Process for preparing a barium titanate film

A process for preparing a tetragonal barium titanate film with a thickness of from about 0.1 to about 1.5 millimeters is disclosed. In the first step of this process, a mixture of a barium compound, a titanium compound, and a boron oxide glass former is provided in a specified ratio. The reaction mixture is melted at a temperature of 1300-1400 degrees centigrade and then rapidly quenched in form glass. The glass is then place upon a polycrystalline isostructural substrate, and the glass/substrate assembly is then remelted and, thereafter, subjected to a temperature of from 950 to 1,050 degrees centigrade for from about 25 to about 60 minutes.

FIELD OF THE INVENTION 
A process for the preparation of a tetragonal barium titanate film in which 
a specified mixture of a barium compound, a titanium compound, and a boron 
oxide glass forming compound are melted and rapidly quenched to form a 
glass, the glass is then placed upon a polycrystalline isostructural 
substrate, and the substrate/glass assembly is then remelted and subjected 
to a specified heat treatment. 
The process of this invention can be utilized to prepare a unique barium 
titanate glass-ceramic film with a thickness of from about 0.1 millimeter 
to about 1.5 millimeter. 
BACKGROUND OF THE INVENTION 
As is known to those skilled in the art, tetragonal barium titanate is 
useful for the production of capacitors, dielectrics, piezoelectrics, 
positive temperature coefficient resistance devices(PTCR's), sensors, and 
the like. 
For the aforementioned uses, tetragonal barium titanate should ideally be 
substantially pore free with substantially zero percent open porosity; a 
higher porosity barium titanate will generally have high energy losses and 
degradation of its desired properties. Furthermore, the barium titanate 
should also have a uniform microstructure with a controlled grain size on 
the order of from about 0.5 to 1.5 microns micron; barium titanate with a 
substantially different grain size will have substantially poorer 
properties. 
To the best of applicant's knowledge, a process for the production of 
tetragonal barium titanate glass-ceramic film containing barium titanate 
as the only crystalline material with a uniform microstructure on an 
isostructural substrate has not been provided by the prior art. 
It is an object of this invention to provide a process for the preparation 
of tetragonal barium titanate with a uniform microstructure of from about 
0.5 to about 1.5 microns in a controllable, reproducible manner. 
SUMMARY OF THE INVENTION 
In accordance with this invention, there is provided a process for 
preparing a tetragonal barium titanate film with a thickness of from about 
0.1 millimeter to about 1.5 millimeter, comprising the steps of 
sequentially: (a)providing a batch of from about 46 to about 54 mole 
percent of a barium compound, from about 18 to about 32 mole percent of a 
titanium compound, and from about 32 to about 18 mole percent of a a boron 
oxide glass former, wherein each of said reagents is calculated on the 
oxide basis in mole percent; (b)melting said batch at a temperature of 
from about 1300 to about 1400 degrees centigrade for from about 25 to 
about 40 minutes until it is molten; (c)reducing the temperature of the 
molten batch from the temperature of the melt to ambient temperature in a 
period of less than about 30 seconds, thereby producing glass; (d)placing 
the glass upon a polycrystalline isostructural substrate, thereby 
producing a substrate/glass assembly; (e)subjecting the substrate/glass 
assembly to a temperature of from about 1150 to about 1250 degrees 
centigrade for from about 10 to 30 minutes until the glass becomes molten 
and flows over the surface of the substrate; (f)reducing the temperature 
of the assembly to from about 950 to about 1,050 degrees centigrade; and 
(g)maintaining the temperature of the assembly at a temperature of from 
about 950 to about 1,050 degrees centigrade for from about 25 to about 60 
minutes. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS. 
The process of this invention allows one to produce a barium titanate with 
desired microstructure in a controllable, reproducible manner. In general, 
the process involves the steps of sequentially (1)providing a barium 
compound, a titanium compound, and a boron oxide glass former, (2)mixing 
said materials, (3)melting the batch, (4)rapidly quenching the melt, 
(5)transferring the cooled melt(glass) to an isostructural substrate, 
(6)reheating the substrate/glass assembly to the melting temperature of 
the glass, and (7)cooling to allow crystallization of the melt. 
