JP6565588B2 - Piezoelectric composition and piezoelectric element - Google Patents

Description

  The present invention relates to a piezoelectric composition and a piezoelectric element that are widely used in fields such as an ink jet head, a piezoelectric actuator, and a thin film sensor.

Piezoelectric elements using piezoelectric compositions have the effect of generating distortion when voltage is applied from the outside, and the effect of generating charge on the surface when receiving external stress, and are widely used in various fields. ing. For example, a piezoelectric element using a lead-based piezoelectric composition such as lead zirconate titanate generates a strain proportional to an applied voltage, and its displacement is as small as 1 × 10 ⁻¹⁰ m / V and has a response. For example, it is used for highly accurate position adjustment such as fine adjustment of an optical system.

  The piezoelectric composition generates an electric charge having a magnitude proportional to the applied stress or the amount of deformation caused by the stress, and is therefore used as a sensor for reading a minute force or amount of deformation. Furthermore, since the piezoelectric composition has excellent electric field responsiveness, it is possible to excite and resonate the piezoelectric composition itself or an elastic body bonded to the piezoelectric composition by applying an alternating electric field. It is also used for piezoelectric transformers, ultrasonic motors, etc.

  In general, a piezoelectric composition is obtained by polarizing a ferroelectric composition. Polarization treatment refers to applying a direct current electric field to a sintered ferroelectric composition in which the direction of spontaneous polarization is random, aligning the direction of the domain of the ferroelectric material in a certain direction, and forming a ferroelectric composition. This is an operation for imparting polarity. In particular, in the perovskite structure, since the spontaneous polarization is easily three-dimensionally oriented, most of the piezoelectric compositions in practical use have a perovskite structure.

The perovskite structure is a kind of crystal structure and is generally represented by a composition formula of ABO ₃ . Specifically, large alkali metal ions of the ion radius or alkaline earth metal ions A site, such as a small transition metal ions of the ionic radius is positioned at the B site, BO ₆ oxygen octahedral three-dimensional networks vertex shared, In this structure, A-site ions are filled in the voids.

Currently, most piezoelectric compositions having a perovskite structure in practical use are lead-based piezoelectric compositions composed of lead zirconate (PbZrO ₃ : PZ) and lead titanate (PbTiO ₃ : PT). A wide variety of products have been developed to meet a wide variety of needs by adding subcomponents or additives. For example, the piezoelectric constant (d ₃₃ ) is large instead of a small mechanical quality factor (Q _m ), and d ₃₃ is small because it is used for a position adjusting actuator or the like that requires a large amount of displacement by DC usage. large Q _m instead, to what is suitable for the alternating-current use, such as ultrasonic wave generating element such as an ultrasonic motor, there are various.

In addition to the PZT system, there is a piezoelectric composition that has been put into practical use, but it also has a lead-based perovskite composition such as lead magnesium niobate (Pb (Mg _1/3 Nb _2/3 ) O ₃ ). Most of the solid solution is the main component.

  However, these lead-based piezoelectric compositions contain about 60 to 70% by mass of lead oxide having a low melting point, and lead oxide (PbO) is likely to volatilize during firing. Therefore, it is desired to reduce the lead oxide used in consideration of the environment. In addition, as the application fields of piezoelectric compositions and piezoelectric single crystals expand in the future, the use amount of lead-based piezoelectric compositions is expected to increase, and lead sulfate generated by the chemical reaction between acid rain and lead will elute into the soil. This threatens to threaten the traditional ecosystem. Therefore, lead-free piezoelectric compositions have become a very important issue.

