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Патент USA US2128289

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Patented Aug. 30, 1938
2,128,289
UNITED STATES PATENT OFFICE
2,128,289
CERAMIC DIELECTRIC MATERIAL AND
PROCESS OF MAKING THE SAME
William Dubilier and Josef Oppenheimer,
' New York, N. Y.
No Drawing.- Application November 16, 1936,
Serial No. 111,082
14 Claims. (Cl. 25—156)
This invention relates to ceramic electricalcon
cannot deteriorate the titanium oxide, whereas
densers and similar electrical devices.
the carbon is either deposited or combined with
It is an object of the invention to increase the the material of the oven, or gives cause to super
capacity of such condensers and devices without ?cial formation of a minute layer of titanium car
5
increasing their volume.
'
It is another object of the invention to increase
the ef?ciency of such condensers, in, particular
when used .for high voltages.
It is a further object of the invention to in
10 crease the ei’?ciency of such condensers, in par—
ticular when used for high frequencies.
These and other objects of the invention will
appear more clearly’when the description pro
ceeds.
_
It is to be understood however that the inven
tion is by no means restricted to any exempli?
cation given in the speci?cation, but is to be un
derstood in its broadest aspect from the append
ed claims.
'
It has been suggested to make the dielectric of
electric condensers 'of ceramics, and materials
have been developed the dielectric constant of
which substantially exceeds that of paper, mica,
and ordinary porcelain, having a dielectric con
‘:5 stant below 10. The dielectric constants are
brought up to '70 and 80. Such material causes,
however, high electric losses.
i:
o.
According to this invention the dielectric is
made substantially of an oxide of an element be
bide on the outside of the sintered body. Titani
um carbide is, as known to the art, a very poor
conductor of electricity, and therefore does not
substantially impair the qualities of the body ob
tained which is substantially still titanium oxide.
Furthermore,‘v such super?cial minute layer can
easily be removed after the body is solidi?ed by
grinding with a hard substance such as corun~'
dum powder, or other known hard grinding'ma
terial. As another means for preventing deoxida
tion of oxide present in the body during sintering 15
a vacuum of the highest ossible degree may be
applied to the furnace, or ydrogen introduced as
a protective atmosphere.
The bodies obtained may be densi?ed during
solidi?cation by applying high pressure of sev 20
eral hundred atmospheres to the mould. The
highly sintered or melted bodies so obtained are
dense, and of the high dielectric constants re
ferred to above. Now the electrodes of the con
densers may be applied in any well known way. 25
Thus metal foils may be cut to the desired shape
and applied to the body, then treated in vacuo,
and resiliently pressed against the oxide body,
longing to the fourth group of the periodical sys
while still in vacuo.
The dielectric body with the electrodes may be
tem and one or more oxides of elements of the
positioned between cushions of resilient material,
second, third, and fourth groups of the periodical
system.
According to the invention, a presintering step
35 is applied in which the shaped and preferably
highly pressed body is treated at a temperature
of about 100° C. to 250° C. below high sintering
temperature which is between about 1620° C. to
arranged in a chamber which is connected over
a conduct with valve to a vacuum pump.
A
plunger may resiliently press the electrodes with
any desired pressure upon the sintered titanium
oxide body. Thereby a tight adherence of the
electrodes to the body is obtained, and no paste or
other binding material is generally necessary any
1680° C. Such a presintered or fritted body may h more, in particular if the electrodes are made of
40 then be introduced into the oven or furnace in
aluminium foil, lead, or any other relatively plas
which at least high sintering is performed.
.In order to prevent any deoxidation of ti
tanium oxide if it is used as a fourth group metal
oxide a neutral atmosphere may be maintained
45 in the oven during treatment, particularly at
sintering temperatures. Such neutral atmosphere
may be obtained by introducing a neutral gas
which is stable at such high» temperatures and
does not reduce the titanium oxide. In particular,
50 there may be used carbon-dioxide as such a gas.
It will not be stable at the high temperatures in
volved, but will decompose partly into carbon
monoxide, carbon and oxygen. However, the
equilibrium between these gases will remain sta
55 ble, and if it is disturbed, the oxygen developed
tic metal or alloy composition. The condenser
body so formed may then be varnished, if de
sired, for instance with bakelite-varnish, and it
may also be baked at a low temperature up to
about 200° C. to 300° C., or less, and never near
a temperature at which the metal of the elec
trodes may soften. Such heating may be per
formed while the condenser is still in the chamber
and to this effect in the cushions electric heat re
sistors may be positioned by which the cushions
and the electrodes are heated to the desired tem
perature, while the electrodes are pressed against
the condenser body.
