DE1771143C3 - Process for the production of sodium vapor-resistant glass ceramics on the basis of CaO-AI deep 2 O deep 3 and their use - Google Patents

Description

Limits

is obtained, first V »to 2 hours with a ^ ₃ Q 24 to 50

Temperature between 700 and 900 ⁰ C, then _A jq 35 to 575

Vs up to 2 hours between 900 and 1000 ⁰ C and 40 _m * q ³ ""' 0 to I2! '

finally for 1 to 4 hours between 1,000 ß _'a Q 0 to 16 *

and 1200 ⁰ C is heated. γ ₀ ""';;;' _{0 to 10} \

_{3. Use of the RO} 0 to 9 1 according to claims 1 or 2

obtained glass ceramics as sealing material 2rO * ...... 0 to 17.5 [^ i ^ a + ^^ t + ^ hO

for high pressure sodium vapor discharge lamps with 45 y q 0 to 3 * 1 ^ ^s ^ '

a shell made of densely sintered, polycrystalline *

Alumina with a purity of at least is obtained, first Va to 2 hours on one

99.5%. Temperature between 700 and 900 ⁰ C, then 0 to

4. Use of the glass ceramics obtained according to claim 1 or 2 for 2 hours between 900 and 1000 ⁰ C and finally obtained as a cladding material for 50 for 1 to 6 hours between 1000 and 1200 ⁰ C discharge lamps. is heated.

The glass-ceramic obtained in this way, the

is finely crystalline, has a sodium vapor resistance compared to glass of the same composition.

The invention relates to a method for ness 55, the temperatures up to about 200 ° C higher to Tempe-producing resistant to sodium vapor glass, ie, to about 900 ⁰ C, is satisfactory. For ceramics based on CaO - Al ₂ O ₃ and on a shell of a high-pressure sodium vapor discharge lamp, for which either the connection lamp is just not suitable. In contrast, training between the densely sintered polycrystalline it is when using medium pressures as a linem material, z. B. aluminum oxide, existing 6 ° shell applicable. A number of glass ceramics inner shell and the electrode metal from the glass ceramic produced according to half of the above composition area have a transparency that is comparable to that of densely sintered aluminum oxide or in which the shell itself is completely or partially comparable. You are made of this glass ceramic. work, e.g. B. to tubular bodies by means of the

Dense sintered, polycrystalline aluminum oxide 65 extrusion process, suitable that described in DT-PS

(US-PS 3026 210) consists of at least 99.5% 15 36 545 has been described.

Al ₂ O ₃ . It is translucent, gas-tight and has a According to a preferred embodiment of the invention

Excellent resistance to the action of moderate process is a glass made by melting

a mixture with a composition in percent by weight, calculated as oxides, within the limits:

CaO 30 to 50

Al ₁ O ₃ 35 to 55

MgO 2 to 7

BaO 4 to 16

Y _t O, 0 to 10

B ₁ O ₃ 3 to 9

ZrO _t 0 to 10

is obtained first * /, up to 2 hours at a temperature between 700 and 900 ⁰ C, then Vs to 2 hours between 900 and 1000 ° C and finally heated for 1 to 4 hours 1000-1200 ⁰ C.

The treatment in three stages, ie with a treatment at a temperature between 900 and 1000 ⁰ C between the nucleation and the Keimanwachsung, the risk of cracking in the material is reduced considerably.

In the manufacture of high pressure halide lamps with a shell of densely sintered polycrystalline aluminum oxide offers the invention produced glass ceramic offers the possibility of a much simpler sealing than has been used up to now would.

The F i g. 1 shows a known seal. Here, 1 is the tubular casing made of densely sintered aluminum oxide, in which an annular piece 3 made of the same material is clamped at both ends. The ring 4 is also made of the same material. Niobium is used as the electrode leadthrough 2, while the two rings 5 consist of pressed glass powder mixed with a binding agent. The glass has, for example, the composition (in percent by weight): CaO 38.8; Al ₄ O ₃ 45.6; MgO 5.2; BaO 8.7 and B ₁ O ₃ 1.7 according to the

5 OE-PS 2 74137. When heated, the binder burns and forms a vacuum-tight connection between Cover 1 and electrode lead-through 2.

In Fig. 2 it is indicated how the sealing with the material obtained according to the invention much

ίο is brought about more easily. Accordingly, the one-piece glass plug 7 after melting by a suitable thermal treatment transferred into the glass ceramic according to the invention. With this type of seal, the Electrode leadthrough 6 consist, for example, of the much cheaper molybdenum.

When the invention came about it has been found that in the first phase of the thermal Treatment from the glass finely divided

ao germs, e.g. B. in the form of 3 CaO · B ₂ O ₃ , precipitate. During the further thermal treatment, the compound CaO.Al ₂ O ₃ , which has excellent resistance to the action of sodium vapor, crystallizes on these nuclei. Relevant for

As a suitable glass ceramic is the choice of the composition as well as the temperature program, since apart from CaO · Al ₂ O _{3 also the phase 12 CaO · 7 Al 1} O ₃ , which is very poorly resistant to the action of sodium vapor, can precipitate.

