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Патент USA US3051666

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United States Patent
lQQ
3,551,555
Patented Aug. 28, 1962
1
2
3,051,656
The typical procedure employed in the above experi
mental batches comprised the following steps: A thorough
METHOD OF PREPARING MAGNETIC GARNET
CRYSTALS
Bernhard Krarnarsky, % Microwave Chem. ‘Lab. Inc.
282 7th Ave., New York, N.Y.
No Drawing. Filed May 8, 1959, Ser. No. 811,807
7 Claims. (Cl. 252-625)
mixture of the oxide powders in the proportion indicated
was made, and a weighed portion thereof placed in a 375
ml. platinum crucible so as to ?ll it. (The average batch
weight was 400 gms.) The crucible was covered tight
ly with a platinum lid and placed in a furnace. The fur
nace temperature was raised to 1325 ° and maintained at
that point for 10 hours to insure complete solution of the
.10 ingredients. The temperature was then lowered at a
steady rate of l.9° per hour, to allow for optimum crystal
More speci?cally, this invention has to do with a sig
growth, until 925° C. was reached.
ni?cant improvement in method whereby single crystals of
This invention is concerned with methods of growing
magnetic garnet crystals.
certain rare-earth iron garnets may be produced which are
The crucible and its contents were then cooled rapidly
to room temperature, and the resultant mass repeatedly
considerably larger in average size and in far greater yield.
The identity of these ferrimagnetic garnets, whose gen 15 boiled in dilute nitric acid and washed until the matrix was
suf?ciently reduced to permit dislodgement of the crystals
eral formula is M3Fe5O12 (M=rare earth, e.g. yttrium,
within. Separation of the garnet from the non-garnet
gadolinium, erbium, Samarium) was ?rst reported in 1956.
crystals was accomplished magnetically in the usual man
(F. Bertaut and F. Forrat: Comptes Rendus 242, 382,
ner, taking advantage of the difference in Curie tempera
1956; S. Geller and M. A. Gilleo; Acta Cryst. 10, 239,
The ?rst efforts to prepare these compounds re 20 tures of the aforesaid crystals.
The magnetic garnet crystals formed in the above man
ner are well-developed in crystal structure and quite pure,
properties of these garnets and their potential use in micro
1957.)
sulted in polycrystalline products. Interest in the physical
the total impurities running less than 0.2%, and the quan
wave systems indicated the desirability of growing single
tity of boric anhydride in the crystals less than 0.09% de
crystals of these compounds of maximum size. At present,
single magnetic garnet crystals have found important use 25 termined spectroscopically. The weight of these crystals
ranges from 100 mg. to 2.0 gms. when prepared as above.
in parametric ampli?ers for radar systems; and because
It should be noted here that while the crystal sizes and
they have the property of transparency to infra-red, their
yields in these experimental batches are comparable among
use as infra-red transmission modulators is projected.
themselves, better yields and larger crystals are to be ex
I. P. Rerneika (J. Amer. Chem. Soc. 78, 4259, 1956) ?rst
reported single crystals. J. W. Nielsen and E. F. Dear 30 pected from using larger crucibles and bigger batches.
Returning to consideration of the experimental results
born (J. Phys. Chem. Solids 5, 202-207, 1958) have in
shown in the table above, it is evident that the range of
vestigated and outlined the general methods of producing
effectiveness of the B203 additive is clearly marked and
these magnetic garnets as single crystals from three-com
quite specific. A signi?cant in?uence is shown when 5
ponent systems, i.e. iron oxide, Fe2O3, with lead oxide,
35 mole percent is added; the optimum amount appears to
PbO, as ?ux.
be in the range of 10 mole percent; and over 15 mole per
Nielsen has de?ned the composition range in which mag
cent, no garnet crystals form, since new phases appear
netic garnets will grow and the conditions favorable to
and glassy products result.
their growth. However, his methods have produced at
The function of the boric anhydride additive is evi
best crystals of generally small size and poor yield, with
40 dently that of nucleus suppression, similar to that of
only an occasional large crystal.
“mineralizers,” so that a few large crystals, rather than
The present invention departs from Nielsen’s method
many small crystals, are encouraged to grow. Variation
by adding a fourth component to the system, which sup
of the other three components, namely, lead oxide, iron
presses the formation of many nuclei for multiple crystal
oxide, and rare-earth oxide will in?uence the formation
growth, and encourages the formation of few, larger in—
dividual crystals. It has been found that the addition of 45 of garnet crystals as indicated in the phase diagrams of
Nielsen, as will modi?cations of temperature, batch size,
suitable quantities of bon'c anhydride, B203, to the three
component system of Nielsen provides a remarkable in
etc. However, as indicated in Experiment 6 in the table
crease in the size and yield of magnetic garnet crystals.
above, under conditions Where garnet crystals Will form
at all in the three-component system, the addition of
The following table of typical experimental results clear
boric anhydride in the indicated range will enhance the
ly shows the eifect of the addition of boric anhydride:
yield and quality of said crystals.
Suitable ranges within the contemplation of the in
Exp’t
No,
Composition
of Bulk
Material
(In Mole
B203
Added
(In
Mole
Percent
Yield of
Yttriumiron
Garnet
Average
Size
(Diarn)
of Y.I.G.
Single
Total
Wt. of
Y,I. G.
