DE1771697C2 - Piezoelectric ceramics - Google Patents

Description

Pb (Zn ₁ Z ₃ Nb ₂ ^ Ti ₅ Zr ₂ O ₃

. · Ι λλι λ ,,.

consists, where x + y + z = \ is, χ between 0.01 and 0.500, y between 0.125 and 0.750 and ζ between 0.125 and 0.865, thereby geke ηη-ζ calibrate η et that they additionally contain a combination of 0, 1 to 5% by weight NiO and 0.1 to 5% by weight MnO ₂ , with the proviso that the sum of their proportions is a maximum of 7%.

2. Use of the piezoelectric ceramic according to claim 1 as an active element for one electromechanical converter.

On the other hand, when using piezoelek ceramics as a filter, it is desirable that the _{value for the mechanical}

and a high electromechanical uMJ _{Fmer have to}

^ a great persistence with

_{Temperature and} time in terms of resonance and other electrical properties.

Ale viplversDrechende pottery with regard to Als ^ ™ ^ ^eC . _{Lead titanium} t-lead zirconate has been in et. However, it is a ^ _{high mechanical} quality factor

g, nianaren Konnlun "

together with «™ ^m ^ ütoit ^ SkoÄeS" coefficients for the Ble.titanat Ble.znkonat Kera-

^mi SodektSche ceramics of the basic together-PiczoeleKtriscne jvciam

Settlement

Pb (Zn ₁ J ₃ Nb ₂ Z ₃ ) O ₃ -PbTiO ₃ -PbZrOs

The invention relates to piezoelectric ceramics, in particular new ferroelectric ceramics which are polycrystalline aggregates of certain components. These piezoelectric ceramics are sintered by ceramic techniques known per se and then polarized by applying a direct voltage between the electrodes, as a result of which electromechanical transducer properties are imparted in accordance with the known piezoelectric effect. ? The invention further relates dit use of piezoelectric ceramics in electromechanical ^W Di 'erfindünesgemäße ceramics hauptsächlieh fistln from a solution of the ternary system, without further additives are known (DT-AS 16 46 698, GB-PS 11 16 510); Such ceramics also do not have nearly a good combination of a high quality factor and a high planar coupling coefficient. . .

A _US of DT-AS 1116 742 is a ceramic material called the basis of the system

PhZrO PbTiO PbSnO ₃ -PbZrO ₃ -PbHO ₃

with additions of E «« o «d. Ngdox ^ d and KobaU oxide from 0.01 to 1.0G ^ · ". *« tonnt, a Mod 1-

zation with emer ^^^^^^ f ^ plus manganese oxide is not provided From J. Amer. Ceram. Soc 49, p. 577 b ^ 582! (1961Ust it known the ternary system of composition

Pb (Mg _1/3 Nb _2/3 ) O ₃ - Pb 11U ₃ -

PWZn, Nb, 10 -
Pb ^ n _1/3 Nb _2/3 jU ₃

PbZrO ₃ ,

which has been modified with combined MnO ₂ and NiO additives up to a maximum of 7% by weight.

The application of piezoelectric materials in the various fields of application for transducers Production, measurement and determination of the sense of direction of a sound, a shock, a vibration, a pressure etc. is constantly increasing. Both crystal and ceramic types are widely used. Because of the lower cost and ease of manufacture in various shapes and sizes and their Greater resistance to high temperature and / or humidity compared to crystalline Piezoelectric ceramics have found materials like Rochelle's salt in numerous fields of application increasingly important for converters.

The requirements for the piezoelectric properties of ceramics change depending on the application. For example, require electromechanical Transducers, such as a pickup and a microphone, have piezoelectric ceramics that pass through a fairly high electromechanical coupling coefficient and a fairly high dielectric constant are excellent.

_4Y .

50 with additions of NK), Cr ₂ O ₃ , Fe ₂ O ₃ , MnO ₂ and CoO. Open..thch it is be. This known ceramic is very difficult _{to achieve both high planar coupling coefficients and} high mechanical quality factors at low firing temperatures. The best results at a firing temperature of 1260 C are a coupling coefficient of 0.553 and a mechanical good factor of 2OM. Ceramics based on the ternary system

Pb (Mg ₁ Z ₃ Nb _{2 3} ) O ₃ - Pb 11U ₃ - 1 bz, ru ₃

are furthermore in J. Amcr Ceram ooe 48 (1965), Pp. 630 to 635, as well as vol. 4SI (1966; pp. 5/7 to 582 of the GB-PS 10 66 752 and US-PS 32 68 4d3.