Known piezoelectric compositions containing no lead include, for example, barium titanate (BaTiO ₃ : BT) or a bismuth layered ferroelectric. However, BT has a low Curie temperature (T _c ) at which the piezoelectric properties disappear, as low as 120 ° C., and lacks practicality when considering use at high temperatures such as soldering or in-vehicle use. Bismuth layered ferroelectrics usually have a _{Tc of} 400 ° C. or higher and are excellent in thermal stability. However, since the anisotropy of piezoelectric characteristics is large, a lead-based piezoelectric composition is used in a normal ceramic process. It is difficult to obtain a high d ₃₃ comparable to In order to obtain a high d ₃₃ in a bismuth layered ferroelectric, it is necessary to orient spontaneous polarization during firing by a hot press method or a hot forging method, which causes a problem in terms of productivity.

On the other hand, recently, as a new piezoelectric composition that has a high T _c and is expected to have good d ₃₃ , sodium bismuth titanate (Bi _0.5 Na _0.5 TiO ₃ : BNT) system is used. The piezoelectric composition is mentioned. For example, Patent Document 1 discloses a piezoelectric composition in which BT and calcium titanate (CaTiO ₃ : CT) are added to BNT.

JP 2004-18321 A

However, the piezoelectric composition disclosed in Patent Document 1 cannot be said to have superior piezoelectric characteristics and temperature characteristics compared to lead-based piezoelectric compositions, and further improvements in d ₃₃ and T _c are required. Yes.

Therefore, the present invention has been proposed in view of such a conventional situation, and an object thereof is to provide an environment-friendly piezoelectric composition and a piezoelectric element having high d ₃₃ and T _c .

In order to solve the above problems, the present inventor has found an environmentally friendly piezoelectric composition having high d ₃₃ and T _c .

The present invention has the formula _{(1-y) x [(} Bi 0.5 Na 0.5) a TiO 3] + (1-y) (1-x) [Ba b TiO 3] + y [Bi c AlO 3] (1)
0.90 ≦ x ≦ 0.96
0.01 ≦ y ≦ 0.20
0.90 ≦ a ≦ 1.10
0.90 ≦ b ≦ 1.10
0.90 ≦ c ≦ 1.10
x + y = 1
It is represented by.

With the above composition range, an environmentally friendly piezoelectric composition having high d ₃₃ and T _c can be obtained.

In addition, a piezoelectric element using the piezoelectric composition, for example, an inkjet head, a piezoelectric actuator, a thin film sensor, and the like can provide a piezoelectric element with high actuator displacement and sensor sensitivity. Furthermore, since it has a high _Tc , a piezoelectric element having a wide practical temperature range can be provided.

According to the present invention, it is possible to provide an environment-friendly piezoelectric composition and a piezoelectric element having a high d ₃₃ and T _c.

It is a perspective view showing the example of 1 structure of the piezoelectric element using the piezoelectric composition concerning one Embodiment of this invention. It is sectional drawing showing another structural example of the piezoelectric element using the piezoelectric composition concerning one Embodiment of this invention.

  FIG. 1 shows a partial configuration example of a piezoelectric element using the piezoelectric composition according to the present embodiment. The piezoelectric element includes a piezoelectric substrate 1 made of the piezoelectric composition of the present embodiment, and a pair of electrodes 2 and 3 provided on a pair of opposing surfaces 1a and 1b of the piezoelectric substrate 1, respectively. Examples of the electrodes 2 and 3 include silver (Ag) and palladium (Pd).

  FIG. 2 shows another configuration example of the piezoelectric element using the piezoelectric composition according to the present embodiment. This piezoelectric element includes, for example, a laminate 10 in which a plurality of piezoelectric layers 11 and a plurality of internal electrodes 12 made of the piezoelectric composition of the present embodiment are alternately laminated. Examples of the internal electrode 12 include silver (Ag) and palladium (Pd). The thickness per layer of the piezoelectric layer 11 is preferably about 1 μm to 100 μm, for example, and the number of stacked layers of the piezoelectric layer 11 is determined according to the target displacement.

From Formula _{(1) (1-y)} x [(Bi 0.5 Na 0.5) a TiO 3] + (1-y) (1-x) [Ba b TiO 3] + y [Bi c AlO 3] As can be seen, the piezoelectric composition according to the present embodiment is composed of BNT, barium titanate (BaTiO ₃ : BT), and bismuth aluminate (BiAlO ₃ : BAO).

