JP6914151B2 - Lead-free electromagnetic composition and piezoelectric element - Google Patents

Description

The present invention relates to lead-free porcelain compositions and piezoelectric elements.

Most of the pressure electromagnetic devices (piezoelectric ceramics) that have been mass-produced conventionally are composed of PZT-based (lead zirconate titanate-based) materials and contain lead. However, in recent years, the development of lead-free piezoelectric porcelain has been desired in order to eliminate the adverse effects of lead on the environment. As the material of such a lead-free porcelain (referred to as "lead-free porcelain composition"), for example, sodium niobate ((K, Na) NbO ₃ ) has a composition formula ANbO ₃ (A is an alkali metal). The composition represented by is proposed. However, Anbo ₃ lead-free piezoelectric ceramic composition itself has a problem of poor sinterability. Such contrast problems, in Patent Document 1, Cu in Anbo ₃ lead-free piezoelectric ceramic composition, Li, by adding Ta or the like, to improve the sinterability, the piezoelectric constant d ₃₃ and the electrical By extension A method for improving the mechanical coupling coefficient kr is disclosed. Further, in Patent Document 2, a lead-free pressure electromagnetic composition represented by _{the general formula {Li x} (K _1-y N _y ) _1-x } (Nb _1-z Sb _z ) O _{3 (0 ≦ x ≦ 0.} It is disclosed that relatively good sinterability and piezoelectric characteristics can be achieved by 2,0 ≦ y ≦ 1.0, 0 ≦ z ≦ 0.2, except for x = z = 0).

Japanese Unexamined Patent Publication No. 2000-313664 Japanese Unexamined Patent Application Publication No. 2003-342069

However, in the pressure electromagnetic composition described in Patent Document 1, although the sinterability is improved, the piezoelectric constant d ₃₃ and the electromechanical coupling coefficient kr are inferior to those of the conventional lead pressure electromagnetic composition. Practically insufficient. On the other hand, although the pressure electromagnetic composition described in Patent Document 2 exhibits relatively high piezoelectric characteristics, the piezoelectric constant d ₃₃ and the electromechanical coupling coefficient kr are still inferior to those of the lead pressure electromagnetic composition. Insufficient to replace the porcelain composition. Therefore, in order to put various devices using the lead-free pressure porcelain composition into practical use, it is desired to develop a lead-free pressure porcelain composition having a _{higher piezoelectric constant d 33 and an electromechanical coupling coefficient kr.}
Further, it is generally difficult to obtain a high coupling coefficient for many of the alkali niobate-based lead-free piezoelectric materials, and at present, many materials have an electromechanical coupling coefficient kr of less than 50%. Therefore, in _{order to obtain a high d 33} value, compounding with a compound having a high dielectric constant is performed, but in _{order to obtain a higher d 33} value, a high electromechanical coupling coefficient kr is indispensable.
As described above, the lead-free pressure electromagnetic composition having a practical piezoelectric property has not been developed yet.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lead-free pressure porcelain composition having excellent sinterability and practical piezoelectric characteristics. The present invention can be realized as the following forms.

[1] A lead-free pressure electromagnetic composition comprising an alkali niobate perovskite oxide having piezoelectric properties as a main phase and having the same element at the A site and the B site in the main phase.

The lead-free pressure electromagnetic composition having this structure has excellent sinterability and practical piezoelectric characteristics. It is presumed that the reason for having a practical piezoelectric property is that the presence of the same element at the A site and the B site in the main phase causes distortion in the crystal and improves the piezoelectric property.

[2] Ti exists as the same element at the A site and the B site in the main phase, and Ti is present.
The lead-free pressure electromagnetic composition according to [1], wherein one or more elements selected from the group consisting of Ba, Zr, and Fe are present as the same element at the A site and the B site in the main phase.

The lead-free pressure electromagnetic composition having this structure has excellent sinterability and practical piezoelectric characteristics.

[3] A piezoelectric porcelain formed of the lead-free pressure porcelain composition according to [1] or [2].
A piezoelectric element comprising an electrode attached to the pressure electromagnetic device.

