JPH0244062A - Ferroelectric ceramics - Google Patents

Abstract

PURPOSE:To obtain the title ceramics having excellent specific inductive capacity, electromechanical coupling coefficient and piezoelectric coefficient by regulating PbTiO3, PbZrO3, Pb(Mg1/3Nb2/3)O3 and SrTiO3 to its fundamental compsn. and incorporating small amt. of Sb thereto. CONSTITUTION:In the above ferroelectric ceramics, the improvement of specific inductive capacity epsilon, elelctromeshanical coupling coefficient K and piezoelectric constant (d) is shown by incorporating Sb into the above fundamental compsn. At the same time, high value can be obtd. in the Curie temp. Tc and the deterioration of dielectric loss (tan) delta does not occur. By the coexistence of Si and Zn including Sb, further improvement of various characteristics can be shown. Furthermore, by the increase of the Mg content under the presence of Sb, elelctromechanical coupling coefficient K can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in ferroelectric ceramics.

[Conventional technology]

As ferroelectric ceramics, conventional PbZr O3-P
bTi O3 solid solution porcelain, PbZrO3-PbTi
The ternary solid solution porcelain of O3-Pb (Mg1/Jb2/3)O3 is well known, and various attempts have been made to further improve various properties.

For example, in Japanese Patent Publication No. 44-17103, the above PbZr0a-PbTiO3-Pb (MHI/lNb
2h) In 03 series porcelain, some of the pb atoms are replaced by Sr,
It is described that the pb atoms are substituted with Ba or Ca, and Japanese Patent Publication No. 45-30151 discloses a ternary porcelain as described above in which a part of the pb atoms are substituted with Bi. Further, Japanese Patent Publication No. 45-30151 discloses adding MgO in excess to the above three-component porcelain. Furthermore, in Japanese Patent Application Laid-Open No. 62-286291, Z
It is described that nO and Bi2O3 are added together. In JP-A No. 63-64962, some of the Pb atoms in the three-component porcelain were replaced with Sr, SnO was added, and ZnO and old 203
Alternatively, one to which NiO is added is disclosed.

[Problem to be solved by the invention]

The relative dielectric constant (ε), electromechanical coupling coefficient (k), and piezoelectric constant (d) are used as indicators of the characteristics of ferroelectric ceramics.
There is. However, with any of Tamade's conventional techniques,
It has been extremely difficult to obtain ferroelectric ceramics that have excellent values that simultaneously satisfy all of ε, d, and d.

The present invention has excellent values for both ε and d, and at the same time has other characteristics such as rust dissipation (t
The object of the present invention is to provide ferroelectric ceramics that exhibit good values also in terms of Curie temperature (c) and Curie temperature (c).

(Means for Solving the Problems) A feature of the present invention is that Sb is contained in the composition of ferroelectric ceramics.
This is due to the inclusion of i.e. PbTiC)+.

PbZrO3, Pb (Mg1/INb%) Q3,
In addition, a small amount of Sb is included in the ferroelectric ceramic whose basic composition is 5rTiO3.

In this case, it is preferable to coexist a small amount of 81 and Zn with Sb. Furthermore, by increasing the content of ng, various properties can be further improved.

Further, the present invention has the above basic composition, and also has Pb (
It is also effective for ferroelectric ceramics having Fe'% W 1/3 ) 03 as a subcomposition.

[Effect]

The ferroelectric ceramic according to the present invention has S in its basic composition.
By allowing b to exist, the relative dielectric constant ε.

Improvements are seen in both the electromechanical coupling coefficient k and the piezoelectric constant d. At the same time, a high Curie temperature Tc4) can be obtained, and no deterioration of dielectric m loss tan δ occurs. It is presumed that this improvement in dielectricity and piezoelectricity is due to Sb atoms, which are impurity elements, acting on the crystal grain boundaries of the ferroelectric ceramic and having some kind of influence. In addition, when Bi and Zn are allowed to coexist with Sb,
Further improvements in various properties can be seen. Furthermore, by increasing the Mg content in the presence of Sb, the electromechanical coupling coefficient kr can be improved.

Furthermore, even when Pb (Fe%W1/1) 03 is included as a sub-composition, various properties are improved by adding Sb. Moreover, in the case of having a sub-composition, a higher ε value can be obtained than in ferroelectric ceramics consisting only of the basic composition.

〔Example〕

Examples of the present invention will be described below using Tables 1 to 3 listed later.

In order to produce the ferroelectric ceramics according to the present invention, basic raw materials, auxiliary raw materials, and additive raw materials are blended in the ratio shown in Table 1, and this is mixed using a resin pot mill and a resin ball for 20 minutes.
After time-mixing, the mixture is dried and granulated into 32-mensunder particles. Next, 500 kg of granulated powder
Pressure molded at f/cd, and the resulting molded product was heated to 1000
Calcinate at ℃ for 2 hours. Subsequently, the calcined product is crushed and pulverized for 16 hours using a resin bot mill and a resin ball, a small amount of PVA is added as an adhesive, and the mixture is granulated using a spray dryer. The granules thus obtained were 1001
After pressure forming at 00 O/cj into a disc with a diameter of 20 mm and a thickness of 2 mm, the final firing was performed for 2 hours in a magscrew pot.