Among the above three components, BNT is a main component, and thus has a relatively high _Tc .

Of the three components, in the binary system of BNT and _BT, the maximum value of _{d 33} was confirmed by 0.94BNT-0.06BT. This is because BNT having a rhombohedral structure and BT having a tetragonal structure form a crystal phase boundary (MPB).

However, since BT has a low _Tc of about 120 ° C., _Tc is lowered when dissolved in BNT having a _Tc of about 330 ° C.

On the other hand, among the above three components, BAO has a tetragonal structure similar to BT, but _Tc is as high as 520 ° C.

That is, in the ternary system according to the aforementioned item, it is possible to obtain a high _{d 33} by the formation of MPB in BNT and BT, and the BAO with high _{T c,} it is possible to maintain a high _{T c.} Therefore, by setting the composition range, a piezoelectric composition having high d ₃₃ and T _c can be obtained.

In addition, the composition range of the piezoelectric composition mainly composed of the three components BNT, BT, and BAO according to the present embodiment is represented by the chemical formula (1) (1-y) x [(Bi _0.5 Na _0.5 ) _{a TiO 3] + (1-y} ) (1-x) [Ba b TiO 3] + in _{y [Bi c AlO 3],} x, y ranges and a are respectively 0.90 ≦ x ≦ 0.96,0 .01 ≦ y ≦ 0.20,0.90 ≦ a ≦ 1.10,0.90 If a ≦ b ≦ 1.10,0.90 ≦ c ≦ 1.10 , while with high _{d 33,} A higher _Tc can be obtained.

In the above composition range, 0.90 ≦ x ≦ 0.96, but when x is less than 0.90, the content of BT having a low _Tc increases and _Tc decreases. Further, _{d 33} is also reduced by away from the MPB composition. When x exceeds 0.96, d ₃₃ decreases because it moves away from the MPB composition. On the other hand, the range of y is 0.01 ≦ y ≦ 0.20. However, when y is less than 0.01, T _c decreases, and when y exceeds 0.20, the distance from the MPB composition is d. ₃₃ decreases.

In addition to the region described above, the composition of the piezoelectric composition mainly composed of the three components BNT, BT, and BAO according to this embodiment is represented by the chemical formula (1) (1-y) x [(Bi _0.5 Na _{0.5 ) a TiO 3] + (1} -y) (1-x) [Ba b TiO 3] + y [Bi c AlO 3] in the range of x, y, respectively, 0.95 ≦ x ≦ 0.96,0. In the case of 01 ≦ y ≦ 0.10, higher T _c and d ₃₃ can be obtained, which is more preferable.

Formula _{(1) (1-y)} x [(Bi 0.5 Na 0.5) a TiO 3] + (1-y) (1-x) [Ba b TiO 3] + y of _[Bi c AlO _3] a, b, and c represent the A / B ratio that is the composition ratio of the A site and B site atom of the perovskite structure compound in the entire piezoelectric composition. When a, b, and c exceed 1.10, it is not preferable because high sinterability is difficult to obtain. On the other hand, if a, b and c are 1.10 or less, the sinterability can be improved, and if a, b and c are 1.00 or less, higher piezoelectric characteristics can be obtained, which is more preferable. . However, if a, b, and c are less than 0.90, the resistivity is lowered due to the generation of a secondary phase having a non-perovskite structure, and piezoelectric characteristics cannot be obtained. From the above, the ranges of a, b, and c may be 0.90 ≦ a ≦ 1.10, 0.90 ≦ b ≦ 1.10, 0.90 ≦ c ≦ 1.10. , B and c should be the same.

