JPH0891928A - Piezoelectric ceramic and its production - Google Patents

Abstract

PURPOSE: To obtain a piezoelectric ceramic capable of improving lowering of insulation resistance in high temperature region while keeping good piezoelectric characteristic of three-component composition by replacing a part of PbTiO3 of Pb(Ni1/3 Nb2/3 )O3 (hereinafter referred to as PNN)-PbTiO3 (as PT)-PbZrO3 (as PZ)-based three-component solid solution composition with MnZrO3 . CONSTITUTION: This method is to obtain preferable piezoelectric ceramics using a laminate piezoelectric actuator capable of improving deterioration of insulation resistance under high temperature circumference (e.g. 120150 deg.C) without impairing good vertical effect piezoelectric stain characteristics of PNN-PT-PZ-based three-component solid solution composition and usable even at high temperature. These piezoelectric ceramics are produced by using, e.g. PbO, NiO, Nb2 O5 , TiO3 , ZrO2 and MnZrO3 , weighing these components so as to afford a prescribed composition ratio, carrying out wet mixing of these components by a ball mill, filtering and drying the resultant slurry, pre-baking the powder and re-powdering the pre-baked material, processing the material into a green sheet, carrying out screen printing of an electrically conductive paste having a prescribed pattern on the green sheet, laminating the sheets (by 22 layers) and baking the laminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to piezoelectric ceramics and a method for manufacturing the same, and more particularly, to lead nickel niobate (Pb).
(Ni _1/3 Nb _2/3 ) O ₃ ) and lead titanate (PbTiO 3
₃ ) and lead zirconate (PbZrO ₃ ), which is a four-component piezoelectric ceramic obtained on the basis of a three-component solid solution composition, which is suitable for use in, for example, a piezoelectric actuator element having a laminated structure, and its production. Regarding the method.

[0002]

2. Description of the Related Art A device utilizing the electric / mechanical energy conversion function of ceramics showing piezoelectricity is, for example, a piezoelectric actuator element (hereinafter referred to as a piezoelectric actuator) such as a filter, a piezoelectric ceramic transformer or an ultrasonic motor. ON / OFF control of displacement that occurs rigidly with respect to the applied electric field, such as those that use displacement due to mechanical resonance when an alternating electric field is applied to, and piezoelectric inkjet printer heads and piezoelectric relays. Such as an XY stage of an exposure apparatus for LSI manufacturing or a valve opening / closing device of a mass flow controller,
There are various devices such as a device that uses a rigid displacement by servo-driving, and there are various usage forms.

Piezoelectric actuators used in the above-mentioned various devices are roughly classified into simple type elements and composite type elements because of their structure. The simple type element uses the electric field-induced strain of the ferroelectric material as it is, and the piezoelectric vertical effect in the ferroelectric material is used, such as a single plate structure element made of a single plate of piezoelectric ceramics or a laminated structure element in which they are laminated. Are used, and those using the lateral effect such as a single tube, a separation tube or a honeycomb tube are classified. On the other hand, the composite element does not use the induced strain of the ferroelectric itself as it is, but combines it with other elastic materials such as unimorph, bimorph, notch, worm structure, etc. , It expands in time. Among these various types of piezoelectric actuators, a piezoelectric actuator having a laminated structure (hereinafter, referred to as a laminated piezoelectric actuator) has a smaller displacement generation amount than other actuators, but has a large generated force, a high response speed, and durability. Since it has many features such as richness, high efficiency of electrical / mechanical energy conversion, and small hysteresis, it is widely used and research and development for improving its performance are being actively conducted. The present invention relates to piezoelectric ceramics suitable as a material for such a laminated piezoelectric actuator.

As described above, since the laminated piezoelectric actuator has a relatively small amount of displacement generated as compared with other actuators, increasing the amount of displacement generated has been a major technical problem in the past. Development is progressing in terms of structure and materials. The actuator of this structure uses the thin-film multilayer technology cultivated in the practical process of ceramic capacitors because the piezoelectric ceramics of each layer are made as thin as possible to increase the applied electric field per layer. This is because the amount of displacement generated with respect to the drive voltage is increased and the piezoelectric vertical effect, which has a relatively large electric field induced strain and a small hysteresis, is used. On the other hand, from the viewpoint of materials, of course, ceramics with high electrical / mechanical energy conversion efficiency and large strain are selected, but along with this, even for ceramics with the same main component, changing the composition ratio or adding a small amount of additives, etc. Therefore, it is attempted to exhibit properties suitable for the application.