'
There may also be provided any desired bind:
ing materials, such as waterglass, between the 55
2,188,989
electrodesandthecondenserbodywhich how
stant exceeding 14 and containing at least one
ever do not evaporate at operating temperatures
and cause thereby the formation of dangerous
inorganic oxide of an element of the fourth group
and at least one other inorganic oxide of an
intersticesandinvisiblespacesbetweentheelec
trodesandthecondenserbody. 'I‘heelectrodes
also be formed by precipitation upon the
eg :
f a metal from a suitable solution.
ofthebody on whichnoelectrode
§§
beappliedmayalsobecoveredwithasuit
10
material,suchasplasterof?aris,andthen
g2
15
oltenmetal,suchastin. 'I‘heelec
also be applied by spraying on-the
ahotand ?nely divided form, asfor
element selected from the second, third and
fourth group of the periodical system—the steps
of shaping under high pressure and presintering
a ?nely divided, powdery mixture containing said
oxides at a temperature substantially below its
?nal sintering temperature, and thereupon com
pacting said mixture by heat treatment at least 10
at sintering temperature in a selected atmos
phere. --
-
5. In‘ a method of manufacturing a dense
meansofaBchooppistol.
ceramic dielectric material, in’ particular adapted
However, any other method of applying the
for electric condensers, having a dielectric con
stant exceeding 14 and containing at least one
electrodestightlyonthecondenserbodymay
inorganic oxide of an‘elementof the fourth group
Our invention includes the mixing of two or and at least one other inorganic oxide of an ele
more oxides of elements of the fourth group of ‘ ment selected from the second, third and fourth
the periodical system, and there ‘may be added group of the periodical system-the steps of
shaping and presintering a ?nely divided, pow
third group which are not or poorly electrically dery mixture containing said oxides at a tem
conductive, such as boron and boron oxide of the perature substantially below its ?nal sintering
third group and aluminum oxide (alumina) of temperature, and thereupon compacting said
mixture by heat treatment at least at sintering
the second group. There may also be used ele
ments of the fourth group. such as silicon, or temperature in a carbide forming atmosphere.
6. In a method of manufacturing a dense
silicon oxides, as suitable additions.
beused.
What we claim is:
1. In a method of manufacturing a dense
ceramic dielectric material, in particular adapted
for electric condensers, having a dielectric con
stant exceeding 14 and containing at least one
inorganic oxide of an element of the fourth group
and at least one other inorganic oxide of anele
ment selected from the second, third and fourth
group of the periodical system-the steps of
shaping and presintering a ?nely divided, pow
dery mixture containing said oxides at a tem
ceramic dielectric material, in particular adapted
for electric condensers, having a dielectric con
stant exceeding 34 and containing at least one
inorganic oxide of an element of the fourth group
and at least one other inorganic oxide of an ele
ment selected from the second, thirdand fourth
group of the periodical system-the steps of
shaping and presintering a finely divided, pow 35
dery mixture containing said oxides at a tem
perature substantially below its final sintering
temperature, and thereupon compacting said
perature substantially below its ?nal sintering
temperature, and- thereupon compacting said
mixture by heat treatment at least at sintering
mixture by heat treatment at least at sintering
temperature in a highly rari?ed atmosphere.
temperature in a selected atmosphere.
ceramic dielectric material, in particular adapted
2. In a method of manufacturing a dense
7. In a method of manufacturing a dense
for electric condensers, having a dielectric con
ceramic dielectric material, in particular adapted
stant-exceeding 14 and containing at least one
for electric condensers, having a dielectric con
inorganic oxide of an element of the fourth group 45
and at least one other inorganic oxide of an
element selected from the second, third and
stant exceeding 14 and containing at least one
inorganic oxide of an element of the fourth group
and at least one other inorganic oxide of an ele
ment selected from the second, third and fourth
group of the periodical system-v-the steps of
shaping and presintering a ?nely divided pow
dery mixture containing said oxides at a tem
perature substantially below its ?nal sintering
temperature, applying intense pressure for den
sifying the presintered mixture, and thereupon
compacting said mixture by heat treatment in a
fourth group of the periodical system-the steps
of shaping and presintering a ?nely divided, pow
dery mixture containing said oxides at a tem
perature substantially below its final sintering
temperature, and thereupon compacting said
mixture by heat treatment at least at sintering
temperature in a protective atmosphere.
