DE1464462B1 - METHOD OF MANUFACTURING ELECTRIC CAPACITORS - Google Patents

Description

The invention relates to a method for producing electrical Capacitors, in which glass strips with metal foils alternate in a stack be built up and surrounded by an envelope made of glass and this Structures then fused under pressure to form a hermetically sealed body will.

A method for the production of capacitors is already known, in which preformed parts for the dielectric cladding and for the dielectric Intermediate layer (s) put together with the electrically conductive layers and the Parts of the envelope with the application of heat and pressure with one another and with the Connecting wires are fused (USA: Patent 2,696,577). According to the invention a capacitor is now to be developed using glasses that are can be converted into a glass crystal mixed body by heat treatment and here in the most economical way of working to a capacitor with the desired properties, as they would only provide ceramic interlayers per se.

The invention is not intended to be limited by use a special glass to get a condenser of particularly small dimensions, its layers between the metal layers with a corresponding increase in the Dielectric constants and dielectric strength the low required for this Have thickness dimensions, but also provide information on how to proceed has to get the desired result in the fastest and most economical way to get.

This is achieved according to the invention in a method for the production of electrical capacitors, in which glass strips with metal foils are alternately built into a stack and surrounded by an envelope made of glass, and this structure is then fused under pressure to form a hermetically sealed body, in that for the glass strips and the enveloping body, a composition of oxide-based, a total amount of 30 to 90 mol percent of the constituents of at least one ferroelectric oxygen octahedral compound from the group of BaT'03 CdT'03 NaNb03 KNb03 Cdo, 5Nb03 Sro, 5Nb03 Pbo, 5Nb03 Bao "Nb03 CdNb03_5 SrNb03.5 BaNb03,5 PbNb03,5 CdZr03 CaZr03 and PbZr03 and a glass-forming oxide from the class SiO2, B203 and P205 is used and the condenser is cooled after fusing, heated again and at a temperature between the peak temperature of the crystallization of the ferrite temperatures, until a sufficient of the lowest point of the is in the glass first melting drop of the DTA curve of the glass for a period of at least one hour at the lowest temperature, up to at least half a minute at the higher temperature for crystallization of the ferroelectric compound and then completely cooled.

A glass body that has good dielectric properties is became known (French patent specification 1,177,799), in which a mixture of ferroelectric octahedral compounds and glass-forming oxides with one another are fused, whereupon this material is brought into the desired shape. The finished molded body is cooled to a temperature that is between the peak temperature of crystallization and tempering temperatures is until has formed a sufficient number of crystal nuclei in the glass and then back to one Heated temperature at which the forming crystals have not yet re-formed to solve. This temperature is kept until the viscosity of the material at this temperature practically infinite due to the progressive crystal formation will.

As an example of this well-known doctrine, glasses are named, the one Develop lead titanate crystal phase during heat treatment. Such only at However, high temperature ferroelectric materials are for the purposes of the invention unusable, since lead titanate is only used at elevated temperatures in the range from 400 to 500 ° C ferroelectric properties and no useful ferroelectric property in the range between room temperature and working temperatures up to about 200 ° C. Mixtures of Ba0, TiO2, S'02 and A1203 are also given, the content of which is BaT'03 is less than 30 mole percent. The well-known glasses are for the purpose according to unsuitable for the invention.

Further advantages of the invention including a method for Manufacture of this capacitor as well as novel compositions for manufacture this capacitor by the process mentioned are to be used in the following with reference to the Drawings are explained in more detail.

The drawings show in FIG. 1 is a graphical representation for Reproduction of the relationship between the temperature in ° C and the dielectric constant Illustrative K of capacitor dielectrics according to the present invention the influence of fluorine in the composition of BaTi03, S'02 and A1203, FIG. 2 one of the F i g. 1 similar graph to show the effect of a additional stable oxide in the compositions; where the expression means "Stable oxide" is an oxide of a metal or a metalloid which is absorbed into the molten Glass composition for the capacitor according to the invention can be incorporated and without substantial losses through decomposition and / or volatilization in this Glass composition remains, FIG. 3 is a curve of a differential thermal analysis a glass composition consisting essentially of Ba0, T'02, SiO2 and A1203, being the approximate temperatures of the tempering point of the glass, the formation of the ferroelectric crystal phase in the glass and the melting of this phase as it progresses Increase in the temperatures of the glass are shown, F i g. 4 is a differential thermal analysis curve according to FIG. 3 for one consisting essentially of Ba0, T'02 and CaO existing Glass composition to reproduce the approximate temperatures of the tempering point, crystal phase formation and melting of the glass, FIG. 5 is a differential thermal analysis curve a glass composition consisting essentially of Nb205, Na20, CdO and S'02 showing the approximate temperatures of the tempering point, the crystal phase formation and melting the glass, FIG. 6 some curves to show the relationship between dielectric constant and temperature of some semi-crystalline bodies, F i g. 7 shows a section through a capacitor according to the invention.

It has been found that a ceramic body containing at least one ferroelectric crystalline phase with a high dielectric constant, which is to be referred to below in the usual way with K, a low loss factor (LT) and a high flashover voltage and a higher insulation resistance than in known products together with Other desirable physical and electrical properties are obtained when a glass body of the desired size and shape with oxide constituents which combine to form one or more such ferroelectric crystalline phases is subjected to controlled crystallization by heat treatment.

The new products have, because they are made from comogenic, from liquid melts produced glasses have a porosity that is practically zero, an optimal homogeneity and an even distribution of the crystalline phase or phases in very small particle size, so that their specific resistance at Temperatures up to 400 ° C reached values of 10'1 ohm cm and their dielectric constants and flashover voltages are unexpectedly higher than those of the bodies which consist of the same or substantially the same oxide compositions, however are bound and sintered by the known methods. The temperature at the Heat treating these products has an extraordinarily large effect on value of K of the capacitor manufactured in this way and. gives a comfortable and practical Means of its control.

In addition, the thermal expansion coefficients of the starting glass and the semi-crystalline product derived therefrom, at least in some cases so similar to each other that in relatively thin bodies, for example discs or layers, no breaking forces arise, so that these thin bodies can be seen locally can heat and crystallize to such different areas in different parts Achieve K values.

In these cases, any change in volume of the semicrystalline part during its crystallization due to the comparatively low viscosity of the surrounding glass occur, which for these glasses are above their softening point is characteristic and allows a readjustment of the volume.