The process of this invention produces tetragonal barium titanate. As is 
known to those skilled in the art, the term tetragonal refers to a system 
of crystallization having all three axes at right angles and the two 
lateral angles equal. Thus, with tetragonal barium titanate, the crystals 
have a form in which there are three mutually perpendicular axes, two of 
which are of equal length. 
In the first step of the process, a mixture of a barium compound, a 
titanium compound, and a boron oxide glass former is provided. 
Any barium compound which, after having been subjected to a melting 
temperature of from about 1100 to 1350 degrees centigrade, does not leave 
a residue of ions in the melt, can be used in the process. As used in this 
specification, the term "ions" includes any electrically charged atom, 
radical, or molecule, but it specifically excludes oxygen ions, barium 
ions, titanium ions, and boron ions. 
Thus, by way of illustration, barium oxide can be used in this process. 
Although barium and oxygen ions may be left in the melt, they are not 
"ions" within the meaning of this term as used in this case. 
Thus, by way of illustration, barium carbonate can be used. The carbonate 
portion of the molecule will form carbon dioxide and will leave the melt. 
The barium ions left in the melt are not ions within the meaning of this 
specification. 
Thus, for example, barium nitrate may be used; in this case, the nitrate 
portion of the molecule forms gaseous oxides of nitrogen which leave the 
melt. 
Thus, barium oxalate can be used; the oxalate portion of the compound forms 
gaseous oxides of carbon. 
Other barium compounds which can be used include barium hydroxide, barium 
peroxide, barium per-hydrateoxide, barium acetate, and the like. 
The preferred barium compounds are selected from the group consisting of 
barium oxide and barium carbonate. The most preferred barium compound is 
barium carbonate. 
It is preferred that the barium compound used in the process of this 
invention contain less than about 1.0 percent, by weight of barium 
compound, of impurity. It is preferred that the barium compound contain 
less than 0.75 percent, by weight, of impurity. In the most preferred 
embodiment, the barium compound contains less than 0.7 percent, by weight, 
of impurity. Thus, for example, in one embodiment, Fisher Certified Grade 
barium carbonate purchased from the Fisher Scientific Company of New 
Jersey was used. As used in this specification, the term Fisher Certified 
Grade refers to a reagent which meets or surpasses the most recent 
American Chemical Society Standard for purity. 
It is preferred that the barium compound have a particle size such that 100 
percent of its particles are smaller than 10 microns. 
The barium compound used in the process of this invention is mixed with a 
titanium compound selected from the group consisting of titanium dioxide, 
titanium monoxide, titanium sesquioxide, titanium oxalate, and mixtures 
thereof. The preferred titanium compound is titanium dioxide. The titanium 
compound preferably is reagent grade, with an impurity level less than 
about 0.1 percent by weight. It is preferred that the titania contain less 
than about 0.05 weight percent of impurity. It is most preferred that the 
titania contain less than about 0.02 weight percent of impurity. 
The titanium compound used in this process preferably has a particle size 
distribution such that 100 percent of its particles are finer than 10 
microns. 
The barium compound and the titanium compound are mixed with a boron oxide 
glass former. As those skilled in the art are aware, suitable boron oxide 
glass formers include boron oxide, boric acid, metaboric acid, tetraboric 
acid, mixtures thereof, and the like. 
The boron oxide glass former should preferably contain less than about 0.1 
weight percent of impurity and, more preferably, less than about 0.05 
weight percent of impurity. In the most preferred embodiment, the glass 
former is reagent grade material which contains less than about 0.03 
weight percent of impurity and has all of its particles smaller than about 
10 microns. 
The preferred boron oxide glass former is boric acid. 
Suitable amounts of the barium compound, the titanium compound, and the 
boron oxide glass former are mixed so that the mixture is comprised of 
from about 46 to about 54 percent, by total mole percent of the mixture, 
of barium compound, calculated on the oxide basis in cationic mol percent. 
