DE1646814C2 - Ferroelectric ceramics and process for their manufacture - Google Patents

Description

XPb (W ₁₇₄ Ma ₁ Z ₄ ) O ₃ • ^ PbTiO ₃ • ZPbMbO ₃

Compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and

χ = 0.5

y = 0.4

ζ = 0.1

and χ + y + ζ = 1.0, and the compound contains as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr as well as an additional 0.5% by weight MnO ₂ .

6. Ferroelectric ceramic, characterized in that it consists of one represented by the formula

.rPb (Wj _{/ 2} Ma _{l / 2} ) O _s - ^ PbTiO ₃ · ZPbMbO ₃

Compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and

χ = 0.3

y = 0.6

Z = 0.1

and x + j> + z = 1.0, and the compound contains as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr and an additional 0.5 wt .-% MnO ₂ .

7. A method for producing a ferroeiektrischen ceramic according to any of claims 1-6, characterized in that the starting substances, preferably oxides or carbonates, are mixed in proportions corresponding to the desired end products, pre-annealed at 700 to 1000 ⁰ C and after renewed mixing and shaping are sintered at 1000 to 1400 ° C in a PbO atmosphere and in that the sintered ceramics thus obtained at preferably about 8O ⁰ C in fields of a few ten are kV / cm polarized.

45 The invention relates to a ferroelectric ceramic and a method for its production.
In particular, these are ferroelectric ceramic bodies which can be electrostatically polarized and thereby have electromechanical energy conversion properties that are similar to the known piezoelectric effect. Such substances, further referred to as "piezoelectric ceramics", from which the invention is based, have already become known.

Ferroelectric ceramics for use in piezoelectric and electrostrictive elements have a perovskite structure which can be expressed by the formula ABO ₈ , where A is a divalent metal ion and B is a tetravalent metal ion. However, not all compounds with a perovskite structure have piezoelectric and electrostrictive properties. Some of these compounds, such as B. barium titanate, BaTiO ₃ , have piezoelectric and electrostrictive properties on their own. Others, such as B. the double compound lead titanate-zirconate, PbTiO ₃ -PbZrO ₃ , have

not as a single compound, lead titanate or lead zirconate. but as a solid solution of at least two individual compounds, for example the two mentioned, piezoelectric and electrostrictive properties. An ABO _S structure, on the other hand, in which the place of the tetravalent B ion is occupied by two ions with different ion valences, e.g. B. t MfJ) d (Mfö MLt

(With
^8th

or (Mfö MLt), wherein M ²⁺ , M ⁸ + and i

M ^{8+ denotes} divalent, hexavalent and pentavalent metal ions, generally show _{piezoelectric and electrostrictive properties alone or as a solid solution with another ABO 3} compound, while it was found that Pb (W ₁₁₂ Ma ₁₁₂ ) O ₃ with a perovskite structure, where WM ⁸⁺ and Ma M ²⁺ and M ²⁺ Ni and / or Zn, and W and Ma _{occupy the B-sites in the ABO 3} structure, similar to PbTiO ₃ alone does not have any piezoelectric and electrostrictive properties.

The invention is therefore based on the object of a new and versatile ferroelectric To create ceramics of the type under consideration, especially for use in electromechanical Energy conversion elements is suitable.

Another object of the invention is to find a ferroelectric ceramic compound which has a very high mechanical quality factor of at least 950 and also an electromechanical coupling coefficient kp of at least 0.10 and a dielectric constant e of at least 300.

These objects are achieved according to the invention by a ceramic which is characterized in that them from one through the formula

· ^ PbTiO ₃ · 2PbMbO ₃

The compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and χ = 0.3, y = 0.5, ζ = - 0.2 and χ + y + ζ = 1.0 , and the compound contains as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr and additionally MnO ₂ between 0.3 and 2.0% by weight.

Advantageous ferroelectric ceramics according to the invention also go from claims 2 to 6 emerges.

The above-mentioned ceramic material is prepared advantageous in that the starting substances, preferably oxides or carbonates, are mixed in proportions corresponding to the desired end products, pre-annealed and at 700 to 1000 ⁰ C after remixing and molding at 1000-1400 ⁰ C in be sintered in a PbO atmosphere and that the sintered ceramics obtained in this way are polarized at preferably about 80 ³ C in fields of a few tens of kV / cm.

