US2931712A - Method of growing synthetic quartz - Google Patents

Description

April 1960 'r. J. TUROBINSKI 2,931,712

METHOD OF GROWING SYNTHETIC QUARTZ Filed May 27, 1955 INVENTOR. A THADDEUS J.TUROB|NSK| igs) ATTORNEY METHOD GROWENG SYNTHETIC QUARTZ Thaddeus .i. Turohinski, Cleveland Heights,- Ohio, assignor to Clevite Corporation, Cleveland, Ohio, a corporation of Ghio Application May 27, 1955, Serial No. 511,667

2 Claims. (11. 23-301 the copending application of Hans Jatle and Thaddeus I. Turobinski, Serial No. 459,052, filed September 29, 1954, and assigned to the same assignee a's the present invention. A i

' In the following specification the Standards on Piezoelectric Crystals (1949) of the Institute of Radio Engineers as set forth in the Proceedings of the I.R.E., vol. 37, pp. 1378-1395, are adhered to. i 1

Broadly speaking, a Y-bar seed is one which is elongated in the direction of the Y crystal axis and has a width and thickness, i.e., cross-sectional dimensions, much smaller than its length, for example, in the ratio of l to 20 or more. A Y-bar crystal is one grown from 'Y-bar seed and is similar in length to the seed but larger in the other dimensions.

The term extra-length or extended is used herein to describe Y-bar seeds and/or crystals having a length in the direction of the Y-crystal axis exceeding that which it has been possible to obtain heretofore in electronically useful quality from either natural or synthetic quartz crystals.

As set forth in detail in the aforementioned applica- -tion, quartz crystal plates have for many years been used extensively as frequency-controlling elements in-r'adio frequency oscillators, electrical filters, and the'like. In consequence of the continuing and growing requirements of the electronics industry for such plates much research and development work has been performed in an effort to evolve methods and appparatus for synthesizing large single crystals of quartz from which such plates may be fabricated.

Among the more important recent advances in the quartz crystal growing field wasthe discovery and development of the Y-bar seed fully disclosed in the abovementioned application.

The length of the Y-bar seed (within the limits imposed by availability as hereinafter explained) and the period of crystal growth are so selected thatthe resulting Y-bar crystal is characterized by a unique and highly advantageous configuration in which the primary prism faces, which retard growthand render large sections of ordinary quartz crystals unusuable for cutting into plates, develop only to a moderate extent during the growing period. Consequently, Y-bar crystals properly grown according to the disclosure of the aforesaid Letters Patent No. 2,923,605 are elongated in the direction of the Y crystal axis and possess an intermediate portion of substantially rectangular cross-section i'n the plane of the X and 2 crystal axes, which portion extends for about 4 inches of the customary 6 inch length of such crystals.

'Thus the intermediate portion of the Y-bar crystalap proximates a regularly shaped block or rectangular parallelepiped of quartz about 4 inches long practically all of. which is usable for crystal plate blanks;-for example, the entire block may be cut along spaced parallel planes disposed at an angle of about 35 15' to the Z crystal axis to obtain the extensively used AT plates.

While the Y-bar seed and the crystals grown therefrom are significant improvements over previously known seeds and crystal shapes as regards the proportion of usable quartz in a crystal, the ratio of crystal to seed weight, and the number of crystal plate blanks that can be cut from a single crystal, there is still room for considera ble improvement in the way of increased yields of usable material and decreased production costs.

The length of the Y-b'ar seed available up to the time of the present invention extending as it does transverse- 1y to the '2 crystal axis, that is, between opposite m faces of the single crystal from which it is cut, is limited by the relatively small dimension of a single quartz crystal in the direction of the Y crystal axis. Since natural quartz crystals of electronic grade, as well as those synthetically produced, having a dimension of more than six inches in the Y direction are rare, they are correspondingly expensive, costing hundreds or thousands of dollars for a single good specimen. Crystals of electronically useful quality having a Y axis dimension much in excess of eight inches are hardly obtainable at any price. The foregoing factors have concomitantly limited the length of available Y-bar seeds to approximately six inches.

