JPH09183652A - Ferroelectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferroelectric ceramic composition stabilized in the characteristics. SOLUTION: This ferroelectric ceramic composition consists of Pb-titanate, Ca-titanate, and Sb-titanate as base components and the base composition is represented by the formula; (1-x-y)PbTiO3-x CaTiO3-y Sb2/3 TiO3 wherein (x) is expressed by 1.0-35mol%, (y) being by 1.0-30mol% and Ti is replaced with Mn by 0.5-5mol%. Any one of dielectric constant, dielectric loss, Curie point, coupling coefficient, pyroelectric coefficient and temp. coefficient of resonance frequency of the obtained ferroelectric ceramic composition satisfies the standard values.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a ferroelectric ceramic composition containing lead titanate, calcium titanate and antimony titanate as basic components.

[0002]

2. Description of the Related Art Ferroelectric porcelain compositions are used for pyroelectric elements, ceramic filters, ceramic resonators, etc., and examples of such compositions include single crystals of glycine sulfate, lithium niobate, lithium tantalate, etc. Also known are lead zirconate titanate and lead titanate porcelain materials.

As the pyroelectric element, the pyroelectric coefficient (dPs / dT) is larger as the change in spontaneous polarization corresponding to the temperature change is larger, and the smaller the relative dielectric constant is, the more excellent the pyroelectric element is. It is practically desirable that inexpensive and highly stable products are provided.

As the voltage element for the high frequency filter, a material having a small dielectric constant and tan δ and a small temperature coefficient of resonance frequency is desirable.

[0005]

However, according to the results of studying the effectiveness of each of the above materials, glycine sulfate is a water-soluble crystal, so it is weak in temperature and difficult to process, and the Curie point is 49 ° C. Since it is extremely low, it was found that the operating temperature range is extremely limited as a pyroelectric pyroelectric element and a piezoelectric element for a high frequency filter, which is not preferable.

Lithium niobate has good workability, but has a low pyroelectric coefficient and is expensive. Lithium tantalate has good workability and a relatively large pyroelectric coefficient, has a zero temperature coefficient depending on the cutting direction, and has a piezoelectric property. Although it is excellent as an element, it is expensive for a few minutes because it is a single crystal, which is disadvantageous for industrial use.

Lead zirconate titanate-based porcelain has good workability, and it is possible to choose one having a larger pyroelectric coefficient in composition, and its characteristics can be controlled by composition as a piezoelectric material. Therefore, development of this material system is actively conducted. Has been done to.

This lead zirconate titanate-based material is Pb
(Zr-Ti) be one of O ₃ as a main component, further Mn, Cr, Nb, Co, or the addition of metal oxides such as _{Fe, Pb (Mg 1/3 Nb 2/3} ) O 3 , etc. Improvements such as solid solution of the complex oxide are widely made in the field of piezoelectric materials.

However, in such a lead zirconate titanate porcelain, a composition having a good temperature characteristic generally has a high dielectric constant of about 500 to 1200 and is not suitable as a pyroelectric material or a high frequency piezoelectric material. Therefore, a material having a small dielectric constant has been studied, but it is difficult to make the effective dielectric constant smaller than 350.

Further, the lead titanate porcelain has a large pyroelectric coefficient and a relatively small dielectric constant, but it is difficult to sinter,
There is a drawback that it is difficult to obtain a porcelain having a uniform composition and stable piezoelectric characteristics because lead evaporates during firing. Moreover, this porcelain requires a fairly high voltage for polarization. On the other hand, in order to improve these drawbacks, lead titanate-based porcelain to which rare earths and other metal oxides are simultaneously added or substituted is known. This material has a dielectric constant of about 150 to 300, which is lower than that of lead zircon titanate and has good piezoelectric characteristics, but has a slight difficulty in sinterability, making it difficult to obtain a large porcelain and strict polarization conditions. Therefore, there are drawbacks such that it is difficult to increase the yield in industrialization, and since an expensive rare earth additive is used, there is a problem in commercialization thereof.

