JP3084401B1 - High performance piezoelectric ceramics and their manufacturing method - Google Patents

Abstract

The present invention provides a piezoelectric ceramic material having excellent piezoelectric properties equivalent to conventional piezoelectric ceramics, and a novel method for manufacturing the piezoelectric ceramic. SOLUTION: The complex perovskite type compound Pb (S
c _1/2 Nb _1/2 ) O ₃ and simple perovskite compound P
Among ceramics containing bTiO ₃ and PbZrO ₃ as main components, Pb (Sc _1/2 Nb _1/2 ) O ₃ , PbT
In triangular coordinates with iO ₃ and PbZrO ₃ as vertices, Pb
When (Sc _1/2 Nb _1/2 ) O ₃ is X mol%, PbTiO ₃ is Y mol%, and PbZrO ₃ is Z mol% (X + Y + Z = 100), the composition (X = 90, X = 90,
Y = 10, Z = 0), composition (X = 10, Y = 90, Z =
0) and a composition (X = 10, Y = 10, Z = 80) as a main component, and a method for producing the solid solution ceramic. [Effect] High-purity PScN-P showing excellent piezoelectric characteristics
T-PZ solid solution piezoelectric ceramic raw material powder and ceramics can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic used as a material for a sensor or a ceramic actuator and a method for manufacturing the same.
Pb (Sc _1/2 Nb _1/2 ) O ₃ -PbTiO ₃ -PbZ exhibiting excellent piezoelectric properties equivalent to conventional piezoelectric ceramics
The present invention relates to a rO ₃ solid solution piezoelectric ceramic and a method for producing the solid solution ceramic. Since the piezoelectric ceramics of the present invention have excellent piezoelectric characteristics, improvement in the performance of sensors, actuators, and the like can be expected when applied to piezoelectric elements.

[0002]

2. Description of the Related Art In recent years, with the development of the electronics industry such as electric appliances and communication devices, miniaturization and intelligentization of sensors, actuators, motors, etc. have been required.
Piezoelectric ceramics are used as a material for realizing these. At present, the piezoelectric ceramic materials are PbZrO ₃ -PbT, which is a solid solution of perovskite-type compounds PbTiO ₃ (hereinafter sometimes referred to as PT) and PbZrO ₃ (hereinafter sometimes referred to as PZ).
iO ₃ solid solution (hereinafter sometimes referred to as PZT)
Are mainly used. However, recently, with the expansion of application fields of piezoelectric elements, further improvement in piezoelectric characteristics has been desired, and PbZrO ₃ has been developed for the purpose of improving piezoelectric characteristics.
-PbTiO ₃ solid solution is to introduce a complex perovskite type compound as the third component have been investigated.

[0003]

SUMMARY OF THE INVENTION Pb (Sc_1/2 Nb
_1/2 ) O_Three (Hereinafter, it may be described as PScN.)
Is a complex perovskite compound, and PbZrO_Three 
-PbTiO_ThreeWide range by dissolving in solid solution
Expected to show excellent piezoelectric properties in solid solution composition
It is. In general, complex perovskite compounds are
Perovskite single phase obtained in ceramic manufacturing
Is difficult, and Pb (Sc_1/2 Nb_1/2 ) O_Three The main
The conventional PScN-PT-PZ solid solution
Of high-purity ceramics by the ceramic manufacturing method
It is difficult. In other words, conventional ceramic manufacturing
The solid-phase reaction used in the method is a solid solution from the contact point of the raw material particles.
This is a heterogeneous reaction in which the body synthesis reaction proceeds. one
In general, the mass transfer rate in the solid phase is
Because it is extremely slow compared to the reaction field,
It is extremely difficult to synthesize a solution.
Some compositional fluctuations occur in the particles produced by the manufacturing method.
You. Thus, it is manufactured by the conventional ceramic manufacturing method.
Particles have a diffuse compositional distribution, which can be
It is difficult to obtain solid solution particles with high uniformity.
Was. Thus, the present inventors have proposed a PScN-PT-PZ solid solution.
As a result of intensive studies on the production method of the body, PScN-P
Novel manufacturing method of T-PZ solid solution piezoelectric ceramics and
And excellent piezoelectric properties equivalent to conventional piezoelectric ceramics
PScN-PT-PZ Solid Solution Piezoelectric Ceramics
And completed the present invention.

