JP4828570B2 - Piezoelectric ceramic composition, piezoelectric ceramic composition manufacturing method, and piezoelectric ceramic component - Google Patents

Description

  The present invention relates to a piezoelectric ceramic composition, a method of manufacturing a piezoelectric ceramic composition, and a piezoelectric ceramic component, and in particular, a material such as a piezoelectric ceramic component such as a piezoelectric sounding body, a piezoelectric sensor, a piezoelectric actuator, a piezoelectric transformer, and a piezoelectric ultrasonic motor. The present invention relates to a lead-free piezoelectric ceramic composition, a method for producing a lead-free piezoelectric ceramic composition, and a piezoelectric ceramic component using the lead-free piezoelectric ceramic composition.

As a piezoelectric ceramic composition, _PCM composed configured _PZT (PbTiO 3 -PbZrO ₃₎ based porcelain or ternary with two-component _{[PbTiO 3 -PbZrO 3 -Pb (Mg} 0.5 Nb 0.5 ) TiO ₃ ] based porcelain has been mainly used.

  However, these porcelain compositions are all composed mainly of lead, and there is a problem of environmental influences caused by lead components such as lead oxide that volatilizes during firing.

Conventionally, as an alternative to this, among the materials having the perovskite structure of ABO ₃ , (Bi _0.5 Na _0.5 ) TiO ₃ , (Bi _0.5 K _0.5 ) TiO ₃ and (Bi, Na, K ) TiO ₃ , (Bi, Na, Ba) Materials having a composite perovskite structure including Bi (Bi perovskite) such as TiO ₃ , these solid solutions, and (Bi, Na, K) TiO ₃ with Fe ₂ O ₃ , Cr Lead-free piezoelectric ceramic composition to which ₂ O ₃ , MnO ₂ , NiO, Co ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , Al ₂ O ₃ , BaCO ₃ , Sb ₂ O ₃ , Nb ₂ O _{5 and the} like are added Has been proposed.
Japanese Patent Application Laid-Open No. 11-171643 Japanese Examined Patent Publication No. 04-60073 JP 2001-151666 A JP 2001-48642 A JP 11-217262 A JP 2000-22235 A Japanese Patent Application Laid-Open No. 2000-272962

  Bi perovskite has a low piezoelectric constant as a piezoelectric ceramic component using displacement such as a sounding body, a sensor, and an actuator, and a mechanical quality factor Qm is low in a piezoelectric ceramic component using power such as a transformer and an ultrasonic motor. In addition, Bi perovskite has abnormal grain growth during molding and after firing, and easily forms a non-uniform structure (Duplex Structure) in which crystal grains exceeding 100 μm and fine crystal grains of several μm are mixed. Difficult to control.

  Piezoelectric ceramic components made by forming a piezoelectric ceramic composition with a thickness of several μm to several tens of μm, then laminating them through electrode materials and firing them simultaneously, a ceramic composition in which the size of crystal grains exceeds the sheet thickness Cannot be used. Therefore, improvement of material properties is essential for use as an alternative to PZT.

Among the prior arts, JP-A-11-217262, JP-A-2000-22235, and JP-A-2000-272926 include these Bi perovskites with Fe ₂ O ₃ , Cr ₂ O ₃ , MnO ₂ , Co ₂ O ₃ , La _2. It is suggested that the piezoelectric characteristics can be improved by adding oxides such as O ₃ , BaCO ₃ , Sb ₂ O ₃ , and Nb ₂ O ₃ .

  However, in actuality, in the composition system in which these oxides are added to Bi perovskite when synthesized as in the prior art, the constituent elements of Bi perovskite such as Bi during reaction synthesis, heat treatment process such as sintering process, etc. And the added oxide react to form a secondary phase other than Bi perovskite. Therefore, the effect of lowering the piezoelectric characteristics due to the secondary phase and the effect of improving the characteristics due to the added oxide are contradictory, and the improvement as shown cannot be obtained stably. Furthermore, since the microstructure of the sintered body cannot suppress the generation of the secondary phase, the effect is not mentioned.

  An object of the present invention is to provide a piezoelectric ceramic composition having a good piezoelectric characteristic, a method for producing a piezoelectric ceramic composition, and a piezoelectric ceramic component, which are made of a lead-free compound.

The piezoelectric ceramic composition according to the present invention is mainly composed of a perovskite-type composite oxide represented by the general formula ABO ₃ , and A in the general formula is selected from Bi, Na, K and Ba It consists of more than seed elements, B in the general formula consists of Ti, and a part of B (= Ti) in the general formula is substituted by a pentavalent element M (V) Is.