As those skilled in the art are aware, one can calculate how many moles of 
barium oxide will be produced by a specified weight of barium compound at 
decomposition of the respective barium compound. Thus, for example, barium 
carbonate decomposes to barium oxide and carbon dioxide at a temperature 
of about 1,450 degrees centigrade, and each gram of barium carbonate 
yields about 0.78 grams of barium oxide; 153.33 grams of barium oxide are 
equal to one gram mole of barium oxide. The titanium compound and the 
boron oxide glass forming compound are also converted to the respective 
molar ratios of titanium oxide and boron oxide, and then the molar ratio 
of the barium oxide to the total moles of the all the oxides is 
calculated. Sufficient barium compound is used so that the barium oxide 
yield of the barium compound is from about 48 to about 52 mole percent. In 
one preferred embodiment, sufficient barium compound is used so that the 
barium oxide yield is about 50 mole percent. 
In addition to the barium compound, the mixture is also comprised of from 
about 18 to 32 mole percent of titanium oxide, also calculated from the 
titanium compound used. It is preferred that the mixture be comprised of 
22 to 28 mole percent of the titanium compound, on oxide basis. In one 
embodiment, the mixture is comprised of about 25 mole percent of the 
titanium compound, on oxide basis. 
The mixture is also comprised of from about 18 to about 32 mole percent of 
the boron oxide glass former, provided that the total sum of the oxide 
yields of the barium oxide, titanium oxide, and boron oxide equals 100, in 
mole percent. It is preferred that from about 22 to about 28 mole percent 
of the boron oxide glass former be used, calculated on the basis of oxide 
mole percent. 
Table 1 illustrates various mixtures which can be used in the process of 
this invention. 
TABLE l 
______________________________________ 
Mole Percent 
Mole Percent Mole Percent 
Composition 
Barium Oxide 
Titanium Dioxide 
Boron Oxide 
______________________________________ 
1 50 20 30 
2 50 25 25 
3 50 30 20 
4 48 25 27 
5 48 27 25 
6 50 18 32 
7 50 22 28 
______________________________________ 
Once suitable amounts of the barium compound, the titanium compound, and 
the boron oxide glass former have been weighed out, they are intimately 
mixed. These raw materials may be mixed by means well known to those 
skilled in the art. Thus, for example, the mixing processes disclosed on 
pages 21-30 to 21-38 of Perry and Chilton's "Chemical Engineers' 
Handbook," Fifth Edition (McGraw-Hill Book Company, New York, 1973), the 
disclosure of which is hereby incorporated by reference into this 
specification, may be used. 
If necessary, the mixture of reagents is ground by conventional communition 
means so that all of the particles in the mixture are smaller than about 
10 microns. 
The mixture thus provided in the first step of this process, often referred 
to as the "batch," is then melted at a temperature of from about 1300 to 
about 1400 degrees centigrade for from about 25 to about 40 minutes. It is 
preferred to melt the batch at a temperature of from about 1350 to about 
1375 degrees centigrade for from about 25 to about 35 minutes. In one 
preferred embodiment, the batch is melted for about 30 minutes at a 
temperature of about 1,370 degrees centigrade. 
The batch may be melted by means well known to those skilled in the art. 
Thus, for example, one may melt the batch in a platinum crucible, a 
platinum-gold crucible, and the like. Thus, one can use conventional glass 
melting refractory blocks to conduct the melting on a large scale 
involving tons of material. Other means of melting the batch will be 
apparent to those skilled n the art. 
The melting of the batch is continued until the batch is molten. One can 
determine when the batch is molten by visual means, by viscosity 
measurements, and by other means well known to those skilled in the art. 
Once the batch has melted, it is rapidly quenched by conventional means 
well known to those skilled in the art, thereby producing a glass. The 
quenching cools the melt suddenly so that its temperature is preferably 
reduced to ambient in about less than about 30 seconds and, more 
preferably, in less than about 15 seconds. 
The quenching may be conducted by means well known to those in the art. 
Thus, by way of illustration and not limitation, one can use the 
techniques disclosed by Andrew Herczog in his paper entitled 
"Microcrystalline BaTiO.sub.3 by Crystallization from Glass," Journal of 
the American Ceramic Society, Vol. 47, No. 3, pages 107-115 (Mar. 21, 
1964), the disclosure of which is hereby incorporated by reference into 
this specification. By way of illustration, one can pour the melt onto a 
plate of aluminum and roll it with an aluminum roller. Other suitable 
means of quenching will be apparent to those in the art. 