The piezoelectric composition according to the present embodiment has a chemical formula (1) (1-y) x [(Bi _0.5 Na _0.5 ) _a TiO ₃ ] + (1-y) (1-x) [Ba _b TiO. _3] + _{y [mixed} forms of the components as long as it applies to Bi c AlO _3] is not limited. That is, it contains the three components of BNT as the first compound, BT as the second compound, and BAO as the third compound as main components, and they are in solid solution, but are completely in solution. It does not have to be.

In addition, the piezoelectric composition of the present invention contains BNT, BT, and BAO as main components, and, as a subcomponent, a transition metal element other than the elements constituting the main component (elements of Groups 3 to 11 in the long-period periodic table) ), An alkali metal element, an alkaline earth metal element, a group 12 element in the long-period periodic table, and a group 13 metal element in the long-period periodic table. The main component here means 99% or more with respect to the total molar ratio of the components constituting the material composition.

  Specifically, for transition metal elements (excluding rare earth elements), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), tungsten ( W) or molybdenum (Mo). For rare earth elements, yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb) Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and the like.

Examples of the alkali metal element include lithium (Li), potassium (K), rubidium (Rb), and cesium (Cs). Examples of alkaline earth metal elements include magnesium (Mg) and strontium (Sr). If it is a group 12 element, zinc (Zn) etc. will be mentioned. Examples of the group 13 metal element include gallium (Ga) and indium (In).

  In addition, although the piezoelectric composition concerning this embodiment may contain lead as an impurity, it is preferable that the content is 1 mass% or less, and it is more preferable that lead is not included at all. The volatilization of lead during firing and the release of lead into the environment after being distributed to the market as piezoelectric components and disposed of can be minimized. This is because it is preferable.

  Moreover, it is preferable that the crystal grain diameter of this piezoelectric composition is, for example, 0.5 μm to 20 μm from the viewpoint of exhibiting piezoelectric characteristics and mechanical strength.

  The piezoelectric composition having such a configuration can be manufactured, for example, as follows.

First, as starting materials, bismuth oxide _{(Bi 2 O} 3), sodium carbonate (Na 2 CO _3), titanium oxide _(TiO 2), barium carbonate (BaCO _3), optionally a powder such as aluminum oxide _(Al 2 _{O 3)} Prepared and weighed according to the target composition.

  In addition, it may replace with an oxide and may use what turns into an oxide by baking like carbonate or an oxalate as a starting material.

  Next, the weighed starting materials are sufficiently mixed in an organic solvent or water for about 5 to 20 hours using, for example, a ball mill, and then sufficiently dried. The drying temperature is, for example, about 90 ° C. However, this drying step may be omitted when the above-mentioned starting materials are carried out by dry mixing.

  These dried starting materials are powdered or press-molded and then calcined at 750 ° C. to 950 ° C. for about 1 hour to 20 hours. Both the temperature increase and temperature decrease rates during the preliminary firing are, for example, about 50 ° C./hour to 300 ° C./hour. Although the preliminary firing atmosphere in the present embodiment is air firing, it is not limited to high or low oxygen partial pressure.

By the steps described above, a pre-baked product of the composition having a perovskite structure represented by the general formula ABO ₃ is obtained. In the examples described later, it was confirmed by XRD that it had a perovskite structure, and it was confirmed by inductively coupled plasma emission spectroscopy and fluorescent X-ray analysis that it was within the above composition range. In the examples described later, the presence or absence of a secondary phase having no perovskite structure was confirmed by XRD. In the present embodiment, the method for confirming that the composition has a perovskite structure and the composition range is not limited to the above method. In the general formula ABO ₃ , A includes Bi, Na, and Ba, and B is Ti and Al.

  The calcined product is sufficiently pulverized in an organic solvent or in water for about 5 to 20 hours using, for example, a ball mill, and then sufficiently dried. The drying temperature is, for example, about 90 ° C.

  An organic binder solution (Polyvinyl Alcohol: PVA) is added to these dried calcined products, mixed and granulated. After granulation, the granulated powder is uniaxial press molded to obtain a compact. Although the shape of a molded object is not limited, For example, it is set as a cylinder, a prism, a disk, or a square plate.