The piezoelectric element having this configuration is excellent in piezoelectric characteristics.

It is a flowchart which shows the manufacturing method of the piezoelectric element in one Embodiment of this invention. It is a perspective view which shows the piezoelectric element as one Embodiment of this invention. It is an X-ray incoherent channeling figure of sample S5. It is a graph which shows the temperature dependence of tan δ.

1. 1. Lead-free electromagnetic composition The lead-free electromagnetic composition of the present embodiment is characterized in that the main phase is an alkali niobate perovskite oxide having piezoelectric properties, and the same elements are present at the A site and the B site in the main phase. And.

(1) Main phase The alkaline component of the alkali-based niobate perovskite oxide contains at least alkali metals (K (potassium), Na (sodium), Li (lithium), Rb (rubidium), Cs (cesium), etc.). , Also may contain alkaline earth metals (Ca (calcium), Sr (strontium), Ba (barium), etc.).
The same element existing at the A site and the B site in the main phase is not particularly limited. It is preferable that Ti exists as the same element and at least one element selected from the group consisting of Ba, Zr, and Fe exists as the same element.

As such an alkaline niobate-based perovskite oxide, those represented by the following composition formula (formula (1)) are preferably exemplified. The amount of O atom is such that the perovskite structure can be maintained. Moreover, in this composition formula, each site is standardized to 1. In the following composition formula, the so-called A sites of the perovskite structure include Ka (potassium), Na (sodium), Li (lithium), Ca (calcium), Ba (barium), Zr (zirconium), Ti (titanium), Fe. (Iron) is placed. Nb (niobium), Ba (barium), Zr (zirconium), Ti (titanium), Fe (iron), and Mg (magnesium) are arranged at the so-called B site of the perovskite structure.

_{(K a Na b Li c Ca} d Ba e Zr f Ti g Fe h) (Nb i Ba j Zr k Ti l Fe m Mg n) O 3-δ ... (1)

In the above composition formula, the respective element ratios are preferably in the following ranges from the viewpoint of electrical characteristics or piezoelectric characteristics (particularly piezoelectric constant d _{33) of the lead-free pressure electromagnetic porcelain composition.}
0.1000 ≦ a ≦ 0.8000, 0.1000 ≦ b ≦ 0.8000, 0.0050 ≦ c ≦ 0.0800, 0.0050 ≦ d ≦ 0.0800,
0.0050 ≦ e ≦ 0.0800, 0.0005 ≦ f ≦ 0.0050, 0.0001 ≦ g ≦ 0.0020, 0.0050 ≦ h ≦ 0.0500,
0.8000 ≦ i ≦ 0.9600, 0.0020 ≦ j ≦ 0.0100, 0.0100 ≦ k ≦ 0.0500, 0.0050 ≦ l ≦ 0.0300,
0.0050 ≦ m ≦ 0.0300, 0.0050 ≦ n ≦ 0.0500, and σ are arbitrary values constituting the perovskite structure, and a typical value is about 3. The value of σ can be calculated from the electrically neutral condition of the composition of the main phase, but the composition of the main phase slightly deviating from the electrically neutral condition is also acceptable.
a + b + c + d + e + f + g + h = 1
i + j + k + l + m + n = 1

In the above composition formula, the ratio of each element is more preferably in the following range.
0.3000 ≦ a ≦ 0.6500, 0.2500 ≦ b ≦ 0.6000, 0.0050 ≦ c ≦ 0.0600, 0.0100 ≦ d ≦ 0.0300,
0.0100 ≦ e ≦ 0.0500, 0.0005 ≦ f ≦ 0.0030, 0.0002 ≦ g ≦ 0.0020, 0.0100 ≦ h ≦ 0.0300,
0.8500 ≦ i ≦ 0.9400, 0.0040 ≦ j ≦ 0.0080, 0.0200 ≦ k ≦ 0.0400, 0.0100 ≦ l ≦ 0.0250,
0.0050 ≤ m ≤ 0.0200, 0.0050 ≤ n ≤ 0.0300
a + b + c + d + e + f + g + h = 1
i + j + k + l + m + n = 1