In one embodiment, the melt is rapidly quenched by fritting. As those 
skilled in the art are aware, the melt may be fritted by allowing the 
stream of molten glass to fall into water. Alternatively, one can expose 
the stream of molten glass to a blast of air and water, or pass the stream 
between water-cooled rolls. Suitable methods of fritting are disclosed in 
A. E. Dodd's "Dictionary of Cermaics..,".(Philosophical Library, Inc., New 
York, 1964), the disclosure of which is hereby incorporated by reference 
into this specification. 
The quenching of the melted batch produces pieces or strips of glass which 
generally are from about 1 to about 2 millimeters of uniform thickness. 
These pieces or strips of glass are placed onto an isostructural 
substrate. Alternatively, the strips or pieces of glass can be ground into 
a fine powder, and the powder then be transferred to the isostructural 
substrate. 
In one embodiment, the melt is quenched by fritting, thereby producing a 
frit which can be easily converted to a fine powder, and the fine powder 
thus produced is then transferred to a polycrystalline isostructural 
substrate for further processing. In general, the fine powder should have 
all of its particles smaller than about 10 microns. 
The term polycrystalline, as used in this specification, refers to a 
material which is composed of many crystals, which is an aggregate, as 
distinct from a single crystal. 
The term "isostructural," as used in this specification, refers to a 
material with the perovskite crystal structure. This perovskite crystal 
structure is described on page 67 of W. D. Kingery et al.'s "Introduction 
to Ceramics," Second Edition (John Wiley and Sons, New York, 1976), the 
disclosure of which is hereby incorporated by reference into this 
specification. As those skilled in the art are aware, some materials which 
exhibit the perovskite crystal include barium titanate, barium niobate, 
barium tantalate, strontium titanate, strontium niobate, strontim 
tantalate, lead titanate, calcium titanate, mixtures thereof, and the 
like. 
The preferred isostructural substrate is barium titanate, for it is the 
closest in structure to the barium titanate being produced by the process 
of this invention. This substrate is a solid material which is formed by 
sintering by conventional means. 
The polycrystalline barium titanate substrate may be produced by 
conventional means well known to those skilled in the art. Thus, for 
example, one can used solid state reaction synthesis, co-precipitation, 
sol-gel synthesis, and the like. 
The glass material produced by the rapid quenching is placed upon the 
polycrystalline isostructural substrate. If the glass material is in 
powder form, it is spread evenly over the substrate. If it is solid form, 
it is placed substantially evenly on the substrate. In either case, the 
substrate should be of large enough dimensions so that the glass material 
is within the boundaries of the substrate's surface and the film which 
forms upon the melting of the glass does not run outside the boundaries of 
the substrate. 
After the glass material is placed upon the substrate, it is subjected to a 
specified heat treatment in which it is first remelted for a specified 
period of time, and then subjected to a certain temperature for a 
specified period of time. 
The glass material on the substrate is generally remelted at a temperature 
of from about 1150 to about 1250 degrees centigrade for from about 10 to 
30 minutes until it molten and flows on the surface of the substrate. It 
is preferred to remelt the glass at a temperature of from 1175 to about 
1225 degrees centigrade for from about 15 to about 20 minutes. In one 
embodiment, the glass is remelted at a temperature of about 1,200 degrees 
centigrade for about 15 minutes. 
The remelting may be accomplished by means well known to those skilled in 
the art. Thus, for example, the substrate/glass assembly can be introduced 
into a furnace at the specified temperature. 
Once the glass has been remelted and is molten, it is then cooled to a 
temperature of from 950 to about 1,050 degrees centigrade. It is preferred 
to cool it to a temperature of from about 975 to about 1,025 degrees 
centigrade. In one embodiment, it is cooled to a temperature of about 
1,000 degrees centigrade. 
The glass can be cooled by means well known to those in the art. Thus, for 
example, one can reduce the set point of the furnace in which the 
substrate/glass assembly is being held. 