[0004]

The present invention for solving the above problems comprises the following technical means. ( 1 ) Pb (Sc _1/2 N ) of complex perovskite compound
b _1/2 ) O ₃ and simple perovskite compound PbTiO
₃ and PbZrO ₃ as main components
And Pb (Sc _1/2 Nb _1/2 ) O ₃ , PbTiO ₃ ,
In the triangular coordinates having PbZrO ₃ as a vertex, Pb (Sc _1/2
Nb _1/2 ) O ₃ is X mol%, PbTiO ₃ is Y mol%, P
When bZrO ₃ is Z mol% (however, X + Y + Z
= 100. ), Composition (X = 90, Y = 10, Z =
0), composition (X = 10, Y = 90, Z = 0) and set
Triangle with vertices at the top (X = 10, Y = 10, Z = 80)
A method for producing a piezoelectric ceramic mainly composed of a composition in a shape , wherein lead materials (PbO), scandium oxide (Sc ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ) are used as starting materials.
), Titanium oxide (TiO _2), and using zirconium oxide (ZrO _2), than perovskite composition of the above-described solid solution weighed so lead oxide (PbO) is excessive, after mixing by wet mixing or the like , Molding and heat treatment in the air, then dissolving the unreacted material, separating the particles, molding the resulting particles, and firing to produce a sintered body of Pb ( Sc _1/2 Nb _1/2 ) O ₃ −
PbTiO ₃ -PbZrO ₃ manufacturing method of a solid solution piezoelectric ceramics. ( 2 ) Add excessive lead oxide to the perovskite composition and perform heat treatment in air at 950 to 1000 ° C. for 1 to 2 hours.
The method of the above (1) .

[0005]

Next, the present invention will be described in detail. The present invention that solves the above-mentioned problems is based on Pb (Sc _1/2) having excellent piezoelectric characteristics equivalent to those of conventional piezoelectric ceramics.
The present invention relates to a Nb _1/2 ) O ₃ -PbTiO ₃ -PbZrO ₃ solid solution piezoelectric ceramic and a method for producing a piezoelectric ceramic. When the piezoelectric ceramics manufactured by this manufacturing method is used as a piezoelectric material, the performance of sensors, actuators, motors, and the like can be improved.

In the method of the present invention, lead oxide (PbO), scandium oxide (Sc ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ) and zirconium oxide (ZrO ₂ ) are used as starting materials. used. These raw materials have a predetermined ratio, for example, 40 mol% PScN-40 mol% PT, which is expected to exhibit excellent piezoelectric properties.
When synthesizing a −20 mol% PZ solid solution, 6PbO
+ 0.4Sc ₂ O ₃ + 0.4Nb ₂ O ₅ + 1.6TiO
After mixing with ₂ + 0.8 ZrO ₂ , the mixture is formed into an appropriate form such as a tablet, a prism, or the like, and 850 ° C. or higher, preferably 95
Heat treatment at 0 to 1000 ° C. for 1 to 2 hours. As a method of mixing the materials, dry mixing, wet mixing, and molding methods, such as a die pressing method and a wet pressing method, and a heat treatment method, heat treatment in the atmosphere is exemplified as a preferred method. It is not limited to these. In the heat-treated material, unreacted substances are dissolved using an acidic aqueous solution, for example, a 1N acetic acid aqueous solution, and the particles are separated by a filtration operation.
Next, after the obtained particles are molded by a mold press, the mixture is heated at about 1300 ° C. to 1 to 3 in a PbO atmosphere or air.
It is fired for a time to produce a sintered body. Examples of the sintering means include, but are not limited to, a normal sintering method and a pressure sintering method.

In the present invention, the addition of PbO in excess to the perovskite composition and the heat treatment at 850 ° C. or higher, preferably 950 to 1000 ° C.
It is important to produce single phase particles of perovskite. In this case, if the temperature falls below 850 ° C., excessively added P
Since a liquid phase of bO is not sufficiently generated and the generation of the perovskite phase mainly proceeds by a solid-phase reaction, a single phase of perovskite cannot be obtained. Further, when the heat treatment is performed at 1000 ° C. or more, the viscosity of the liquid phase of PbO becomes extremely low, so that efficient powder production becomes difficult. In addition, since the evaporation of PbO from the liquid phase becomes remarkable, the production environment becomes poor. The load increases. As will be described later, in a sample in which PbO is excessively added to the perovskite composition, the yield of the perovskite phase increases, and it becomes possible to produce a high-purity PScN-PT-PZ solid solution piezoelectric ceramic. The piezoelectric ceramic of the present invention is manufactured by the above method, and the piezoelectric ceramic includes Pb (Sc _1/2 Nb _1/2 ) O.
₃ and ceramics containing PbTiO ₃ and PbZrO ₃ as main components, Pb (Sc _1/2 Nb _1/2 ) O ₃ ,
In triangular coordinates having PbTiO ₃ and PbZrO ₃ as vertices,
X mole% of Pb (Sc _1/2 Nb _1/2 ) O ₃ , PbTiO
_{When 3} is Y mol% and PbZrO ₃ is Z mol% (provided that X + Y + Z = 100), the composition (X = 9)
0, Y = 10, Z = 0), composition (X = 10, Y = 90,
Z = 0) and composition (X = 10, Y = 10, Z = 80)
Piezoelectric ceramics whose main component is a composition within a triangle having a vertex as a vertex are used as suitable ones. In this case, PbZrO ₃ -PbTi
O ₃ solid solutions and _{Pb (Sc 1/2 Nb 1/2) O} 3 -Pb
Since the TiO ₃ solid solution exhibits good piezoelectric properties over a wide range of compositions, these solid solutions, Pb (Sc _1/2
This is because the Nb _1/2 ) O ₃ -PbTiO ₃ -PbZrO ₃ solid solution is expected to achieve excellent piezoelectric properties in the composition region near the triangle. In order to improve or stabilize the piezoelectric characteristics, a small amount of manganese oxide (MnO), strontium oxide (SrO),
Tungsten oxide (WO ₃ ), tantalum oxide (Ta ₂ O)
Additives such as ₅ ) are appropriately added. The solid solution produced by the method of the present invention is cubic particles of 0.5 to 3 μm having excellent dispersibility, and by sintering these, a dense sintered body having a relative density of 93% or more can be obtained. This sintered body
For example, excellent piezoelectric properties equivalent to PZT solid solution (Kp =
About 40%).