In the above composition formula, the ratio of each element is more preferably in the following range.
0.3500 ≦ a ≦ 0.6000, 0.3000 ≦ b ≦ 0.5500, 0.0100 ≦ c ≦ 0.0400, 0.0200 ≦ d ≦ 0.0450,
0.0150 ≦ e ≦ 0.0350, 0.0010 ≦ f ≦ 0.0025, 0.0002 ≦ g ≦ 0.0018, 0.0130 ≦ h ≦ 0.0250,
0.9000 ≦ i ≦ 0.9250, 0.0045 ≦ j ≦ 0.0075, 0.0250 ≦ k ≦ 0.0350, 0.0100 ≦ l ≦ 0.0200,
0.0100 ≦ m ≦ 0.0250, 0.0080 ≦ n ≦ 0.0200
a + b + c + d + e + f + g + h = 1
i + j + k + l + m + n = 1

The composition of the main phase is an oxide containing K, Na and Nb as main elemental components. Since this main phase contains K, Na, and Nb as main elemental components, the material composed of the main phase is also referred to as "KNN" or "KNN material", and the main phase is also referred to as "KNN phase".

(2) Subphase The lead-free pressure electromagnetic composition according to the embodiment of the present invention may contain a metal oxide different from the main phase as the subphase. The subphase preferably contains, for example, one or more metal oxides selected from the following (a) to (e).
(A) Mg (magnesium), Ni (nickel), Co (cobalt), Fe (iron), Mn (manganese), Cr (chromium), Zr (zirconium), Ti (titanium), Ag (silver), Zn ( Single metal oxide consisting of a metal element selected from zinc), Sc (scandium), and Bi (bismas) (b) M—Ti—O spinel compound (element M is a 1- to pentavalent metal)
(C) A ₂ B ₆ O ₁₃ system compound (element A is a monovalent metal, element B is a 2 to 6 valent metal)
(D) A ₃ B ₅ O _15- based compound (element A is a 1 to 2 valent metal, element B is a 2 to 5 valent metal)
(E) A-Ti-BO compound (element A is an alkali metal, element B is at least one of Nb and Ta)

The sub-phase containing these compounds does not have piezoelectric properties by itself, but has a function of improving sinterability and compactness by mixing with the main phase. Further, by adding these subphases, it is possible to obtain a lead-free pressure porcelain composition having _{an excellent piezoelectric constant d 33 and an electromechanical coupling coefficient kr.} The total value of the content ratio of the subphase is preferably 5% by volume or less, more preferably 2% by volume or less, based on the whole lead-free pressure electromagnetic composition. If the total value of the content ratios of the subphases exceeds 5% by volume, the piezoelectric constant d ₃₃ and the electromechanical coupling coefficient kr may decrease.

Examples of the single metal oxide include MgO, NiO, CoO, Co ₃ O ₄ , FeO, Fe ₂ O ₃ , MnO, MnO ₂ , Cr ₂ O ₃ , ZrO ₂ , TiO ₂ , Cu ₂ O, and CuO. Ag ₂ O, Zn O, Sc ₂ O ₃ , and Bi ₂ O ₃ can be used. Of these, it is particularly _{preferable to use one, two, or three of Co 3} O ₄ , ZnO, and Fe ₂ O ₃ as the subphase because the structure of the main phase can be stabilized.

