EP3658520A1

EP3658520A1 - Hard pzt ceramic, piezoelectric multilayer component and method for producing a piezoelectric multilayer component

Info

Publication number: EP3658520A1
Application number: EP18732297.9A
Authority: EP
Inventors: Denis OROSEL; Markus Puff; Bernhard Döllgast; Alexander Glazunov
Original assignee: TDK Electronics AG
Current assignee: TDK Electronics AG
Priority date: 2017-07-26
Filing date: 2018-06-12
Publication date: 2020-06-03
Also published as: DE102017116925A1; CN110914219B; CN110914219A; DE102017116925B4; JP7033615B2; JP2020524655A; US20200131093A1; WO2019020265A1; US11608301B2

Abstract

The invention relates to a hard lead-zirconate-titanate (PZT) ceramic of general structure ABO₃, which has A areas and B areas, wherein the PZT ceramic has a doping on the B areas with Mn and Nb with the ratio Nb/Mn < 2. The invention also relates to a piezoelectric multilayer component comprising such a PZT ceramic and to a method for producing a piezoelectric multilayer component.

Description

description

Hard PZT ceramic, piezoelectric multilayer component and method for producing a piezoelectric

Multilayer component

It is a hard lead zirconate titanate (PZT) ceramic, a piezoelectric multilayer component and a method for producing a piezoelectric

Multilayer component specified.

PZT ceramics having piezoelectric properties withstand high electrical and mechanical stresses. Hard PZT ceramics can be used in particular for

Resonant applications, for example in the form of

piezoelectric transformers used. For the use of PZT material systems in piezoelectric

Transformers, it is important that the

Material properties are maintained during sintering and the geometry of the components is guaranteed.

The object of at least one embodiment is to specify a hard PZT ceramic with improved properties. Other objects are the provision of a piezoelectric multilayer component with the PZT ceramic and a

Process for producing a piezoelectric

Multilayer component. These objects are achieved by a PZT ceramic, a piezoelectric multilayer component and a method according to the independent claims.

Advantageous embodiments are the subject of the dependent claims. It becomes a hard lead zirconate titanate (PZT) ceramic

having a structure ABO ₃ comprising A sites and B sites, wherein the PZT ceramic has an Mn and Nb doping at the B sites and the ratio Nb / Mn is <2.

Under a PZT ceramic is here and below a

Ceramics based on the system Pb (Zr _x Tii_ _x ) O3. Such a system has a structure ABO ₃ , wherein for the pure lead zirconate titanate Pb occupies the A-site and (Zr _x Tii- _x ) the B-site. If further elements are present in the ceramic, then one speaks of dopings, which may be present on the A-squares and / or on the B squares. The formula ABO ₃ describes the crystal structure of the PZT ceramic wherein A in the basic composition is 2-valent and B 4-valent.

One speaks of a "hard" PZT ceramics, if the

Basic composition Pb (Zr _x Tii_ _x ) O3 is doped with acceptors. Acceptors in this case are cations of lower valency compared to the corresponding lattice atoms on the A and B sites. Hard PZT ceramics can be produced by low mechanical losses (Q _m = 1000 to 2000)

or dielectric losses (tanö = 0.3% to 0.4%) be characterized.

A PZT ceramic having Mn and Nb doping at the B sites and the ratio Nb / Mn <2 can be obtained in their manufacture without significant degradation of hard piezoelectric properties during sintering. Thus, a retention of the

Material properties of the hard PZT ceramic and the

Geometry of the components containing the PZT ceramic guaranteed. In addition, it is achieved that the PZT ceramic over a large formulation area comparable hard

has piezoelectric properties and so on

Process fluctuations in the production of a powdery starting mixture for the production of PZT ceramic barely

Effects on a piezoelectric device containing the PZT ceramic have.

According to one embodiment, 1.4 <Nb / Mn <2,

in particular 1.45 -S Nb / Mn <1.9. For this ratio of Nb to Mn can be no significant degradation of hard

piezoelectric properties during sintering

to be observed. According to one embodiment, the PZT ceramic has the

general formula

(Pb _xPb A _xA) - _y (Zr Ti _XZR _xT IMN _{(1 + Z)} _/ 3Nb (2-z) / 3B _xB) _y 0 _3. In this case, A _xA comprises the doping elements Al _xA i to Aa _xAa , where a is the number of doping elements on the A-sites and a ^ 1. Furthermore, B _xB comprises the doping elements ΒΙχ _Β ΐ to Bb _xB b, where b is the number This means that for a = 1 A _xA = ΑΙχ _Α ΐ or for b = 1 B _xB = Bl _xB i and thus only one doping element on each of the B elements A-place

or only one doping element is present next to Mn and Nb on the B-site. For a> 1 or b> 1 doping elements Al, A2, and so on to Aa or Bl, B2, and so on to Bb on the respective places available, a can be for example 2, b can also be 2, for example. Al to Aa are independently selected from a group comprising Na, K, Nd, La, Ba, Sr, Ca, Bi and Ag. Bl to Bb are independently selected from a group comprising Fe, Zn, Ge, Sn, Al, Ga, Sb and Cu. For example, the A-sites may be doped with Na and / or K. The B-sites can be doped in particular with Cu.