  Preferably, it is more preferable that cold isostatic pressing (CIP) is performed after the above step. At that time, the maximum load pressure is 1.0 MPa to 3.5 MPa, and it is more preferable to perform isotropic pressure pressing for about 1 minute to 3 minutes.

  The molded body obtained by the above-described process is heat-treated at 400 ° C. to 800 ° C. for about 2 hours to 4 hours to volatilize the binder, and then subjected to main firing at 950 ° C. to 1300 ° C. for about 2 hours to 4 hours. Both the temperature increase and the temperature decrease rate during the main firing are, for example, about 50 ° C./hour to 300 ° C./hour. Although the main firing atmosphere in this embodiment is air firing, it is not limited to high or low oxygen partial pressure.

  The average crystal grain size of the sintered body obtained by the above-described process is about 0.5 μm to 20 μm.

  After the main firing, the surface of the obtained sintered body is polished as necessary to provide an electrode. In addition to applying and baking an electrode paste, an electrode film may be formed by vapor deposition, sputtering film formation, or the like. A sintered body with an electrode is obtained by the process described above.

  The electroded sintered body is subjected to polarization treatment by applying an electric field of 5 kV / mm to 10 kV / mm for about 5 minutes to 1 hour in silicon oil at 25 ° C. to 200 ° C. A piezoelectric composition is obtained by the above process.

  FIG. 1 shows a partial configuration example of a piezoelectric element using the piezoelectric composition according to the present embodiment. The piezoelectric element includes a piezoelectric substrate 1 made of the piezoelectric composition of the present embodiment, and a pair of electrodes 2 and 3 provided on a pair of opposing surfaces 1a and 1b of the piezoelectric substrate 1, respectively. The piezoelectric substrate 1 is polarized, for example, in the thickness direction, that is, in the direction opposite to the electrodes 2 and 3, and is longitudinally vibrated in the thickness direction when a voltage is applied via the electrodes 2 and 3. . The electrodes 2 and 3 are made of metal such as gold (Au), for example, and are provided on the entire opposing surfaces 1 a and 1 b of the piezoelectric substrate 1. An external power source (not shown) is electrically connected to the electrodes 2 and 3 via, for example, a wire (not shown).

  The piezoelectric element according to the present embodiment can be manufactured as follows, for example. First, after preparing a piezoelectric composition as described above, it is processed into a predetermined size as necessary to form the piezoelectric substrate 1. Next, the electrodes 2 and 3 are deposited on the piezoelectric substrate 1, for example, to obtain the piezoelectric element shown in FIG.

  FIG. 2 shows another configuration example of the piezoelectric element using the piezoelectric composition according to the present embodiment. This piezoelectric element includes, for example, a laminate 10 in which a plurality of piezoelectric layers 11 and a plurality of internal electrodes 12 made of the piezoelectric composition of the present embodiment are alternately laminated. The thickness per layer of the piezoelectric layer 11 is preferably about 1 μm to 100 μm, for example, and the number of stacked layers of the piezoelectric layer 11 is determined according to the target displacement.

  The internal electrode 12 contains a conductive material. The conductive material is not particularly limited, but for example, at least one of the group consisting of silver (Ag), gold (Au), platinum (Pt) and palladium (Pd), or an alloy thereof is preferable. The internal electrode 12 may contain various trace components such as phosphorus (P) in addition to these in an amount of about 0.1% by mass or less. The thickness of the internal electrode 12 is preferably about 0.5 μm to 3 μm, for example.