The composition of the M—Ti—O spinel compound can be represented by the following formula (2).
M _x TiO _y … (2)
Here, the element M is a 1- to pentavalent metal element, and Li (lithium), Na (sodium), K (potassium), Mg (gallium), Al (aluminum), Sc (scandium), Cr (chromium). ), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), Zn (zinc), Ga (gallium), Y (yttrium), Zr (zirconium), Sn (tin), Sb (antimon) ), Nb (niob), Ta (tantal), Si (silicon), Hf (hafnium). When Li is contained as the element M, it is preferable that one or more metal elements other than Li among the above metal elements are contained together with Li in order to form a spinel compound. The coefficients x and y are relative values when the Ti content is 1. In order to form the spinel compound, the coefficient x preferably satisfies 0.5 ≦ x ≦ 8.0, and more preferably 0.5 ≦ x ≦ 5.0. The coefficient y is an arbitrary value for forming the spinel compound, but typically satisfies 2 ≦ y ≦ 8. Specific spinel compounds include, for example, NiFeTIO ₄ , MgFeTIO ₄ , Ni ₂ (Ti, Zr) O ₄ , Ni ₂ (Ti, Hf) O ₄ , Ni _{1.5 FeTi 0.5} O ₄ , CoMgTIO ₄ , _{CoFeTiO 4, (Fe, Zn,} Co) it is preferred to use 2 TiO _4, CoZnTiO 4. Since the spinel compound stabilizes the structure of the main phase, _{a piezoelectric composition having an excellent piezoelectric constant d 33} and an electromechanical coupling coefficient kr can be obtained.

The spinel compound may be a positive spinel compound or a reverse spinel compound. Whether or not it is a spinel compound can be determined by performing Rietveld Analysis using the diffraction result of powder X-ray diffraction (XRD).

As the A ₂ B ₆ O ₁₃ system compound, the element A (monovalent metal) is at least one of Li, Na and K, and the element B (2 to 6 valent metal) is Co, Fe, Mg and Ni. , Zr, Mn, Al, Nb, Ta, W can be used as at least one compound. Specifically, for example, K ₂ (Ti, Nb, Mg) ₆ O ₁₃ and K ₂ (Ti, Nb, Co, Zn) ₆ O ₁₃ can be used.

As the A ₃ B ₅ O ₁₅ system compound, the element A (1-2-valent metal) is at least one of Ba, Ca, Sr, Na, K, and Li, and the element B (2-5-valent metal) is used. Can be used as a compound in which at least one of Nb, Mn, Fe, Ni, Co, Zn, and Zr is used. Specifically, for example, (Ba, Na, K) ₃ (Nb, Ni, Fe) ₅ O ₁₅ , (Ba, Na, K) ₃ (Nb, Co, Ni) ₅ O ₁₅ , (Ba, Na, K) ₃ (Nb, Zn) ₅ O ₁₅ , (Ba, Na, K) ₃ (Nb, Mn) ₅ O ₁₅ , (Ba, Na, K) ₃ (Nb, Fe, Zn, Co) ₅ O ₁₅ etc. It is possible to use.

As the A-Ti-BO compound, a compound having the composition of the following formula (3) or formula (4) can be used.
A _1-x Ti _1-x B _{1 + x} O ₅ (3)
A ₁ Ti ₃ B ₁ O ₉ (4)
Here, the element A is at least one of alkali metals (K (potassium), Rb (rubidium), Cs (cesium), etc.), and the element B is at least one of Nb (niobium) and Ta (tantalum). It is one kind. The coefficient x in the above equation (3) is an arbitrary value. However, the coefficient x preferably satisfies 0 ≦ x ≦ 0.15. When the coefficient x takes a value in this range, the structure of the compound is stable and a uniform crystal phase can be obtained.

Specific compounds according to the above formula (3) include KTiNbO ₅ , K _0.90 Ti _0.90 Nb _1.10 O ₅ , K _0.85 Ti _0.85 Nb _1.15 O ₅ , RbTiNbO _5. , Rb _0.90 Ti _0.90 Nb _1.10 O ₅ , Rb _0.85 Ti _0.85 Nb _1.15 O ₅ , CsTiNbO ₅ , Cs _0.90 Ti _0.90 Nb _1.10 O ₅ , KTiTaO ₅ and CsTiTaO _{5 and the} like can be used. From the viewpoint of structural stability of this compound, the coefficient x preferably satisfies 0 ≦ x ≦ 0.15 when the element A is K (potassium) or Rb (rubidium), and the element A is. In the case of Cs (cesium), it is preferable to satisfy 0 ≦ x ≦ 0.10. If K (potassium) is selected as the element A and Nb (niobium) is selected as the element B, _{a piezoelectric composition having an excellent piezoelectric constant d 33} and an electromechanical coupling coefficient kr can be obtained.