As a rule, the glasses used in the invention soften without Crystallization at about 10 to 50 ° C or more below the temperature at which crystallization begins. This allows the one piece of glass to be fused with the other before their crystallization.

It has been found that the ferroelectric compounds before other phases at temperatures. in the total range of about 700 to 1100 ° C begin to shape and crystallize and that because of the low molding temperatures fewer defective crystals with a lack of oxygen in the method according to the invention are produced than in the known sintering process, what for the dielectric Properties of the product according to the invention means a further advantage. Further Another possibility of changing the compositions is possible, and you can apply electrodes made of silver or copper to the glass body and burn together with the body in the final semi-crystalline state, since in this temperature range these metal electrodes are not adversely affected will. Ferroelectric compounds can generally be divided into four classes subdivide those of the oxygen octahedron family, followed by an octahedral Arrangement of the oxygen ions in the crystal lattice is characterized here ceramic ferroelectrics mentioned (Proceedings of I. R. E., Vol. 43, p. 1738 to 1793, especially p. 1740).

The ferroelectric oxygen octahedron compounds, crystallographically as perovskite of the most important group, "pyrochlore", etc., as well as Mixtures thereof are particularly suitable for the purposes of the present invention.

Ferroelectric perovskite compounds have the general oxide formula AB03, where A and B are large and small radius ions, respectively, and the total their valences is 6 and individually either refer to the corresponding values 3 and 3, as for example in LaGa03, or on 2 and 4, as for example in BaT'03, or on 1 and 5 as calculated in NaNb03. In general, the A ions can be made from the 1st, 1st and 11I. Group of the periodic table and the B ions from the 1I. to V. group can be selected. Other ferroelectric oxygen octahedral compounds are for example CdNb206 and W03. Solid solution formation is among ferroelectrics widespread, and a structural excess or lack of oxygen related the octahedral shape can be determined by a suitable choice of the constituents of the solid solutions compensate.

Although the invention applies generally to the manufacture of capacitors is applicable which ferroelectric compounds of the oxygen octahedron families and mixtures thereof have bodies with perovskite-like ferroelectric Compounds, especially BaT'03, particularly advantageous properties, and the Invention is intended in the following for the sake of brevity, but not for Purposes of limitation and limitation with respect to such preferred capacitors, their compositions and the processes for their preparation are described in more detail will. As a result, the following dispute is primarily related on ferroelectric ceramic capacitors, in which the ferroelectric crystalline Phase BaT'03 is. However, the invention in its broad scope also includes capacitors, in which the crystalline phase or phases are one or more others ferroelectric compounds of the oxygen octahedron families or solid solutions or mixtures thereof, as can be seen from the compositions to be discussed later recognizes. For making a group of ferroelectric ceramics BaTi03 capacitors are built into the composition preferably Si02 and A1203 to promote glass formation. The addition of small amounts of fluorine improves the dielectric properties of the semi-crystalline product and the melt properties of the glass. It has been found to be the broadest range of such compositions based on oxide in cation. Mole percent 30 to 45% Ba0, 15 to 40% Ti02, 7 to 26% Si02, 3 to 30% AlO1.5, whereby the proportion of AlOl, s no longer differs from the proportion of Si02 differs than about four thirds of the amount of Si02, and consists of 0.5 to 1.5% fluorine, the total amount of Ba0, TiO2, SiO2, A101.5 and fluorine being at least 90%. The proportion of BaO should preferably be 0 to 100% in excess of the 1: 1 stoichiometric Equivalent of BaTi03 based on the amount of Ti02 present, where the excess is preferably higher as the proportion of T'02 decreases.

Cation. Mole percentages are used in the specified compositions in order to avoid inaccuracies resulting from calculating, on the assumed oxide basis, the mole percentages of compositions with an oxide containing two or more of a given cation. According to this method of determining the appropriate proportions, any given oxide formula expresses that it contains a metal atom as the cation. When individual elements in one of the compositions are in fluoride form, the cation. Mole percentage of the element still given on an oxide basis. The oxide components of such compositions make a total of 100 cations. Mol percent fluorine, calculated as F2, is specified separately and comes in cation. Mole percent of the total amount expressed. Since the fluorine content is very small, the error resulting therefrom is negligible.

A narrow range of compositions falling within the range given above, where the presence of fluorine is optional contains oxide based in cation. Mol percent 30 to 40% Ba0, 15 to 40% T'02, the amount of BaO being 0 to 100% in the excess of the 1: 1 stoichiometric equivalent of BaT'03 based on the amount of the T'02 present, and the lower the excess, the higher it is the amount of T'02 is 0.5 to 26% S'02 and 7 to 25% AIO "5, the amount of A101.5 does not differ by more than about four thirds from the amount of S'02, and the The total amount of Ba0, T'02, S'02 and A101.5 is at least 90%.

When using one of the compositions given above goes one pretends to melt them, cool them quickly to form a glass, and then the glass by heating it to preferably between 850 and 1150 ° C, for a Time of at least one hour at 850 ° C or at least 1/2 minute at 1150 ° C treated in heat to crystallize the glass 2: u. During a minimal warm time is essential, longer heating times are not disadvantageous, but for economic reasons Reasons undesirable. The ferroelectric resulting from this heat treatment The crystalline phase is BaT'03, whose advantageous dielectric advantages are known are. The ranges given above for the components Ba0, Ti02, S'02, A1203 and F are critical for the purposes of the present invention for the following reasons. As the desired dielectric properties of the capacitors in the first place depend on their proportions of crystalline BaTi03, leads to a substantial deviation of the minimum and maximum limit percentages of BaO and Ti02 given above to an undesirable reduction in the proportion of crystallized BaTi03 and thus the dielectric constant. An excess of BaO is required for optimal results up to 100% of the 1: 1 stoichiometric equivalent of the amount of T'02 present desirable, this excess apparently causing the formation of other titanium compounds, like that of titanium silicates of barium with a corresponding loss the advantageous properties of the BaTi03 prevented. This excess must be so be higher, the lower the amount of Ti02 is, in order to favor the formation of BaTi03 and hinder the formation of other undesirable crystal phases.

