JP3058490B2 - Ferroelectric composite material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferroelectric composite material and a method for producing the same.

[0002]

2. Description of the Related Art Generally, ferroelectric materials are used as dielectrics for capacitors and the like, focusing on their electrical properties.
Paying attention to mechanical properties, it is used as a piezoelectric element such as a piezoelectric actuator.

It has been proposed to produce such a ferroelectric material from ceramics. In this case, it is demanded today that the mechanical properties as well as the electrical properties of the ferroelectric material be further improved.

[0004] Therefore, in order to improve the mechanical properties of ferroelectric materials made of ceramics, various devices such as fine particles of ceramics have been conventionally used.

For example, mechanical properties are improved by adding ceramic fibers such as alumina fibers to lead zirconate titanate (hereinafter referred to as PZT), which is a kind of ferroelectric material.

[0006]

However, although the mechanical properties of the ferroelectric material have been confirmed to be slightly improved by the above-mentioned conventional means, ceramic fibers which are one kind of insulator are added. The dielectric constant (ε ₃₃ / ε ₀ ) and the dielectric loss (tan δ) indicating the electrical properties
Decreases as the amount of added alumina increases, as shown in FIGS.

As described above, the conventional ferroelectric material has a problem that not only its mechanical properties are not greatly improved but also its electrical properties are further reduced.

The present invention has been made in view of these points, and it is possible to improve the original electrical properties of a ferroelectric material by mixing ceramics from the surface of the ferroelectric material. It is an object of the present invention to provide a ferroelectric composite material capable of greatly improving its mechanical properties and a manufacturing method capable of reliably manufacturing the same.

[0009]

To SUMMARY OF THE INVENTION To achieve the above object, a ferroelectric composite material of the present invention, strong surface of the dielectric material
The portion is composed of a ferroelectric material in which the dispersion material is dispersed as a dispersion phase and formed in a composite shape ,
Except for the surface of the ferroelectric material
The inside is made of a ferroelectric material having no dispersed phase .

[0010] Further , the method for producing a ferroelectric composite material is as follows.
On the surface of the dielectric material, the dispersed material is separated as a dispersed phase.
Scattered to form a composite, and a ferroelectric
The inside of the material other than the composite formed surface
The ferroelectric composite material so that no dispersed phase is formed.
It is characterized by being manufactured. Still further , the method for producing a ferroelectric composite material of the present invention is a method of forming a ferroelectric material pulverized after calcination into a predetermined shape, and transforming the ferroelectric material into a liquid substance that becomes a ceramic by heat treatment. The ferroelectric material is immersed to allow the liquid substance to penetrate into the ferroelectric material from the surface, and then sinter the dried ferroelectric material to disperse the substance in a composite form at least on the surface as a dispersion material. It is characterized by producing a dielectric composite material.

[0011]

The ferroelectric composite material of the present invention is a composite in which a dispersion material is dispersed from a surface to a predetermined depth in a ferroelectric material formed into a predetermined shape, and the ferroelectric material is strongly induced.
Inside of the electrical material other than the composite formed surface
In, because it consists of a ferroelectric material without a dispersed phase ,
The electrical properties of the ferroelectric material, such as the original dielectric constant and dielectric loss, are greatly improved, and the mechanical properties are also greatly improved.

In the case of manufacturing a ferroelectric composite material,
On the surface of the dielectric material, the dispersed material is separated as a dispersed phase.
Scattered to form a composite, and a ferroelectric
The inside of the material other than the composite formed surface
The ferroelectric composite material so that no dispersed phase is formed.
To produce a ferroelectric composite material having the above-mentioned excellent electrical and mechanical properties greatly improved.
be able to. Furthermore , according to the method for producing a ferroelectric composite material of the present invention, a liquid substance serving as a dispersing material is made to penetrate into the ferroelectric material from its surface side, and is sintered after drying. Therefore, a ferroelectric composite material having excellent electrical and mechanical properties as described above can be reliably manufactured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The ferroelectric composite material of the present invention is obtained by forming a ferroelectric material pulverized after calcination into a predetermined shape, and immersing the ferroelectric material in a liquid substance that becomes a ceramic by heat treatment. Then, a liquid substance is permeated into the ferroelectric material from the surface, and thereafter, the dried ferroelectric material is sintered, and the substance is dispersed at least on the surface as a dispersion material in a composite form.

