JP2015222781A - Crystal-oriented piezoelectric ceramic and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a crystal-oriented piezoelectric ceramic arranged by use of a non-lead niobate alkali compound having a piezoelectric constant d33 comparable to that of a lead-containing material; and a method for manufacturing such a crystal-oriented piezoelectric ceramic.SOLUTION: A method for manufacturing a crystal-oriented piezoelectric ceramic comprises the steps of: preparing molding powder of a composition satisfying the general formula 1, i.e. (1-s)A1B1O-sM1M2O(where A1 represents an alkali metal, B1 represents at least one element of transition metal elements and includes Nb, M1 represents a divalent element, M2 represents a quadrivalent element, 1.02<α1≤1.10, and 0.05<s≤0.15); obtaining an oriented mold; and sintering the oriented mold under an atmosphere of which the oxygen partial pressure is 1×10kPa or less. In the sintering step, the alkali metal A1 is volatilized, and a sintered mold of a composition expressed by the general formula 2:(1-s)A1B1O-sM1M2O(where 0.94≤α2<1, and α2≤α1-0.045) is obtained.

Description

  The present invention relates to a lead-free crystal-oriented piezoelectric ceramic and a manufacturing method thereof.

In recent years, the tendency to eliminate heavy metal harmful elements such as Pb, Hg, Cd, Cr ^{6+ has} increased due to the heightened awareness of environmental protection, and a ban on use (RoHS directive) has been issued and enforced mainly in Europe. Lead oxide (PbO), which is a raw material that plays an important role in enhancing the functionality of electronic materials, is also subject to environmental concerns regarding disposal issues.

By the way, a wide variety of materials have been developed for piezoelectric materials constituting piezoelectric elements that have been widely put into practical use in fields such as electronics, mechatronics, and automobiles, mainly piezoelectric ceramics. Conventional piezoelectric ceramics are Pb-based perovskite ferroelectric ceramics, and the mainstream is PbZrO ₃ —PbTiO ₃ (PZT). A piezoelectric ceramic having this composition contains a large amount of lead oxide as a main component, and thus has a problem with respect to disposal.

  In view of this situation, research into environment-friendly lead-free piezoelectric ceramics is considered urgent and indispensable. The performance of high-performance lead-free piezoelectric ceramics comparable to that of conventional PZT piezoelectric ceramics R & D is attracting interest.

  Lead-free piezoelectric ceramics are used for laminated piezoelectric elements as shown in FIG. 9, for example. The laminated piezoelectric element has a structure in which ceramic layers 11 made of lead-free piezoelectric ceramics and electrode layers 12 are alternately laminated.

  For example, Patent Document 1 describes a multilayer piezoelectric element containing a lead-free alkali niobate compound. Moreover, the point which should adjust oxygen partial pressure with the material of an electrode is disclosed (refer paragraph number (0013), (0014), (0096)).

In addition, as a performance index of piezoelectric ceramics, the piezoelectric constant d33 (mechanical displacement ratio per electric field in 33 directions) is often used.
As a polycrystalline ceramic having a relatively high piezoelectric constant d33, a powder having a uniform crystal orientation (hereinafter referred to as an orientation powder) is mixed with a material compared to a conventional non-oriented piezoelectric ceramic that is simply formed and fired. Attention has been paid to piezoelectric ceramics in which crystals are oriented by molding and firing (hereinafter referred to as crystal oriented piezoelectric ceramics).
For example, Patent Document 2 discloses a perovskite type compound represented by the general formula: ABO ₃ , wherein the main component of the A site element is K and / or Na, and the main component of the B site element is Nb, Sb, and / or Or a crystal-oriented piezoelectric ceramic comprising a polycrystal having a main phase of the first perovskite-type pentavalent metal acid alkali compound of Ta, and having a specific crystal plane of each crystal grain constituting the polycrystal Is described.
Moreover, in the Example of patent document 2, it describes that manufacturing oriented powder, such as plate shape, column shape, and scale shape, first. Further, this oriented powder and other raw materials are mixed, shaped to orient the oriented powder, and fired to grow other raw materials along the crystal orientation of the oriented powder to obtain crystal oriented piezoelectric ceramics. It is described.