As such a piezoelectric ceramic, Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -P has hitherto been used.
bZrO ₃ system (hereinafter, Pb (Ni _1/3 Nb _2/3 ) O ₃ is PNN, PbTiO ₃ is PT, PbZrO ₃ is PZ.
, And is called PNN-PT-PZ system) ceramics are known. This piezoelectric ceramic has a high electric-mechanical energy conversion efficiency and is suitable as a ceramic for a laminated piezoelectric actuator, as described in, for example, Japanese Patent Application Laid-Open No. 2-71569. In particular, Kenji Uchino, JME Material Science. Near the morphotropic phase boundary between rhombohedral and tetragonal ferroelectric phases, as described in the series "Introduction to Electrical Properties for Ceramicists", pages 128-130, Mitsutsuru Uchida. exhibits good piezoelectric properties when a composition ratio, the longitudinal effect piezoelectric constant d ₃₃
Is known to be large.

The above PNN-PT-PZ ceramics are NiO, Nb ₂ O ₅ , PbO, TiO ₃ and ZrO.
_It is obtained by using 5 kinds of metal oxides of 2 as main raw materials, mixing these main raw materials, pulverizing and mixing with a wet ball mill etc., drying and calcining this, and further re-pulverizing with a wet ball mill etc. However, as described above, by adding a trace amount of elements or oxides thereof to the main raw material, or by substituting a part of the specific main raw material with those elements or oxides thereof, It is well known that piezoelectric properties, mechanical strength or electrical properties of ceramics can be improved. For example, JP-A-63-2992
No. 84, PNN-PT-P having high mechanical strength obtained by further adding Fe ₂ O ₃ to the above five main raw materials.
Z-based ceramics are disclosed. Also, Japanese Patent Laid-Open No. 3-1
Japanese Patent No. 90176 discloses a ceramic having improved mechanical strength for a piezoelectric filter by adding Mn and a Group Va element of the periodic table.

By the way, in recent years, the above-mentioned laminated piezoelectric actuator has been more and more widely used, and along with it, not only the conventional use environment of normal temperature and normal pressure but also high temperature, high pressure or irritating gas, corrosiveness. It has come to be used even in a bad environment such as in gas. For example, when a piezoelectric clamper is attached to the tip of the robot hand to form a manipulator, the actuator used as the displacement generation source of the piezoelectric clamper is 120 to 1
It may be placed in a high temperature work environment such as 50 ° C. However, under such a high temperature, the insulation resistance of the PNN-PT-PZ ceramics, which is the piezoelectric material of the actuator, is significantly deteriorated.

As described above, the PNN-PT-PZ ceramics used for the laminated piezoelectric actuator are required not only to have a large piezoelectric constant d ₃₃ but also to have a small deterioration of insulation resistance at high temperatures. Is becoming more common. As a general answer to such a request,
It has been conventionally known that the addition of Mn to the above three-component solid solution improves the insulating property.

[0009]

As described above, the PN
N-PT-PZ-based three-component solid solution composition, especially ceramics having a composition ratio near the morphotropic phase boundary in its phase diagram has a large longitudinal effect piezoelectric constant d _{33 and} is suitable as a piezoelectric material for a laminated piezoelectric actuator. is there. Furthermore, since the deterioration of the insulation resistance under a high temperature environment of 120 to 150 ° C. is reduced when Mn is added, the addition of Mn reduces the operating temperature range of the laminated piezoelectric actuator to a high temperature region. , It can be said to contribute to the expansion of its applications.

However, the piezoelectric ceramic in which Mn is simply added to the PNN-PT-PZ-based three-component solid solution composition has a side effect of decreasing the piezoelectric constant d ₃₃ . That is, from this viewpoint, the simple addition of Mn to the PNN-PT-PZ-based piezoelectric ceramics may impair the characteristics of the laminated piezoelectric actuator and narrow its application.