The invention is illustrated with reference to the following examples.

obtained product was molded and tempered at a temperature of 700 to 900 ° C and then re-ground and shaped and then ^{sintered in a PbO atmosphere at a temperature of 1000 to 1300 0} C to form a disk with a diameter of about 20 mm and a Thickness of 0.8 mm. The disc was coated on the main surface with a long Silbereiektrode and then for 1 hour polarized using a DC electric field of 3.2 kV (40 kV / cm) at a temperature of 8O ⁰ C.

This disk was then left in the air at room temperature for 1 week, and the electromechanical coupling coefficient kp, dielectric constant e, and mechanical quality factor Qm of the disk were measured. The results obtained are shown in Table 1 below.

table 20th Rehearse- 1 Electrical Dielectric Mechanical No. mechaniscber constant Sqm salary Coupling ε at MnO ₁ coefficient (Ge kp weight percent)

25 *) 0 0.23 770 70 51 0.05 0.31 1460 181 52 0.1 0.39 2045 284 30 53 0.3 0.27 1044 1015 54 0.5 0.22 1100 2000 55 1.0 0.22 1240 1195 56 2.0 0.19 1547 1115 ³⁵ 57 3.0 0.15 1638 847 58 4.0 0.12 1745 531 59 5.0 0.10 1800 233 40 ·) Compare -.- h.

As can be seen from Table 1, the addition of up to 5.0 percent by weight of MnO ₂ makes it possible to obtain an electromechanical coupling coefficient kp of over 0.10, which is particularly suitable in practice for use in piezoelectric and electrostrictive ceramics and the mechanical quality factor Qm considerably improved. That is, the addition of at least 0.05% by weight of MnO ₂ enables Qm to be increased by two times the size that it is when MnO ₂ is not added. The addition of 0.5 percent by weight of MnO ₂ shows the maximum value of Qm.

Example 2

PbO, WO ₃ , NiO, ZnO, TiO ₂ , ZrO ₂ , SnO ₂ , BaCO ₃

CaCO ₃ , SrCO ₃ and MnO ₈ were combined so that ceramics having the compositions shown in Tables 2 and 3 below were obtained. The samples were treated in a manner similar to that illustrated in Example 1. The examples treated in this way were polarized, and the electromechanical coupling coefficient kp, the dielectric

0.3 Pb (W _{l / 2} Ni _1/2 ) O ₃ · 0.5 PbTiO ₃ · 0.2 PbZrO ₃ 65 see constant ε and the mechanical quality factor Qm

the samples were measured; the results obtained are shown in Tables 2 and 3 below shown.

example 1

PbO, WO ₃ , NiO, TiO ₈ and ZrO ₂ were added together to form the basic compound expressed by the formula

was obtained. The compound thus obtained was further provided with MnO ₈ and ground. That so