An excess of S'02 or a lack of AIO's above or below the specified limits further increases the tendency in the direction of the undesirable Formation of silicates and the resulting lowering of the value of K, however, too little S'02 or too much A10 causes,, 5 spontaneous devitrification of the molten composition regardless of the Speed of cooling. In order to make a satisfactory glass, should so the amount of A101.5 of the amount of S'02 does not exceed four thirds of the amount available Amount of S'02 may differ.

Although the presence of fluorine is optional when the amount of Ba0 and T'02 are close to their maxima, since it promotes the formation of BaT'03 and suppresses the formation of less desirable crystalline compounds, especially when the proportions of Ba0 and T'02 are high. Excessive amounts of fluorine make the glass sensitive to a reduction during the melting process, which results in a decrease in dielectric properties.

The fluorine is present in the glass as a metal fluoride, preferably as a fluoride of a metal of the I. or II. Periodic groups introduced, which are more thermally stable than others are fluorides. As a result of the fluctuations in their molecular weight changes the proportion of fluorine as such in this composition, depending on the metal. For the sake of clarity, both are in cation below. Mole percent indicated Compositions are the percentages of fluorine and oxide of the corresponding metal indicated separately. On this basis, the maximum amount of fluorine should be a proportion of about 1.5%.

To further illustrate the invention, compositions with BaT'03 as ferroelectric compounds, S'02 as glass-forming oxide and AlO1.5 are in cation within the above-mentioned ranges mentioned in Table 1 for carrying out the invention. Mol percent based on oxide, calculated from their mixtures, together with the time (in hours) and temperature ('C) of the heat treatment, as well as the dielectric constant K and the loss factor (L.7.) In percent of the finished ceramic body, each measured at 25 ° C, indicated. Table I. 1 2 3 4 5 6 7'- 8 BaO ................ .......... 44.3 31.2 35.7 37.8 33.4 36.6 36.4 36.1 Ti02 .......................... 22.5 23.0 28.2 32.3 19.7 35.0 35.2 36, 1 S'02 .......................... 15.6 21.4 16.5 14.9 21.7 13.2 9.9 16.7 A101.5 ......................... 16.2 23.3 17.2 13.7 23.7 13.9 17.2 9 ,8th F2 ... - ......................... 0.6 0.5 1.3 0.5 0.6 0.5 0, 6 0.6 CaO. . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 1.1 2.4 1.3 1.5 1.3 1.3 1.3 Excess Ba0,%. . . . . . . . . . . . . 97.0 35.6 26.6 17.0 69.6 4.6 3.4 - Hours ....................... 2 2 3 3, 2 2 2 2.5 ° C ............................ 1000 1000 925 925 925 1000 1075 915 K ............................. 240 260 820 1370 300 860 840 600 LT ........................... 1.5 2.8 3.1 2.8 3.2 3.1 2.9 2 , 4 Table I (continued) 9 10 11 12 13 14 15 16 BaO .......................... 36.1 36.7 36.7 36.8 36.9 37.9 35.2 33, 7th T'02 .......................... 31.8 32.4 32.4 32.5 32.5 32.0 37.4 36.9 S'02 .......................... 14.8 14.2 14.2 14.2 14.1 14.3 16.4 8.0 A101.5 ......................... 17.3 15.4 15.4 15.6 15.6 15.8 9.8 18 , 4 F2 ............................. - 0.6 0.6 0.6 0.5 0.7 1.2 1 , 2 CaO .......................... - 1.3 - - - - 1.2 3.0 Mg0 .......................... - - 1.3 - - - - - Zn0 .......................... - - - 0.9 - - - - Sr0 ........................... - - - - 0.9 - Excess Ba0, ° fo. . . . . . . . . . . . . 13.5 13.3 13.3 13.3 13.5 18.4 - - Excess T'02,%. . . . . . . . . . . . . - - - - - - 6.3 9.5 Hours ....................... 2 2 3 2 2 3 2 2 ° C ............................ 1075 1 075 1000 1075 1075 925 950 950 K ............................. 800 1340 1370 1220 1320 1350 500 1300 LT ........................... 3.6 3.0 2.9 3.2 2.5 2.8 2.2 1 , 2 The compositions for the capacitors according to the present invention are melted in pans, crucibles or containers for 1 to 8 hours or more at 1400 ° C. or above to produce homogeneous melts, depending on the size of the melt. Since the viscosities of the resulting glasses are generally comparatively low - they are on the order of 1 poise above 1400 ° C - refining the melts is not a problem and the use of refining agents in the baths is therefore unnecessary. The melting is preferably carried out under neutral or oxidizing conditions. If necessary, barium nitrate or other nitrates can be used as the oxidizing agent. The use of reducing agents worsens the dielectric properties. The preferred source of BaO is BaCO 3, which has the advantage that the CO 2 evolved maintains an equilibrium with its dissociation products CO and O, as a result of which the state of oxidation of the melt is stabilized.

These compositions crystallize spontaneously if one does not have the correct composition used and the glasses from a temperature above the liquefaction state in a few seconds, for example 2 to 10 seconds, cools to temperatures of about 700 ° C or below. The speed of the cooling process limits to some extent the strength of objects that can be removed from the can produce molten state. It has been found that the viscosity when molten is so low - it is on the order of 1 to 10 poise at 1350 to 1400 ° C - that the glasses are particularly suitable for production thin panes of glass by rolling them out.

Such thin glass panes are particularly suitable for dielectric layer bodies of capacitors, as can be seen from FIG. 7 recognizes why the thin glass layers can be alternately layered with metal foil strips in a manner known per se or coated with an electrically conductive coating before being layered together. The glass layers are then sealed to one another again by heating to 700 ° C. under pressure so that they enclose the metal layers (see US Pat. No. 2,405,529). The glass is then converted into the semicrystalline state by the heat treatment described above. According to Table 1, the basic compositions of Examples 4 and 9 to 14, inclusive, are similar to one another and differ in principle only in their fluorine proportions, composition 9 being free of fluorine and compositions 4 and 10 to 14 containing different metal fluorides. It can be seen that the introduction of fluorine into the glass leads to a substantial increase in the values of the dielectric constants and a small decrease in the dissipation factor. The change in the dielectric constant at room temperature is, however, small and not critical in the case of the particularly added metal fluoride. The curves according to FIG. 1 generally show the influence of the change in the TiO2 content in compositions with an excess of BaO and also the influence of the presence or absence of fluorine on the dielectric constant versus temperature in capacitor dielectrics made according to the invention and having the above composition. Examples 2, 3 and 11 of Table 1 contain fluorine and 23.0, 28.2 and 32.4 cation, respectively. Mole percent of TiO2 and are represented by curves 2, 3 and 11, while Example 9 is 31.3 cation. Mol percent Ti02, but does not contain fluorine and is shown by curve 9. Small changes in the heat treatment and / or in the Si02-A1203 ratio, BaO-Ti02 ratio and the fluorine content have an insignificant influence on the curves. The Curie point, which is indicated by the maximum value of K at around 120 ° C., can be determined for every curve 2, 3 and 11 and is in agreement with the known data for BaTi03 alone. A large difference in dielectric constant and Curie point is found in curve 9 compared to curve 11 and indicates that fluorine present promotes the formation of BaTiO 3 during the heat treatment of the glass compositions. The compositions 15 and 16 according to Table I contain an excess of TiO2.