The method for producing a piezoelectric ceramic composition according to the present invention includes a calcining step of calcining a raw material compound, a molding step of molding a calcined powder obtained in the calcining step, and a molding obtained in the molding step. The raw material compound is mainly composed of a perovskite-type composite oxide represented by the general formula ABO ₃ , and A in the general formula is selected from Bi, Na, K, and Ba. 1 or 2 or more elements, B in the general formula is made of Ti, and a part of B (= Ti) in the general formula is substituted by a pentavalent element M (V). It is characterized by this.

The piezoelectric ceramic component according to the present invention includes one or more piezoelectric bodies and two or more electrodes sandwiching the piezoelectric bodies, and the piezoelectric bodies are made of a perovskite type complex oxide represented by the general formula ABO _3. And A in the general formula consists of one or more elements selected from Bi, Na, K and Ba, B in the general formula consists of Ti, and B in the general formula A part of (= Ti) is substituted with a pentavalent element M (V).

The general formula ABO ₃ may be a perovskite complex oxide represented by the following formula (3) or (4). In this case, pentavalent element M (V) can be used as M.

Bi _0.5 (Na _1-α K _α ) _0.5-x Ti _1-x M _x O ₃ (3)

(Bi _0.5-0.5β Na _0.5-0.5β-x ) Ba _β Ti _1-x M _x O ₃ (4)

  Here, the range of α is preferably 0 ≦ α ≦ 1, and the range of β is preferably 0 <β <1.

  Further, the substitution ratio x in which a part of B (= Ti) in the general formula is substituted by the pentavalent element M (V) is preferably 0.005 ≦ x ≦ 0.020. The range of the substitution ratio x is set to 0.005 ≦ x ≦ 0.020 because the particle size distribution is non-uniform when x is less than 0.005, the pores remain, and when x exceeds 0.020, Although the next phase increases and polarization becomes impossible, there is no such inconvenience in the range of 0.005 ≦ x ≦ 0.020, and a dense composition with good piezoelectric characteristics (Qm, kr, d31) can be obtained. Because.

  Moreover, as said pentavalent element M (V), it can be set as Nb, Sb, V, or Ta, for example.

  In the above description, the phrase “perovskite complex oxide as a main component” means that other components may be included as long as the characteristics of the piezoelectric ceramic composition are not impaired.

  In the method for producing a piezoelectric ceramic composition, the calcined powder is formed not only when the calcined powder is pressed and molded, but also when a sheet is formed using a calcined powder slurry, This includes the case where a powdery slurry and electrodes are alternately applied to form a laminate.

  Examples of the piezoelectric ceramic component include a piezoelectric sounding body, a piezoelectric sensor, a piezoelectric actuator, a piezoelectric transformer, and a piezoelectric ultrasonic motor. However, any other electrical component that can use a piezoelectric ceramic composition may be used. You may apply.

  In the porcelain composition according to the present invention, at least one element selected from the pentavalent element M (V) = Nb, Sb, V, Ta substituted for Ti acts as a donor. Moreover, since such a porcelain composition has a stoichiometric composition as represented by a general formula, it does not induce a secondary phase unlike the prior art. Furthermore, since the above-mentioned porcelain composition has a reduced molar ratio of Ti, an effect of suppressing the formation of a Ti-rich low-melting liquid phase during firing occurs.

  In the porcelain composition according to the present invention, deterioration of the piezoelectric characteristics due to the secondary phase is suppressed by the above action. In addition, when Ti is substituted with at least one element selected from the pentavalent element M (V) = Nb, Sb, V, and Ta, the donor site of the pentavalent element M (V) causes the A site. As a result, the lattice of the alkali metal element is easily distorted and the piezoelectric constant is improved. Furthermore, abnormal grain growth is suppressed by the action of no Ti-rich low melting point phase being generated, and when Ti is replaced with the pentavalent element M (V), the microstructure is such that the crystal grain size is 10 μm or less. Make uniform.

  As a result of the above, a lead-free piezoelectric ceramic composition useful for piezoelectric ceramic parts is obtained.

  The objective of providing a piezoelectric ceramic composition comprising a lead-free compound, a method for producing the piezoelectric ceramic composition, and a piezoelectric ceramic component using the piezoelectric ceramic composition was realized without impairing the piezoelectric characteristics.

First, Bi ₂ O ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , and TiO ₂ as raw material compounds were weighed at a ratio of the composite oxide of formula ( 2) .