In piezoelectric ceramics, in the alkali niobate compound represented by the general formula: ABO ₃ , the ratio of the A site and the B site is intentionally changed from 1: 1 to have an A site rich composition or B site rich. It has been studied to improve the characteristics.
For example, Patent Document 3, the general formula {(1-x) (K 1-ab Na a Li b) m (Nb 1-cd Ta c Sb d) O 3 -xM1 n M2O 3} ( however, M1 is Ca And at least one metal element selected from Sr and Ba, and M2 represents at least one metal element selected from Ti, Zr and Sn.) (Claim 1), it is described that m, which is the ratio of the A site to the B site in this general formula, should be 0.9 ≦ m ≦ 0.99 (Claim 2).
Patent Document 3 can contain a total of 0.1 to 10 mol of at least one metal element selected from Mn, Ni, Fe, Zn, Cu and Mg with respect to 100 mol of the main component. (Claim 5).

JP 2006-108652 A JP 2003-12373 A International Publication No. 2006/117990

  However, the crystal-oriented piezoelectric ceramics using the non-lead alkaline niobate compounds described in these patent documents still have a low piezoelectric constant d33, and have not reached the same characteristics as lead-containing materials.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and to provide a crystal-oriented piezoelectric ceramic using a lead-free alkaline niobate compound having a piezoelectric constant d33 equivalent to that of a lead-containing material and a method for manufacturing the same.

The method for producing a crystal-oriented piezoelectric ceramic according to the present invention comprises: (1): A1 and B1 (where A1 is at least one element selected from alkali metals, and B1 is at least one element of a transition metal element; A step of preparing an oriented powder having a perovskite-type compound structure and containing an internal crystal orientation, and (2): adding an additive raw material to the oriented powder; : (1-s) A1 _α1 B1O ₃ -sM1M2O ₃ (where A1 is at least one element selected from alkali metals, B1 is at least one element of transition metal elements and contains Nb, and M1 is A divalent element, M2 is a tetravalent element, and a step of adjusting to a molding powder having a composition satisfying 1.02 <α1 ≦ 1.10, 0.05 <s ≦ 0.15); (3): The molding powder is contained in the molding powder. And obtaining the orientation of the molded body by molding so that the crystal orientation of the orientation powders are aligned to, (4): the orientation moldings, oxygen partial pressure under the following atmosphere 1 × 10 -4 ^kPa A step of firing, and A1 is volatilized in the step (4), and the general formula 2: (1-s) A1 _α2 B1O ₃ -sM1M2O ₃ (provided that 0.94 ≦ α2 <1 and This is a method for producing a crystal-oriented piezoelectric ceramic that obtains a fired body having a composition represented by α2 ≦ α1-0.045). In addition, after the firing step (4), (5): a step of reoxidation in an atmosphere having an oxygen partial pressure exceeding 1 × 10 ⁻⁴ kPa, and in the steps (4) and (5) A1 is volatilized, and a fired body having a composition represented by the general formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where 0.94 ≦ α2 <1 and α2 ≦ α1-0.045) It can also be set as the manufacturing method of the crystal orientation piezoelectric ceramic which obtains. Furthermore, the A1 is represented by _{K 1-x-y Na x} Li y (0 <x <1,0 <y <1), wherein B1 is _{Nb 1-z Q} z (where, Q is a transition other than Nb It is at least one of metal elements, represented by 0 ≦ z ≦ 0.3), wherein M1 is Ba, and M2 is at least one element of Group 4A and preferably contains Zr. Further, in the step of adjusting the molding powder of (2), when the general formula 1 is 100 mol, it is selected from Mn, V, Cr, Fe, Co, Ni, Cu, Zn, Hf, Ta and W It is preferable to adjust to a composition containing 0.1 to 5 mol in total of at least one or more metal elements. The crystal-oriented piezoelectric ceramic obtained by the present invention has a general formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where A1 is at least one element selected from alkali metals, and B1 is a transition) It is at least one element of metal elements and includes Nb, M1 is a divalent element, M2 is a tetravalent element, and is expressed by 0.94 ≦ α2 <1, 0.05 <s ≦ 0.15). And the piezoelectric constant d33 is 400 pC / N or more. The A1 is represented by K _1-xy Na _x Li _y (0 <x <1, 0 <y <1), and the B1 is Nb _1-z Q _z (where Q is a transition metal element other than Nb) And is represented by 0 ≦ z ≦ 0.3), wherein M1 is Ba, and M2 is at least one element of Group 4A and preferably contains Zr. When the general formula 2 is 100 mol, at least one metal element selected from Mn, V, Cr, Fe, Co, Ni, Cu, Zn, Hf, Ta, and W is 0 in total. It is preferable that the composition is contained in an amount of 1 to 5 mol.