Once the substrate/glass assembly has been cooled to the specified 
temperature, it is then maintained at that temperature for a specified 
period. Thus, the assembly is maintained at a temperature of from about 
950 to about 1050 degrees centigrade for from about 25 to about 60 
minutes. It is preferred to maintain the assembly at a temperature of from 
about 975 to about 1,025 degrees centigrade for from about 30 to about 40 
minutes. In the most preferred embodiment, the assembly is maintained at a 
temperature of about 1,000 degrees centigrade for about 30 minutes. 
Thereafter, the assembly is allowed to cool and it is then processed for 
further use. 
In another embodiment of this invention, a barium titanate film is produced 
by a process in which the intermediate rapid quenching and remelting steps 
are omitted. In this embodiment, the same barium compound/titanium 
compound/boron oxide glass former compound mixture is provided. 
Thereafter, this batch is also melted at a temperature of from about 1300 
to about 1400 degrees centigrade for from about about 25 to about 40 
minutes; this melting occurs on the polycrystalline isostructural 
substrate defined above directly, without any intermediate melting or 
rapid quenching steps. Alternatively, the batch can be melted on a 
crucible and then poured onto the isostructural substrate. Thereafter, the 
melted material and the substrate are maintained at a temperature of from 
about 950 to about 1050 degrees centigrade for from about 25 to about 60 
minutes. 
In another embodiment of this invention, the aforementioned mixture of 
barium compound/titanium compound/boron oxide compound is provided, the 
mixture is melted at a temperature of from about 1300 to about 1400 
degrees centigrade for from about 25 to about 40 minutes, and a rod or 
tube made of isostructural material is inserted into the melt and used to 
draw fibers or rods from the melt. Alternatively, fibers can be extruded 
through dies comprised of isostructural material. 
In yet another embodiment of this invention, the barium compound/titanium 
compound/boron oxide glass former compound mixture described above is 
provided, melted, and rapidly quenched as described above to produce the 
glass. Thereafter, the glass is heat treated in a conventional heat 
treatment schedule without the isostructural substrate. Via such a 
process, barium titanate glass ceramics can be produced at a temperature 
of 850 degrees centigrade. However, the product produced is mixed and 
contains both barium titanate and barium borate. The product, however, 
does have all the advantage of a conventional glass ceramic. 
In yet another embodiment of this invention, the process is modified to 
produce superconducting glass ceramic materials. In this embodiment, a 
mixture of oxides in provided in a specified mole ratio to yield a 
required stoichiometry. Thereafter, this mixture is melted, rapidly 
quenched to yield a glass, remelted on an isostructural substrate, and 
cooled to crystallize the phase(s) known to superconduct in substantially 
the same manner as that described above.

The following examples are presented to illustrate the claimed invention 
but are not to be deemed limitative thereof. Unless otherwise specified, 
all parts are by weight and all temperatures are in degrees centrigrade. 
EXAMPLES 
Example 1 
8.7354 grams of Fisher Certified Grade barium carbonate (lot number 775836, 
available from the Fisher Scientific Company of New Jersey), 1.7719 grams 
of Fisher Certified Grade titanium dioxide (lot number 792740, available 
from Fisher Scientific Company) and 2.8009 grams of reagent grade boric 
acid (lot number 733530, available from Fisher Scientific) were charged 
into a mortar and thoroughly mixed with a pestle for about 30 minutes. 
This batch was then transferred to a Spec Mixer vibratory mill (Catalog 
number 8000, manufactured by Spec Industries, Inc. of Scotch Plains, N.J.) 
and mixed for 30 minutes. 
The mixed batch was then transferred to a platinum crucible. The crucible 
containing this batch was then inserted into a melting furnace (type 
51333, serial number 858019, manufactured by the Lindberg Company of 
Watertown, Wis.). The batch was heated to a temperature of 1370 degrees 
centigrade in the furnace and maintained at this temperature in the 
furnace for 30 minutes, at which time it was molten. 
The crucible containing the molten glass was lifted out of the furnace, and 
the melt was poured onto an aluminum plate which had a surface of about 
one square foot. The poured melt was simultaneously rolled with an 
aluminum roller with a diameter of about 2.0 inches and a length of about 
6.0 inches in order to cool it. Glass fragments were formed about 1 
millimeter thick and about 1.0 inch long. 