[0011] Therefore, the present invention improves the deterioration of the puncture resistance in a high temperature environment without impairing the good longitudinal effect piezoelectric strain characteristics of the PNN-PT-PZ-based three-component solid solution composition, and can be used even at high temperatures. It is another object of the present invention to provide a piezoelectric ceramic suitable for use in a laminated piezoelectric actuator.

Another object of the present invention is to provide a method for manufacturing the above high temperature piezoelectric ceramics.

[0013]

The piezoelectric ceramic of the present invention contains lead nickel niobate with a mole fraction x, lead titanate with a mole fraction y, and lead zirconate with a mole fraction z as main components. Add the component solid solution composition to {Pb (Ni _1/3 Nb _2/3 ) O
₃ } _x (PbTiO ₃ ) _y (PbZrO ₃ ) _z (however,
x + y + z = 1), a part of PbTiO ₃ in the three-component solid solution composition has a molar fraction γ of MnZ.
substituted with rO ₃ , {Pb (Ni _1/3 Nb _2/3 )
_{O 3} x (PbTiO 3)} (y- r) (PbZrO 3)
_z (MnZrO ₃₎ is a piezoelectric ceramic composed of 4 components solid solution composition represented by _r.

The above-mentioned piezoelectric ceramics are manufactured by a manufacturing method characterized by using MnZrO ₃ as a starting material for manufacturing the four-component solid solution composition.

[0015]

Next, preferred embodiments of the present invention will be described. As one embodiment of the present invention, a PNN-PT-PZ solid solution composition in which the molar ratio of the three components is on the morphotropic phase boundary line between the rhombohedral ferroelectric phase and the tetragonal ferroelectric phase on the phase diagram Of PT of PT was replaced with MnZrO ₃ to form a multilayer ceramic capacitor type chip, and from the temperature characteristics of the chip's insulation resistance and strain amount, the specific resistance and longitudinal effect of the ceramics were calculated. The temperature characteristic of the piezoelectric constant d ₃₃ was obtained.

In this embodiment, as starting materials, PbO, N
iO, Nb ₂ O ₅ , TiO ₃ , ZrO ₂ , MnZrO ₃
Using, the raw materials were precisely weighed so that the composition ratios shown in Table 1 were obtained. The purity of each raw material is 98% or more.

Next, the weighed raw materials were wet pulverized and mixed in a ball mill, the powder slurry was filtered, dried and then pre-fired, and the pre-baked powder was re-pulverized in a wet pole mill. The pre-baking conditions are a temperature of 850 ° C. and a time of 2 hours.

The re-pulverized powder was processed into a green sheet, and a conductive paste having a predetermined pattern to be an internal electrode was screen-printed on the green sheet. The thickness of the green sheet is 75 μm.

The green sheets printed with the above conductive paste were laminated to prepare an unfired laminated ceramic type chip. The number of laminated layers is 22 layers.

Next, the unfired chips were heated to burn off the molding binder contained in the chips (debinding), and then the chips after the binder removal were baked. The temperature of the binder removal is 300 to 400 ° C. The firing conditions are a temperature rising rate of 100 ° C./h, a holding temperature of 1100 ° C., and a holding time of 2 hours.

The specific resistance and the longitudinal effect piezoelectric constant d ₃₃ of the fired chips obtained by the above steps are tabulated and shown in FIG.
Also, a graph is shown in FIGS. 2 and 3. 1 to 3, the sample number No. 1 (PNN _38.5 PT _25.9 PZ
_35.6 ) is a ceramic with a composition ratio located on the morphotropic phase boundary (edited by the Japan Ceramic Association,
"Ceramic Engineering Handbook", Gihodo Publishing, No. 19
Page 10; see the phase diagram shown in FIG.
This is a sample in which PT is not replaced by ZrO ₃ . Sample No. 2 is the sample number No. This is a sample in which the PT in 1 was replaced with MnZrO ₃ having a mole fraction of 0.05% with respect to the whole, and the mole fraction of PT was 25.85%.
Further, the sample number No. Sample No. 3 was a sample in which the amount of substitution with MnZrO ₃ was increased, PT was substituted with 0.10% MnZrO ₃ of the whole, and the mole fraction of PT was 25.8%.
The mole fraction of PNN and PZ in the whole sample is constant.