According to the present invention, there is provided a crystal-oriented piezoelectric ceramic having a piezoelectric constant d33 equal to or higher than 400 pC / N and a lead-containing material while being a crystal-oriented piezoelectric ceramic using a lead-free alkali niobate compound and a method for manufacturing the same. Can be provided.
In addition, a laminated piezoelectric element having a large displacement can be obtained by forming and laminating electrodes on this crystal-oriented piezoelectric ceramic.

It is a figure which shows an example of the process (until preparation of orientational powder) of the manufacturing method of this invention. It is a SEM observation photograph (500 times) of the 1st crystal powder used for the manufacturing method of the present invention. It is a figure which shows the X-ray-diffraction result of the 1st crystal powder used for the manufacturing method of this invention. It is a figure which shows the detail of a composition of the 1st crystal powder used for the manufacturing method of this invention. It is a figure which shows the SEM observation photograph (1000 time) of orientation powder. It is a figure which shows an example of the process (after the process of FIG. 1) of the manufacturing method of this invention. It is a schematic diagram of the layered structure of the 1st crystal powder used for the manufacturing method of this invention. It is a cross-sectional schematic diagram which shows the sheet-like molded object which the orientation powder used for the manufacturing method of this invention orientated. 1 is a schematic view of a laminated piezoelectric element.

The present inventors have studied the following to increase the piezoelectric constant d33 as an A1B1O ₃ type crystal-oriented piezoelectric ceramic, and as a result, have found the following points. In the molding powder stage, the ratio α1 of the A1 site to the B1 site is intentionally larger than 1, and then the element of A1 is volatilized at the time of firing or firing and reoxidation. The ratio α2 of the A1 site to the B1 site is 0.94 ≦ α2 <1, which is smaller than 1, and the difference between the ratio α1 of the molding powder and the ratio α2 after firing (α1-α2: hereinafter referred to as Δα) is 0. 0.04 or more was found to be effective, and the present invention was reached.

The crystal-oriented piezoelectric ceramic obtained by the production method of the present invention has a piezoelectric property that is remarkably excellent, with a piezoelectric constant d33 of 400 pC / N or more. Even if α2 of the fired body is in the same range as the present invention of 0.94 ≦ α2 <1, those produced with Δα of less than 0.45, that is, other than the present invention produced with less A1 volatilization The crystal-oriented piezoelectric ceramic cannot obtain the high piezoelectric constant d33 as in the present invention. The reason for this is presumed that the final composition has a composition of 0.94 ≦ α2 <1 in which a large amount of A1 is volatilized at the time of firing, whereby the density is improved as compared with normal firing and the orientation is likely to increase. It seems to be because. In addition, the piezoelectric constant d33 can be set to 450 pC / N or more by further preferable α1, α2, and Δα described later.

