JP4321526B2 - Dielectric porcelain composition and electronic component using the same - Google Patents

Description

  The present invention relates to a dielectric ceramic composition containing no Pb, and a piezoelectric ceramic electronic component such as a piezoelectric actuator, a piezoelectric sensor, a piezoelectric buzzer and a piezoelectric filter using the dielectric ceramic composition, and a dielectric ceramic electronic component such as a multilayer capacitor.

Perovskite oxides containing Pb such as lead zirconate titanate (Pb (Zr, Ti) O ₃ ; hereinafter referred to as “PZT”) and lead titanate (PbTiO ₃ ) are ferroelectrics and have a high dielectric constant. Therefore, it is widely used for electronic parts such as capacitors and piezoelectric elements.

  However, these piezoelectric ceramics mainly composed of PZT and lead titanate contain Pb, so there is a concern about the influence on the environment, and also due to evaporation of lead compounds used as raw materials in the manufacturing process. This may lead to a decrease in product uniformity.

  On the other hand, a piezoelectric ceramic mainly composed of a bismuth layered compound, which is a lead-free ferroelectric material, has been developed. This type of piezoelectric ceramic is widely used because of its low electromechanical coupling coefficient. It has not reached. For this reason, a material having a novel composition not containing Pb has been demanded, and various proposals have been made.

For example, Patent Document 1, the perovskite oxide of the general formula ABO _3, Sn ferroelectric simple perovskite structure mainly composed of A-site, SnTiO ₃ of Ti occupy B sites is disclosed.

Moreover, in this patent document 1, it is a solid solution of (Ba, Sr) TiO ₃ and SnTiO _{3 in} which Ba and Sn occupy the A site and Ti occupy the B site in the perovskite oxide of the general formula ABO ₃ (Ba, A ferroelectric material having a simple perovskite structure mainly composed of Sr, Sn) TiO ₃ is shown. That is, a ferroelectric in which (Ba, Sr) of (Ba, Sr) TiO ₃ is partially replaced with Sn is disclosed.

In Patent Document 1, a dielectric thin film of SnTiO ₃ or (Ba, Sr, Sn) TiO ₃ is formed on a SrTiO ₃ single crystal substrate by pulse laser deposition (hereinafter referred to as “PLD method”). Formation, thereby obtaining the above ferroelectric.

That is, the difficulty of generating the perovskite structure is generally evaluated by a tolerance factor, but the tolerance factor of a normal perovskite oxide is 0.8 to 0.95 (for example, PbTiO ₃ is 0.88, BaTiO ₃ is 0.93), but the tolerance factor of SnTiO ₃ is slightly small, 0.79, and Sn is usually stable at a tetravalent level, so synthesis of SnTiO ₃ is expected to be extremely difficult.

Therefore, in Patent Document 1, the above dielectric thin film is formed by the PLD method under non-equilibrium using an excimer laser, whereby SnTiO ₃ having a relative dielectric constant of about 400 and a residual polarization of about 50 μC / cm ² A (Ba, Sr, Sn) TiO ₃ ferroelectric thin film having a relative dielectric constant of about 500 is obtained.

JP 2003-146660 A

However, in Patent Document 1, since an excimer laser is irradiated on a SrTiO ₃ single crystal substrate and each TiO ₂ layer and SnO layer of one molecular layer are alternately stacked, the manufacturing method becomes very complicated. In addition, the use application is limited in a thin film form. Moreover, the relative dielectric constant obtained is as small as about 400 for SnTiO ₃ and about 500 for (Ba, Sr, Sn) TiO ₃ , which is still insufficient.

  The present invention has been made in view of such circumstances, and a dielectric ceramic composition having a high phase transition temperature (Curie point), remanent polarization, and high relative dielectric constant even if it is a lead-free lead-free system. Further, it is an object of the present invention to provide a piezoelectric ceramic electronic component and a multilayer ceramic electronic component using the dielectric ceramic composition.

The inventors of the present invention have intensively studied to achieve the above object, and as a result, a part of Ba of BaTiO ₃ which is a stable perovskite compound (general formula ABO ₃ ) is substituted with divalent Sn within a predetermined range, The knowledge that a lead-free dielectric ceramic composition having a high phase transition temperature, remanent polarization, and relative dielectric constant can be obtained by blending so that the molar ratio of the A site and the B site is within a predetermined range. Obtained.