In composition 14, fluorine was introduced as BaF2, of which the barium is included as Ba0 in the total Ba0.

In Fig. 2 graphs are shown which show the influence on the dielectric constant versus temperature caused by the addition of stable oxides to a semicrystalline body according to Example 10 of Table 1. Similar effects are produced by the same oxides when added to other Table I compositions. The amount of such oxides should be about 10 cation. Mole percent and preferably about 4 cation. Do not exceed mole percent either alone or together. In particular, curve A shows the composition according to Example 10 alone, and curves B, C, D, E and F in comparison show the same composition with the incorporation of stable oxides, as shown for example in Table 1I. There the individual columns mean: 1. The amount of the corresponding glass-forming oxides in cation added to the composition 10. Mole percent; 2. the corresponding dielectric constant K at 25 ° C, 3. the loss factor LT at 25 ° C; 4. the Curie point (CP) in ° C; 5. the dielectric constant K in the Curie-Purikt; 6. the type of curve A, B, C, D, E or F corresponding to the Curie point; 7. the maximum amount of oxide added, if marked with "best". The dielectric constant and the dissipation factor are measured at a frequency of 1 MHz. Table I1 Cation, mole percent K LT, of the added 25'C 250 ° C CP ICK for CP Curve type Comments Oxyds 1.2 KOo, 5 ...... 1100 2.5 120 1400 A - 3.6 Li0 0 .5. . .... 1 1 00 2.5 120 1400 A - 2.2 BeO ........ 1200 3.0 110 1900 A - 1.3 Mg0 ....... 1 700 3.0 50 1900 C best 2.9 CaO ....... 850 3.1 120 1 770 A - 1.6 Sr0. . . . . . . . 1 150 2.5 100 2050 AB - 2.7 Zn0 ....... 2350 0.5 15 2450 D best 1 , 3 CdO ....... 1500 3.1 105 2280 AB - 0.8 Ga01.5 ..... 1230 3.0 120 2250 A - 1,2In01,5 ...... 1520 2.7 80 1720 B - 0.2 T10, .5 ...... 1100 2.9 120 1850 A - 1.0 Y01.5 ...... 1140 3.3 120 2100 A - 1.2 La0 "5 ...... 1420 3.3 105 2300 AB - 0.9 Ce02 ....... 1340 3.0 90 1900 B - 1.3 Zr02 ....... 1400 2.8 80 1600 B - 1.0 Ge02 ....... 1250 2.9 110 2200 A - 1.3 Sn02 ....... 1700 2.8 50 2100 C best 1.4 Sb01.5 ...... 900 2.7 90 1350 B - 0.8 Bi01.5 ...... 780 3.4 150 1500 G - continuation Table 1I Cation, mole percent K LT, of the added 25'C 250 ° C_P 'C K for CP Curve type Comments Oxyds 1.8 vo "5 ...... 800 2.9 l20 1300 A - 1.2 Nb02.5 ..... 1500 2.1 80 2100 B - 0.4 Ta02.5 ..... 1250 2.8 120 1860 A - 0.8 Cr01.5 ..... . 820 2.8 105 1900 AB best 0.4M003 ...... 1250 2.8 120 2000 A - 0.2 W03 ....... l150 3.0 120 2100 A - 1.0 Te02 ....... 950 4.0 l20 1350 A - 0.4 U02 ....... 1050 2.5 105 1600 AB - 1.0 Mn01 " ..... 1050 0.6 65 l200 E best 0.6 Fe0 "5 ...... l500 3.3 80 2100 B best 0.7 Co0 ....... 1600 2.2 50 1750 C best 1.1 NiO ........ 1200 0.6 0 1230 F best 0.7 Pb0 ....... 1100 3.0 120 1950 A - 0.4 Cu0 ....... 1300 2.5 100 2350 AB best In some cases the changes in the Curie point due to the various oxides added are not more than 20 ° C, and the percentage of oxide added is not critical. Some of the added oxides, such as the oxides of Ca, B, Ga, P, As, TI, Y, Ge, In, Ce, Zr, Sb, Nb, Fe, Cd, La, Sn, Zn, Bi and PB, improve the glass former properties of the compositions and lower the temperature coefficient of the dielectric constant of the other products, and one can therefore advantageously add larger amounts, ie up to 10% of these oxides.

The addition of oxides of In, Ce, Zr, Sb, Nb or Fe lowers the Curie point to about 80 ° C., as can be seen from curve B in FIG. 2 recognizes the characteristic for compositions containing such oxides.

A generally between curves A and B , but shown in FIG. The curve not shown in Figure 2 is obtained by adding the oxides of Sr, Cd, La, Cr or Cu.

Curve C illustrates the influence of the addition of the oxides of Mg, Sn or Co, which lowers the Curie point in the vicinity of 50 ° C.

As can be seen from curve D, the addition of Zn0 creates Curie points close to room temperature and also significantly reduces the loss factor.

A low loss factor can also be achieved by adding oxides of Mn, as can be seen from curve E, and by adding an oxide of Ni, how to recognizes from the curve F.

The addition of an oxide of Bi, as indicated in Table II, increases the Curie point, as can be seen from curve G.