"x" in the above formula stands for the proportion of the respective element, ie doping element. Further, 0.9 ^ x Zr / x Ti <1.2, 0.4 <y <0.6, 0.0001 <xA <0.05 for each AI to Aa, 0.0001 <xB <0.05 for each Bl to Bb and 0 <z <0.25.

In particular, xZr / xTi can be equal to 1, y can in particular be equal to 0.5.

According to another embodiment, xMn = (l + z) / 3 and xNb = (2-z) / 3 and b

xZr + xTi + xMn + xNb + Σ xBn = 1

n ^{= 1}

This means that all possible B-seats are occupied. Furthermore: b a

xZr + xTi + xMn + xNb + Σ xBn = xPb + ΣχΑη

n = l n = l

This means that all A-seats and all B-seats are occupied. If these equations are met, that is, all possible A-slots and B-slots are occupied, the PZT ceramics are used

or a component which the PZT ceramic contains particularly good hard piezoelectric properties and good sinterability.

Furthermore, a piezoelectric multilayer component is specified which comprises a stack of ceramic layers and

has at least two electrodes arranged between ceramic layers. The ceramic layers contain a PZT hard ceramic according to the above. The

means all disclosed in relation to the PZT ceramic properties also apply to the multilayer component and vice versa.

The piezoelectric multilayer component can be designed monolithic. The ceramic layers are

arranged one above the other. Because of that

Ceramic layers contain a PZT ceramic as described above, the multilayer component has a high

Shape accuracy and a uniform deflection behavior.

The at least two electrodes contain according to a

Embodiment elemental copper. In particular, the at least two electrodes may consist of elemental copper. They can therefore also be referred to as copper inner electrodes. Copper is a cheap one

Electrode material, which can contribute to the low-cost production of such a multilayer component.

According to one embodiment, the piezoelectric

Multi-layer component of a piezoelectric transformer. The piezoelectric transformer may be

in particular to act a plasma generator. It will continue a process for producing a

piezoelectric multilayer component according to the above statements. The method comprises the steps of preparing a powdery starting mixture in

Stoichiometric ratio containing starting materials, the oxides and / or carbonates of Pb, Zr, Ti, Mn, Nb, at least one of the group Na, K, Nd, La, Ba, Sr, Ca, Bi and Ag and at least one of the group Fe, Zn, Ge, Sn, Al, Ga, Sb and Cu include, producing green sheets from the

Starting mixture, alternately stacking green sheets and electrode layers and sintering the stack. All features disclosed with respect to the multilayer component also apply to the method and vice versa. The starting materials according to one embodiment are in powder form, are mixed and used to prepare the

Milled starting mixture. The green sheets are produced by preparing the pulverulent starting mixture and grinding it again and tempering it. The green sheets are stacked one above the other such that electrode layers are sandwiched between two green sheets. When

Electrode layers can be used in particular copper electrodes. According to one embodiment, at a temperature

sintered, ranging from 900 ° C up to and including

1000 ° C, in particular from the range 950 ° C to 1000 ° C, is selected. This allows a PZT ceramic with high

Density can be produced, which has a low dielectric loss and a high electromechanical coupling efficiency. The sintering may be carried out in an inert gas atmosphere according to an embodiment. Furthermore, the sintering can also be carried out under reducing conditions.

Due to the above-mentioned advantageous properties of the PZT ceramic, the method can be used to produce a multilayer component whose geometry is maintained during sintering and whose piezoelectric

Material properties are maintained during sintering.

In the following the invention with reference to figures and

Embodiments described in more detail.

FIG. 1 shows a schematic sectional view of a

piezoelectric multilayer component.

In the figure, the same or equivalent components are each provided with the same reference numerals. The

Elements shown are not to be regarded as true to scale, but individual elements may be exaggerated to better understand. Figure 1 shows the schematic sectional view of a

piezoelectric multilayer component. This contains ceramic layers 10 which are stacked on top of each other. Between two ceramic layers 10 are

Electrodes 20, for example copper inner electrodes, which are contacted via external electrodes 30. In which

Multi-layer component is a monolithic multilayer component. This can be called piezoelectric Transformer can be used. In particular, it may be a plasma generator.