Referring to FIGS. 1 and 2, MnZrO ₃
The replacement amount by 0.05% (No. 2), 0.1% (N
o. 3) as the total temperature range (2
5 to 150 ° C.), the absolute value of the specific resistance increases, and the decrease in specific resistance due to the temperature rise decreases. In particular, the effect of MnZrO ₃ substitution in the high temperature region (120 to 150 ° C.) is remarkable, and the specific resistance at 120 ° C. and 150
When compared with the specific resistance at ° C. 1 is about 1 /
No. 6 decreases to 6.5. 2 and No. At 3, it is only about 1 / 2.5, and its absolute value is 10 ¹⁰ Ω.
・ It is at a practical level, at least cm.

On the other hand, referring to FIG. 1 and FIG.
1-No. The temperature characteristic curve of the piezoelectric constant d ₃₃ of 3 is in good agreement in the entire temperature region. That is, PNN-PT-PZ
Almost no decrease in the piezoelectric constant d ₃₃ that occurs when Mn is simply added to the system ceramics, and it can be seen that the ceramics that have been subjected to the substitution operation with MnZrO ₃ also maintain good piezoelectric characteristics.

[0024]

As described above, according to the present invention,
By substituting a part of PT of the PNN-PT-PZ-based three-component solid solution composition with MnZrO ₃ , 120 to 150 ° C. while maintaining good piezoelectric characteristics of the above three-component composition.
It is possible to improve the decrease in insulation resistance in the high temperature region. If the piezoelectric ceramics of the present invention is applied to a laminated piezoelectric actuator element, its application can be further expanded, so that the industrial value of the present invention is great.

[Brief description of drawings]

FIG. 1 is a table showing the relationship between the composition ratio of piezoelectric ceramics and the temperature characteristics of specific resistance and insulation resistance in an example of the present invention.

FIG. 2 is a diagram showing the temperature characteristics of the specific resistance of the piezoelectric ceramic according to one embodiment of the present invention and the conventional PNN-PT-PZ-based three-component piezoelectric ceramic.

FIG. 3 is a diagram showing temperature characteristics of piezoelectric constants of a piezoelectric ceramic according to an embodiment of the present invention and a conventional PNN-PT-PZ-based three-component piezoelectric ceramic.

Claims (4)

[Claims] 1. A three-component solid solution composition mainly composed of lead nickel niobate having a mole fraction x, lead titanate having a mole fraction y, and lead zirconate having a mole fraction z is prepared as {Pb (Ni _{1 / 3} Nb
_2/3 ) O ₃ } _x (PbTiO ₃ ) _y (PbZrO ₃ ) _z
(However, when expressed as x + y + z = 1), a part of PbTiO _{3 in} the three-component solid solution composition is expressed as MnZ having a molar fraction γ.
Substituted with rO ₃ , {Pb (Ni _1/3 Nb _2/3 ) O ₃ }
_x (PbTiO ₃ ) _(yr) (PbZrO ₃ ) _z (MnZ
rO ₃ ) A piezoelectric ceramics composed of a four-component solid solution composition represented by _r . 2. The piezoelectric ceramic according to claim 1, wherein the composition ratio of the three-component solid solution composition is a composition ratio near a morphotropic phase boundary between a rhombohedral ferroelectric phase and a tetragonal ferroelectric phase. Piezoelectric ceramics characterized by being present. 3. The piezoelectric ceramic according to claim 2, wherein the molar fraction γ of MnZrO ₃ in the four-component solid solution composition is in the range of 0.05% or more and 0.10% or less of the entire composition. Piezoelectric ceramics characterized by the above. 4. The method for producing a piezoelectric ceramic according to claim 1, 2, or 3, wherein MnZrO ₃ is used as a starting material for producing the four-component solid solution composition. Manufacturing method.