US4350558A
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US
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Process for the manufacture of polycrystalline garnet and corresponding monocrystals
Assignee: Rhone Poulenc Industries SA
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Filing: 1980-11-07
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Granted: 1982-09-21
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Expires: 2000-11-07
Abstract
Abstract A process for the manufacture of a polycrystalline garnet containing aluminium and/or gallium and/or indium and at least one element taken from the group comprising the rare earths and yttrium, and to the corresponding monocrystal. The process comprises the following steps: (1) a solution containing the salts of the constituent cations of the garnet, in the proportions corresponding to the composition of the latter, is prepared; (2) corresponding hydroxides are co-precipitated by means of a base in order to obtain a co-hydroxide, the solution of salts and the base being added simultaneously at a temperature between ambient temperature and the boiling point of the solution of salts, in such a way that the pH of the medium is between about 5 and 10 and that, within these limits, it is kept at a constant value throughout the co-precipitation; (3) if appropriate, the co-hydroxide is left to age; (4) it is filtered off; (5) it is washed; (6) it is dried; and (7) it is then calcined at a temperature above the temperature for the formation of the desired garnet structure. The monocrystals obtained by Czochralski drawing of the polycrystalline garnets of the invention can be used, in particular, as substrates in magnetic bubble memory devices.
Inventors
- 👤 Bernard Boudot
- 👤 Georges Nury
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 16:28
CPC Classifications
C; C01; C01G; C01G15/00; C01B; C01B13/00; C01B13/14; C01B13/36; C01B13/363; C01F; C01F17/00; C01F17/30; C01F17/32; C30; C30B; C30B15/00; C30B29/00; C30B29/10; C30B29/16; C30B29/22; C30B29/28; C01P; C01P2004/00; C01P2004/01; C01P2004/03; C01P2004/50
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
219 words
A process for manufacturing a pure polycrystalline garnet consisting essentially of aluminium and/or gallium and/or indium, oxygen and at least one element taken from the group consisting of the rare earths and yttrium, which process comprises the following steps: (1) a solution is prepared consisting essentially of the salts of the constituent cations of the garnet, in the proportions corresponding to the composition of the desired garnet structure; (2) the corresponding hydroxides are co-precipitated by means of a base in order to obtain a co-hydroxide, the solution of salts and the base being added simultaneously at a temperature between ambient temperature and the boiling point of the solution of salts so that the pH of the medium is between about 5 and 10 and the pH is kept at a constant value, within these limits, throughout the co-precipitation, said constant pH value being that at which no aluminum hydroxide and/or gallium hydroxide and/or indium hydroxide is redissolved, and at which the precipitation of the rare earth hydroxides and yttrium hydroxide is complete; (3) the co-hydroxide is filtered off; (4) the co-hydroxide is washed; (5) the co-hydroxide is dried; and (6) the co-hydroxide is then subjected to a single calcination at a temperature between about 800° C. and 1500° C. until completely reacted, whereby said pure polycrystalline garnet is produced.
Claim 2
Dependent Claim
219 words
A process for manufacturing a pure polycrystalline garnet consisting essentially of aluminium and/or gallium and/or indium, oxygen and at least one element taken from the group consisting of the rare earths and yttrium, which process comprises the following steps: (1) a solution is prepared consisting essentially of the salts of the constituent cations of the garnet, in the proportions corresponding to the composition of the desired garnet structure; (2) the corresponding hydroxides are co-precipitated by means of a base in order to obtain a co-hydroxide, the solution of salts and the base being added simultaneously at a temperature between ambient temperature and the boiling point of the solution of salts so that the pH of the medium is between about 5 and 10 and the pH is kept at a constant value, within these limits, throughout the co-precipitation, said constant pH value being that at which no aluminum hydroxide and/or gallium hydroxide and/or indium hydroxide is redissolved, and at which the precipitation of the rare earth hydroxides and yttrium hydroxide is complete; (3) the co-hydroxide is filtered off; (4) the co-hydroxide is washed; (5) the co-hydroxide is dried; and (6) the co-hydroxide is then subjected to a single calcination at a temperature between about 800° C. and 1500° C. until completely reacted, whereby said pure polycrystalline garnet is produced.