The invention was based on the object of developing new

to develop improved piezoelectric ceramics, which is characterized by an advantageous combination of a high mechanical quality factor and a high distinguish piezoelectric coupling coefficient should, with which at the same time piezoelectric ceramics were aimed at, with which certain properties can be adapted to the various applications. After all, that was also the aim of the invention the use of the new ceramics as active components in electromechanical converters.

The object on which the invention is based has been achieved with the new piezoelectric ceramic, which

mainly from a solid solution of three components according to the formula

consists, where χ + y -τ ζ - I , χ between 0.01 and OpOO, y between 0.125 and 0.750 and ζ between 0.125 and 0.865, which is characterized in that it is additionally a combination of 0.1 to 5 Contains percent by weight NiO and 0.1 to 5% by weight MnO ₂ , with the proviso that the sum of their proportions is a maximum of 7 % .

The progress that can be achieved with the new ceramic compared to ceramics of the same basic composition (DT-AS 16 46 698) or ceramics, as described by DT-AS 11 16 742, is off can be seen in the following table.

additive

Firing temperature

( ⁰ C)

comment

No

0.5 wt% NiO
0.5 wt% MnO ₂
0.1 wt% NiO

98 0.481 1240
2124 0.67 1210
- 0.56 1270

S The invention is blasphemed with reference to the drawings, in which
% F i g. 1 is a cross-sectional view of an electrical

■ "! mechanical transducer shows

^l * JF i g. Figure 2 is a three-sided composite diagram of materials that can be used in accordance with the present invention;

■ *> F i g. 3 and 4 graphical representations of the effect

^L i of additional quantities on the mechanical quality factor \ (Q _m ) and the planar coupling coefficient (K _p )

>" of ceramics of the invention at 20 ⁰ C and 1 KiIo-

\ hertz are.

In Fig. 1, numeral 7 denotes an electromechanical converter, which is preferably an active component disc-shaped body 1 made of piezoelectric

-i has a ceramic material of the invention.

The body is electrostatically polarized and equipped with a pair of electrodes 2 and 3, which are inserted into attached to the opposite surfaces of the body 1 in a suitable and per se usual manner are. The lead wires 5 and 6 are conductive to the electrodes 2 and 3 by means of a solder 4 connected. If the ceramic is subjected to a shock, vibration or other mechanical impact is exposed, the resulting electrical line can be picked up by the lead wires 5 and 6 will. On the other hand, as with other piezoelectric transducers, the application of an electrical Stress at the electrodes S and 6 a mechanical deformation of the ceramic body. It goes without saying that the expression "electromechanical converter", as it is used here, is in its broadest Meaning is to be understood and piezoelectric filters, frequency control devices and the like that the invention is applied to and adapted to various other fields of application materials with dielectric piezo-., electrical and / or electrostrictive properties

^ ■ 'require.

'*'. It has been found that the ternary system consists of

Pb (Zn ₁₁₃ Nb ₂ Z ₃ ) O ₃ , PbTiO ₃ and PbZrO ₃

-has a morphotropic phase boundary and that the piezoelectric property is close to the morpho-

? "■■ 'ironic pottery is excellent. The present DT-AS 16 46 698

present patent application, example 22

DT-AS 11 16 742, table II, column 10

The invention is based on the finding that, within special areas of the ternary basic system, the _{samples modified with common MnO 2} and NiO additives have a very high mechanical quality factor in conjunction with a high planar coupling coefficient.

The present invention has several advantages in the manufacture of ceramic transducers and application to ceramic transducers. It is known that the evaporation of PbO during firing is a problem in sintering lead compounds such as lead titanate zirconate. However, the ceramic according to the invention has a lower proportion of vaporized lead than conventional lead titanate zirconate. The ternary system can be fired without special control of the PbO atmosphere. A well sintered body of the invention is obtained by firing in a ceramic crucible with a cover _{made of Al 2} O _3. A high sintering density is desirable in order to obtain moisture resistance and high piezoelectric responsiveness when the sintered body is to be used as a resonator and the like.
All sorts of ceramics that can be found within the ter-

nary system

Pb (Zn _1/3 Nb _{s 3} ) O ₃ - PbTiO ₃ - PbZrO ₃

are represented by the three-sided diagram, the F i g. 2 of the drawings. However, some of the ceramics represented by the diagram do not have high piezoelectricity and many are only electromechanically active to a negligible extent. The present invention relates only to those ceramics which have piezoelectric responsiveness of substantial magnitude. For the sake of simplicity, the planar coupling coefficient (K _p ) of the test disks is taken as a measure of the piezoelectric activity. Thus, within the range indicated by the points A BCDE (FIG. 2), which constituents range from O ₁ O O to 0.500 mol percent