Bi _0.5 (Na _1-α K _α ) _0.5-x Ti _1-x M (V) _x O ₃ (2)

In addition, in this formula ( 2) , α = 0 to 1 and M (V) are Nb ₂ O ₅ , Sb ₂ O ₃ , V ₂ O ₅ , and Ta ₂ O ₅ in the ratios shown in the x column of Table 1. Each was weighed.

Next, each raw material compound and additive components were put in a ball mill together with ethanol under the sample conditions shown in Table 1 , and wet-mixed. The resulting slurry was dried and calcined at 750 ° C. for 3 hours. By this calcination, a perovskite complex oxide is synthesized under each sample condition.

  Next, this calcined product was put into a ball mill together with ethanol, wet pulverized, the resulting slurry was dried, and an organic binder (PVA) was added to dry granulate.

  Next, this granulated material was molded into a 10 mmφ × 0.5 mmt disc with a uniaxial press and fired at 1000 to 1300 ° C. for 1 to 4 hours to prepare a sample.

Next, for this sample, the generated phase was identified by an X-ray diffractometer (XRD), and the microstructure was observed and evaluated by a scanning electron microscope (SEM). The results were as shown in Table 1 .

Moreover, it polarized at 2-5 kV / mm at 50-150 degreeC in insulating oils, such as a silicone oil, the dielectric property at 1 kHz was measured with the LCR meter, and the piezoelectric property was measured by the resonance antiresonance method with the impedance. The results were as shown in Table 1 .

In this example, when the pentavalent element M (V) is substituted in the range of x = 0.005 to 0.02, the generation of the secondary phase is suppressed, and a uniform sintered body with a fine structure is formed. It was done. Piezoelectric ceramics with good piezoelectric characteristics and good microstructure and piezoelectric characteristics were obtained as compared with the comparative examples described later. Table 1 shows the results when α = 0.07 in which the piezoelectric characteristics increase as a typical characteristic in the vicinity of the morphotropic phase boundary.

Comparative Example: Bi ₂ O ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , and TiO ₂ were weighed in such a ratio that the composite oxide of formula (5) was formed.

(Bi _0.5 Na _1-α K _α ) TiO ₃ + additive ………… (5)

Further, as an additive component in the formula (5), were each weighed _{S b 2 O 3, Nb 2} O 5 in proportions shown in x column of Table 2.

  Samples were prepared using these compounds in the same manner as in Example 1, and the formation phase was identified and the microstructure was evaluated by XRD and SEM in the same manner as in Example 1. The secondary phase formed by reacting with the element was confirmed, and the presence of the secondary phase became significant as the amount of additive added increased. The microstructure was non-uniform because the secondary phase segregated locally.

Further, the piezoelectric characteristics were measured in the same manner as in Example 1. Table 2 shows typical results when α = 0.07. According to this example (comparative example), the piezoelectric characteristics were only slightly improved due to the influence of the secondary phase caused by the reaction between the additive and Bi perovskite.

First, Bi ₂ O ₃ , Na ₂ CO ₃ , BaCO ₃ , and TiO ₂ as raw material compounds were weighed at a ratio of the composite oxide of formula ( 4) .

(Bi _0.5-0.5β Na _0.5-0.5β-x ) Ba _β Ti _1-x M (V) _x O ₃ (4)

In this formula ( 4) , 0 <β <1 and M (V ) are Nb ₂ O ₅ , Sb ₂ O ₃ , V ₂ O ₅ , and Ta ₂ O ₅ in the ratios shown in the column x in Table 3. Each was weighed.

Using these compounds, sample disks were prepared in the same manner as in Example 1, and the characteristics were evaluated. Discs manufactured, when the pentavalent element M a (V) was replaced with a range of x = 0.005 to 0.02, the generation of secondary phases is suppressed, uniform sintered body microstructure Been formed. Piezoelectric ceramics with good piezoelectric properties and fine structure and good piezoelectric properties compared to the prior art were obtained. Table 3 shows a result of β = 0.06 in which the piezoelectric property becomes high in the vicinity of the morphotropic phase boundary as a typical property.

When x = 0.00, abnormal grain growth was observed as shown in FIG. 1, and the size of the crystal grains was extremely inhomogeneous, 1 μm to several 100 μm. Qm = 224 , d31 = 34 pm / V, kr = 28 %, and the piezoelectric characteristics were insufficient for practical use between hardware and software.

Pentavalent element M (V), x = 0.01, as shown in FIG. 2, the crystal grains was homogeneous. The piezoelectric characteristics were improved to Qm = 88 and d31 = 70 pm / V. Piezoelectric properties have been improved to a level that can be applied to sounding bodies and actuators.