The crystal phases represented by the above equations (3) and (4) are both compound oxidations of element A (alkali metal), Ti (titanium), and element B (at least one of Nb and Ta). It is common in that it is a thing. As described above, the composite oxide of the element A, Ti (titanium), and the element B is called "A-Ti-BO-based composite oxide". Uses A-Ti-BO composite oxide (element A is an alkali metal, element B is at least one of Nb and Ta, and the contents of element A, element B and Ti are not zero). It is possible to do.

FIG. 1 is a flowchart showing a method for manufacturing a piezoelectric element according to an embodiment of the present invention. Although the detailed mechanism is unknown, in this production method, the particle size of the powder of the raw material of the subphase is made finer than the particle size of the powder of the raw material of the main phase, so that the A site and the B site in the main phase are made finer. A phenomenon is observed in which the same element (Ba, Ti, Zr, Fe, etc.) is incorporated into both of them. _{For example, it is preferable that the D 50} (median diameter) of each raw material powder of the main phase _{is 2.5 to 3.9 μm and the D 50} of each raw material powder of the sub-phase is 2.0 μm or less.
In step T110, as raw materials for the main phase (KNN phase), K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Li ₂ CO ₃ powder, CaCO ₃ powder, SrCO ₃ powder, BaCO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, TiO ₂ powder, ZrO ₂ powder, MgO powder, Al ₂ O ₃ powder, Sc ₂ O ₃ powder, MnO ₂ powder, Fe ₂ O ₃ powder, Co ₃ O ₄ powder, NiO powder, ZnO powder , Ga ₂ O ₃ powder, Y ₂ O ₃ powder, and other raw materials are selected and used as the value of the coefficient in the composition formula of the main phase (for example, a to n in the composition formula of the main phase above). Weigh accordingly. Then, ethanol is added to these raw material powders and wet-mixed with a ball mill for preferably 15 hours or more to obtain a slurry. In step T120, the mixed powder obtained by drying the slurry is calcined at, for example, 600 ° C. to 1100 ° C. for 1 to 10 hours in an air atmosphere to produce a main phase calcined powder.

In step T130, as raw materials for the subphase, NbTiKO ₅ powder, Fe ₂ TiO ₄ , Li ₂ TiO ₃ , BaZrO ₃ powder, Fe ₂ O ₃ powder, Li ₂ CO ₃ powder, Na ₂ CO ₃ powder, K ₂ CO ₃ Powder, Co ₃ O ₄ powder, Fe ₂ O ₃ powder, MgO powder, NiO powder, ZrO ₂ powder, MnO ₂ powder, Al ₂ O ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, WO ₃ powder, etc. Select the required one from the above and weigh it according to the composition formula of the subphase. Then, ethanol is added to these raw material powders and wet-mixed with a ball mill for preferably 15 hours or more to obtain a slurry. In step T140, the mixed powder obtained by drying the slurry is calcined at, for example, 600 ° C. to 1100 ° C. for 1 to 10 hours in an air atmosphere to produce a subphase calcined powder.

In step T145, the main phase temporary baking powder and the sub-phase temporary baking powder are weighed, and a dispersant, binder and ethanol are added in a ball mill, and the mixture is pulverized and mixed to form a slurry. Further, the mixed powder obtained by drying this slurry is calcined at 600 ° C. to 1100 ° C. for 1 to 10 hours in an air atmosphere to produce a calcined powder. As will be described later, in the present embodiment, the preferable ratio of the subphase in the piezoelectric composition is defined by volume%. On the other hand, the mixing ratio of the main phase temporary baking powder and the sub-phase temporary baking powder in the step T145 is performed using the weights of the main phase temporary baking powder and the sub-phase temporary baking powder. At this time, the relationship between the subphase ratio (% by weight) at the time of mixing in step T145 and the subphase ratio (volume%) in the finally obtained lead-free pressure electromagnetic composition should be empirically determined in advance. Is possible.