In a crystal 6 inches long, the usable intermediate portion is only about 4 inches in length. The ends of the crystal, representing about /3 its total length, develop the characteristic rhombohedral faces during the growing process and consequently, much of this must be trimmed as scrap.

painstaking set-up work in order to cut up a block of material only' 4 inches long; the entire procedure must be repeated for each crystal to be cut into plates.

Another handicap characterizing the present production of synthetic-quartz crystals is the fact that each seed mustbe individually loaded into a seed holder for,placement in an autoclave, for example, as described in United States Letters Patent No. 2,675,303 granted to Andrew Sobek and Danforth R. Hale and assigned to the same assignee as the present invention. Inasmuch as production considerations require large autoclaves and presently obtainable seeds are only 6 to 8 inches in length, a

single run may require the loading of 200 or more individual seeds into suitable holders.

In accordance with the present invention the difficulties and disadvantages outlined above are overcome by the provision and use of a novel, and improved Y-bar" quartz. seed which is limited in length solely by pracproperly oriented, to grow a single Y-bar crystal of extended length. which may be used as a source of seedto grow additional extra-length seed material and/or crystals.

More specifically extra-length crystals of quartz are obtained according to the present invention from two .or

more Y-bar s eed s placed in end-to-end contact with their corresponding atomic planes aligned; splinting' the joint cut from the same mother crystal.

between the seeds with crystal so as to preclude relative movement therebetween; and exposing the seeds, s'o splinted, to a chemical and physical environment conducive to crystal growth, as hereinafter described in detail.

With the foregoing state of the art in view, it is a fundamental object of the present invention to provide novel and improved methods and means for the production of synthetic single crystals of quartz.

Another object of the invention is the provision of extra-length Y-bar type synthetic quartz crystals and seeds.

. Still another object of the invention resides in the provision of a method for uniting individual quartz crystal "seeds with .axes aligned in the Y-directio'n to form single seeds of extra-length from which single Y bar crystals of comparable length may be grown.

A further object of the invention is to provide novel and improved methods for the synthesizing of quartz crystals wherein a higher percentage of quartz usable for crystal plate fabrication is obtained on the grown crys- 'tals.

A further object of the invention is the provision of novel methods of synthesizing quartz single crystals which may be more quickly, easily, and less-expensively fabricated into crystal plates.

These and ancillary objects of the invention and the manner of their accomplishment will be clearly apparent to those conversant with the art from a reading of the following description and subjoined claims in conjunction with the annexed drawing wherein like reference characters denote like parts throughout the several views and wherein,

Figure 1 is a perspective elevational view of a pair of quartz Y-bar seed bodies fastened together and immobilized by a crystal splint, in the manner of the presem invention;

Figure 2 is a view similar to Figure 1 showing the same seeds after having been subjected to a conventional cryst'al-growing environment;

Figure 3 is a view similar to Figures 1 and 2 showing the same seeds subsequent to trimming; and

Figure 4 is a perspective elevational view of a composite Y-b'ar crystal grown in accordance with the precepts of the present invention. I

Referring now to the drawings, Figure 1 shows a pair of conventional Y-bar seed bodies and 12 each having its Y crystal axis so designated. The seed bodies are necessarily of the same handedness and preferably are Each of the seed bodies which, in any practical application of the invention foreseen at the present time would be substantially identical, is in the form of an elongated rectangular parallelepiped having mutually perpendicular pairs of substantially parallel major longitudinal surfaces designated by reference numerals 14, 16, 18, and 20 for seed body 10 and 14', 16, 18', and 20 for seed body 12. For purposes of the present disclosure faces 14 and 18 of seed body 10 and 14 and 18' of seed body 12 are arbitrarily designated the Z surfaces of the crystal, i.e., surfaces perpendicular to the Z crystal axis, while 16, 20, 16' and 20' are X surfaces, being perpendicular to'the X crystal axis. The X, Y and Z crystal axes, appropriate ly marked, are shown in Figures 1, 2 and 3 of the draw ing. It is pointed out at this time as a matter of importance that Y-bar seeds grow fastest and at the same rate on both Z surfaces, and at a slower and dissimilar rate on respective +X and X faces.