  For example, the internal electrodes 12 are alternately extended in opposite directions, and a pair of terminal electrodes 21 and 22 electrically connected to the internal electrode 12 are provided in the extending direction. The terminal electrodes 21 and 22 are formed by baking terminal electrode paste, for example. This terminal electrode paste contains, for example, a conductive material, glass frit, and a vehicle. The conductive material includes, for example, at least one selected from the group consisting of Ag, Au, Cu, Ni, Pd, and Pt. Examples of the vehicle include an organic vehicle and an aqueous vehicle. The organic vehicle is obtained by dissolving a binder in an organic solvent, and the aqueous vehicle is obtained by dissolving a water-soluble binder and a dispersant in water.

  The piezoelectric element according to the present embodiment can be manufactured as follows, for example. First, after the pre-fired powder is formed in the same manner as the method for manufacturing the piezoelectric composition described above, a vehicle is added and mixed to prepare a piezoelectric layer paste. Next, the conductive material described above for forming the internal electrode 12 or various oxides, organometallic compounds, and the like that become the conductive material described above after firing are mixed with a vehicle to prepare a paste for internal electrodes. Note that additives such as a dispersant, a plasticizer, a dielectric material, and an insulator material may be added to the internal electrode paste as necessary.

  The piezoelectric layer paste obtained by the above process is applied onto, for example, a PET film to obtain a piezoelectric layer green sheet. The internal electrode paste is printed thereon, cut to a predetermined size, and alternately laminated to produce a green chip that is a precursor of the laminate 10. The green chip obtained by the above process is subjected to binder removal treatment and fired to form the laminate 10.

  The laminated body 10 obtained by the above-described process is subjected to end face polishing by, for example, barrel polishing or sand blasting, and printed or transferred with a terminal electrode paste produced in the same manner as the internal electrode paste, 22 is formed. Thereby, the piezoelectric element shown in FIG. 2 is obtained.

  The piezoelectric composition according to the present embodiment can be used for, for example, a piezoelectric sounding body, a piezoelectric sensor, a piezoelectric actuator, a piezoelectric transformer, a thin film sensor, a thin film actuator, or a piezoelectric ultrasonic motor. For example, you may apply to things other than these.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

(Examples 1-17 and Comparative Examples 1-16)
Bismuth oxide (Bi ₂ O ₃ ), sodium carbonate (Na ₂ CO ₃ ), titanium oxide (TiO ₂ ), barium carbonate (BaCO ₃ ), and aluminum oxide (Al ₂ O ₃ ) powder have the mixing ratios shown in Table 1. Weighed as follows. At this time, a, b, and c were set to the same value. Then, the weighed starting materials were wet mixed in water for 16 hours by a ball mill and then dried at 120 ° C. to obtain mixed powder. This was press-molded and calcined at 800 ° C. for 2 hours in the air to obtain a calcined product. The calcined product was pulverized in water for 16 hours with a ball mill and then dried at 120 ° C. to obtain a pulverized powder.

  For example, a binder such as a PVA aqueous solution was added to the pulverized powder obtained by the above process and granulated. And the obtained granulated powder was press-molded by applying a load of 3.2 MPa with a press molding machine to obtain a flat molded body. The obtained flat molded body was subjected to a heat treatment at 700 ° C., and further fired at 1180 ° C. to obtain a sintered body. And the surface of the obtained sintered compact was grind | polished, it was set as the parallel plate shape of thickness about 0.6 mm, and the opposing silver electrode was provided by vapor deposition on both surfaces of the parallel plate-shaped sintered compact. Furthermore, an electric field of 5 kV / mm was applied in silicon oil at 50 ° C. for 15 minutes for polarization treatment. By the said process, the test piece for the piezoelectric property evaluation of Examples 1-17 and Comparative Examples 1-16 shown in Table 1 was obtained.

The d ₃₃ and T _c of the test pieces (piezoelectric element) piezoelectric compositions for piezoelectric property evaluation of Examples 1 to 17 and Comparative Examples 1 to 16 obtained by the above steps were measured. At that _time, the measurement of _{d 33} was carried out by PIEZO d ₃₃ METER MODEL ZJ-4B at room temperature (manufactured INSTITUTE OF ACOUSTIC SACADEMIASINICA). _Tc is measured by placing the above test piece in a gold furnace (made by Ishikawa Sangyo), measuring the capacitance with PRECISION LCR METER (made by HEWLETT PACKARD) at each temperature while raising the temperature, and determining from the peak temperature. did. The obtained results are shown in Table 1.

