US1886234A - Method of making high grade dielectric materials - Google Patents

Description

Nov. 1, 1932. A. MEISSNER 1,386,234

METHOD OF MAKING HIGH GRADE DIELECTRIC MATERIALS Filed Nov. 19, 1928 INVENTOR ALEXAND R EISSNER BY Wl/L/ ATTORNEY Patented Nov. 1, 1932 UNITED STATES PATENT OFFICE ALEXANDER MEISSNER, OF BERLIN, GERMANY, ASSIGNOR TO TELEFUNKEN GESELL- SCHAF'L FDR DRAHTLOSE TELEGRAPHIE MLB. H., OF BERLIN GERMANY, A CORPORA- TION F GERMANY METHOD 0! MAKING HIGH GRADE DIELECTRIC MATERIALS Application filed November 19, 1928, Serial No. 320,549, and in Germany December 21, 1927.

cation of percussions, pressures, or for the production of electric actions, by the supply of thermal energy, etc.

As is generally known dielectric materials possessing these properties are not at present easily obtainable,-and when obtained are expensive. Especially is this true of piezo-electric crystals which are found only'in the natural state and which must be put through an expensive process of grinding and finish- 9 ing before they have the desired electrical characteristics. Considerable research at great expense has been made to obtain material which possesses the above characteristics, but which can be obtained in large quantities at less expense. Heretofore, such research has met with slight success.

Briefly, the primary object of this invention is to provide a method by which at. small expense dielectric material possessing all of the desirable features enumerated above may be roduced.

complete understanding of my novel method and the various advantages gained by the use thereof will be had from the following specification, and therefrom when read in connection with the drawing which serve to illustrate the invention and its application.

Whether or not a given dielectric material is suited for these or similar objects depends essentially upon its structure, which in turn depends largely upon the orientation of the electric moments of the different molecular complexes or aggregations of the material. I have found by experiment that when finely divided quartz is submitted to the action of an electric field so that the constituent particles are caused, by action of this electric field, to become orientated in a definite sense, and if then these bodies are held together in some suitable manner, say, by the admixture of a convenient binder or cement such as paraffin or the like, there results a dielectric body which, as regards its piezoelectric actions, substantially excels the normal quartz body or crystal. Similarly, finely divided turmaline may be used.

This invention consists in the generalization of my novel method in connection with the production of dielectric materials, and according to my invention dielectric and more particularly piezo-electric bodies or substances in finely subdivided form, say, in powdered or pulverulent condition, are submitted to an electric field so that the constituent particles become orientated in the same sense as regards their electrical mo ments. This metho d may suitably be carried into practice in the presence of strong heating or else bythe applicationof strong pressures. The purpose in the case of several substances of applying pressure or heat maybe to cause the constituent particles to unite with one another so that they are caused to hold together and form a homogeneous body without the use of accessory substances.

However, as pointed out before, it is also possible by the addition of a hinder or cement to hold the constituent particles orientated under the influence of the electric field together.

The molecules or molecule complexes of Idielectric substances show polar characteris- Figure 1 shows the basic molecule complex of the so-called unit cell. of the quartz. From the inspection of this unit cell may be deducted that, observed in the projection, there are always disposed side by side in alternating manner positive and negative ions (atoms). This shows itself externally if quartz powder, in a state which allows a movement of its particle with respect toone another, is subjected to a directional force which may, for instance, be produced by an electric field. In this case the polar axes of the particles then arrange themselves mainly in the direc-' tion of the external electric field and maintain subsequently this direction. Exteriorly this straightening out may be recognized by together as a uniform body the fact that the solidified mass has. received a distinct piezo-electric moment. The individual bodies are suitably held together after the assuming of their directions insome manner-gor other, for instance by the admixture of a suitable binding agent, such as paraflin, resin, asphaltum or the like. The admixture of the binding agent may be accomplished in liquid form, whereby the mass is made to solidify by means of a subsequent treatment by temperature or pressure. But lt 1S also feasible to add the binding mass in powderform, for instance,.to'the quartz powder. In this manner there is produceda dielectric body which considerably excels the standard quartz body with respect to its piezo-electric eflt'ects. Now, the present invention consists in the generalizing of this process for the preparation of dielectrics and this in the manner that in accordance with the invention dielectric bodies, particularly piezo-electric bodies in finely divided form, hence perhaps as powder, are subjected to an electric field so that the individual bodies are directed with respect to their electric moments in the same sense. This process may suitably be accomplished accompanied by a simultaneous strong heating or also using high pressures. Various substances may be prepared by pressure or heating so that the individual particles bind to one another so that they keep without the addition of a special substance. But, as said before, it is also possible, by the admixtures of a binding agent, to keep together the individual particles arranged in one direction under the influence of the electric field. For use as piezo-electric oscillators it suits the purpose best to prepare such dielectrics in thin layers. Such layers may then be provided in the various apparatuses with elec trodes, connected in numbers in parallel or in series in order to thereby increase the piezo-electric action. As is known, such layers provided with electrodes are arranged for the purpose of obtaining a strong piezo-electric efi'ect above one another and subjected to the same pressure. Dielectric layers which have been prepared according to the above indicated method, produce a strong pyro-electric action whereby with the use of several layers all may simultaneously be heated together, or cooled together. 4

Figure 2 shows an arrangement for the preparation of dielectric layers. The quartz powder Q, mixed with a powdery binding agent, falls through a heating device A on the base support, suitably moved slowly past this device, striking the said support as thin layer and hardening thereon. The electric iiglignment is accomplished by the condensers In using the term fpowder to designate the state of the particles of dielectric substance and of the, binder when used therewith, it will be understood that the size of the particles of dielectric and/or of binder may vary in size through a wide range and still be defined by the term powder. Asize of .2 mm has been used with excellent results.

When used as piezo-electric oscillators it is of advantage to make dielectric materials of the kind here disclosed in thin laminae. Laminae of this kind provided with electrodes as required for various devices may be connected in parallel or in series in order to thus increase the piezo-electric effects. It is known from the earlier art that, in order to insure a marked piezo-electric action, a plurality of electrode-equipped layers or laminae may be superposed and be acted upon by the same pressure source. Dielectric laminae made according to the above method also result in a marked pyro-electric effect, and if a plurality of layers are employed, all of the latter may be jointly heated or cooled.

Having now fully described my novel method what I desire to protect by Letters Patent is:

1. A synthetic piezo-electric crystal, composed of powder like dielectric particles, the electrical axes of which are orientated in similar sense.

2. A piezo-electric crystal composed of a plurality of layers of synthetic piezo-electrie laminae.

3. The method of preparing a piezo-electrio crystal from pulverized quartz particles which includes permanently orienting such particles with reference to their electric moment in a definite sense.

ALEXANDER MEISSNER.

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