The material obtained according to the invention can be used not only as a sealing material for high pressure sodium lamps or for medium pressure sodium lamps, but also for other highly stressed lamps.

Composition (in percent by weight) CaO Al ₁ O, MgO BaO B ₁ O,

ZrO ₁

Y ₁ O, L, O

1 37.2 43.4 4.9 8.3 6.2 - 2 38.0 44.4 2.8 8.5 6.3 - 3 36.3 42.3 2.6 8.2 6.0 4.6 4th 34.5 40.4 2.5 7.9 3.57 9.0 5 36.7 40.2 2.7 8.3 6.1 - 6th 36.8 43.0 5.9 8.2 6.1 - 7th . 47.9 43.6 - - 8.5 - 8th 46.2 46.9 - - 6.9 - 9 34.4 40.2 4.5 15.3 5.6 - 10 34.5 50.3 - - - 15.2 11th 29.3 46.7 7.9 - - 16.1 12th 41.8 52.0 - - - 4.2 13th 24.2 56.0 4.9 - - 14.9 14th 25.0 51.8 7.7 - - 15.5 15th 26.0 47.2 10.7 - - 16.1 16 29.3 46.6 7.9 - - 16.2 17th 26.8 54.5 14.5 - - 4.2 18th 35.5 35.9 11.4 - - 17.2 19th 49.1 34.3 - - - 16.6 20th 34.8 53.7 - - - 11.5 21 45.3 54.7 - - - - 22nd 37.6 58.5 3.9

5.8

2.0

The invention is illustrated by means of a few examples. The compositions given in the table in percent by weight were melted from a mixture containing calcium carbonate, aluminum oxide, boric acid and optionally magnesium carbonate, barium carbonate, zirconium oxide and yttrium oxide. Rods drawn from the melt are first heated ^{to a temperature between 750 and 850 ° C. for 2 hours.} Subsequently, the temperature is increased at a rate of 4 ° to 5 ° C per minute to 950 ⁰ C and held for one hour at that value. Thereafter, the temperature is again raised at a rate of 4 ° to 5 ° C per minute to 1100 ⁰ C, held for 2 to 4 hours to this, and finally cooled in air to room temperature.

_{The phases 3 CaO · B 2} O ₃ and CaO · Al ₂ O ₃ could be detected by X-ray in the end products; the phase 12 CaO.7 Al ₂ O ₃ was present in traces.

The sodium resistance is for all samples

a treatment for 48 hours at 85O ^P C

ίο very good; in samples 1, 2 and 6 causes a Such a stress at 950 ° C hardly any attack.

1 sheet of drawings

Claims (3)

from CaO .. .. 24 until 50, Al ₈ O,. . 35 until 57.5, MgO .. . 0 until 12, BaO ... . 0 until 16, Y ₈ O, .. . 0 until 10, B ₂ O, .. . 0 until 9 ZrO, .. . 0 until 17.5 Li ₂ O .. . 0 until 3 ι ² Sodium vapor up to very high temperatures. This Claims: Material is therefore used as a cover for high- jraicuuuiay ^ ckiiatrium vapor discharge lamps. of a mixture with a composition in loops based on alkaline earth _{oxide and Al 2} O ₃ percent by weight, calculated as oxides, to be used within, which upon solidification provide a glassy-crystalline product. The crystalline phases arise at most of the compositions of this type spontaneously and quickly, that is, uncontrollably. This greatly reduces the mechanical strength and the gas tightness of the connection obtained. Material can actually only be used as solder and not for the production of B ₂ O ₃ + ZrO ₂ + Li ₂ O larger bodies. 3 to 20, In the manufacture of sodium vapor discharge lamps one was previously forced to final or is obtained, first Vs up to 2 hours at an ao insert pieces of densely sintered polycrystalline temperature between 700 and 900 ° C, then using aluminum oxide. This brings with it, 0 to 2 hours between 900 and 1000 ° C and that for adaptation of the expansion coefficient must eventually exist for 1 to 6 hours between the metal of niobium, which is heated to 1000 and 1200 ⁰ C. The disadvantage is that the fusion in noble gas 2. The method according to claim 1, characterized as must be performed. distinguishes that a glass which is obtained by melting a According to the method according to the invention is a Mixture with a composition in Ge against the action of sodium vapor resistant glass weight percent, Calculated as oxides, made within the ceramic, in which the crystalline phase is very Limits: is fine-grained. This glass ceramic is therefore suitable , ₀ .., "30 not only as a well-adhering, gas-tight sealing «V« material, but also for the manufacture of • · ■ ·, Jr ° ~ bodies. P ^ ί κ- ι λ ^The method according to the invention is thereby ^ßau η b'slO indicates that a glass that melts 3 b '9 ^{35 emes Gemen} ß ^it "υ * ^emer composition in Ge η Kc m percent by weight, calculated as oxides, within the