As a prior art example for solving this problem, Japanese Patent Application Laid-Open No. 63-144165 discloses (Pb _1- x.Cax).
In the basic composition represented by [(Mn1 / 2 · Sb1 / 2 ) y · Ti 1-y ] O _3, x, ranges shown below the y, x = 0.10~0.40 y = 0.01 The oxide porcelain material for a pyroelectric element is characterized by being about 0.20. In this prior art example, pure PbTiO ₃ porcelain, which is known as a material for a pyroelectric element, is expected to be a material for a pyroelectric element from the prior art, but it still has sufficient performance due to the strictness in manufacturing. Since PbTiO ₃ is not produced, PbTiO ₃ is subjected to a specific modification,
It aims to provide an inexpensive and high-performance pyroelectric element material suitable for mass production under the condition of n1 / 2 · Sb1 / 2. In this attempt, the effect of being excellent in characteristics as compared with the conventional material by collecting data of the relative permittivity, the pyroelectric coefficient, and the pyroelectric effect output index of the sample is emphasized. .

Ferroelectric porcelain compositions used for the above purposes have been expanding their applications in recent years, and the properties required for the compositions are wide-ranging with the expansion of their applications. There is a strong demand for the development of a ferromagnetic porcelain composition which has become more and more strict, is not satisfactory at the level of conventional characteristics, and has even more excellent characteristics and is stable.

An object of the present invention is to satisfy the above requirements, a ferroelectric ceramic composition having a high dielectric constant and a high coupling coefficient, and excellent sinterability over a wide composition range while maintaining piezoelectric characteristics, dielectric characteristics and pyroelectric characteristics. To provide things.

[0014]

To achieve the above object, in a ferroelectric ceramic composition according to the present invention, a ferroelectric ceramic composition containing lead titanate, calcium titanate and antimony titanate as basic components. Where the basic composition is represented by the chemical formula: (1-x-y) PbTiO ₃ -xCaTiO ₃ -ySb
_2/3 TiO ₃ where x is 1.0 to 35 mol% and y is 1.0 to 30 mo
It is represented by 1% and Ti in the above chemical formula is 0.5 to Mn.
5 mol% is substituted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies conducted by the inventors to provide an excellent element as a pyroelectric element, lead titanate,
A specific composition containing calcium titanate and antimony titanate as a basic constituent, in which Ti is replaced by Mn in a specific ratio, is excellent in dielectric properties, piezoelectric properties, pyroelectric properties and its temperature properties. Moreover, they have found that they have good sinterability and have mild polarization conditions, and have completed the present invention based on this finding.

The ferroelectric ceramic composition of the present invention has a basic composition of the chemical formula: (1-x-y) PbTiO ₃ -xCaTi.
The composition is composed of lead titanate, calcium titanate, and antimony titanate represented by O ₃ -ySb _2/3 TiO ₃ as basic constituent components. The content ratio of calcium titanate in this composition is represented by the above chemical formula. X is 1.0 to
It should be in the range of 35 mol%. When the value of x is less than 1.0 mol%, both the piezoelectric characteristics and the temperature characteristics are deteriorated, the pyroelectric coefficient is small, and the pyroelectric element is not suitable. Further, when it exceeds 35 mol%, the dielectric constant exceeds 300, which makes it unsuitable for pyroelectric use and high frequency use.

On the other hand, the content ratio of antimony titanate is
It is necessary that y is in the range of 1.0 to 30 mol%.

When the value of y is less than 1.0 mol%, the sinterability of the porcelain is poor, the deformation of the element body is remarkable, and the length is 30 m.
If it exceeds ol%, a heterogeneous phase precipitates at the grain boundaries and the piezoelectric characteristics deteriorate, so that it cannot be used as a pyroelectric material.

Further, in the porcelain composition of the present invention, Ti in the above chemical formula needs to be replaced by Mn by 0.5 to 5 mol%. If this ratio is less than 0.5 mol%, dielectric breakdown tends to occur during polarization, which is not preferable in manufacturing. If it exceeds 5 mol%, the sinterability deteriorates, and the electrical characteristics significantly decrease, making polarization impossible. Therefore, it cannot be used as a pyroelectric element or a piezoelectric element.

The porcelain of the present invention can be easily manufactured by a usual ceramic method as described below.