The temperatures to which the capacitors must be heated to convert your dielectric into ferroelectric semi-crystalline ceramic bodies, change with composition and are generally lower for the glass forming Compositions containing oxide B203 or mixtures of B203 and Si02 or P205. The correct heat treatment temperature also changes with the desired proportion the ferroelectric crystalline phase and the higher the higher the desired Amount of ferroelectric phase or phases. It is therefore impossible to have one Specify temperature or a temperature range common to all compositions is suitable or effective, but with the help of the well-known »differential thermal analysis or DTA method "according to" Differential Thermal Analysis: Theory and Practice "by W. J. S m o t h e r s, 1958, the approximate tempering and softening points and the Heat treatment temperature for each particular glass used for the condenser easily determine. After this procedure, the temperature becomes a small, one powdered sample of the heat-treated glass containing capsule slowly increased, and by means of a thermocouple inserted into the powdered glass, whose emf is that of a similar one, heated in the same way into an inert one Powder, for example A1203 thermocouple used counteracts, together with automatic temperature recording all endothermic and exothermic reactions recorded on a continuous strip inside the glass at its temperature, whose abscissa indicates the increasing temperature. As long as there is no reaction in the glass occurs, the differential is zero and the curve is essentially straight horizontal line. If the starting point of the glass is reached, then the beginning is a drop visible in the curve, which indicates the beginning of heat absorption. The temperature at the lowest point of this drop is then the softening point of the glass. This drop occurs in the range of about 500 to about 700 ° C for the present Glasses on. If the temperature is increased further, the endothermic reaction continues ends, then the curve returns to the horizontal, and at 50 to 150 ° C above At this point, an exothermic reaction occurs, which is a sudden and pronounced one Caused peak in the curve, which according to X-ray diffraction measurements, the crystallization of the ferroelectric compound as the primary crystalline phase. The separation the other crystallizable phases, if they are present, by appropriate, peaks following the first point are displayed. A few 100 ° above the temperature At the first peak, there is a drop in the curve which the first melting the crystalline phase reproduces. The appropriate range of heat treatment temperatures for the capacitors according to the invention is generally between the temperature the first DTA tip or crystallization of the ferroelectric crystalline phase and a temperature of about 50 ° C below the lowest point of the first melt drop. The time required for the heat treatment varies between one hour the peak temperature of crystallization of the ferroelectric phase to at least 1/2 minute at about 50 ° C below the lowest point of the first drop in enamel the DTA curve of the corresponding glass.

F i g. 3 shows the DTA curve for composition 4 according to Table I, which is typical for compositions with Ba0, Ti02, Si02 and A1203. It can be seen from the curve that the glass of composition 4 has a tempering point of about 670.degree. C., the ferroelectric crystalline phase crystallizes at about 820.degree. C. and the first melting point is about 1280.degree. It has been found that the broad overall range of temperatures suitable for heat treating such glasses and for each of the glasses generally described herein varies from the peak temperature of crystallization of the ferroelectric crystal phase to a temperature of about 50 ° C. below the first melting point drop of the DTA curve of the corresponding glass extends and that the optimal temperature lies in such a range between the tip of the ferroelectric crystal phase and the apex of the first melting point drop of this curve. For composition 4 it can be seen that this temperature range extends from about 820 to about 1230.degree. C. and that the optimum for achieving a high K value is about 1050.degree. By way of illustration, the approximate values for the tempering point, the peak temperature of the ferroelectric crystalline phase and the first melting point of each of the compositions 1 to 14 according to Table I are shown in Table III in ° C. Table III Peak temperature The starting point of the ferroelectric first Glass no. Crystalline phase melting 1 690 880 1270 2,680 860 1280 3 680 850 1280 4,670 820 1280 5 670 820 1260 6 680 830 1260 7 680 840 1280 8 670 830 1260 9 660 800 1270 10 670 830 1280 11 670 820 1270 12 660 800 1270 13 660 820 1280 14 660 790 1270 Although compositions with at least one ferroelectric composition, preferably BaTiO3, together with at least one glass-forming oxide, preferably SiO2, and an additional oxide, preferably A12031 are shown in the preferred compositions according to Table I, it has been found that compositions with at least one ferroelectric compound and at least one glass-forming oxide lead to good glasses which can be treated in the heat to achieve the desired capacitors according to the invention. Such compositions are in cation, for example, in Table IV. Mol percent given together with the corresponding values for K and LT for the resulting semi-crystalline products. Table IV 17 18 19 20 21 22 23 24 Ba0 .......................... 31.5 34.2 32.2 34.2 40.0 36.5 31.6 33, 8th Ti02 .......................... 56.3 44.7 32.2 40.9 33.3 36.5 31.6 33, 8th Si02 .......................... 12.2 - 11.9 3.8 13.4 8.3 - - B01.5 .......................... - 21.1 23.7 21.1 - - 18.4 15.2 P02.5 ......................... - - - - 13.3 18.7 18.4 17.2 Excess Ba0,%. . . . . . . . . . . . . . - - - - 20.1 - - - Excess TiO2,%. . . . . . . . . . . . . 70.8 30.7 - 19.5 - - - - K ............................. 42 47 40 68 35 45 115 63 LX,%. . . . . . . . . . . . . . . . . . . . . . . . . <1 0.8 8.0 1.0 <1 <1 <1 5.0 In compositions 17, 18 and 20 of Table IV, the corresponding amounts of TiO2 are 70.8, 30.7 and 19.5% in excess of the 1: 1 stoichiometric corresponding amount of BaO, which affects the meltability and favorable glass-forming properties Properties of these glasses. The compositions 19 to 24 are examples of glasses which individually contain two of the three glass-forming oxides SiO2, B203 and P205. The resulting increased amount of glass-forming oxide contributes to its glass-forming properties. Compositions 19, 22, 23 and 24 contain stoichiometric amounts of Ba0 and Ti02.