A more specific embodiment will be described.

Embodiment In this embodiment, PZT is used as a ferroelectric material serving as a parent phase, and alumina sol is used as a liquid substance serving as a dispersed phase.

1) Manufacturing Method To explain according to the manufacturing process, first, PZT powder is manufactured. That is, PbO, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ ,
Each material of MgO, NiO ₂ and MnO ₂ was prepared by a composition formula of 0.435PbTiO ₃ + 0.44PbZrO ₃ +0.
125 (Mg _1/3 Nb _2/3 ) O ₃ +0.5 (wt
%) NiO + 0.5 (wt%) MnO ₂ , weighed, and wet-mixed in a polyethylene ball mill using pure water for a predetermined time. Next, this mixture is dried and then granulated to produce PZT powder.

Next, after calcining the PZT, pure water is added and ground by a urethane ball mill. Thereafter, the ground PZT is dried and then granulated again.

Next, PZT is formed by cold isostatic pressing (CI
P) is formed into pellets of a predetermined shape at a pressure of 2500 kgf / cm ² by P), and the pellets are immersed in alumina sol for a predetermined time. Thereby, the alumina sol is made to permeate from the surface side into the pellet made of the molded PZT.

Then, PZT impregnated with alumina sol
Is dried at 120 ° C. for 12 hours and then sintered to form a composite in which alumina as a dispersing material is dispersed as a dispersed phase on at least a surface portion of PZT as a ferroelectric material. A dielectric composite is produced.

Next, the ferroelectric composite material of this embodiment manufactured as described above will be described.

1) Tissue The thus prepared ferroelectric composite material sample was mirror-polished, then gold was sputtered on its surface, and the tissue imaged by a scanning electron microscope (SEM) is shown in FIG. As shown in FIG. 3, it can be seen that alumina (black portion in the photograph) penetrates into the PZT (white portion in the photograph) to a depth of about 100 μm from its surface and is in a substantially uniformly dispersed composite state.

2) Electrical Properties and Mechanical Properties The ferroelectric composite material of this embodiment and PZT have dielectric properties (ε ₃₃ / ε ₀ ) and dielectric loss (ta) as electrical properties.
nδ) is measured, and as mechanical properties, electromechanical coupling coefficient (Kr) of spread vibration and mechanical quality coefficient (spread vibration)
(Qm) was measured. These measurement items were respectively measured based on the Electronic Materials Engineering Standards standard EMAS-6001, and the dielectric characteristics and the piezoelectric characteristics were measured at room temperature using a vector impedance meter.

The results are shown in Table 1.

[0025]

When the present embodiment is evaluated based on the above measurement results for a dielectric material whose electrical properties are important, the dielectric constant is larger than the dielectric constant of PZT itself, and is much larger than the calculated value. And it is extremely excellent as a ferroelectric composite material.

The increase in the dielectric constant is due to PZT
It is considered that this is because the internal stress changes due to the dispersion of alumina as fine particles in the particles. That is, it is said that a compressive force acts as an internal stress on the derivative. On the other hand, it is considered that this is because, by dispersing alumina having a larger thermal expansion coefficient than PZT in the crystal grains of PZT to form a composite, a tensile force acts to offset the compressive force.

When this embodiment is evaluated on the basis of the above measurement results for a piezoelectric material whose mechanical properties are important, the electromechanical coupling coefficient Kr of the spread vibration is larger than the value of PZT itself. Mechanical quality factor (spread vibration)
Since Qm is larger than the value of PZT itself, it is extremely excellent as a ferroelectric composite material.

3) Pile Folding Strength The ferroelectric composite material of the present embodiment is compliant with JIS-R16
01, using a DCS-50M manufactured by Shimadzu Corporation with a span of 30 mm and a crosshead speed of 0.5 m
Table 1 shows the results obtained by the three-point bending method under the measurement conditions of m / min.

As is evident from Table 1, the ferroelectric composite material of this example has a transverse rupture strength larger than that of PZT itself, and is extremely excellent.