An isostructural substrate of barium titanate was prepared by solid state 
synthesis. 20 grams of reagent grade barium titanate (code 219-9, lot 
number MI-676, available from Transelco Division, Ferro Corporation, Pen 
Yam, N.Y.) were dry pressed into a disc about 1 centimeter in diameter and 
about 2 millimeters thick, using a steel die. The dry pressing was done on 
a Carver Laboratory Press, (Model M, Unit Serial Number 23505-414, made by 
Fred S. Carver, Inc. of Menomanee Falls, Wis.); A pressure of 5,000 pounds 
was applied for 30 seconds; no binder was used. The pressed disc was then 
sintered at a temperature of 1370 degrees centigrade for two hours in a 
high temperature furnace (type 46100, model number F46128C, serial number 
46100130, manufactured by the Thermodyne Corporation of Debuque, Iowa), 
thereby forming the substrate. 
The glass pieces were evenly distributed over the surface of the barium 
titanate substrate. The substrate/glass assembly thus produced was then 
placed back into the Thermodyne high temperature furnace which was at a 
temperature of 1200 degrees centigrade, and it was maintained at this 
temperature for 15 minutes. Thereafter, the furnace set point was reduced 
to 1,000 degrees centigrade. After the furance reached the 1,000 degree 
temperature, it was maintained at this temperature for 60 minutes. Then 
the furnace was shut off and allowed to cool. 
The barium titanate glass ceramic produced was evaluated by Powder X-Ray 
Diffraction on a Siemens D-500 Diffractometer (model number 
C72298-A223-B-9- POZ-288, manufactured by Siemens Company of West Germany) 
using copper K-alpha radiation and a diffracted beam graphite 
monocrometer. The results of this experiment are shown in Table 2. As can 
be seen from this data, the only crystalline phase in the sample is 
tetragonal barium titanate. 
TABLE 2 
______________________________________ 
d-observed (.ANG.) 
d-calculated (.ANG.) 
Rel. Int. 
hkl 
______________________________________ 
4.0278 4.0304 6 001 
3.9982 3.9934 11 100 
2.8382 2.8368 100 101 
2.3135 2.3127 24 111 
2.0516 2.0152 10 002 
1.9971 1.9967 19 200 
1.7873 1.7873 7 210 
1.6329 1.6328 21 211 
1.4185 1.4184 5 202 
1.4124 1.4119 8 220 
1.2731 1.2734 2 103 
1.2627 1.2628 4 310 
1.2046 1.2051 2 311 
1.1563 1.1563 2 222 
1.1083 1.1076 3 320 
1.0783 1.1083 3 213 
1.0699 1.0701 4 312 
1.0677 1.0677 4 321 
1.9710 0.9706 3 322 
0.9686 0.9686 2 410 
______________________________________ 
A sample of the barium titanate film also was subjected to differential 
scanning calorimetry on a 910 Differential Scanning Calorimeter using a 
9900 Computer/Thermal Analyzer (model number 910001-908, serial number 
1650, manufactured by E. I. DuPont de Nemours & Company, Wilmington, 
Del.). The sample showed a Curie temperature of about 124 degrees 
centigrade. The ferro to para transition was clearly visible. 
Another sample of the barium titnate film was observed under a secondary 
mode of an scanning electron miscroscope (type Autoscan, serial number 52, 
manufactured by the ETEC Corporation of Hayward, Calif.). A fine grained 
microstructure with a very narrow grain size distribution was observed. 
Example 2 
2 729 grams of barium oxide (stock number 0810, purchased from Apache 
Chemicals of Seward, Ill.), 1.549 grams of copper oxide (Fisher Certified 
Grade, lot 870578, purchased from Fisher Scientific of New Jersey), 0.4350 
grams of yttrium oxide (lot number Y-0-4-256, purchased from Research 
Chemicals of Phoenix, Ariz.), and 5.536 grams of boron oxide were charged 
into a mortar and thoroughly mixed for about 30 minutes. The batch was 
then transferred to a Spex Vibratory Mill (Catalog number 8000) and mixed 
for 30 minutes. The mixed batch was transferred to a slip cast silica 
crucible (type 138506, lot number 4-81-542, available from the Fireline 
Co., Ohio). 