In other words, the production method of the present invention comprises (1): A1 and B1 (where A1 is at least one element selected from alkali metals, and B1 is at least one element of transition metal elements and contains Nb) And a step of preparing an oriented powder having a perovskite type compound structure and having the same internal crystal orientation, and (2): adding an additive raw material to the oriented powder, s) A1 _α1 B1O ₃ -sM1M2O ₃ (where A1 is at least one element selected from alkali metals, B1 is at least one element of a transition metal element and contains Nb, and M1 is a divalent element) , M2 is a tetravalent element, and a step of adjusting the molding powder to a composition satisfying 1.02 <α1 ≦ 1.10, 0.05 <s ≦ 0.15), (3): Of each orientation powder contained in the molding powder Have the orientation-molded body, the oxygen partial pressure is calcined under less atmosphere 1 × 10 -4 ^kPa Step: a step of obtaining a molded to oriented moldings as crystal orientation aligned, (4) In the step (4), A1 is volatilized and general formula 2: (1-s) A1 _α2 B1O ₃ -sM1M2O ₃ (provided that 0.94 ≦ α2 <1 and α2 ≦ α1-0. 045) is obtained. Below, the manufacturing method of this invention is demonstrated for every manufacturing process (1)-(4).

  Hereinafter, the first step (1) of the production method of the present invention will be described. The first step (1) includes A1 and B1 (where A1 is at least one element selected from alkali metals, and B1 is at least one element of transition metal elements and contains Nb). This is a step of preparing an orientation powder having a type compound structure and having the same internal crystal orientation. However, the following is merely an example, and the present invention is not limited to this method.

First, by the steps of FIGS. 1 (S1) to (S5), as shown in the schematic diagram of FIG. 7, a (Bi ₂ O ₂ ) ²⁺ layer 2 and a pseudo-perovskite layer 1 are alternately stacked. 1 crystal powder is manufactured, and this 1st crystal powder is converted into said orientation powder by the process of (S6)-(S10) after that. The first crystal powder has an anisotropic shape (plate shape in this description), and the composition can be changed while maintaining the same shape in the subsequent steps (S6) to (S10). Can be used. Details will be described later.

The first crystal powder has a general formula: (Bi ₂ O ₂ ) ²⁺ (Bi _0.5 A3 _m-1.5 Nb _m O _{3m + 1} ) ²⁻ (where A3 is at least one element selected from alkali metals) And m is an integer of 2 or more). In this general formula, the left side shows the (Bi ₂ O ₂ ) ²⁺ layer, and the right side shows the composition of the pseudo-perovskite layer.
In addition, as the first crystal powder in which the pseudo-perovskite layer does not contain Bi, the general formula: (Bi ₂ O ₂ ) ²⁺ (A3 _m−1 B2 _m O _{3m + 1} ) ²⁻ (where A3 is selected from alkali metals) And at least one element selected from the group consisting of 4, 5 and 6 valent elements, and m is an integer of 2 or more. A3 is preferably at least one element selected from Li, K, or Na. B2 is preferably at least one element of Nb and Ta.

  First, raw materials are prepared (S1), mixed (S2), the mixed raw materials are dried, and a first flux such as NaCl is added (S3). As the first flux, for example, an alkali metal chloride or fluoride such as NaCl or KCl, nitrate, sulfate, or the like can be used.

  Thereafter, the raw material to which the first flux is added is heated in the atmosphere at 700 ° C. or higher and 1300 ° C. or lower (S4. This step is hereinafter referred to as first heating). By the first heating, a crystal can be grown to obtain a reaction product (hereinafter referred to as a first intermediate fired body) composed of the first crystal powder and a flux. Multi-stage heat treatment can also be applied to the first heating. In order to sufficiently react the first crystal powder and the flux, the heating time is preferably set to 1 minute or longer. Long-time heating tends to increase the treatment time and reduce the aspect ratio of the obtained plate-like powder shape, and is preferably 10 hours or less. The first intermediate fired body is filled with a flux and becomes a lump.

Thereafter, the first flux is removed from the first intermediate fired body (S5). In this step, means for immersing the reaction product in warm water and melting the first flux can be employed.
Thereby, only the first crystal powder can be taken out.