As described above, in the ferroelectric composite material of the present invention produced by the method of the present invention, at least the surface portion of PZT is formed in a composite shape with alumina, and as a result, the electrical properties are reduced. The mechanical properties are greatly improved as well as greatly improved.

Therefore, the ferroelectric composite material of the present invention can be used for various applications by utilizing its excellent properties.

For example, it is needless to say that it can be used in the same manner as the conventional dielectric and piezoelectric elements, and moreover, it has more effects than the conventional one.

That is, it can be used as a dielectric of a capacitor by utilizing a high dielectric constant, and can have high strength by having high bending strength.

Further, by utilizing the excellent characteristics of the piezoelectric element, the present invention is applied to a piezoelectric actuator, a drive source of an ultrasonic motor, a piezoelectric buzzer, a piezoelectric filter, an acceleration sensor, a piezoelectric speaker, an oscillator, etc. It is good to improve efficiency and the like. In the piezoelectric actuator, it is preferable to improve the efficiency by taking advantage of the fact that the electromechanical coupling coefficient (Kr), the mechanical quality factor (spread vibration) (Qm), and the pile breaking strength of the spread vibration are increased. In an ultrasonic motor, it is preferable to use a range in which the electromechanical coupling coefficient (Kr) of the spread vibration is large, which is effective for preventing the occurrence of cracks.

In the present invention, the dispersion depth and the dispersion concentration of the dispersion material in the ferroelectric material are changed by changing the immersion time, or by changing the pressing force when immersion is performed in a pressurized state. Adjustment may be made to obtain characteristics according to design conditions and the like.

The ferroelectric material serving as the mother phase includes PZ
Materials other than T can be used, and other materials such as silica sol, zirconia sol, and spinel obtained by liquefying materials other than alumina can be used as the dispersion material serving as the dispersed phase.

The present invention is not limited to the above embodiment, but can be modified as required.

[0039]

As described above, the ferroelectric composite material of the present invention and the method for producing the same are constructed and operated.
The original electrical properties of the ferroelectric material can be greatly improved, and the mechanical properties can also be greatly improved, so that it has excellent applications, its manufacture is simple, and it is reliable. It can be manufactured and has the effect of reducing the cost.

[Brief description of the drawings]

FIG. 1 is a 200 × scanning electron micrograph showing the metal structure of the surface of a ferroelectric composite material of the present invention.

FIG. 2 is a scanning electron micrograph at 400 × showing the metal structure of the surface of the ferroelectric composite material of the present invention.

FIG. 3 is a scanning electron micrograph (× 1000) showing the metal structure on the surface of the ferroelectric composite material of the present invention.

FIG. 4 is a diagram showing a relationship between a mixed amount of alumina of a conventional ferroelectric material and a relative dielectric constant.

FIG. 5 is a diagram showing a relationship between a mixed amount of alumina of a conventional ferroelectric material and a dielectric loss.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-115168 (JP, A) JP-A-3-115167 (JP, A) JP-A-4-108659 (JP, A) JP-A-4-115 108658 (JP, A) JP-A-4-108657 (JP, A) JP-A-4-108656 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/00-35 / 49

Claims (3)

(57) [Claims] A surface portion of a ferroelectric material is formed in a composite shape by dispersing a dispersion material as a dispersion phase.
Made of ferroelectric material
In the interior other than the surface formed as a positive,
A ferroelectric composite material comprising a ferroelectric material without phase scattering . 2. A dispersing material is provided on the surface of the ferroelectric material.
Is dispersed as a disperse phase to form a composite
In both cases, a table formed in a composite shape of ferroelectric material
Strongly so as not to form a dispersed phase inside other than the surface
A method for producing a ferroelectric composite material, which comprises producing a dielectric composite material. 3. A ferroelectric material pulverized after calcination is removed by a predetermined method.
The ferroelectric material is shaped into a ceramic by heat treatment.
Dipping in a liquid substance
Strength that has been permeated into the dielectric material from the surface and then dried
Sintering the dielectric material so that at least the surface
Ferroelectricity in which composites are dispersed as a dispersion material
A ferroelectric composite material characterized by producing a composite material
Production method.