[0008]

According to the conventional ceramic manufacturing method, it has been difficult to manufacture a high-purity PScN-PT-PZ solid solution piezoelectric ceramic containing PScN as a main component. However, using the manufacturing method developed by the present inventors, high purity PSc
N-PT-PZ solid solution piezoelectric ceramic powder can be produced, and as a result PScN-P exhibiting excellent piezoelectric properties
T-PZ solid solution piezoelectric ceramics have been discovered.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. However, the present invention is not limited by the embodiments. Example 1) Method The ceramics synthesized in this example were a composite perovskite compound Pb (Sc _1/2 Nb _1/2 ) O ₃ and simple perovskite compounds PbTiO ₃ and PbZrO.
₃ solid solution, so-called Pb (Sc _1/2 Nb _1/2 ) O ₃ −
It is a PbTiO ₃ -PbZrO ₃ solid solution. With this compound, it is difficult to obtain a single phase of perovskite by a normal ceramic synthesis method with a composition containing a large amount of PScN, and by using the revolutionary production method described below, it is relatively simple. The production procedure has resulted in single phase particles of perovskite.

In the present embodiment, PScN, PScN-PT solid solution and PScN-
While synthesizing particles of a PT-PZ solid solution, 40 mol% PScN- is expected to exhibit excellent piezoelectric properties.
A sintered body was prepared with a composition of 40 mol% PT-20 mol% PZ, and its piezoelectric characteristics were evaluated.

2) Synthesis of particles As starting materials, reagent-grade lead oxide (PbO), oxide
Scandium (Sc_Two O_Three ), Niobium oxide (Nb_Two O
_Five ), Titanium oxide (TiO)_Two ) And zirconium oxide
(ZrO_Two) Was used. Wet mixing these to a specified ratio
After that, it is molded into tablets and heated at 950 ° C for 1 hour in air
Processing was performed. For the heat-treated sample, 1N acetic acid
Unreacted substances were dissolved using an aqueous solution to separate particles.

3) Production of Sintered Body The sintered body was subjected to press molding of the particles obtained by the above-mentioned synthesis method into a disc having a diameter of 12 mm at 200 MPa, and then fired at 1320 ° C. for 3 hours in a PbO atmosphere. Thereafter, the surface of the sintered body was polished to a thickness of 1 mm, and silver electrodes were formed on both surfaces of the sintered body by a baking method. afterwards,
The piezoelectric characteristics were examined using an impedance analyzer.