The present invention has been made on the basis of such knowledge, and the dielectric ceramic composition according to the present invention is mainly composed of a perovskite type compound represented by a composition formula: (Ba _1-x Sn _x ) _m TiO _3. The Ba site represented by (Ba _1-x Sn _x ), wherein x and m are in the range of 0.01 ≦ x ≦ 0.3 and 0.9 ≦ m ≦ 1.1, , Which is substantially free of Sr.

  In addition, as a result of further diligent research by the present inventors, it was found that low-temperature sinterability is improved by containing at least one of Mn oxide and Si oxide as a subcomponent.

  That is, the dielectric ceramic composition of the present invention is characterized by containing at least one of Mn oxide and Si oxide as a subcomponent.

  It has also been found that by controlling the content of Mn oxide and Si oxide to 10 parts by weight or less in total with respect to 100 parts by weight of the main component, low temperature firing can be performed while maintaining dielectric properties.

That is, in the dielectric ceramic composition of the present invention, at least one of Mn oxide and Si oxide is converted to MnO ₂ and SiO ₂ with respect to 100 parts by weight of the main component, respectively, and 10 parts by weight in total. It is characterized by being contained in the following range (excluding 0 part by weight).

  In addition, an electronic component according to the present invention is characterized by having an element body formed of the above dielectric ceramic composition and a conductor provided on the element body.

  According to the dielectric ceramic composition of the present invention, since a part of Ba is replaced with Sn, the phase transition temperature becomes about 130 ° C. or more and shifts to the high temperature side, and the characteristics as a ferroelectric are obtained. The effect that the temperature range to show can be expanded is acquired.

Further, the remanent polarization is as high as about 20 μC / cm ² or more, and good characteristics as a ferroelectric can be obtained. Furthermore, the relative dielectric constant can be made larger than 700. Therefore, even a lead-free dielectric ceramic composition containing no Pb can obtain piezoelectric and dielectric characteristics equal to or higher than those of conventional PZT and lead titanate.

  Moreover, a desired dielectric ceramic composition can be obtained by low-temperature sintering by containing at least one of Mn oxide and Si oxide as a subcomponent.

  Further, by controlling the subcomponent to 10 parts by weight or less (excluding 0 parts by weight) with respect to 100 parts by weight of the main component, a dielectric ceramic composition having a low sintering temperature is obtained while maintaining dielectric properties. be able to.

  Since the dielectric ceramic composition of the present invention has a high remanent polarization, it can be suitably used as a material for a piezoelectric ceramic electronic component such as a piezoelectric actuator. Moreover, since the phase transition temperature is shifted to the high temperature side, the temperature range showing the characteristics as a ferroelectric substance is expanded, so that it can be suitably used as a capacitor material.

  That is, since the electronic component of the present invention has an element body formed of the above dielectric ceramic composition and a conductor provided on the element body, the piezoelectric actuator has high remanent polarization and good piezoelectric characteristics. Various electronic components such as piezoelectric ceramic electronic components such as monolithic ceramic capacitors having a high relative dielectric constant can be obtained.

It is sectional drawing which shows one Embodiment (1st Embodiment) of the piezoelectric actuator as an electronic component manufactured using the dielectric material ceramic composition which concerns on this invention. It is sectional drawing which shows one Embodiment (2nd Embodiment) of the multilayer ceramic capacitor as an electronic component manufactured using the dielectric material ceramic composition which concerns on this invention.

Explanation of symbols

2a, 2b Piezoelectric substrate (element body)
3, 4a, 4b Electrode (conductor)
12 Multilayer dielectric ceramic body (element body)
14a First dielectric ceramic layer 14b Second dielectric ceramic layer 16 Internal electrode (conductor)
18 External electrode (conductor)

  Next, an embodiment of the present invention will be described in detail.

The dielectric ceramic composition according to one embodiment of the present invention is mainly composed of a perovskite compound represented by a composition formula: (Ba _1-x Sn _x ) _m TiO ₃ , and x and m are 0.01 ≦ x ≦ 0.3, 0.9 ≦ m ≦ 1.1, and the Ba site represented by (Ba _1-x Sn _x ) is blended so as not to substantially contain Sr. ing.