Pb (Zn ₁₃ Nb ₂₁₃ ) O ₃ ,

0.125 to 0.750 mole percent of PbTiO ₃ and 0.125 bi: 0.865 Moiprozent PbZiO ₃ includes connecting lines is limited, all polarized and tested

Ceramics have a planar coupling coefficient of about 0.1 or higher. In particular, show the ceramics in the area of the diagram by the points FGHIJK (Fig. 2), which components from 0.010 to 0.375 mol percent of Pb (Zn ₁ Z ₃ Nb ₂ Z ₃ ) Os, 0.250 to O _s 625 mol percent of PbTiO ₃ and 0.250 to 0.625 mole percent of PbZrO ₃ , is bounded by connecting lines, (! in planar coupling coefficients of approximately 0.3 or higher. The mole percentages of the three components of the ceramics ABCDEFGHIJK are as follows:

Pb (Zn ₁ ^ Nb ₈ Z ₃ ) O ₃ PbTiO ₃ PbZrO ₃ A. 1.0 62.5 36.5 B. 12.5 75.0 12.5 C. 50.0 37.5 12.5 D. 50.0 12.5 37.5 E. 1.0 12.5 86.5 F. 1.0 50.0 49.0 G 12.5 62.5 25.0 H 37.5 37.5 25.0 I. 37.5 25.0 37.5 J 12.5 25.0 62.5 K 1.0 36.5 62.5

Furthermore, the compositions result in close to the morphotropic phase boundary, in particular

Pb (Zn, _{/ 3} Nb ₂ , ₃ ) ₀ , 3, ₅ Ti ₀ ,: _{13 Zr 0> 295} O ₃ ,
Pb (Zni _{/ 3} Nb _{2/3) 0> i,} Ti Zr _{0i36 0i44} O ₃ and
Pb (Zn ₁₁₃ Nb ₂ Z ₃ ) O ₁₀₇ Ti _0-11 Zr _0-49 O ₃

ceramic products with a planar coupling coefficient of 0.56 and higher.

It has been found that the addition of joint additions of nickel oxide and manganese oxide, the Q _m and the K _{p of} the ternary solid solution defined by the polygonal area in FIG. 2, which consists of three components, according to the formula

where ν '■ y \ ζ \ ,. χ between 0.010 and 0.500, ν between 0.125 and 0.750 and ζ between 0.125 and 0.o (S5 is larger than a single addition of nickel oxide and magnesium oxide. An effective combination of the additives contains 0.1 to 5 percent by weight nickel oxide (NiOi and O ₁ I to 5 weight percent manganese oxide (MnO ₂ ).

/ ur imcluig a high Q _m and a high λ _ρ ; : ·. '■ _ ■; ur: ·. ::;: · _ ■ ,, ü,; l · u. ··. mentioned combination of *> ° / lisät / c on nickel oxide and manganese oxide has a weight ratio of 0.2 to 10. Effective weight levels of the mentioned combination are no more; i! Sd ⁿ "1 in addition of the mentioned combination \ on more than *. 7 (icuicht per cent reduces Ick iii (th K ₁ , and clearly the Q _{m of} the ternary fixed I i'Minp. I ine advantageous improvement of the K _p and Q _n , Jer; crn; iren fixed 1 osunp. Which by the polygonal area FGHIJK in Fig. 2, which consists of three components according to the formula

Pb (Zn ₁ Z ₃ Nb ₂₁₃ ) ^ Ti ₁₁ Zr ₂ O ₃ ,
5

wherein χ + y + ζ = 1 , χ between 0.010 and 0.375, y between 0.250 and 0.625 and ζ between 0.250 and 0.625 can be defined and contained therein by using 0.5 to 1 weight percent of the

ίο to be added combination of NiO and MnO ₂ in a weight ratio of 0.5 to 2 can be achieved. The table below shows the beneficial effects of additives.