4) Results Regarding the synthesis of PScN-PT-PZ solid solution, first,
With regard to PScN in which it is difficult to obtain a single phase of perovskite in a normal ceramic synthesis method, synthesis of single phase particles of perovskite was attempted, and the results were used to refer to PScN-
A PT-PZ solid solution was synthesized. Hereinafter, the synthesis result of PScN will be described.混合 Mixture of lobskite composition (4
PbO + Sc ₂ O ₃ + Nb ₂ O ₅ ) in air at 900 ° C.
In a sample synthesized by repeating calcination twice for 5 hours, the perovskite phase yield was 96%, and a single perovskite phase was not obtained. On the other hand, in a sample obtained by heat-treating a mixture in which PbO was excessively added to the perovskite composition, the perovskite yield clearly increased, for example,
_{6PbO + Sc 2 O 3 + Nb} 2 O 5 The mixture was heated for 1 hour treatment at 900 ° C., the acid treatment of the perovskite phase yield was about 100%, a single phase perovskite was obtained. As in the case of PScN, the PScN-PT solid solution and PScN-PT-PZ solid solution are subjected to a heat treatment of a mixture to which lead oxide has been previously added in excess, and then to an acid treatment to obtain perovskite single-phase particles. Was done. That is, for the PScN-PT solid solution, PbO was weighed in advance so that PbO became excessive.
The mixture of O + Sc ₂ O ₃ + Nb ₂ O ₅ + TiO ₂ is 900
After heat treatment at 1 ° C. for 1 hour, acid treatment resulted in a perovskite phase yield of about 100%, and a single perovskite phase was obtained. Further, PScN-PT-PZ For solid solution were weighed so as to advance over the _{PbO PbO + Sc 2 O 3 +} Nb 2 O 5 + TiO 2 + ZrO 2
The mixture was heat-treated at 900 ° C. for 1 hour, and then subjected to an acid treatment, whereby the yield of the perovskite phase was about 100%, and a single perovskite phase was obtained. The solid solution produced by this production method was cubic particles of 0.5 to 3 μm excellent in dispersibility, and when these particles were sintered, a dense sintered body having a relative density of 93% or more was obtained.

5) Piezoelectric Properties of Sintered Body For a sintered body, 3 kV /
After performing a polarization treatment at 30 mm for 30 minutes, the piezoelectric properties were evaluated by measuring the electromechanical coupling coefficient (Kp).
As a result, 40 mol% PScN-40 mol% PT-
The Kp of the 20 mol% PZ sintered body was 40%. PbZrO ₃ known as a typical piezoelectric ceramic
Since the -PbTiO ₃ solid solution has a maximum Kp of about 50% without adding any additive, the sintered body produced in this example has piezoelectric properties as excellent as the PbZrO ₃ -PbTiO ₃ solid solution. You can see that it is. (References:
"Ceramic Dielectric Engineering" by Kiyoshi Okazaki, Gakuensha, 1
992)

[0015]

As described in detail above, the present invention relates to a method for producing a piezoelectric ceramic having excellent piezoelectric properties equivalent to that of a conventional piezoelectric ceramic and a method for producing a raw material powder thereof. High-purity PScN-PT-PZ solid-solution piezoelectric ceramic powder containing, as a main component, 2) a piezoelectric ceramic powder having excellent piezoelectric properties equivalent to conventional piezoelectric ceramics. 3) When the piezoelectric ceramics of the present invention is used as a piezoelectric material, the performance of sensors, actuators, motors, and the like can be improved, and the special effect that the industrial value is extremely large can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a specific composition range within a triangle defined by the present invention.

FIG. 2 is an explanatory view showing a manufacturing method according to an embodiment of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-305830 (JP, A) JP-A-7-267733 (JP, A) P. A. COMYN, et al. "The Effect of Atmosphere Controlled Sintering on the Piezoelectric Shear Mode Active of the PZT Base Ceramics" 1998, BETHER CRAMS, BETTER CRAM. Int.Cl. ⁷ , DB name) C04B 35/49 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A composite perovskite compound of Pb (S
c _1/2 Nb _1/2 ) O ₃ and simple perovskite compound P
Ceramic containing bTiO ₃ and PbZrO ₃ as main components
Pb (Sc _1/2 Nb _1/2 ) O ₃ , PbT
In triangular coordinates with iO ₃ and PbZrO ₃ as vertices, Pb
(Sc _1/2 Nb _1/2 ) O ₃ is X mol%, PbTiO ₃ is Y mol%, and PbZrO ₃ is Z mol%.
(When X + Y + Z = 100), the composition
(X = 90, Y = 10, Z = 0), composition (X = 10, Y
= 90, Z = 0) and composition (X = 10, Y = 10, Z
= 80) is a method for producing piezoelectric ceramics whose main component is a composition within a triangle having a vertex at the apex, and as starting materials, lead oxide (PbO), scandium oxide (Sc ₂ O)
₃ ), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ )
_2), and using zirconium oxide (ZrO _2), before
The serial was a solid solution of perovskite oxide of lead than the composition (Pb
O) is weighed so as to be excessive, mixed by wet mixing or the like, molded, subjected to a heat treatment in the atmosphere, then, the unreacted material is dissolved, the particles are separated, and the obtained particles are separated. After forming, firing is performed to produce a sintered body.
_{b (Sc 1/2 Nb 1/2) O} 3 -PbTiO 3 -PbZr
A method for producing O ₃ solid solution piezoelectric ceramics. 2. A perovskite was excessively added lead oxide to the composition, method of claim 1, wherein performing the 1-2 hours of heat treatment at 950 to 1000 ° C. in air.