  And by comprising a dielectric ceramic composition with the said component composition, even if it does not contain lead, a dielectric ceramic composition with high phase transition temperature, remanent polarization, and a relative dielectric constant can be obtained.

  Here, the range of x is set to 0.01 ≦ x ≦ 0.3 because the phase transition temperature and remanent polarization can be improved by replacing a part of Ba with divalent Sn. This is because when the molar ratio x of Sn is less than 0.01, the desired effect cannot be exhibited, and when the molar ratio x exceeds 0.3, the sinterability deteriorates. .

  The range of m is set to 0.9 ≦ m ≦ 1.1 because when the molar ratio m of the Ba site is less than 0.9, the composition becomes semiconductive, and the molar ratio m is 1. It is because sinterability will deteriorate when it exceeds 1.

  Further, the Ba site does not substantially contain Sr as described above. Here, “substantially does not contain Sr” means that up to a very small amount of Sr as an impurity that may be inevitably contained in the production within a range that does not affect the characteristics of the electronic component such as piezoelectric characteristics and dielectric characteristics Is not excluded, specifically, 0.2% by weight or less, preferably 0.02% by weight or less, more preferably 0.002% by weight or less in terms of SrO. preferable.

  From the viewpoint of performing low-temperature sintering, it is preferable that at least one of Mn oxide and Si oxide is contained as a subcomponent in the main component.

  Further, the content of the subcomponents is preferably 10 parts by weight or less (not including 0 parts by weight) in total with respect to 100 parts by weight of the main component. That is, even if the total amount of Mn oxide and Si oxide exceeds 10 parts by weight, there is no practical problem in the dielectric properties themselves, but the relative permittivity tends to decrease slightly and the dielectric loss tends to increase slightly. Therefore, in order to perform low-temperature sintering (for example, 1050 ° C. or less) while maintaining good dielectric properties, a total of 10 parts by weight or less (excluding 0 parts by weight) with respect to 100 parts by weight of the main component It is preferable that

  Next, electronic parts manufactured using the dielectric ceramic composition will be described.

  FIG. 1 is a cross-sectional view of a piezoelectric actuator as an embodiment of an electronic component manufactured using the above dielectric ceramic composition.

  The piezoelectric actuator 1 includes two piezoelectric substrates 2a and 2b that are stacked. The piezoelectric substrates 2a and 2b are both formed of the above dielectric ceramic composition. Each of the piezoelectric substrates 2a and 2b is polarized in the same thickness direction. An electrode 3 is formed between the piezoelectric substrate 2a and the piezoelectric substrate 2b. Furthermore, an electrode 4a is formed on the upper surface of the piezoelectric substrate 2a, and an electrode 4b is formed on the lower surface of the piezoelectric substrate 2b. The first terminal 5 is connected to the electrode 3, and the second terminal 6 is connected to the electrodes 4a and 4b. In the piezoelectric actuator 1, when a voltage is applied to the first terminal 5 and the second terminal 6, the piezoelectric substrates 2a and 2b are displaced in the thickness direction.

  In the piezoelectric actuator 1, since the piezoelectric substrates 2a and 2b are manufactured using the dielectric ceramic composition, a piezoelectric actuator having high remanent polarization and good piezoelectric characteristics can be obtained.

  FIG. 2 is a cross-sectional view of a multilayer ceramic capacitor as another embodiment of the electronic component.

  The multilayer ceramic capacitor 10 includes a multilayer dielectric ceramic body 12 formed of the above dielectric ceramic composition. The laminated dielectric ceramic body 12 is formed by laminating a plurality of first dielectric ceramic layers 14a and two second dielectric ceramic layers 14b. These dielectric ceramic layers 14a and 14b are laminated with the internal electrode 16 interposed therebetween. Further, the external electrode 18, the first plating film 20a, and the second plating film 20b are formed in this order on both end faces of the multilayer dielectric ceramic body 12. Nickel, copper or the like is used as the first plating film 20a, and solder, tin or the like is used as the second plating film 20b.

  In this multilayer ceramic capacitor 10, since the multilayer dielectric ceramic body 12 is produced using the dielectric ceramic composition, a multilayer ceramic capacitor having a high relative dielectric constant and good dielectric characteristics can be obtained.