The compositions of Table 1I individually contain the oxide components of BaTi03 together with SiO2, A1203 and an oxide selected from the stable oxides of a large number of elements. These glass compositions result in semi-crystalline bodies with useful and desirable dielectric properties. It has also been found that a large number of glass compositions which, when heat treated in accordance with the present invention, provide useful semicrystalline products can be prepared by incorporating such stable oxides into compositions comprising oxide components of BaTiO 3 and a glass-forming oxide. Examples of such compositions, which consist of oxide components of BaTi03 and one of the glass-forming oxides Si02, B203 and P205 and the additional stable oxide, are shown in Table V in cation. Mole percent listed along with their corresponding values of K, LT . The compositions according to Table V all lead to glasses if their melts are cooled rapidly. Some of these compositions contain stoichiometric amounts of Ba0 and Ti0z, and the cation. Mol percentages are always the same in such cases. If either Ba0 or TiO2 is in excess over the stoichiometric amount, as is evident from the corresponding percentages given, then the percentage of such an excess can, if appropriate, be calculated using customary methods. Compositions in which the glass forming oxide is B203 are heat treated at about 850 ° C for 2 hours. All other compositions according to Table V are treated for 2.5 hours at about 1000 ° C. Table V 25 26 27 28 29 30 31 32 Ba0 .......... 31.8 28.4 30.4 35.2 31.8 35.2 31.8 33.6 Ti02 .......... 38.1 34.0 30.4 42.2 31.8 42.2 31.8 28.1 S'02 .......... 18.0 - - 12.7 - 12.7 - - B01.5 .......... - 27.8 - - 29.1 - 29.1 29.2 P02.5 ......... - - 31.3 - - - - - Cu0 .......... 12.1 9.8 7.9 - - - - - BeO ..........: - - - 9.9 7.3 - - - MgO .......... - - - - - 99 73 - Ca0 .......... - - - - - - - 9.1 K ............. 34 68 37 54 46 75 40 420 LT.,% ......... <1 5.0 <1 <1 <1 <1 <1 2.5 (Continuation) 33 34 35 36 37 38 39 40 r BaO .......... 32.9 28.1 33.6 31.8 30.4 32.7 29.3 28.1 T'02 .......... 26.6 28.1 28.1 31.8 30.4 32.7 29.3 28.1 S'02 .......... - - - - - 17.3 - - B01.5 .......... 31.7 - 29.2 29.1 - - 27.6 - P02.5 ......... - 29.2 - - 31.3 - - 29.2 Ca0 .......... 8.8 14.6 - - - - - - Zn0 .......... - - 9.1 - - - - - SrO ........... - - - 7.3 7.9 - - - Cd0 .......... - - - - - - - 17.3 13.8 14.6 K ............. - 63 79 540 32 250 200 55 LX%. . . . . . . . . - 1.5 1 1 1 1 2.5 1.3 (Continuation) 41 42 43 44 45 46 47 48 BaO .......... 26.0 40.0 31.6 31.5 34.2 32.5 31.5 34.8 _ T'02 .......... 31.2 33.3 31.6 37.8 40.8 38.9 37.8 34.8 S'02 .......... - 13.4 - 12.2 - - 12.2 - B01.5. . . . . . . . . . 16.2-18.4-21.1 20.3-20.3 Y0 "5 ......... 26.6 - - - - - - - A101.5 ......... - 13.3 18.4 - - - - - Zr02 .......... - - - 18.5 3.9 - - - Th02 .......... - - - - - 8.3 - - Ge02 ......... - - - - - - 18.5 10.1 K ............. 32 560 126 63 74 106 40 66 LX%. . . . . . . . . <1 1.7 1.7 1.1 0.9 2.5 <1 '0.9 Table V (continued) 49 50 51 52 53 54 55 56 Ba0 .......... 34.8 34.2 40.0 31.6 32.1 33.8 32.9 27.6 T'02 .......... 34.8 40.8 33.2 31.6 32.1 33.8 39.4 33.1 S'02 .......... - - 12.6 - 11.9 - - - B01.5. . . . . . . . . . 20.3 21.1 - 18.4 - - 20.3 - P02.5 ......... - - - - - 17.2 - 15.1 Sn02 .......... 10.1 - - - - - - - Pb0 .......... - 3.9 - - - - - - V02.5 ......... - - 13.2 18.4 - - - - Nb02.5 ........ - - - - 23.9 15.2 - - Ta02 "........ - - - - - - 7.4 24.2 K ............. 210 230 21 43 80 52 43 130 LX% ......... 3.6 <1 - <1 <1 <1 <1 3.0 (Continuation) 57 58 59 60 61 62 63 64 Ba0 .......... 31.6 24.5 32.9 34.2 31.5 34.8 31.5 34.2 T'02 .......... 3 1 , 6 24.5 39.4 40.8 37.8 34.8 37.8 40.8 S'02 .......... - - - - 12.2 - 12.2 - B01.5 .......... 18.4 - 20.3 21.1 - 20.3 - 21.1 P02.5 ......... - 25.5 - - - - - - Sb01.5 ......... 18.4 25.5 - - - - - - B'01.5 ......... - - 7.4 - - - - - M003 ......... - - - 3.9 - - - - W03 .......... ---- 18.510.1-- Te02. . . . . . . . . . - - - -. - - 18.5 3.9 K ............. 105 55 250 65 68 250 26 170 LT% ......... <1 1.5 <1 <1 <1 <1 - <1 (Continuation) 65 66 67 68 69 70 71 72 Ba0 .......... 39.9 30.9 28.1 32.0 34.7 35.2 30.4 35.2 T'02 .......... 39.9 36.1 28.1 38.4 34.7 42.2 30.4 42.2 S'02 .......... 13.4 - - 11.6 - 12.7 - 12.7 B01.5 .......... - 18.7 - - 20.4 - P02.5 ......... - - 29.1 - - - 31.3 - U02 .......... 6.8 - - - - - - - Mn0 "5 ........ - 15.3 14.7 - - - - - Fe01.5 ......... - - 18.0 10.2 - - - N'0 ........... - - - - - 9.9 7.9 - C00 .......... - - - - - - - 9.9 K ............. 68 28 33 65 42 28 23 52 LX% ......... <1 <1 <1 <1 <1 <1 <1 <1 ( Continuation) 73 74 Ba0 ................. 36.6 27.0 T'02 ................ 36.6 32.6 B01.5 ................ 21.4 - 73 74 I. P02.5. . . . . . . . . . . . . . . . - 30.1 65 C00 ................ 5.4 10.3 K ..: ................ 52 33 L. T, .............. <1 <1 F i g. 4 shows the DTA curve for composition 33 of Table V, which contains the oxide components of BaTiO3 and the glass-forming oxide B203. The temperatures of the corresponding drops and peaks of this curve are generally lower than the corresponding temperatures of the DTA curve of FIG. 3. From this curve it can be seen that the glass composition 33 has approximately a tempering point of about 530 ° C., the ferroelectric crystalline phase forms at about 660 ° C. and a first drop in melting point at about 970 ° C. is present. The total range of temperatures that is suitable for the heat treatment of this glass is between 660 and 920 ° C with an optimum at around 790 ° C.