In step T150, a dispersant, binder and ethanol are added again to the calcined powder obtained in step T145, pulverized and mixed to form a slurry, and this slurry is granulated while being dried by a spray dry dryer, and then, for example, Uniaxial pressing is performed at a pressure of 20 MPa to form a desired shape. The shape of a typical piezoelectric device suitable for various devices according to the embodiment of the present invention is a disk shape, a columnar shape, a rectangular flat plate shape, or the like. Then, for example, a CIP treatment (cold hydrostatic molding treatment) is performed at a pressure of 150 MPa to obtain a molded product. In step T155, the obtained molded product is held at, for example, 500 ° C. to 800 ° C. for 2 to 10 hours in an air atmosphere to perform a degreasing step of degreasing the binder. In step T160, the obtained molded product after the degreasing step is held and fired at a specific temperature (for example, 1150 ° C.) selected from, for example, 1000 ° C. to 1300 ° C. in an air atmosphere for 2 to 50 hours. Obtain a piezoelectric device. The firing in the step T160 is preferably a sealed firing performed in a state where the molded product is sealed in a closed container. The reason for this is to prevent metal elements such as alkali metals (Li, Na, K) contained in the molded product from disappearing to the outside during firing. As such a closed container, for example, Alumina Saya A-1174 manufactured by Otake Serum Co., Ltd. can be used. In step T170, the piezoelectric element is processed according to the dimensional accuracy required for the piezoelectric element. In the step T180, an electrode is attached to the piezoelectricizer thus obtained, and a polarization treatment is performed in the step T190.

The manufacturing method described above is an example, and various other steps and processing conditions for manufacturing the piezoelectric element can be used. For example, instead of forming the main phase and the sub-phase separately in advance as shown in FIG. 1 and then mixing and firing the powders of both, the raw materials are mixed in an amount ratio according to the composition of the final lead-free pressure porcelain composition. The piezoelectric composition may be produced by firing. However, according to the production method of FIG. 1, since the composition of the main phase and the sub-phase can be controlled more strictly, it is possible to increase the yield of the piezoelectric composition.

2. Piezoelectric element FIG. 2 is a perspective view showing a piezoelectric element as an embodiment of the present invention. The piezoelectric element 200 has a configuration in which electrodes 301 and 302 are attached to the upper surface and the lower surface of the disc-shaped pressure electromagnetic device 100. As the piezoelectric element, it is possible to form a piezoelectric element having various shapes and configurations other than the above.

3. 3. Use of lead-free electromagnetic composition and piezoelectric element The lead-free electromagnetic composition and piezoelectric element according to the embodiment of the present invention can be widely used in vibration detection applications, pressure detection applications, oscillation applications, piezoelectric device applications, and the like. Is. For example, sensors that detect various vibrations (knock sensors, combustion pressure sensors, etc.), piezoelectric devices such as vibrators, actuators, filters, high voltage generators, micro power supplies, various drive devices, position control devices, vibration suppression devices, etc. It can be used for various devices such as a fluid discharge device (paint discharge, fuel discharge, etc.). Further, the lead-free pressure electromagnetic composition and the piezoelectric element according to the embodiment of the present invention are particularly suitable for applications requiring excellent thermal durability (for example, a knock sensor and a combustion pressure sensor).

The present invention will be described in more detail with reference to Examples.
Samples S2 to S12 correspond to Examples, and Samples S1 and S13 are reference examples.

1. 1. Preparation of sample compositions Various sample compositions were prepared by appropriately selecting the types and amounts of the raw materials for the main phase and the raw materials for the sub-phase.