  The present invention is not limited to the above embodiment. In the above embodiment, the piezoelectric actuator and the multilayer ceramic capacitor are exemplified as the electronic component. However, it is needless to say that the present invention can be applied to various electronic components such as a piezoelectric sensor, a piezoelectric buzzer, and a piezoelectric filter.

  Next, examples of the present invention will be specifically described.

First, each powder of BaCO ₃ , SnO, and TiO ₂ was prepared so that a composition of the composition formula (Ba _1-x Sn _x ) _m TiO ₃ as shown in Table 1 was obtained to obtain a preparation raw material. This blended raw material was calcined in an N ₂ reducing atmosphere at about 500 ° C. to 1000 ° C. for 2 hours to obtain a calcined product. The calcined product was pulverized by a pulverizer to obtain a pulverized product. Next, 10 parts by weight of polyvinyl alcohol was mixed with 100 parts by weight of the pulverized product and dried to obtain a mixture. This mixture was molded into a diameter of about 12 mm and a thickness of about 2.5 mm with a uniaxial press (pressure 9.8 × 10 ² MPa) to obtain a disk-shaped molded body. This compact was fired at a temperature shown in Table 1 in a reducing atmosphere of H ₂ —N ₂ —H ₂ O gas (oxygen partial pressure of about 10 ⁻¹² MPa to 10 ⁻¹⁶ MPa) to obtain a dielectric ceramic. . Thereafter, an Ag electrode paste was applied to the end face of the dielectric ceramic, and baked at about 800 ° C. to form electrodes, and measurement samples (capacitors) of sample numbers 1 to 13 were produced.

  With respect to the measurement sample thus obtained, the relative dielectric constant (εr) and dielectric loss (tan δ) at room temperature (25 ° C.) and measurement frequency of 1 kHz were measured with an LCR meter (manufactured by Hewlett-Packard, type 4284). The phase transition temperature was measured for the measurement sample in the temperature range of −55 ° C. to 450 ° C. by a measurement system using an impedance analyzer. The remanent polarization was measured at 25 ° C. with a measuring device using a Soya tower circuit.

The results are shown in Table 1. In Table 1, * is attached | subjected to the composition outside the range of this invention. Although a similar disk-shaped molded body was fired in the air, a portion of Sn is oxidized, were unable SnO ₂ next sintering.

From Table 1, sample numbers 2 to 7 and 10 to 12 in which a part of Ba was replaced with Sn. It was found that the phase transition temperature shifted to the high temperature side in the temperature range of 130 ° C to 230 ° C. On the other hand, Sample No. 1, which is a conventional barium titanate, has a phase transition temperature of 120 ° C., which is lower than that of the dielectric ceramic composition of the present invention. In addition, since Sn is usually tetravalent and stable, substitution at the Ti site is likely to occur, and it is generally known that when the Ti site is substituted with Sn, the phase transition temperature shifts to a lower temperature side. However, in the present invention, since the phase transition temperature is shifted to a higher temperature side, it is understood that (Ba, Sn) TiO ₃ , which is a perovskite type compound in which a part of Ba is substituted with divalent Sn, is synthesized. .

Further, in the sample numbers ^{2 to 7} and 10 to 12, the remanent polarization is as large as 21.0 to 32.9 μC / cm ^2, and therefore the remanent polarization is improved, so that good characteristics as a ferroelectric can be obtained. I understood.

  Furthermore, it was found that Sample Nos. 2 to 7 and 10 to 12 had a high relative dielectric constant of 708 to 1362, and it was possible to produce a dielectric ceramic composition having a high relative dielectric constant.

In the case of BaTiO _3, the relative dielectric constant is usually improved by substituting part of Ba with Sr. However, in the dielectric ceramic composition of the present invention, although the Ba site does not substantially contain Sr, It was found that the relative dielectric constant can be improved as compared with the case of containing Sr. That is, it is possible to improve both the relative permittivity and the phase transition temperature by replacing part of Ba with Sn without adding Sr.

From the above, it was confirmed that (Ba, Sn) TiO ₃ has an effect of shifting the phase transition temperature to the high temperature side, as in the case of adding Pb to BaTiO ₃ . Due to this effect, the usable temperature range as a ferroelectric can be expanded as compared with the conventional BaTiO ₃ .