A piezoelectric ceramic composition of x = 0.01, α = 0.06, and M (V) = Nb is dispersed in an organic solvent such as ethanol, and an organic binder such as PVB is added to form a slurry, which is then molded into a sheet. layered with the electrodes, such as, heat-treated binder removal at 400 to 500 ° C., the a and fired in the same manner to form a piezoelectric ceramic sintered laminate to prepare a sound, such as in FIG. In the figure, 10 is a piezoelectric ceramic, 12 is an electrode, and 18 is a diaphragm.

The Evaluation of the acoustic properties of the sounding body, the frequency dependence of the sound pressure level was as shown in FIG. For comparison, PZT-based representative of the results of the acoustic characteristics and inserted into FIG.

As seen in FIG. 4 , a sounding body having a sound pressure characteristic equivalent to that of a typical PZT was obtained. Therefore, it was verified that the porcelain composition according to the present invention is useful as a piezoelectric ceramic part.

  The present invention can be applied to materials for piezoelectric ceramic parts such as piezoelectric sounding bodies, piezoelectric sensors, piezoelectric actuators, piezoelectric transformers, and piezoelectric ultrasonic motors.

6 is an explanatory diagram showing a microstructure of a comparative sample (x = 0.00) formed in Example 2. FIG. It is explanatory drawing which shows the fine structure of the sample (M (V), x = 0.01) formed in Example 2. FIG. It is explanatory drawing of the piezoelectric sounding body produced in Example 4. FIG. It is a graph which shows the relationship between a frequency and a sound pressure.

Explanation of symbols

10 piezoelectric ceramic 12 electrodes
1 8 Diaphragm

Claims (3)

A perovskite-type composite oxide represented by the general formula ABO ₃ is a main component, and A in the general formula is composed of one or more elements selected from Bi, Na, K and Ba, and the general formula And B in the general formula is partially substituted by the pentavalent element M (V), and the general formula ABO ₃ is represented by the following formula (3) or (4): Consisting of a perovskite type complex oxide represented,
Bi _0.5 (Na _1-α K _α ) _0.5-x Ti _1-x M _x O ₃ (3)
(Bi _0.5-0.5β Na _0.5-0.5β-x ) Ba _β Ti _1-x M _x O ₃ (4)
In the formulas (3) and (4), the range of α is 0 ≦ α ≦ 1, the range of β is 0 <β <1, the range of x is 0.005 ≦ x ≦ 0.020, the pentavalent element M A piezoelectric ceramic composition characterized in that (V) is Sb, V or Ta. A calcining step of calcining the raw material compound; a molding step of molding the calcined powder obtained in the calcining step; and a firing step of firing the molded body obtained in the molding step. Is composed of a perovskite-type composite oxide represented by the general formula ABO ₃ as a main component, and A in the general formula is composed of one or more elements selected from Bi, Na, K and Ba, B in the general formula consists of Ti, and a part of B (= Ti) in the general formula is substituted with a pentavalent element M (V), and the general formula ABO ₃ is represented by the following formula (3) or (4 ) And a perovskite type complex oxide represented by
Bi _0.5 (Na _1-α K _α ) _0.5-x Ti _1-x M _x O ₃ (3)
(Bi _0.5-0.5β Na _0.5-0.5β-x ) Ba _β Ti _1-x M _x O ₃ (4)
In the formulas (3) and (4), the range of α is 0 ≦ α ≦ 1, the range of β is 0 <β <1, the range of x is 0.005 ≦ x ≦ 0.020, the pentavalent element M (V) is Sb, V, or Ta, The manufacturing method of the piezoelectric ceramic composition characterized by the above-mentioned. One or two or more piezoelectric bodies and two or more electrodes sandwiching the piezoelectric bodies, and the piezoelectric body is mainly composed of a perovskite complex oxide represented by the general formula ABO ₃ , A consists of one or more elements selected from Bi, Na, K and Ba, B in the general formula consists of Ti, and a part of B (= Ti) in the general formula is 5 Substituted with a valent element M (V), and the general formula ABO ₃ comprises a perovskite type complex oxide represented by the following formula (3) or (4):
Bi _0.5 (Na _1-α K _α ) _0.5-x Ti _1-x M _x O ₃ (3)
(Bi _0.5-0.5β Na _0.5-0.5β-x ) Ba _β Ti _1-x M _x O ₃ (4)
In the formulas (3) and (4), the range of α is 0 ≦ α ≦ 1, the range of β is 0 <β <1, the range of x is 0.005 ≦ x ≦ 0.020, the pentavalent element M A piezoelectric ceramic component, wherein (V) is Sb, V or Ta.

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