8. A ceramic dielectric material compacted by 55
heat treatment at least at sintering temperature
3. In a method of manufacturing a dense
and having a dielectric constant exceeding 14,
said material substantially consisting of at least
ceramic dielectric material, in particular adapted
one oxide selected from a first group of oxides of
for electric condensers, having a dielectric con
the elements titanium, zirconium, and at least
stant exceeding 14 and containing at least one
inorganic oxide of an element of the fourth group
and at least one other inorganic oxide of an ele
ment selected from the second, third and fourth
one additional inorganic oxide other than that
belonging to said first group and selected from
a second group of oxides of elements of the sec
selected atmosphere.
ond, third and_fourth group of the periodical
group of the periodical system-the steps of
system.
shaping and presintering a ?nely divided, pow
dery- mixture containing said oxides at a tem
ramic dielectric material, in particular adapted
perature substantially below its ?nal sintering
temperature, and thereupon compacting said
for electric condensers, having a dielectric con
70 mixture in a crucible of highly refractory car
bide by heat treatment at least at sintering tem
perature and in a selected atmosphere.
4. In a method of manufacturing a dense
9. A method of manufacturing a dense ce
stant exceeding 14, comprising the steps of form
ing a finely divided powdery mixture containing
at least one inorganic oxide of an element of the
fourth group of the periodical system and at
ceramic dielectric material, in particular adapted
least one other inorganic oxide of an element
selected from the second through fourth group
for electric condensers, having a dielectric con
of the periodical system, presintering said mix- I‘
3
2,128,289
ture at a temperature substantially below its
sintering temperature, and thereupon compact
ing said presintered mixture by a treatment in
cluding heat treatment at least at sintering tem
perature in a selected atmosphere.
10. A method of manufacturing a dense ce:
ramic dielectric material, in particular adapted
for electric condensers, having a [dielectric con
stant exceeding 14, comprising the steps of form
10 ing a ?nely divided powdery mixture containing
at least one inorganic oxide of an element of the
fourth group of the periodical system and at
least one other inorganic oxide of an element se
lected from the second through fourth group of
15 the periodical system, presintering said mixture
at a temperature substantially below its sintering
temperature, and thereupon compacting said pre
sintered mixture by a treatment including heat
treatment at least at sintering temperature in a
20 selected atmosphere and under application of
substantial superatmospheric pressure.
11. A method of manufacturing a dense ce
ramic dielectric body, in particular adapted for
electric condensers, having a dielectric constant
25 exceeding 14, comprising the steps of forming a
finely divided powdery mixture containing at least
one inorganic oxide of an element of the fourth
group of the periodical system, at least one other
inorganic oxide of an element selected from the
30 second through fourth group of the periodical
system, and an addition of at least one element
having poor electrical conductivity as exempli
fled as to conductivity by boron and silicon and
selected from the second through fourth group
35
of the periodical system, presintering said mixture
at a temperature substantially below its sintering
temperature, and thereupon compacting said pre
sintered mixture by a treatment including heat
treatment at least at sintering temperature in a
40
selected atmosphere.
12. A method of manufacturing a dense ce
ramic dielectric body, in particular adapted for
electric condensers, having a dielectric constant
exceeding 14, comprising the steps of forming a
45 ?nely divided powdery mixture containing at
least one inorganic oxide of an element of the
fourth group of the periodical system, at least
one other inorganic oxide of an element selected
from the second through fourth group of the
periodical system, and an addition of at least one 5
element having poor electrical conductivity as
exemplified as to conductivity by boron and sili
con and selected from the second through fourth
group of the periodical system, presintering said
mixture at a temperature substantially below its 10
sintering temperature, and thereupon compact
ing said presintered mixture by a treatment in
cluding heat treatment at least at sintering tem
perature in an oxygen containing atmosphere.
13. A ceramic dielectric body compacted by
heat treatment at least at sintering temperature
and having a dielectric constant exceeding 14,
said body substantially consisting of at least one
oxide selected from oxides of titanium and zir
conium, at least one other inorganic oxide of an
element selected from the second through fourth
group of the periodical system and at least one
additional element of poor electrical conductiv
ity as exempli?ed as to conductivity by boron and
silicon and selected from the second through
fourth group of the periodical system, the out
side of said body substantially consisting of ox
ide of elements contained.
14. A ceramic dielectric body compacted by
heat treatment at least at sintering temperature
and having a dielectric constant exceeding 14,
said body substantially consisting of at least one
oxide selected from oxides of titanium and zir
conium, at least one other inorganic oxide of an
element selected from the second through fourth
group of the periodical system and at least one
additional element of poor electrical conductivity
as exempli?ed as to conductivity by boron and
silicon and selected from the second through
fourth group of the periodical system, the out
side of said body substantially consisting of ox
ide and carbide of elements contained.
20
25
30
35
40
WILLIAM DUBILIER.
JOSEF OPPENHEIMER.
45
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