The piezoelectric ceramics can be produced by various ceramic processes known per se. One advantageous method is to use PbO or Pb ₃ O ₄ , ZnO, Nb ₂ O ₆ , TiO ₂ , MnO ₂ and NiO.

The starting materials, namely lead oxide (PbO), zinc

»0 oxide (ZnO), niobium pentoxide (Nb ₂ O ₆ ), titanium dioxide (TiO ₂ ), zirconium dioxide (ZrO ₂ ), MnO ₂ and NiO ₁ , all of a relative degree of purity (e.g. of the degree: chemically pure) intimately mixed with distilled water in a rubber-lined ball mill.

Some care must be taken when grinding the mixture to avoid contamination Avoid wear and tear on the grinding balls or stones, unless the proportions are in the ingredients changed in such a way that it compensates for an impurity

will.

After wet milling, the mixture is dried and mixed to ensure that the mixture is as homogeneous as possible. The mixture is then brought into the desired shapes in a suitable manner by a pressure of 400 kg / cm ^2. The compacts are preheated with calcination at a temperature of about 850 ° C. for 2 hours.

After calcination, the reacted material is allowed to cool and then it is ground into one small particle size. Again, this must be done carefully steps are taken to avoid contamination from wear and tear on the grinding balls or stones, unless the proportions of the constituents are changed in such a way that an impurity

is retired. Depending inter alia on the desired shapes, a mixture or a slurry can be formed from the material which is suitable for pressing, slide casting or extrusion, depending on the individual case, according to ceramic processes known per se. The examples which are the data given below were prepared by mixing 200 g of the ground, presintered mixture with 10 cm ^{3 of} distilled water. The mixture then became slices

of 20 mm in diameter and 2 mm in thickness with a pressure of 700 kg / cm ² . The pressed disks were fired at a temperature shown in the table for a heating time of 45 minutes. After the present

- ...- v. _{i £} . uv v, j !!!,. in tiluiuti 11t.11, uic gepreuier

Burning disks in a PbO atmosphere and is not a special oversight of temperature rise required in the furnace compared to the prior art. So can after the present

Invention uniform and excellent "piezoelectric ceramic products in a convenient manner by simply covering the samples with a clay earth crucible are preserved.

at Desired composition additions in NOK Brenn 24 hours after the P < game Basic composition Weight percent no temperature Mechanical Planar MnO ₂ 1.0 Figure of merit Coupling
koeffa no - ( ⁰ C) Qn, ■ 1 Pb (Zn _{l / 3} Nb _2/3) o. ₂ Ti _0i36 Zr _{0> 44} 03 - 1.0 1220 253 0.56 ^% 2 the same 0.1 - 1190 259 0.67 3 the same 0.1 1.0 1210 712 0.57 4th the same 0.2 - 1210 1150 0.68 5 the same 0.2 1.0 1210 1100 0.59 6th the same 0.5 - 1190 1632 0.69 7th the same 0.5 1.0 1210 1797 0.60 8th the same 1.0 - 1190 1998 0.66 9 the same 1.0 1.0 1210 1605 0.57 10 the same 3.0 - 1190 1802 0.63 11th the same 3.0 1.0 1190 950 0.45 12th the same 5.0 - 1190 1163 0.49 13th the same 5.0 1.0 1170 504 0.42 14th the same 7.0 0.1 1190 652 0.45 15th desrl. 7.0 0.1 1150 298 0.39 16 the same - 0.2 1170 335 0.40 17th the same 0.5 0.2 1210 258 0.60 18th the same - 0.5 1210 1870 0.63 19th the same 0.5 0.5 1210 260 0.62 20th the same - 1.0 1210 1996 0.64 21 the same 0.5 3.0 1210 265 0.69 22nd the same 0.5 3.0 1210 2124 0.67 23 the same - 5.0 1190 2002 0.66 24 the same 0.5 5.0 1190 270 0.63 25th the same - 7.0 1190 1915 0.62 26th the same 0.5 7.0 1190 281 0.59 27 the same - no 1190 1870 0.57 28 the same 0.5 0.5 1190 288 0.55 29 the same no 0.5 1190 1540 0.53 30th Pb (Zn _{i; 3} Nb _2/3 ) or similar ₃₇₅ Ti _0i33 Zr _0i2e5 0 ₃ - 0.5 1200 135 0.60 31 the same 0.5 1.0 1200 139 0.66 32 the same 1.0 1.0 1200 1698 0.65 33 the same - no 1200 1860 0.61 34 the same 0.5 - 1200 127 0.68 35 the same no 0.5 1200 1625 0.66 36 Pb (Zn ₁₃ Nb ₂ Za) ₀₁₀₇ Ti ₀₁₄₄ Zr ₀₁₄₉ O ₃ 0.5 - 1220 143 0.61 37 the same 0.5 0.5 1220 1190 0.58 38 the same 1.0 1220 1352 0.60 39 the same 1.0 1220 1304 0.53 40 the same 1220 1493 0.55

