10 '"P (20 to 300'C) modification Zinc spinel, ZrO ₂ seed phase 42 2.72 75 2.82 Quartz, zinc spinel, celsian, 1 600 7.87 Zr O ₂ seed phase 37 2.77 75 2.86 / 3-eucryptite solid solution, 2 634 3.68 Celsian, ZrO ₂ seed phase 43 2.48 67 2.53 / S-eucryptite solid solution, 3 607 3.25 ZrO ₂ seed phase 41 2.50 29 2.58 ß-eucryptite solid solution, 4th 670 2.02 ZrO ₂ seed phase 37 2.62 24 2.73 ß-eucryptite solid solution, 5 683 3.20 Zinc spinel, ZrO ₂ seed phase 36 2.50 24 2.55 ß-eucryptite solid solution, 6th 629 4.20 ZrO ₂ seed phase 41 2.60 23 2.69 ß-eucryptite solid solution, 7th 666 2.00 ZrO ₂ seed phase 33 2.61 20th 2.69 / S-eucryptite solid solution, 8th 650 3.46 Zinc spinel, ZrO ₂ seed phase 35 2.47 18th 2.86 iS eucryptite mixed crystals, 9 628 3.06 Celsian, zinc spinel 43 2.66 16 2.74 ß-eucryptite solid solution, 10 585 4.39 Zinc spinel 39 2.76 15th 2.83 / J-eucryptite solid solution, 11th 634 3.02 ZrO ₂ seed phase 45 2.75 13th 2.83 / S-eucryptite solid solution, 12th 637 2.54 ZrO ₂ seed phase 36 2.78 12th 2.84 ß-eucryptite solid solution, 13th 662 2.90 ZrO ₂ seed phase 40 2.62 10 2.67 / S-eucryptite solid solution, 14th 630 2.16 Zinc spinel, ZrO ₂ seed phase 37 2.75 10 2.80 ^ -Eucryptite solid solution, 15th 632 1.92 Celsian, ZrO ₂ seed phase 39 9 16 627 1.82

Claims (1)

Claim: Compositions for the production of opaque glass ceramics containing, in addition to beta-eucryptite mixed crystals as further crystal phases, at least zinc spinil and / or Celsian and / or ZrO ₂ seed phase with specifically adjustable, between 9 and 75 · 10 ~ ⁷ / ° C (20 to 300 ° C), characterized by the following range in percent by weight, calculated on the oxide basis: SiO ₂ ..
B ₂ O ₃ .
Al ₂ O ₃ .
Li ₂ O. 54.0 until 62.0, 0 until 6.4, 14.5 until 22.0, 1.5 until 2.8, CaO BaO at least one of the oxides MgO ZnO. P ₂ O ₅ TiO ₂ ZrO ₂ O until 1.9, O until 7.0, 1Q6
O until 7.5 and O until 12.0 as well as O until 8.0, 0.6 until 1.8, 1.8 until 4.0, 0.15 until 0.30, As ₂ O ₃ 0.15 to whereby the following sums are to be observed: CaO + BaO + MgO + ZnO = 7.5 to 19 percent by weight, P ₂ O ₅ + TiO ₂ + ZrO ₂ = 3.6 to 11.6 percent by weight.