The results of evaluating the piezoelectric properties of the piezoelectric composition are shown in Table 1 as Ox. In this evaluation, it was determined that d ₃₃ was 120 pC / N or higher and T _c was 250 ° C. or higher in order to guarantee practical piezoelectric characteristics. The case where both of these were satisfied was determined as “good”, and the case where either or both were not satisfied was determined as “inadequate”.

As can be seen from Table 1, the composition of the piezoelectric composition mainly composed of the three components BNT, BT, and BAO according to this embodiment is in the ranges of x, y, a, b, and c in the chemical formula (1). 0.90 ≦ x ≦ 0.96, 0.01 ≦ y ≦ 0.20, 0.90 ≦ a ≦ 1.10, 0.90 ≦ b ≦ 1.10, 0.90 ≦ c ≦ 1.10. In some cases, both _d33 and _Tc were good.

(Examples 18 to 19 and Comparative Examples 17 to 18)
In formula (1), x and y are set to x = 0.94, y = 0.10, a, b, and c are set to the same value, and the mixing ratio of the starting materials is changed so that the composition shown in Table 1 is obtained. Except for the above, a piezoelectric composition was produced under the same conditions as in Example 1 described above. Similarly, for Example 18-19 and Comparative Examples 17-18 _were measured _{d 33} and _{T c.} Moreover, the presence or absence of the secondary phase of the obtained piezoelectric composition was confirmed by XRD (SmartLab: manufactured by Rigaku). The results are also shown in Table 2.

As can be seen from Table 2, in Comparative Example 17 in which a, b and c are smaller than 0.90, the resistivity was remarkably lowered due to the remarkable appearance of the secondary phase having a non-perovskite structure. Therefore, dielectric breakdown occurred during the polarization treatment, and d ₃₃ measurement was not achieved. Further, in Comparative Example 18 in which a, b and c were larger than 1.10, high sinterability was not obtained, and d ₃₃ was lowered due to low crystallinity. From the above, a, b, and c are preferably in the range of 0.90 ≦ a ≦ 1.10, 0.90 ≦ b ≦ 1.10, and 0.90 ≦ c ≦ 1.10.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples. In the above-described embodiments and examples, only the case where BNT, BT, and BAO are included has been described. However, in addition to the three components represented by BNT, BT, and BAO, a piezoelectric composition or piezoelectric that includes other compounds. Since elements can be easily recalled, they are included in the scope of the present invention.

The piezoelectric composition of the present invention can provide a piezoelectric element having high actuator displacement and sensor sensitivity even in, for example, an inkjet head, a piezoelectric actuator, a thin film sensor, and the like. Furthermore, since it has a high _Tc , a piezoelectric element having a wide practical temperature range can be provided.

DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2, 3 Electrode 1a, 1b Opposite surface 10 Laminated body 11 Piezoelectric layer 12 Internal electrode 21, 22 Terminal electrode

Claims (2)

When Bi, Na, Ba, Al and Ti contained in the piezoelectric composition are represented by the chemical formula (1),
Formula _{(1-y) x [(} Bi 0.5 Na 0.5) a TiO 3] + (1-y) (1-x) [Ba b TiO 3] + y [Bi c AlO 3] (1)
0.90 ≦ x ≦ 0.96
0.10 ≤ y ≤ 0.20
0.90 ≦ a ≦ 1.10
0.90 ≦ b ≦ 1.10
0.90 ≦ c ≦ 1.10
x + y = 1
The piezoelectric composition characterized by these. A piezoelectric element comprising the piezoelectric composition according to claim 1.

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