After the main firing, both sides of the obtained fired body are polished, and then silver electrodes are fired. Then, immerse it in silicone oil at 40°C.
A DC electric field of 1.5 kv/mm is applied for 30 minutes to cause polarization. In this way, the desired ferroelectric ceramic is manufactured.

In Table 1, fragrances 1 to 17 are related to the present invention, and each contains a total of 100 mol of basic raw materials and auxiliary raw materials.
On the other hand, Bi2O3, ZnO, 5b20a were o
, s:t, o:0.5 molar ratio.

The first fragrances 1 to 5 are systems in which no auxiliary materials are added, and Mg
The amount of CO3 added was gradually increased.

On the other hand, perfumers 6 to 17 are systems in which auxiliary raw materials are added to have a auxiliary composition, and the amounts of not only Mg003 but also auxiliary raw materials Pe203 and WO3 are varied.

However, in this example, the blending ratios of Fe2O3 and W2O3 were set to equimolar amounts. In addition, the blending ratio of the additive raw materials shown in Table 1 is 1% of the total of the basic raw materials and auxiliary raw materials.
It is expressed as

Incense 18 to 22 are related to conventional examples, and fragrance 18
corresponds to the composition described in Japanese Patent Publication No. 44-17103, fragrance 19 corresponds to the composition described in Japanese Patent Publication No. 45-30151, and fragrance 20 corresponds to the composition described in Japanese Patent Publication No. 62-286291. 21 and 22 are published in Japanese Patent Application Publication No. 6
This corresponds to that described in Japanese Patent No. 3-64962.

Fragrances 23 to 26 are also related to the present invention, and in particular, how much improvement can be seen in various properties compared to the above conventional composition depending on the presence or absence of Sb, and changes in the amount of Sb added The purpose of this study is to examine what kind of if-if effects it has on sex. Of these, the incense 24 is the same as the incense 1.

Table 2 shows the composition of the ferroelectric ceramics manufactured based on the raw material blending ratios in Table 1, and also shows the measurement results of various properties. The firing temperature employed in this example was 1230°C. The correspondence between each symbol representing the composition ratio used in Table 2 and each component is as shown below.

In addition, the unit of numerical values showing the composition ratio in the table is mo1%.
It is. However, the ratio of the sub-composition and additive system is the same as the basic composition 1.
It is expressed as mo1%, which is the outer division of 00 mo1%.

a-1bT i O3b-PbZr O3cm1'b(
MgI/INb2h)03m---SrTiO3n-P
b (Fe shame W1/3) Oa) 03 r-'-Bi20
3s--ZnOt--3b203 u-5nO2Δ・
- Increased amount of Mg CO3 Furthermore, the meaning of each term adopted as an index indicating various properties is briefly explained as follows.

Relative permittivity (ε): The ratio between the capacitance of a capacitor filled with two ferroelectric ceramics and the capacitance of a vacuum capacitor with the same electrode arrangement.The higher the value, the better.

Dielectric Ti loss (tan δ): Electrical energy that is converted into heat and lost when a ferroelectric ceramic is placed in a changing electric field.The smaller this value is, the better.

Electromechanical coupling coefficient (k): A coefficient indicating the efficiency of conversion from electrical energy to mechanical energy. The larger the value, the better. In this example, the results of measurement of kr are shown.

Piezoelectric constant (d): A constant that represents the state of coupling between the electrical system and the mechanical system, and the larger the value, the better. In this example, the results of measurement for d31 are shown.

Curie temperature (Tc): The temperature at which the transition from ferroelectricity to paraelectricity occurs, also called the Curie point.The higher this value, the better the temperature stability, so it is applied to things that are subject to temperature changes during use. It is particularly effective.

(Left below) In Table 2, incense 1 to 17 and 23 to 26 and incense 1
As is clear from the comparison with Nos. 8 to 22, the ferroelectric ceramics according to the present invention are overwhelmingly superior to the conventional ones in terms of relative dielectric constant, electromechanical coupling coefficient kr, and piezoelectric constant d31. We have obtained numerical values. That is, the ferroelectric ceramic according to the present invention has an ε of about 5000 to
6300. kr is about 54-62, d31 is about -250
While it has an excellent vi value of ~-320,
Among the products manufactured based on the conventional composition, even the one with fragrance 22, which is thought to have the best characteristics, has an ε of only 4411. kr is only 53.3 and d3+ is -252.

For reference, e and k of the examples that are considered to have the best characteristics from the examples described in each of the earlier application publications mentioned above.
When transcribed, it is as follows.