Table 2 Pb (W ₁ Z ₅ Ni ₁ Zj) O, PbTiO, PbZrO, PbSnO, Content of Electrical Dielectric Mechanical MnO ₁ more mechanical
Coupling constant
ε Figure of merit
Sqm (Weight coefficient Basic sample connection (molar ratio) 0.3 0.7 percent) kp No. 0.3 0.7 - - 0 0.18 460 145 0.03 0.27 0.7 0.5 0.15 423 1015 0.03 0.27 0.7 0 0.14 310 140 61 A 0.1 0.4 0.5 0.5 0.13 170 230 61 B 0.1 0.4 0.5 - 0 0.52 1228 127 62 A 0.1 0.52 0.38 0.5 0.39 597 435 62 B 0.1 0.52 0.38 0 0.50 1200 120 63 A 0.1 0.6 0.3 0.5 0.40 1000 500 63 B 0.1 0.6 0.3 0 0.37 828 161 64 A 0.2 0.15 0.65 0.5 0.29 597 435 64B 0.2 0.15 0.65 0 0.13 310 180 65 A 0.2 0.4 0.4 0.5 0.13 180 260 65 B 0.2 0.4 0.4 - 0 0.54 1090 75 66 A 0.2 0.5 0.3 0.5 0.33 528 598 66 B 0.2 0.5 0.3 0 0.35 880 187 67 A 0.3 0.6 0.1 0.5 0.37 961 857 67 B 0.3 0.6 0.1 - 0 0.21 490 95 68 A 0.3 0.5 0.2 - 0.5 0.13 510 933 68 B 0.3 0.5 0.2 - 0 0.23 770 70 69 A 0.3 0.4 0.3 - 0.5 0.22 1100 2000 69 B 0.3 0.4 0.3 - 0 0.39 1440 15th 25 *) 0.3 0.3 0.4 - 0.5 0.40 2100 1000 54 *) 0.3 0.3 0.4 - 0 0.33 810 60 7OA 0.3 0.2 0.5 - 0.5 0.30 1500 850 7OB 0.3 0.2 0.5 - 0 0.23 780 65 71 A 0.4 0.4 0.2 - 0.5 0.25 670 1700 71 B 0.4 0.4 0.2 - 0 0.25 1300 89 72 A 0.4 0.3 0.3 - 0.5 0.21 1412 1123 72 B 0.4 0.3 0.3 - 0 0.35 2700 78 73 A 0.5 0.4 0.1 - 0.5 0.20 528 610 73 B 0.5 0.4 0.1 - 0 0.22 1230 121 74 A 0.5 0.2 0.3 - 0.5 0.10 2115 1421 74 B 0.5 0.2 0.3 - 0 0.15 2500 147 75 A 0.65 0.25 0.1 - 0.5 0.13 431 345 75 B 0.65 0.25 0.1 - 0 0.10 1700 170 76 A 0.3 0.5 - 0.2 0.5 0.10 1300 220 76 B 0.3 0.5 - 0.2 0 0.25 810 134 77 A 0.3 0.2 - 0.5 0.5 0.15 520 546 77 B- 0.3 0.2 - 0.5 0 0.26 700 143 78 A 0, I ⁺ +) 0.45 0.45 - 0.5 0.21 532 728 78 B 0.1 ++) 0.45 0.45 - 0 0.52 1500 75 79 A 0.2 ++) 0.40 0.40 - 0.5 0.45 1200 340 79 B 0.2 ++) 0.40 0.40 - 0 0.55 1800 72 80A 0.3 ++) 0.35 0.35 - 0.5 0.50 1310 480 80B 0.3 ++) 0.35 0.35 - 0 0.59 2500 80 81 A 0.5 0.51 1420 350 81 B 82 A 82 B

*) Sample Nos. 25 and 54 were the same as those shown in Example 1 Table 1 and were used for comparison with others Samples listed again.

* *) Pb (W ₁ Z ₂ Zn ₁ Z ₂ ) O ₃ was used instead of Pb (Wu ₂ Ni ₁ Z ₂ ) O ₃ .

Table 3

Basic sample connection
No. (Pb _{0 95} Sr _{0, 0} 5) W _{0 05} Ni _{0 05} Ti _{0, 4e} Zr _{0, 44)} O ₃ salary
on MnO ₂
(Weight
percent) Electrical
more mechanical
Coupling
coefficient
kp Dielectric
constant
ε Mechanical
Quality factor
Sqm 46 ») the same O 0.55 1580 75 46 B (Pb _{0> 88} Ca _0i02 ) (W ₀ , ₀₆ Ni _0i0S Ti ₀ , 4 _e Zr ₀ , ₄₄ ) O ₃ 1 0.50 1210 428 47 *) the same O 0.49 1240 79 47 B (Pb _0f85 Ba _{0, 15)} (W _{0th 05} Ni _{0 0f05} Ti, Zr _{4e M4)} O ₃ 1 0.55 1180 334 48 *) the same O 0.53 1580 92 48 B ♦) Comparison. 1 0.56 1490 439

As can be seen from Tables 2 and 3 above, the connection is

^ Pb (W ₁₁₂ Ni ₁₂ ) O ₃ · JPbTiO ₃ · ZPbMbO ₃

where Ma is Ni and / or Zn and Mb is Zr and / or Sn, where χ = 0.03 to 0.5, y = 0.2 to 0.6, 2 = 0.1 to 0.5 and .v + y + ζ = 1.0 and zero to 20 atomic percent of Pb is replaced by Ba, Ca and / or Sr and wherein further 0.5 percent by weight of MnO _{2 is} contained, capable of having an electromechanical coupling coefficient kp of over 0.10, which is greater than piezoelectric and electrostrictive ceramics can be used in practice. The connection is further capable of remarkably improving the mechanical quality factor Qm.