2. Composition Analysis The composition of the piezoelectric porcelain formed of the lead-free pressure porcelain composition was measured using beam locking TEM-EDS analysis. The details were measured as follows. The beam locking TEM-EDS analysis is described in detail in the following documents, and the contents are referred to.
Masahiro Ohtsuka et al., "Quantitative determination of occupation sites
of trace Cosubstituted for multiple Fe sites in M-type hexagonal ferrite using statistical beam-rocking TEM-EDXS analysis ", Microscopy, 65, 127-137 (2016)
Samples for transmission electron microscope (TEM) analysis were prepared as follows. First, the sintered body was punched into a disk shape having a diameter of 3 mm, and mechanical polishing was performed to a thickness of about 50 μm. Then, a mortar-shaped depression was made in the center of the disk plane using a dimple grinder so as to be 10 μm or less. ^{Then, a thin film portion was formed by irradiating the front and back surfaces with Ar +} ions having an acceleration voltage of 2 to 4 kV at an incident angle of 4 degrees, and a sample for TEM analysis was prepared.
As the TEM apparatus, JEM-2100 (JEOL Ltd.) with an acceleration voltage set to 200 kV and an energy dispersive X-ray spectrometer (EDS) was used.
Beam locking TEM-EDS analysis was performed as follows. KNN particles existing in a region where the sample film thickness was processed to about 100 nm were selected, and the crystal zone axis was aligned with [120]. Then, the irradiation region of the electron beam was limited by using a physical diaphragm having a diameter of 1 μm, and the EDS spectrum was measured while scanning the incident direction in the range of ± 2 ° in both the vertical and horizontal directions from the [120] incident direction. The angular resolution at that time was set to 64 × 64 pixels. The intensities of Ba (L line), Zr (K line), Ti (K line), and Fe (K line) are extracted from the EDS spectrum acquired at each measurement point, and the image (X-ray incoherent) in the incident angle space is extracted. Channeling figure) was constructed.
FIG. 3 shows an X-ray incoherent channeling figure of sample S5. Since the X-ray incoherent channeling diagram reflects the crystal sites occupied by the elements, the main elements K (K line) and Na (K line) that occupy the A site and the main elements that occupy the B site Nb (L line) shows different patterns. The pattern data of these main elements is compared with the pattern data of Ba (L line), Zr (K line), Ti (K line), and Fe (K line) to calculate a quantitative value.
From the EDS spectrum data and the X-ray incoherent channeling figure, the concentrations of Ba, Zr, Ti, Fe solidly dissolved in the KNN particles and the occupancy ratios of A sites and B sites were quantified according to the following formula.

Here, c _x indicates the concentration of the element x, and f indicates the ratio of the element x occupying the site j. In addition, α _j represents the regression coefficient, n _j represents the concentration of the element existing at the site j, and k _j and k _x represent the factors used to apply the thin film approximation method. Since the main element at the A site is composed of two types, K and Na, it is linearly dependent and the solution cannot be determined as one. Therefore, the calculation of the quantitative value was taken based on the Na data.
When defined as the following composition formula, each parameter value is as shown in Tables 1 and 2. In Table 1, "BaA" means Ba at the A site, "ZrA" means Zr at the A site, "TiA" means Ti at the A site, and "FeA" means Fe at the A site. Further, in Table 2, "BaB" means Ba at the B site, "ZrB" means Zr at the B site, "TiB" means Ti at the B site, and "FeB" means Fe at the B site. In Comparative Examples 1 to 4, the same element does not exist at the A site and the B site.

_{(K a Na b Li c Ca} d Ba e Zr f Ti g Fe h) (Nb i Ba j Zr k Ti l Fe m Mg n) O 3

3. 3. Piezoelectric characteristics Table 3 shows various piezoelectric characteristic values. The dielectric loss tan δ in Table 3 is the result of measurement at room temperature (25 ° C.).
Further, the temperature dependence of the dielectric loss tan δ in Sample S5 and Comparative Example 4 was measured. The results are shown in FIG.
For the evaluation (measurement) of the temperature dependence, a temperature cycle was used in which the environmental temperature to which the pressure electromagnetic device was exposed changed from room temperature to 150 ° C. to room temperature to -60 ° C. to room temperature. FIG. 4 shows the results of appropriately measuring the dielectric loss tan δ while repeating this temperature cycle twice.