Single
Crystals
Percent)
Percent)
Single
Crystals
(Grams)
Crystals
PbO:52.5__-___
1 ____ __
FezOaz44 _____ __
0
6. 04
2____ __{
8. 0
3 ____ __ {
76. 9
0. 09
1. 92
10. 09
3. 48
0. 250
25. 9
vention are as follows:
Iron oxide, F620,, from 25 to 70 mole percent
Lead oxide, PbO, from 30 to 70 mole percent
Rare-earth oxide, M203, from 0.1 to 10 mole percent
Boric anhydride, B203, from 2 to 15 mole percent
The letter M in the foregoing is intended to represent
60 a rare-earth selected from the group comprising yttrium,
gadolinimum, erbium and samarium.
The foregoing mixtures in the ranges given may be
heated to a temperature in the range of 1315 to 1345
degrees centrigrade.
4 ____ _- {
}
5 ____ __ {
}
30
}
10. 34
6 ____ -_ {
YzO325.25--___
.
1 Better crystal faces than in 1.
0
__________ __
0
0
__________ _-
0
29. 1
0. 1—0. 2
17. 5
The most effective temperature,
It will be under
65 however, is 1325 degrees centigrade.
stood that the material should be maintained at said
elevated temperature for a minimum of 8 to 10 hours
under standard pressure. The cooling rate ranges from
0.5 degrees centigrade per hour, the most eifective rate
70 being 1.9 degrees per hour. Cooling should continue
until optimum or maximum crystal growth is attained.
It will be found that this will occur by the time the
3,051,656
3
temperature is reduced to approximately 925 degrees.
I claim:
1. The method of growing magnetic iron rare-earth
garnet crystals, comprising the steps of providing a mix
ture of iron oxide, lead oxide, rare-earth oxide and boric
anhydride from 2 to 15 mole percent, heating said mix
ture to an elevated temperature su?icient to cause it
to go into solution, and then cooling said heated mixture
at a controlled, sufficiently slow rate to produce crystals.
4
garnet crystals, comprising the steps of providing a mix
ture of iron oxide, approximately 43.75 mole percent,
lead oxide, approximately 51.5 mole percent, yttrium
oxide, approximately 5.25 mole percent, and boric an
hydride, approximately 10.34 mole percent, heating said
mixture to a temperature in the range of 1315 to 1345
degrees centigrade, and then cooling said heated mixture
at a controlled rate in the range of 0.5 to 5 degrees centi
grade per hour to allow for proper crystal growth.
6. The method of growing magnetic iron rare-earth
2. The method of growing magnetic iron rare-earth 10
garnet crystals, comprising the steps of providing a mix
garnet crystals, comprising the steps of providing a mix
ture of iron oxide, approximately 44 mole percent, lead
ture of iron oxide, from 25 to 70 mole percent, lead
oxide, approximately 52.5 mole percent, yttrium oxide,
oxide, ‘from 30 to 70 mole percent, rare-earth oxide,
approximately 3.5 mole percent, and boric anhydride,
from 0.1 to 10 mole percent, the rare earth being selected
from the group consisting of yttrium, gadolinium, erbium 15 approximately 10.34 mole percent, heating said mixture
to a temperature of approximately 1325 degrees centi
and Samarium, and boric anhydride, from 2 to 15 mole
grade, maintaining it at said temperature for approxi
percent, heating said mixture to a temperature in the
mately 10 hours, and then cooling said heated mixture
range of 1315 to 1345 degrees centigrade, and then cool
at the rate of 1.9 degrees centigrade per hour until a
of 0.5 to 5 degrees centigrade per hour to allow for proper 20 temperature of approximately 925 degrees centigrade
is reached in order to allow for proper crystal growth.
crystal growth.
7. The method of growing magnetic iron rare-earth
3. The method of growing magnetic iron rare-earth
garnet crystals of claim 1, wherein the iron oxide is in
garnet crystals, comprising the steps of providing a mix
a range from 25 to 70 mole percent, the lead oxide
ture of iron oxide, from 25 to 70 mole percent, lead
oxide, from 30 to 70 mole percent, yttrium oxide, from 25 ranging from 30 to 70 mole percent and the rare-earth
oxide ranging from 0.1 to 10 mole percent.
0.1 to 10 mole percent, and boric anhydride, from 2 to
15 mole percent, heating said mixture to a temperature
References Cited in the ?le of this patent
in the range of 1315 to 1345 degrees centigrade, and
UNITED STATES PATENTS
then cooling said heated mixture at a controlled rate in
the range of 0.5 to 5 degrees centigrade per hour to 30 2,736,708
Crowley ______________ __. Feb. 28, 1956
ing said heated mixture at a controlled rate in the range
allow for proper crystal growth.
4. The method of growing magnetic iron rare-earth
garnet crystals, comprising the steps of providing a mix
ture of iron oxide, approximately 44 mole percent, lead
oxide, approximately 52.5 mole percent, yttrium oxide, 35
approximately 3.5 mole percent, and boric anhydride,
approximately 10.34 mole percent, heating said mixture
to a temperature in the range of 1315 to 1345 degrees
2,848,310
2,886,530
2,938,183
Remeika ____________ __ Aug. 19, 1958
Greger ______________ __ May 12, 1959
Dillon ______________ __ May 24, 1960
2,957,827
Nielsen ______ __'_ _____ __ Oct. 25, 1960
OTHER REFERENCES
J. Amer. Ceram. Soc., Bauer et al., vol. 33, pp. 140-143.
Comptes Rendus, Aleonard et al., vol. 242, pp. 2531
centigrade, and then cooling said heated mixture at a
2533, May 23, 1956.
controlled rate in the range of 0.5 to 5 degrees centigrade 40
Comptes Rendus, Pauthenet et al., vol. 243, pp. 1499
per hour to allow for proper crystal growth.
1501, Nov. 12, 1956.
5. The method of growing magnetic iron rare-earth
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