Manganese can be added in metallic form or in the form of oxides or other compounds. It can be added in a ratio that corresponds to a total of 0.03 to 2.0 percent by weight of MnO _2. In this case, it is preferable to increase the proportion of lead so that lead equilibrates with the added manganese.

Pb (W ₁ Z ₂ Ma ₁ (J) O ₃ , PbTiO ₃ and PbMbO ₃ , which are involved in the basic composition according to the invention, have a perovskite structure or are expressed by the formula ABO ₃ and alone have no piezoelectric or electrostrictive properties In solid solutions, however, given by the formulas

Ma ₁ ^) O ₃ · (1 - X) PbTiO ₃

where χ = 0.2 to 0.7, or

.vPb (W _{1; 2} Ma _li2 ) O ₃ · VPbTiO ₃ · ZPbMbO ₃

where χ = 0.3 to 0.5, y == 0.2 to 0.6, ζ = 0.1 to. 0.5 and a · + y + ζ = 1.0, they have piezoelectric and electrostrictive properties.
When a part of Pb is in the above composition

VPbTiO ₃ zPbMbO ₃

is replaced by Ba, Ca and / or Sr, this replacement must be less than 20 atomic percent because a substitute that exceeds 20 atomic percent. considerable deterioration in the piezoelectric Properties of the product.

The ceramic compound of the present invention expressed by the above-mentioned formulas exhibits the best piezoelectric and electrostrictive properties. But it is difficult in practice to obtain the atomic ratio as accurately as shown in the above-mentioned formulas. even if the sintering treatment is carried out in a certain atmosphere or an excess is weighed in to compensate for the evaporation losses. A slight deviation from the above-mentioned atomic ratio is permissible as long as the ceramic compound according to the invention is not significantly influenced by the deviation.

In addition to the advantageous properties outlined above, the compositions according to the invention are used to obtain ceramics of good physical quality that can be polarized well.

709 608'41

Claims (5)

Patent claims: 1. FeiToelectric ceramics, characterized in that that they come from one through the formula XPb (W ₁ Z ₄ Ma ₁ Z ₄ ) O ₃ · ^ PbTiO ₃ · zPbMbO _s Compound expressed in which Ma represents Ni Ni and / or Zn and Mb Zr and / or Sn and χ = 0.3 y = 0.5 ζ = 0.2 and χ + y + ζ = 1.0, and the compound as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr and additionally MnO ₂ between 0.3 and 2.0% by weight contains. ao 2. Ferroelectric ceramic, characterized in that it consists of one represented by the formula ZPbMbO ₃ Compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and χ = 0.3
y = 0.4
ζ = 0.3 30th and χ + y + ζ = 1.0 , and the compound contains as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr and additionally 0.5% by weight MnO ₂ . 3. Ferroelectric ceramic, characterized in that it consists of one represented by the formula XPb (Wi ₁₂ Ma ₁ Z ₂ ) O ₃ ■ ^ PbTiO ₃ · 2PbMbO ₃ Compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and χ = 0.3 y = 0.2 Z = 0.5 and χ + y + ζ = 1.0, and the compound contains as a substitute for an equivalent lead content of a total of zero to 0 atomic percent Ba, Ca and / or Sr and an additional 0.5% by weight of MnO ₂ . 4. Ferroelectric ceramics, thereby identified, that they come from one through the formula · ^ PbTiO ₃ · ZPbMbO ₃ Compound expressed consists in which Ma represents Ni and / or Zn and Mb Zr and / or Sn and χ = 0.4 y = 0.4 Z = 0.2 and χ + y + ζ = 1.0, and the compound contains as a substitute for an equivalent lead content of a total of zero to 20 atomic percent Ba, Ca and / or Sr and additionally 0.5% by weight MnO ₂ . 5. Ferroelectric ceramic, characterized in that it consists of one represented by the formula