For example, PbO, TiO ₂ , CaCO ₃ , Sb
₂ O ₃ MnO ₂ or corresponding hydroxides, carbonates, oxalates, nitrates, etc. that can be converted into oxides by firing are used as starting materials, and these raw material powders are blended at a predetermined ratio, and a ball mill or the like is used. The resulting mixture is thoroughly mixed, calcined in the temperature range of 700 to 900 ° C., and further pulverized by a ball mill or the like. Then, a small amount of water or a binder such as polyvinyl alcohol is added to the calcined powder thus obtained, and pressure molding is performed at a pressure of 0.5 to ² ton / cm ² , and then the molded body is heated to 1150 ° C. 1250
The porcelain of the present invention can be obtained by firing in the temperature range of ° C for 2 to 4 hours.

The porcelain according to the present invention can be dense even when it is fired in normal air, but a more dense one can be obtained by using oxygen atmosphere firing, hot pressing, hot isostatic pressing or the like. To be

A composition diagram of the porcelain of the present invention is shown in FIG. FIG. 1 shows Pb (Ti _1-m M _nm ) O ₃ , Ca (Ti _1-m
M _nm ) O ₃ and Sb _2/3 (Ti _1-m M _nm ) O ₃ are shown in triangular coordinates with apexes, and Mn is MnO ₂ of 0.5.
~ 5 mol%. In the figure, the maximum range compatible with the present invention is indicated by a shaded area.

The ferroelectric ceramic composition of the present invention covers a wide area, Is 100 to 260, and the electromechanical coupling coefficient (kt) is 35 to
It shows a high value of 50% and has good sinterability over a wide composition range while maintaining piezoelectric characteristics, dielectric characteristics, and pyroelectric characteristics as a pyroelectric element and high-frequency filter element, and it is easy to make large porcelain. Obtained, the polarization treatment is 80 to 120 ° C.,
It is of extremely high industrial value because it is as easy as 40 KV / cm to 60 KV / cm and is relatively inexpensive because it does not use rare earth elements.

(Examples) Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Chemical formula: (1-xy) Pb (Ti _1-m M
_{nm) O 3 -xCa (Ti 1} -m M nm) -ySb 2/3 (Ti 1-m
The values of x, y, and m in M _nm ) O ₃ are changed, and the sample No. of each composition is changed. 1 to No. Table 1 shows various characteristics of the piezoelectric ceramic of No. 30.

[0027]

[Table 1]

Each characteristic of the piezoelectric ceramic was determined by the following method. (1) Dielectric and Piezoelectric Properties A disk porcelain having a diameter of 20 mm and a thickness of 1 mm was prepared, and Ag electrodes were baked on both sides of the disk porcelain at 80 to 120 ° C. and 40 ° C.
Polarization treatment was performed under the conditions of -60 KV / cm, and after standing for 24 hours, the dielectric constant (ε) and tan δ were measured at 1 KHz, and the electromechanical coupling coefficient in the thickness direction was determined according to the method of the IRE standard circuit. Also, the temperature coefficient frT of the resonance frequency
I also asked for c.

(2) Pyroelectric property A porcelain disk having a diameter of 20 mm and a thickness of 1 mm was prepared, polarized by the method of (1), and then the pyroelectric property was measured.

(Comparative Example) PbO and TiO as starting materials
₃ , Sb ₂ O ₃ , CaCO ₃ , and MnO ₂ powders were used, and these powders were blended at a predetermined ratio, and the mixture was mixed with 900
The calcined product obtained by calcining at 0 ° C. for 2 hours was crushed with a ball mill. Next, a small amount of a binder and polyvinyl alcohol were added, and the mixture was pressure-molded at a pressure of ² ton / cm ² , and the molded body was fired at a temperature of 1150 ° C to 1220 ° C for 3 hours to prepare a piezoelectric ceramic. The performances of the piezoelectric ceramics thus obtained are shown in Table 2 together with their compositions.

[0031]

[Table 2]

The smaller the dielectric constant (ε), the higher the sensitivity of the pyroelectric element. The smaller the high frequency filter is, the better the impedance matching is, and the better the filter characteristics are. From Table 1, according to the present invention, values in the range of 100 to 260 are obtained.

The smaller the dielectric loss (tan δ), the better. Smaller pyroelectric elements have less noise. The transmission characteristics are also improved as a high frequency filter. In the present invention, a value of 0.5 to 1.9% or less is obtained.

The Curie point (Tc) is the temperature at which the ferroelectric characteristic disappears, and the higher the Curie point, the more stable the pyroelectric characteristic and the filter characteristic. In the present invention, a value of 200 ° C. or higher is obtained.