  In Sample No. 8, x is 0.400 and exceeds 0.3, so it does not sinter even if the temperature is raised to 1300 ° C. In Sample No. 9, x is 0.100. Therefore, the composition became semiconducting because it was less than 0.9. Sample No. 13 had m of 1.200 and exceeded 1.1, so it was not sintered even when the temperature was raised to 1300 ° C.

Similarly to [Example 1], each powder of BaCO ₃ , SnO, and TiO ₂ was prepared so that a composition of the composition formula (Ba _1-x Sn _x ) _m TiO ₃ as shown in Table 2 was obtained. , The compound raw material was obtained. This blended raw material was calcined in an N ₂ reducing atmosphere at about 500 ° C. to 1000 ° C. for 2 hours to obtain a calcined product as a main component.

With respect to 100 parts by weight of the main component, each powder of MnCO ₃ and SiO ₂ as subcomponents is prepared so as to have a content as shown in Table ₂ in terms of MnO ₂ or SiO ₂ , and a preliminarily prepared calcined product Got.

Next, the prepared calcined product to which the subcomponent was added was pulverized by a pulverizer to obtain a pulverized product. 10 parts by weight of polyvinyl alcohol was mixed with 100 parts by weight of the pulverized product and dried to obtain a mixture. This mixture was molded into a diameter of about 12 mm and a thickness of about 2.5 mm with a uniaxial press (pressure 9.8 × 10 ² MPa) to obtain a disk-shaped molded body. The compact was fired at a temperature shown in Table 2 in a reducing atmosphere of H ₂ —N ₂ —H ₂ O gas (oxygen partial pressure of about 10 ⁻¹² MPa to 10 ⁻¹⁶ MPa) to obtain a dielectric ceramic. . Thereafter, an Ag electrode paste was applied to the end face of the dielectric porcelain and baked at about 800 ° C. to form electrodes, and measurement samples (capacitors) of sample numbers 14 to 23 were produced.

With respect to the measurement sample thus obtained, the relative permittivity, dielectric loss, phase transition temperature, and remanent polarization were measured under the same measurement conditions as in [Example 1]. The results are shown in Table 2.

In Table 2, since the sample numbers 14 and 15 contain 3 to 10 parts by weight of the Mn oxide in terms of MnO ₂ with respect to 100 parts by weight of the main component, they do not contain this [Example 1 ], It was found that the firing temperature can be lowered to 1050 ° C.

Sample Nos. 17, 18, and 19 contain 3 to 10 parts by weight of Si oxide in terms of SiO ₂ with respect to 100 parts by weight of the main component. Compared with sample numbers 3 and 4, it was found that the firing temperature could be lowered to 1050 ° C.

  In Sample Nos. 21 and 22, the total amount of Mn oxide and Si oxide was 0.4 to 5 parts by weight, and the firing temperature could be lowered as described above.

It was also found that the samples Nos. 14, 15, 17-19, 21, and 22 had a dielectric constant substantially equivalent to that obtained when no Mn oxide or Si oxide was added.
As shown in sample numbers 16, 20, and 23, when the total amount of Mn oxide and Si oxide exceeds 10 parts by weight, the relative permittivity and dielectric loss are slightly inferior to those of other samples. Therefore, in order to lower the firing temperature while maintaining dielectric properties such as dielectric constant and dielectric loss, it is confirmed that the total content of Mn oxide and / or Si oxide is preferably 10 parts by weight or less. It was done.

Claims (4)

The main component is a perovskite type compound represented by a composition formula: (Ba _1-x Sn _x ) _m TiO ₃ ,
x and m are
0.01 ≦ x ≦ 0.3,
0.9 ≦ m ≦ 1.1,
In the range of
And, Ba site represented by (Ba _1-x Sn _x) is, the dielectric ceramic composition characterized by containing substantially no Sr.   2. The dielectric ceramic composition according to claim 1, wherein at least one of Mn oxide and Si oxide is contained as a subcomponent. At least one of the Mn oxide and the Si oxide is converted to MnO ₂ and SiO ₂ with respect to 100 parts by weight of the main component, respectively, and in the range of 10 parts by weight or less (not including 0 parts by weight) in total. The dielectric ceramic composition according to claim 1 or 2, wherein the dielectric ceramic composition is contained.   An electronic component comprising an element body formed of the dielectric ceramic composition according to claim 1 and a conductor provided on the element body.