In general practice of the invention, seed bodies 10 and 12 would be about 6 inches long and about .04 square inch in cross section. The ends to be joined are suitably trimmed to provide complementary end surfaces thereon and with the seed bodies 10 and 12 thus pre-' ment as possible. Due to the difference in growth rates or the X+ and X- surfaces of the seed bodies, the corresponding ones of these surfaces should be matched when the seed bodies are aligned. A simple and expeditious method for accomplishing this important alignment of atomic planes and surfaces is part of the disclosure of United States Letters Patent No. 2,914,383 issued on the application of W. H. Charbonnet, Serial No. 511,614, filed on even date herewith and assigned to the same assignee as'the present invention.

With the seed bodies aligned as described above, the next step of the novel process is to immobilize the mating ends of the bodies so as to preclude any relative movement thereof in order that they be maintained in the same relative position throughout the growing process.

In the present illustrative embodiment of the invention this is accomplished by means of one or more splints, two being shown at 24 and 26, which are placed on opposite surfaces, either X or Z, of the seed bodies overlapping equally on both sides of the interface 22 between the abutting ends thereof.

. Splints 24 and 26 take the form of quartz crystal plates suitably shaped to conform to the surfaces on which they are disposed and are securely fastened in position as by binding with numerous turns of silver wire 28, or equivalent means.

The seed bars, so prepared and appearing as shown in Figure 1, are placed in any suitable seed holder and subjected to a chemical and physical environment 'conducive to crystal growth. Ordinarily, growth of the crystal would be accomplished under conditions of high temperature and pressure in an autoclave as described in United States Letters Patent 2,675,303 referred to herein'above but it is to be understood that any operative method and apparatus for growing synthetic quartz crystals presently known or hereinafter discovered may be availed of.

After a suitable growing period, for example about 6 weeks, the spliced seed bodies will have grown together to form an integral piece of quartz substantially as shown in Figure 2. It will be noted that the interface 22 may still be in evidence and the splint plates 24 and 26 have partially dissolved and assumed an irregular shape partly merged with but for the most part discernibly distinct from the seed bars. On the free ends of the seed bars the characteristic rhombohedral and prism faces 30 have started to form and the entire composite seed has been enlarged by growth on the exposed surfaces.

The new growth on the spliced seed, as it appears in Figure 2 is trimmed by cutting and/ or lapping to remove all irregularities and unevenness so as to produce an elongated composite seed bar with smooth flat surfaces substantially as shown in Figure 3. From this figure it will be clearly evident that the composite seed bar 1012 is similar to a single Y-bar seed cut from a single crystal except for its dimensions, its length being approximately twice that of the single bar, and the presence of a visible remanent of the joint at the interface 22.

The composite seed, so prepared and appearing gem erally as shown in Figure 3 is once again subjected to conditions conducive to crystal growth and allowed to grow for a substantial period of time, for example, about 6 weeks or until suificient growth has taken place to permit cutting extra-length seeds from the crystal. At this stage, the crystal appears generally as shown in Figure 4. It will be noted that the joint at interface 22 (shown in dotted line) is substantially coextensive with the cross-section of the two original seed bars 10 and 12 and may appear as a cleavage plane in the composite crystal. The new growth, however, is continuous over the entire length of the crystal and displays no discontinuity due to the presence of the joint in the composite jse'ed bar. 1 p

, While satisfactory AT cut plates can now be cut from the extended length crystal, the initial crystal would logically be used as a source of extra-length seed bars which could be grown in any conventional manner to produce additional extra-length crystals. It will be apparent that a single extra-long crystal obtained from spliced Y-bar seeds as described above would be the unlimited source of any desired number of extra-length seeds. Thus, the splicing procedure need be carried out only once to obtain seeds twice the usual length. Seeds of greater than double length can be obtained either by splicing two or more double length seeds in the same manner as already described or by splicing any reasonable number of conventional length seeds in the first instance. In this connection, it is pointed out that while the above description has been concerned with the joining of the two seeds, this has been merely for convenience of illustration and description and that the invention is in no way limited as to the number of'seeds which are spliced, originally or subsequently.