The crucible containing the batch was inserted into a Fast Melt melting 
furnace (Serial number 6618-0287, available from Keith Company, Inc. of 
Pico Rivera, Calif.). The batch was heated to a temperature of 1300 
degrees centigrade and held at this temperature for 25 minutes, at which 
time it was molten. The crucible containing the molten batch was then 
taken out of the furnace, and the melt was poured onto an aluminum plate 
and roller quenched in accordance with the procedure of Example 1 to form 
glass fragments about 1 millimeter thick. 
Some of these glass fragments were transferred to a mortar and pestle and 
ground until they were fine, with a particle size less than about 50 
microns. 
4.779 grams grams of barium oxide, 1.715 grams of yttrium oxide, and 3.662 
grams of copper oxide were weighed and and mixed by the mortar and 
pestle/Spex Vibratory Mill procedure described above to form a second 
batch. 1.085 grams of the fine powder with particle size less than 50 
microns was mixed with 4.340 grams of the mixed oxides from this second 
batch in substantial accordance with the procedure described above, and 
this mixture was melted at 1,300 degrees centigrade for 20 minutes in the 
Fast Melt furnace. This glass mixture was then poured out and rapidly 
quenched in accorce with the procedure described above to form glass 
pieces about 1 millimeter thick. 
The glass pieces were transferred onto a platinum trauy and heat treated at 
800 to 950 degrees centigrade in the Thermotyne furnace. X-Ray Diffraction 
analysis was then conducted on the product obtained in accordance with the 
procedure of example 1. The product contained crystalline phases. 
In one embodiment of this invention, a mixture of reagents is used to 
prepare ceramic materials containing Ba.sub.2 YCu.sub.3 O.sub.7-x, a 
compound known to superconduct at or about the temperature of liquid 
nitrogen. In this embodiment, illustrated in Example 2, a mixture of 
oxides is provided is a specified composition ratio to yield a specified 
stoichiometry. Thereafter, this mixture is melted for about 30 minutes at 
a temperature of from about 1250 to about 1300 degrees centigrade, and it 
is thereafter rapidly quenched to yield a glass in accordance with the 
procedure described in other portions of this specification. The glass 
strips are then heat-treated to yield crystralline phases, one of which is 
the aforementioned 3/2/1 copper/barium/yttrium composition. 
Suitable amounts of any of the barium compounds listed in other portions of 
this specification may be used. The yttrium compound may be yttrium oxide, 
yttrium nitrate, yttrium oxalate, yttrium carbonate, yttrium hydroxide, 
and the like. The copper compound may be copper acetate, copper carbonate, 
cooper oxalate, copper oxide, and the like. 
After amounts suitable to obtain the correct stoichiometry of the copper 
compound, the yttrium compound, and the barium compound have been mixed, a 
glass former (called "base glass") is added. The glass former may be boron 
oxide or boric acid; if boric acid is used, it is normalized to yield 
boron oxide. The weight ratio of the glass former to the mixed oxide 
mixture is (u from about 1/2 to about 7/1. 
The mixture of the glass former/mixed oxides is mixed. Thereafter, in 
substantial accordance with the procedure of Example 1, this mixture is 
melted at a temperature of from about 1250 to about 1400 degrees 
centigrade for from about 20 to about 40 minutes and then rapidly quenched 
to yield strips of glass. The glass strips are then heat treated at 
temperatures of from about 750 to about 980 degrees centigrade to yield 
crystalline phases comprised of the 2/1/3 barium/yttrium/copper 
composition. 
In another embodiment, the glass-ceramic may be heated for from about 5 to 
about 20 hours to volatilize a large portion of the glass, leaving 
crystals of the crystalline phases on a substrate. 
In another embodiment, the final glass may be transferred to an 
isostructural substrate and further heat treatment may be conducted in 
accordance with the procedure described above. This process results in an 
enrichment of the Ba.sub.2 YCu.sub.3 O.sub.2-x compound in the glass 
ceramic. 
It is to be understood that the aforementioned description is illustrative 
only and that changes can be made in the apparatus, the ingredients and 
their proportions, and in the sequence of combinations and process steps 
as well as in other aspects of the invention discussed herein without 
departing from the scope of the invention as defined in the following 
claims.