The compositions according to Table VI are in cation. Mole percent stated and contain the oxide components of a variety of ferroelectric compounds including some or more of the titanate of barium or cadmium, the niobate of sodium or potassium or strontium or cadmium or barium or lead, the zirconate of cadmium or barium or lead, the tantalate of sodium or cadmium, the ferrate of lead or lanthanum, the germanate of iron or the oxide of tungsten, namely W03. After the heat treatment, each glass according to Table VI contains one or more such crystal phases (Hi Perm) showing a high dielectric constant. The most likely phases are given for the respective compositions. It is understood, however, that although all high dielectric constant showing crystalline phases or solid solutions may be given for the semicrystalline product of each composition, no attempt has been made to identify all of them here, on the other hand the high dielectric constants indicate the presence of one or more of those given in the table ferroelectric phases. In the finished semicrystalline state, the substances generally show hysteresis effects, which are characteristic of ferroelectric substances. Table VI 75 76 77 78 79 Nb02.5. . . . . . . . 42.7 45.0 40.3 41.3 45.8 NaOo "......... 28.3 29.7 27.0 27.6 14.9 CdO . . . . . . . . . . 7.1 7.4 6.8 6.9 7.2 BaO .......... - - 7.3 - - TiO2 .......... - - - 6.6 - KOo, S ......... - - - - 13.7 Si02. . . . . . . . . . 21.9 1 7.9 18.6 17.6 18.4 ° C ............ 1000 1000 1000 925 925 K ............. 375 590 520 990 308 LX% .. .. .. ... 2.4 2.1 1.6 1.5 2.6 Hi Perm- NaNb03 NaNb03 NaNb03 NaNb03 NaNb03 Crystal Cdo, 5Nb03 Cdo, 5Nb03 Cdo, 5Nb03 Cdo, 5Nb03 KNb03 phases CdNb03,5 CdNb03,5 Bao, 5Nb03 CdTi03 Cdo, 5Nb03 CdNb03 "CdNb03.5 CdNb03.5 BaNb03.5 (Continuation) 80 81 82 83 84 Nb02.5. . . . . . . . 42.6 43.5 40.5 29.8 - Na00.5. . . . . . . . 28.2 26; 6 29.6 33.8 - Cd0. . . . . . . . . . 7.0 7.1 9.8 7.2 - Ta02.5. . . . . . . . 3.5 - - - - Zr02 .......... - 4.5 - - - W03 .......... - - 2.0 12.7 44.5 Si02. . . . . . . . . . 18.7 18.3 18.1 16.5 - B0 "5 .......... - - - - 31.3 P02.5 ......... - - - - 18.2 ° C ............ 1000 1000 850 775 900 K ............. 1138 520 645 90 2100 LX%. . . . . . . . . 2.2 1.5 2.3 1.1 120 Hi Perm- NaNb03 NaNb03 NaNb03 NaNb03 W03 Crystal NaTa03 Cdo, 5Nb03 Cdo, 5Nb03 Cdo, 5Nb03 phases Cdo, 5Ta03 CdZr03 W03 W03 Table VI (continued) 85 86 87 88 89 Nb02.5 ........ - 34.0 45.1 39.6 18.3 CdO . ... . . . . . . 10.5 - - - - Zr03. . . . . . . . . . 30.0 - - - - Na0o, 5 ........ - - 22.6 - - BaO. . . . . :. . . . 10.3 11.1 - 10.4 - Pb0. . . . . . . . . . 23.8 12.5 11.3 10.2 36.2 SrO ........... - 10.5 - 8.8 - Fe01 "......... - - - - 18.3 A10,, 5. . . . . . . . . 5.2 16.2 - 2.3 - B01.5. . . . . . . . . . - - - 11.6 - S'02. . . . . . . . . . 20.2 15.7 21.0 17.1 27.2 F2. . . . . . . . . . . . . 1.1 2.0 - - - ............ ° C 925 1 000 1075 1000 850 K - .......... 161 148 214 1200 1 82 LX%. . . . . . . . . 1.0 0.1 1.4 3.7 3.0 Hi Penn- BaZr03 Bao, 5NbO3 NaNb03 Bao "Nb03 Pbo, 5Nb03 Crystal PbZr03 Sro "Nb03 Pbo, 5Nb03 Sro, 5Nb03 Pb2NbFe06 phases CdZr03 Pbo, 5Nb03 PbNb03,5 Pbo, 5Nb03 Pb2Nb201 BaNb03,5 BaNb03,5 PbNbo, 5Fe03 SrNb03.5 SrNb03 " PbNb03.5 PbNb03.5 (Continuation) 90 91 92 93 Nb02 @ 5. . . . . . . . . . . . . . . . . . . . . . . . 17.4 16.4 - - Na0o, 5. . . . . . . . . . . . . . . . . . . . . . . . 17.4 16.2 - - BaO. . . . . . . . . . . . . . . . . . . . . . . . . . 25.8 24.6 - - Fe01.5 ......................... - - 29.3 33.6 A101.5 ......................... 4.0 3.6, - - B 0.15 5.4 25.9 13.8 S'02. . . . . . . . . . . . . . . . . . . . . . . . . . -9.6 9.3 15.0 13.8 T'02 .......................... 25.8 24.5 - - La01.5 ......................... - - 29.8 34.1 Ge02 ......................... - - - 4.7 ° C ............................ 1000 850 900 850 K ............................. 401 165 1468 11,500 a Hi Perm crystal phases NaNb03 NaNb03 LaFe03 LaFe03 BaTi03 BaT'03 FeGe06 Bao "Nb03 Bao.sNbO3 BaNb03,5 BaNb0 "5 F i g. Figure 5 shows the DTA curve for composition 76 of Table VI, which contains the oxide components of NaNb03 and Cdo, 5Nb03 and the glass-forming oxide S'02.

The corresponding positions of the peaks and slopes of these curves roughly correspond to those of the DTA curve according to FIG. 3. It can be seen from the curve that the glass composition 76 has a tempering point at about 600.degree. C., has a first ferroelectric phase at about 690.degree. C. and shows a first melt drop at about 1170.degree. The total range of temperatures that are suitable for the heat treatment of this glass is between 690 and 1160 ° C, with an optimum at around 905 ° C. A heat treatment lasting 2 hours is required in order to achieve maximum crystallization at the optimal heat treatment temperature.