The advantages of extra-length seeds and crystals are of great economic importance. The longer seeds simplify the process of loading autoclaves by reducing the number of individual seeds whichmust be prepared for growing and loaded into seed holders. able space within the autoclave may be more efiiciently utilized, less volume being occupied by seed holders thus allowing an increase in the volume of seed materialand with a concomitant increase in the yield of quartz per autoclave run.

The longer crystals greatly reduce the amount of set up time required to cut a given number of plates as already explained above and effect important reductions in the amount of waste material per crystal.

be approximately 6 inches in total length as grown. In cutting the crystal into plates the unusable ends bearing the rhombohedral and prism faces are trimmed ofi, leaving a block of crystal about four inches long for fabrication into plates. Thus, up to about 33% of a 6-inch Y-bar crystal is waste. A 12-inch Y-bar still has only two ends, and the 2 inches of waste material resulting therefrom constitutes only about 17% of the crystal length. As the length of the crystal increases, the percentage of waste becomes more and more insignificant. Of equal importance is the fact that increasingly larger numbers of plates can be cut for each crystal-mounting and set-up procedure. Therefore, the longer crystals would be of advantage even if the increase in percentage of usable material is disregarded.

The length of seeds which may be evolved from repeated splicing of Y-bars according to the present in- In addition, the avail- For example, a conventional synthetic quartz Y-bar crystal may vention is limited only by practical considerations involved in handling, growing, cutting, etc.

While there has been described what at present is believed to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claims all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A method of splicing quartz-crystal Y-bar seed bodies comprising: disposing the seed bodies to be joined in end-to-end abutment with their corresponding atomic planes aligned; splinting the joint between said seed bodies with crystal so as to preclude relative movement therebetween; and exposing said seed bodies so splinted to a chemical and physical environment conducive to crystal growth until the seed bodies and splinting crystal have grown together.

2. A method of growing extra lengthsynthetic single crystals of quartz comprising: disposing a plurality of 'Y-bar seed bodies cut from the same crystal in end-toend abutment with their Y crystal axes aligned and corresponding major longitudinal faces matched and disposed in common planes; splinting the joint with crystal; exposing said seed bodies, while so disposed and maintained, to conditions conducive to crystal growth until said seed bodies have grown together into a single com- References Cited in the file of this patent UNITED STATES PATENTS 1,958,014 Nicolson May 8, 1934 2,047,252 Bloomenthal July 14,1936 2,546,305 Jafie et al. .....I Mar. 27, 1951 2,674,520 Sobek etal. Apr. 6, 1954 2,675,303 Sobek Apr. 13, 1954 OTHER REFER EN CES Beane: Marconi Review," v01. XVI, #111, 4th Quarter, 1953, pages and 158.

Claims (1)

1. A METHOD OF SPLICING QUARTZ-CRYSTAL Y-BAR SEED BODIES COMPRISING: DISPOSING THE SEED BODIES TO BE JOINED IN END-TO-END ABUTMENT WITH THEIR CORRESPONDING ATOMIC PLANES, ALIGNED, SPLINTING THE JOIJNT BETWEEN SAID SEED BODIES WITH CRYSTAL SO AS TO PRECLUDE RELATIVE MOVEMENT THEREBETWEEN, AND EXPOSING SAID SEED BODIES SO SPLINTED TO A CHEMICAL AND PHYSICAL ENVIRONMENT CONDUCTIVE TO CRYSTAL GROWTH UNTIL THE SEED BODIES AND SPLINTING CRYSTAL HAVE GROWN TOGETHER.

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