Claim 3
Dependent Claim
24 words
A process according to claim 1, wherein the co-hydroxide subsequent to step (2) is permitted to age before filtering it off in step (3).
Claim 4
Dependent Claim
30 words
A process according to claim 2, wherein the aging is carried out under the same temperature and pH conditions as during the co-precipitation step, for about 1 to 20 hours.
Claim 5
Dependent Claim
24 words
A process according to claim 1, wherein, in step (1), the salts are chosen from among the group consisting of nitrates, chlorides, and sulphates.
Claim 6
Dependent Claim
80 words
A process according to claim 1, wherein, in step (1), the solution containing the salts of the constituent cations of the garnet is prepared in accordance with the process comprising the following steps: (a) the oxides of the cations forming part of the composition of the garnet are calcined; (b) the amounts of oxides fixed by the formula of the garnet are weighed; (c) each oxide is dissolved in an acid; and (d) the resulting solutions of salts are mixed.
Claim 7
Dependent Claim
16 words
A process according to claim 4, wherein, in step (c), the acid is a strong acid.
Claim 8
Dependent Claim
16 words
A process according to claim 4, wherein the oxides are dissolved simultaneously in a strong acid.
Claim 9
Dependent Claim
26 words
A process according to claim 4 wherein the acid is chosen from among the group consisting of hydrochloric acid, nitric acid, sulphuric acid, and perchloric acid.
Claim 10
Dependent Claim
20 words
A process according to claim 8, wherein the dissolution is carried out with pure concentrated acid at the boiling point.
Claim 11
Dependent Claim
31 words
A process according to claim 1, wherein, in step (2), the base is a weak base which is chosen from among the group consisting of ammonia, urea, hexamethylenetetramine and ammonium carbamate.
Claim 12
Dependent Claim
20 words
A process according to claim 1, wherein, in step (2), the concentration of the base is above about 5 N.
Claim 13
Dependent Claim
26 words
A process according to claim 1, wherein, in step (2), the temperature is between about 80° C. and the boiling point of the solution of salts.
Claim 14
Dependent Claim
20 words
A process according to claim 1, wherein, in step (2), the temperature is between about 95° C. and 100° C.
Claim 15
Dependent Claim
35 words
A process according to claim 1, wherein, in step (3), the co-hydroxide is filtered off under pressure or in vacuo, the filtering element used preferably having a pore size of about 1 to 5 microns.
Claim 16
Dependent Claim
29 words
A process according to claim 1, wherein, in step (4), the co-hydroxide is washed with water until the wash waters obtained have a pH in the region of neutrality.
Claim 17
Dependent Claim
35 words
A process according to claim 1, wherein, in step (5), the co-hydroxide is dried in air or in vacuo at a temperature between about 100° C. and 200° C. for about 10 to 48 hours.
Claim 18
Dependent Claim
20 words
A process according to claim 1, wherein, in step (6), the co-hydroxide is calcined for about 1 to 30 hours.
Claim 19
Dependent Claim
43 words
A polycrystalline garnet obtained in accordance with the process of any one of the preceding claims, wherein it consists of crystals, the elementary dimensions of which are of the order of a few microns, and which are agglomerated to give a compact assembly.
Claim 20
Dependent Claim
37 words
A monocrystal obtained by a drawing process from the polycrystalline garnet manufactured in accordance with the process of claim 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 3, 14, 15, 16 or 17.
Claim 21
Dependent Claim
15 words
A monocrystal according to claim 19 wherein the drawing process is a Czochralski drawing process.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-09-20 | 1986-03-22 | 1986-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-20 | 1990-03-22 | 1990-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-20 | 1994-03-22 | 1994-09-21 | $7700.00 | Window Closed / Lapsed |