Sample S1 does not have piezoelectric characteristics due to poor sintering, and is a reference example in this respect. Sample S13 does not have piezoelectric characteristics due to poor polarization, and is a reference example in this respect.
Samples S3 to S8 had a better _{piezoelectric constant d 33 than Comparative Examples 1 to 4.} Samples S10 to S12 had a better mechanical quality coefficient Qm than Comparative Examples 1 to 4.
In Comparative Example 4, although the piezoelectric constant d ₃₃ was good, as shown in FIG. 4, there was a problem that the dielectric loss tan δ increased when the temperature became high. On the other hand, in the sample S5 of the example, the dielectric loss tan δ did not increase even at a high temperature and was stable. Therefore, Comparative Example 4 and Sample S5 have similar characteristic values at room temperature, but Comparative Example 4 has a significantly different value of dielectric loss tan δ at high temperature, and when used in a device in which a thermal cycle occurs, There is concern about durability. On the other hand, it was found that the sample S5 is particularly suitable for applications such as automobiles that require thermal cycle property and heat resistance. In each of the samples S2 to S12 of the examples, similarly to the sample S5, the dielectric loss tan δ did not increase even at a high temperature and was stable. Therefore, the samples S2 to S12 have good thermodynamic cycle property and thermal shock stability.
Compared with Comparative Example 4, the samples S2 and S9 have similar characteristic values at room temperature, but are stable even at high temperatures without increasing the dielectric loss tan δ, so that heat resistance is required. Suitable for applications such as automobiles.

Which of the three properties of the relative permittivity ε ₃₃ ^T / ε ₀ , the piezoelectric constant d _33, and the electromechanical coupling coefficient kr shown in Table 3 is important depends on the application of the porcelain composition. In some cases. For example, a _{composition having a large relative permittivity ε 33} ^T / ε ₀ is suitable for a capacitor. Further, a _{composition having a large piezoelectric constant d 33} is suitable for an actuator or a sensor. Further, a composition having a large electromechanical coupling coefficient kr is suitable for a piezoelectric transformer or an actuator. The piezoelectric composition suitable for each application is determined according to the characteristics required for each application.

<Other Embodiments (Modified Examples)>
The present invention is not limited to the above examples and embodiments, and can be implemented in various embodiments without departing from the gist thereof.

100 ... Pressure porcelain 200 ... Piezoelectric element 301 ... Electrode 302 ... Electrode

Claims (2)

The main phase is an alkaline niobate perovskite oxide having piezoelectric properties, and the same elements are present at the A and B sites in the main phase, and the lead-free composition is represented by the following composition formula (1). Piezoelectric composition.

_{(K a Na b Li c Ca} d Ba e Zr f Ti g Fe h) (Nb i Ba j Zr k Ti l Fe m Mg n) O 3-δ ... (1)

0.1000 ≦ a ≦ 0.8000, 0.1000 ≦ b ≦ 0.8000, 0.0050 ≦ c ≦ 0.0800, 0.0050 ≦ d ≦ 0.0800,
0.0050 ≦ e ≦ 0.0800, 0.0005 ≦ f ≦ 0.0050, 0.0001 ≦ g ≦ 0.0020, 0.0050 ≦ h ≦ 0.0500,
0.8000 ≦ i ≦ 0.9600, 0.0020 ≦ j ≦ 0.0100, 0.0100 ≦ k ≦ 0.0500, 0.0050 ≦ l ≦ 0.0300,
0.0050 ≤ m ≤ 0.0300, 0.0050 ≤ n ≤ 0.0500
σ is an arbitrary value that constitutes the perovskite structure
a + b + c + d + e + f + g + h = 1
i + j + k + l + m + n = 1 A piezoelectric porcelain formed of the lead-free pressure porcelain composition according to claim 1.
A piezoelectric element comprising an electrode attached to the pressure electromagnetic device.

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