The larger the coupling coefficient (kt), the better. The pyroelectric element improves the sensitivity, and the filter has a large bandwidth, which facilitates the filter design. According to the invention 35
% To 50%.

The larger the pyroelectric coefficient (dPs / dT), the higher the sensitivity of the pyroelectric element. According to the invention, 4.0 × 1
It is 0 ^-8 coul / cm ³ K or more.

The smaller the temperature coefficient (frTc) of the resonance frequency, the more stable the transmission characteristics of the filter and the more the center frequency does not shift with respect to the temperature change. According to the invention ± 50 ppm / ° C
It is as follows.

Sample N as a comparative example in Table 2
o. 31 has x of less than 1.0 mol% and has a small pyroelectric coefficient. Sample No. In the case of 32, x exceeds 35 mol%, the pyroelectric coefficient is small, and the dielectric constant far exceeds 300, which is not suitable for both pyroelectric use and high frequency use.

Sample No. In 33, y was less than 1.0 mol%, the sinterability was poor, and the element body was significantly deformed. Sample No. In No. 34, y exceeds 30 mol%, and a different phase is precipitated at the grain boundary, and the piezoelectric characteristics are significantly deteriorated.

Sample No. 35 has Mn of 0.5 mol%
It is less than less than 100%, and the element in polarization is easily cracked and dielectric breakdown is likely to occur. Sample No. In No. 36, Mn was more than 5 mol%, the electric resistance of the element body was low, and an excessive current flowed during polarization, which made polarization difficult. In addition, when the addition amount y (%) of Sb _2/3 is less than 1.0 mol%, the sinterability is inferior and the element body is significantly deformed. Sb _2/3 addition amount y (%)
As shown in Table 1, if the addition amount of Mn is not more than twice the addition amount, only low level electric characteristics can be obtained.

In the present invention, the preferable addition amount y (%) of Sb _2/3 is twice or more the addition amount m (%) of Mn.

The addition amount of Mn, m, is set to m = 0.05 (5 mo
The composition diagram according to the present invention when set to 1%) is shown in a region A of FIG. 2, and the composition diagram when set to m = 0.005 (0.5 mol%) is shown in a region C of FIG.

For comparison, a prior art example (JP-A-63-144)
(Pb _{1- x} · Cax) [(M
In the composition represented by n1 / 2 · Sb1 / 2) y · Ti 1-y ] O _3, the region B at the time of setting the addition amount of Mn to 5 mol% in FIG. 2, when set to 0.5 mol% Regions D are shown in FIG. 3 as comparative examples. As apparent from FIGS. 2 and 3, according to the present invention, the region is specified as a rhombic region, whereas in the comparative example, it is specified as a linear region. That is, according to the present invention, stable characteristics can be obtained over a wide composition range.

[0044]

As described above, according to the present invention, the dielectric constant and electromechanical coupling coefficient are high over a wide range, and the sinterability is excellent over a wide composition range while maintaining the piezoelectric characteristics, dielectric characteristics, and pyroelectric characteristics. , Dielectric constant, dielectric loss, Curie point, coupling coefficient, pyroelectric coefficient, and temperature coefficient of resonance frequency all satisfy the standard values, and are excellent for use in porcelain materials such as pyroelectric elements, ceramic filters, and ceramic resonators. The effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a composition diagram of a porcelain of the present invention.

FIG. 2 is a composition diagram when the amount of Mn added is 5 mol%.

FIG. 3 is a composition diagram when the amount of Mn added is 0.5 mol%.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Keisuke Okabe 1-11-4 Shin-Sayama, Sayama City, Saitama Prefecture Oizumi Manufacturing Co., Ltd. (72) Yoichi Tanaka 1-11-4 Shin-Sayama, Sayama City, Saitama Prefecture Stock company Oizumi Manufacturing (72) Inventor Junichi Osawa 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A ferroelectric ceramic composition containing lead titanate, calcium titanate and antimony titanate as basic components, wherein the basic composition is represented by the chemical formula: (1-x-y) PbTiO ₃ -xCaTiO ₃ -ySb.
_2/3 TiO ₃ where x is 1.0 to 35 mol% and y is 1.0 to 30 mo
A ferroelectric ceramic composition represented by 1%, wherein Ti in the above chemical formula is replaced with Mn in an amount of 0.5 to 5 mol%.