It is to be noted that the composition 90 according to table VI the forming oxides of the ferroelectric compounds BaT'03 and NaNb03 in their Total amount of 86.4 cation. Contains mole percent. The dielectrics for the capacitors according to the invention should preferably not more than 90% of the oxides forming ferroelectric compounds contain, as a small amount of a glassy phase or structure is desirable to that semi-crystalline body to give mechanical strength. On the other hand, the composition contains 5 after Table I a calculated total of only 39.4 cation. Mole percent BaTi03 and has a dielectric constant K = 300. Compositions with less than about 30 cation. Mole percent of the total constituent oxides of one or more ferroelectric Compounds have comparatively low dielectric constants, although they do still a good insulation resistance and a relatively high flashover voltage own.

In general, the capacitors according to the invention are characterized by an unusually high insulation resistance of up to ] 0 ohms at 400 ° C (composition 11 according to Table I) and flashover voltages of up to 4 - 10 ' volts direct current per centimeter or 2 - 105 volts alternating current per centimeter ( an average value of one of the most common compositions in the Ba0-Ti02-Si02-A1203 system). In the curves according to FIG. Figure 6 shows the dielectric constant as a function of temperature for semicrystalline products of a number of the compositions according to Table VI. The curves are indicated by the numerals of the respective compositions, and the temperatures. in which the corresponding compositions are treated in the heat in order to convert them into the semicrystalline state are also indicated. You can see it from the curves. that a variety of changes in capacitance with temperature can be obtained with the aid of the various compositions.

Claims (14)

Claims: 1. A method for the production of electrical capacitors, in which glass strips with metal foils are alternately built into a stack and surrounded by an envelope made of glass and this structure is then fused under pressure to form a hermetically sealed body, dad urchgeken nz eichnet that for the glass strips and the enveloping body, a composition of oxide-based, a total amount of 30 to 90 mol percent of the constituents of at least one ferroelectric oxygen octahedral compound from the group of BaTi03 CdTi03 NaNb03 KNbO3 Cdo, 5Nb03 Sro "NB03 Pbo, 5Nb03 Bao, 5Nb03 CdNb03.5 SrNb03.5 BaNb03.5 PbNb03.5 CdZr03 CaZr03 and PbZr03, and a glass-forming oxide from the class Si02, B203 and P205 is used and the capacitor is cooled after the fusing, reheated and at a temperature between the peak temperature of the crystallization of the ferroelectric compound and about 50 ° C below the lowest point of the first melt drop DTA curve of the glass for a period of at least one hour at the low temperature up to at least half a minute at the higher temperature for crystallization of the ferroelectric compound and then completely cooled. 2. The method according to claim 1, characterized in that as ferroelectric Oxygen octahedron compound perovskite, pyrochlore and mixtures thereof are used will. 3. The method according to claim 2, characterized in that as ferroelectric Oxygen octahedron compound BaTi03 is used. 4. The method according to claim 3, characterized in that a composition of, on an oxide basis, 30 to 90 Mol percent BaTi03, Si02 and at least 3 mol percent of a metal oxide from the group Cu0, Be0, Mg0, Cd0, AlO's Zr02, Ge02, V02.5, W03, Te02 and CoO is used. 5. The method according to claim 3, characterized in that a composition of essentially, on an oxide basis, 30 to 90 mole percent of the constituents of BaTi03, 3 to 30 mole percent of A101.5 and Si02 is used. 6. The method according to claim 3, characterized in that a composition of essentially, based on oxide, 30 to 90 mole percent of the ingredients BaTi03, 3 to 30 mole percent AIO, 5, up to 4 mol percent of an oxide of a metal from the class Na, K, Be, Mg, Ca, Sr, Zn, Cd, Ga, In, TI, Y, La, Ce, Zr, Ge, Sm, Sb, Bi, V, Nb, Ta, Cr, Mb, W, Te, U, Mn, Fe, Co, Ni, Pb and Cu and Si02 is used. 7. The method according to claim 5, characterized characterized in that it uses a composition containing 0.5 to 1.5 mole percent fluorine will. B. Method according to claims 1 to 3 when using B203 as glass-forming Oxide, characterized in that a composition is used that additionally to the forming oxides of BaTi03 and B203 at least 3 mol percent of a metal oxide of the class Cu0, Be0, Mg0, Ca0, Zn0, SrO, CdO, AIOl.s, YOI.s, Zr02, Th02, Ce02, Sn02, Contains Pb0, V02.5, Ta0 "5, Sb01.5, Bi0" 5, Mo03, W03, Te02, Mn01.5, Fe01.5, NiO and CoO. 9. The method according to claim 1 to 3 when using P205 as a glass-forming oxide, characterized in that a composition is used which additionally to the components of BaTi03 and P205 at least 3 mol percent of a metal oxide of the class Cu0, Ca0, SrO, Cd0, Nb02,5 and Ta02 "contains. 10. The method according to claim 2, characterized in that a niobate from the ferroelectric compound Class NaNb03, KNb03, is used. 11. The method according to claim 2, characterized in that as a ferroelectric compound a metaniobate from the class CdNb03.5, SrNb03 ", BaNb03.5 and PbNb03.5 is used. 12. The method according to claim 2, characterized in that that as a ferroelectric compound a zirconate from the class CdZr03, BaZr03 and PbZr03 is used. 13. The method according to claim 1, characterized in that that the ferroelectric compound with tungsten oxide is used. 14. Procedure according to one or more of the preceding claims, characterized in that a composition, on an oxide basis and in mole percent, at 30 to 45% Ba0, 15 to 40% Ti02, the amount of Ba0 to 100% in excess over the 1: 1 stoichiometric The equivalent of BaTi03 based on the amount of Ti02 present is 7 up to 26% S'02, 3 to 30% AlO "s, the amount of A101.5 being from the amount of Si02 does not differ by more than about four thirds of the amount of Si02, and 0.5 to 1.50% F, where the total amount of Ba0, TiO2, Si02, AlO "s and F is at least 90%, melted, the melt is preformed into glass strips and enveloping bodies, these fused with metal foils to form a condenser and cooled, and the condenser by heating to temperatures between 850 and 1150 ° C for a period of at least half a minute at 1150 ° C to crystallize the glass is treated.