The ceramic layers 10 contain a PZT hard ceramic which has an ABO ₃ structure and is deposited on the B-

Places has a doping with Mn and Nb. The ratio Nb / Mn is <2. In particular, the PZT ceramic can

general formula (Pb _xPb A _xA) i_ _y (Zr Ti _XZR _xTi Mn _{(1 + z) / 3} Nb ₍₂ - _Z) / 3B _xB) _y comprise 0. ₃ In this case, 0 <z <0.25, with which the ratio Nb / Mn <2. For example, A can be Na, B can

for example, be Cu. All of the doping elements mentioned above in relation to the general formula on the A-squares and B-squares are also possible. Advantageously, all A-seats and all B-seats are occupied.

Four exemplary embodiments M1 to M4 for PZT ceramics are given below, whose nominal values are calculated in accordance with the weight ratio for the ratio Nb / Mn 1.79 (Ml), 1.61 (M2), 1.45 (M3) and 1.9 (M4 ) are. The by means of RFA measurement (RFA =

X-ray frequency analysis) compositions of the powder and Nb / Mn ratios obtained therefrom are in

Table 1 indicates:

Table 1

Electrical measurement data for these embodiments of wheel samples made from the powders described above (Diameter: 12 mm, height: 1 mm) compared to one

Comparative sample (V) with an Nb / Mn ratio of 2 are given in Table 2:

From Table 2 go the good hard piezoelectric

Properties of Examples Ml to M4. The mechanical loss Q _m , the relative permittivity 833, the

Coupling factors k _p and d33 are in acceptable ranges for use in devices such as piezoelectric transformers or plasma generators.

The invention is not limited by the figures and

Embodiments limited. Rather, the includes

Invention every new feature as well as every combination of

Features, which includes in particular any combination of features in the claims, even if this feature or this combination itself is not explicitly in the

Claims or embodiments is given. Reference sign list

10 ceramic layer

20 electrode

30 outer electrode

Claims

claims

1. Hard lead zirconate titanate (PZT) ceramic having an ABO ₃ structure comprising A sites and B sites, where the PZT ceramics in the B sites have Mn and Nb doping and the ratio Nb / Mn <2.

2. PZT ceramic according to the preceding claim, wherein 1.4 <Nb / Mn <2.

3. PZT ceramic according to one of the preceding claims comprising the general formula

(Pb _xPb A _xA) - _y (Zr _XZR Ti _xT IMN _{(1 + Z)} / 3Nb (2-z) / 3B _xB) _y 0 ₃ wherein A _xA the doping Al _xA i to Aa _Xaa comprises a number of the doping elements on the A-sites, and a ^ 1, where B _xB comprises the doping elements Bl _xB i to Bb _xB b, b is the number of doping elements on the B-sites, and b> 1,

AI to Aa are independently selected from a group comprising Na, K, Nd, La, Ba, Sr, Ca, Bi and Ag,

Bl to Bb are, independently of one another, selected from a group comprising Fe, Zn, Ge, Sn, Al, Ga, Sb and Cu, x is the proportion of the respective element,

0, 9 <x Zr / x Ti <1.2,

0.4 <y <0.6,

0.0001 <xA <0.05 for each AI to Aa

0.0001 <xB <0.05 for each Bl to Bb, and

0 <z <0.25.

4. PZT ceramic according to the preceding claim, wherein xMn = (l + z) / 3 and xNb = (2-z) / 3 and it applies:

b

xZr + xTi + xMn + xNb + Σ xBn = 1

n = l

and

b a

xZr + xTi + xMn + xNb + Σ xBn = xPb + Σ xAn

n = l n = l

5. Piezoelectric multilayer component with a stack of ceramic layers and at least two between

ceramic layers arranged electrodes,

wherein the ceramic layers contain a PZT hard ceramic according to any one of the preceding claims.

6. multilayer component according to the preceding claim, wherein the at least two electrodes contain elemental copper.

7. A multilayer component according to any one of claims 5 or 6 which is a piezoelectric transformer.

8. A multilayer component according to the preceding claim, wherein the piezoelectric transformer is a plasma generator.

9. Method for producing a piezoelectric

Multilayer component according to one of claims 5 to 8 with the steps

- Making a powdery starting mixture in

Stoichiometric ratio containing starting materials, the oxides and / or carbonates of Pb, Zr, Ti, Mn, Nb, at least one of the group Na, K, Nd, La, Ba, Sr, Ca, Bi and Ag and at least one of Fe, Zn, Ge, Sn, Al, Ga, Sb and Cu,

Preparing green sheets from the starting mixture,

Alternate stacking of green sheets and

Electrode layers and

- sintering the stack.

10. The method according to the preceding claim, wherein at a temperature in the range 900 ° C to 1000 ° C is sintered.

11. The method according to any one of claims 9 or 10, wherein is reduced in an inert gas atmosphere.