As is clear from the above, conventionally g, kr + d3
It was difficult to obtain good values for all +. However, the present invention has succeeded in obtaining excellent values for all of t 1 kr+'31. Moreover, this does not mean that other characteristics such as dielectric loss tan δ are sacrificed at all.

Table 3 below shows the results of measuring the Chierie temperature Tc of the ferroelectric ceramics according to the present invention and also investigating the relationship between various properties and firing temperature.

(Margin below) Special Publication No. 44-32343 Special Publication No. 45-30151 Special Publication No. 46-25824 Japanese Patent Publication No. 62-286291 Japanese Patent Publication No. 63-64962 2200 i 67.0 2663 i 63.9 +700: 66 4430 i 52.4 4544 i 59.6 table The following can be seen from Tables 2 and 3.

1) With the addition of Sb, ε, kr and d31 all show a significant improvement (see 20 and 23 in Table 2), but this degree of improvement is greater than when the same amount of Sn is added. It's also big.

1i) By adding Sb, not only a high value of l kr and d3+ but also a high Curie temperature Tc can be obtained. Furthermore, there is no problem such as deterioration of dielectric loss tan δ.

1ii) The preferable addition amount of Sb is Bi2O3 and Zn
Blending molar ratio to O is 1:2:1.0-1
．． This is a range of 5.

iv) As the Mg content increases, the kr value tends to increase. However, excessive increase in Mg is not preferable because it causes a decrease in ε.

v) As the Mg content increases, the Curie temperature Tc also tends to increase.

vi) As the proportion of sub-compositions increases, the ε value increases.

In particular, when the amount of Mg is increased, the ε value increases markedly. However, although kr tends to decrease, it maintains a sufficiently high value compared to the conventional example.

vi) When the firing temperature is increased, both ε and kr tend to improve for systems that do not contain sub-components.

On the other hand, in systems with sub-compositions, it is difficult to recognize any particular tendency of variation in the values of ε and kr due to differences in firing temperature.

As described above, the various properties of the ferroelectric ceramic according to the present invention vary somewhat depending on the types and blending ratios of auxiliary raw materials and additive raw materials, or depending on the firing temperature. However, in any case, it shows very superior values when compared with conventional ones.

Note that embodiments of the ferroelectric ceramics according to the present invention are as follows:
Not limited to the above. For example, P as a blending raw material
Instead of bO, MgCO3, 5b203, Pb3O4, M
Other compounds can also be used as sources of metal elements, such as gO, 5b205, etc. It is also possible to use 5n02 together with 5b20a as an additive raw material. Furthermore, the method of preparing the raw materials, the pressurizing conditions, the firing temperature, the shape of the molded body, etc. can be changed as appropriate depending on the embodiment.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by incorporating Sb into the composition, it is possible to improve the dielectric constant ε and electromechanical coupling coefficient in ferroelectric ceramics, which were difficult to do in the past. It is possible to improve the entire piezoelectric constant d. Moreover, the Curie temperature Tc shows a high value, and the dielectric loss tan δ does not deteriorate.

In short, the ferroelectric ceramic according to the present invention has extremely high practical value due to its excellent dielectricity and piezoelectricity, so it can be widely applied and can be used in a variety of uses.

Claims (6)

[Claims] 1. PbTiO_3, PbZrO_3, Pb(Mg1/
A ferroelectric ceramic having a basic composition of 3Nb2/3)O_3 and SrTiO_3, and containing a small amount of Sb. 2. PbTiO_3, PbZrO_3, Pb(Mg1/
A ferroelectric ceramic having a basic composition of 3Nb2/3)O_3 and SrTiO_3, and containing small amounts of Bi, Zn, and Sb. 3. PbTiO_3, PbZrO_3, Pb(Mg1/
A ferroelectric material whose basic composition is 3Nb2/3)O_3 and SrTiO_3, and which is characterized by containing small amounts of Bi, Zn, and Sb, and further increasing the content of Mg. Ceramics. 4. PbTiO_3,. PbZrO_3, Pb(Mg1
/3Nb2/3)O_3, and SrTiO_3, and further contains Pb(Fe2/3W1
/3) A ferroelectric ceramic having O_3 as a subcomposition and containing a small amount of Sb. 5. PbTiO_3, PbZrO_3, Pb(Mg1/
It has a basic composition consisting of 3Nb2/3)O_3, and SrTiO_3, and further contains Pb(Fe2/3W1/
3) A ferroelectric ceramic having O_3 as a subcomposition and containing small amounts of Bi, Zn, and Sb. 6. PbTiO_3, PbZrO_3, Pb(Mg1/
It has a basic composition consisting of 3Nb2/3)O_3, and SrTiO_3, and further contains Pb(Fe2/3W1
/3) It has O_3 as a sub-composition, and contains small amounts of Bi, Zn, and Sb, and further contains Mg.
A ferroelectric ceramic characterized by having an increased content of.