ίο

The sintered ceramics are ground on both surfaces up to a thickness of one millimeter. The ground disc surfaces can then be coated with silver paint and under formation be burned by silver electrodes. Eventually the panes become polarized while they are in a bath made of silicone oil at 100 ° C. A direct current voltage gradient of 4 kilovolts per millimeter is held for 1 hour and the disks come to room temperature in 30 minutes cooled by a field (field-cooled).

The piezoelectric and dielectric properties of the polarized samples are _{measured at 20 C in a relative humidity of 50 ° 0} and at a frequency of 1 kilohertz. The measurement of the piezoelectric properties was made with the IRE standard equipment, and the planar coupling coefficient was determined by the resonance frequency and anti-resonance frequency method. Examples of specific ceramics according to the invention and various suitable and electromechanical and dielectric properties of these compositions are given in the table and some of these values are shown in FIG. 3 and 4 to illustrate the changes caused by the additions. Piezoelectric ceramics without additives and with only one additive are also shown in the table and in FIG. 3 and 4 given for comparison. From the table it is easy to see that all the exemplary ceramics that have been modified with an addition of both 0.1 to 5 percent by weight of nickel oxide and 0.1 to 5 percent by weight of manganese oxide by a very high mechanical quality factor, a high planar coupling, a relatively high dielectric constant and low damping factor are excellent, all of these properties being significant for the use of piezoelectric ceramics in filter applications. Examples 1 to 29, Examples 30 to 35 and Examples 36 to 40, which are listed in the table, correspond to the ceramics shown in FIG. 2 are defined by X, Y and Z. F i g. 3 shows the effect of the additional MnOj components on the mechanical quality factor (Qm) and the planar coupling coefficient (Kp) of the basic ceramics given as examples with an addition of 1.0 percent by weight of NiO. From this figure of the drawing it can be seen that the ceramics _{modified with common NiO and MnO 2} additions show a remarkable improvement in the mechanical quality factor and the planar coupling coefficient compared with a ceramic with a simple addition of MnO ₂ .

ίο F i g. 4 shows the effect of the additional NiO components on the mechanical quality factor (Q _m ) and the planar coupling coefficient (K _p ) of the basic ceramics given as examples with an addition of 0.5 percent by weight of MnOj. From this figure of the drawing it can be seen that the ceramics _{modified with common MnO 2} and NiO additions show a remarkable improvement in mechanical quality factor compared with a composition with a simple addition of NiO. The planar coupling coefficient of the ceramics that _{are modified with common MnO 2} and NiO additions shows a somewhat lower value, but this value is still higher than that of the basic ceramic without an additive. Improvements in terms of the mechanical quality factor for a different base ceramic can also be seen from Examples 32, 33, 35, 38 and 40 in the table. From the table discussed above and the curves, the values for the mechanical quality factor, the planar coupling coefficient and the dielectric constant can be adjusted by selecting the basic ceramic and the proportions of common additives so that these are suitable for the various applications. In the case of ceramics which contain the common additives in a proportion of more than 7 percent by weight, an improvement in the mechanical quality factor can hardly be determined and the corresponding planar coupling coefficient is low. For this reason, these ceramics are outside the scope of the present invention.

In addition to the surprising properties set out above, the ceramics according to the present invention result Invention of ceramics of good physical quality and good polarizability.

For this purpose 2 sheets of drawings

Claims (1)

17 71 6S7 ... claims: 1. Piezoelectric ceramics, which mainly from a solid solution of three components according to the formula