The first crystal powder, the first additive such as Na ₂ CO ₃ for generating the orientation powder, and the flux such as NaCl that melts at a temperature at which the first crystal powder and the first additive can react (second Flux) is mixed (S6, S7).
As the first additive, the above-described A1 compound of the crystal-oriented ceramic represented by A1B1O ₃ , for example, an A1 oxide or carbonate material can be used. The amount of the first additive added is preferably adjusted so that the molar ratio of A1 and B1 to the first crystal powder becomes 1: 1 after the Bi component is reduced (s10).
In order to mix the first additive, for example, a means of adding a raw material in an organic solvent and mixing with a ball mill or the like can be used.

The second flux is used to promote crystal growth by reacting the first crystal powder and the first additive in the solution. Therefore, it is preferable to use a material that has a melting point that is lower than that of the first crystal powder or the first additive. Moreover, it is preferable that it is a composition which does not contain elements other than the composition of desired orientation powder by reaction. For example, alkali metal chlorides such as NaCl and KCl can be used.
Since the second flux is easily dissolved in water or a solvent, it is preferable to add and mix the second flux after drying the organic solvent or the like. The amount of the second flux added is preferably 10 mass% or more, more preferably 30 mass% or more with respect to the first crystal powder.

Thereafter, the mixed material is heated at a temperature at which the first crystal powder and the first additive can react (S8, hereinafter, this step is referred to as second heating). By the second heating, a reaction product composed of a plate-like powder and a flux (hereinafter referred to as a second intermediate fired body) is obtained.
It is preferable to perform 2nd heating at 600 to 1300 degreeC. When the second heating is less than 600 ° C., composition conversion from the first crystal powder to the oriented powder is difficult to occur, and when it exceeds 1300 ° C., the first crystal powder is dissolved and integrally fired, so that the powder form It becomes difficult to make.
It is preferable to hold | maintain 2nd heating at said temperature for 0.5 hour or more. If the time is less than 0.5 hours, composition conversion from the first crystal powder to the oriented powder hardly occurs. The heating time is more preferably 3 hours or more. Further, if the heating time exceeds 24 hours, the production time becomes long and the productivity is lowered. Therefore, the heating time is preferably 24 hours or less, and more preferably 20 hours or less.

  Next, the second flux is removed from the second intermediate fired body (S9). In order to remove the second flux from the second intermediate fired body, a means for immersing the second intermediate fired body in warm water and stirring and filtering the melted second flux can be employed. Thereby, the second flux can be removed.

Next, the Bi component remaining in the plate-like powder remaining after removing the second flux is reduced (S10). This powder is put into a pickling solution in which water and an acid such as nitric acid are mixed and pickled, and the Bi component is dissolved in the solution. The powder from which the Bi component has been removed becomes the oriented powder used in the present invention and precipitates in the pickling solution. The orientation powder can be extracted by removing the pickling solution from the supernatant and drying the residue. Pickling can be repeated multiple times.
In addition to the above pickling, a method of reducing the Bi component by volatilization by heating can be employed.

  Since this oriented powder maintains a plate shape with the shape of the first crystal powder as a template, an oriented powder having an aspect ratio of * or more can be obtained.

The orientation powder may be a perovskite-type compound represented by the general formula A1B1O _3. In this oriented powder, A1 is at least one element selected from alkali metals. Particularly preferred is at least one selected from the group consisting of Li, K and Na. B1 is an element containing at least one kind of transition metal element and containing Nb.

The step (2) will be described below. In the second step, the additive raw material is mixed with the oriented powder, and the general formula 1: (1-s) A1 _α1 B1O ₃ —sM1M2O ₃ (where A1 is at least one element selected from alkali metals) B1 is at least one element of transition metal elements and contains Nb, M1 is a divalent element, M2 is a tetravalent element, and 1.02 <α1 ≦ 1.10, 0.05 < This is a step of adjusting to a molding powder having a composition satisfying s ≦ 0.15). In FIG. 6, (S11) corresponds to the step of preparing this molding powder. The additive raw material is obtained by mixing raw materials such as oxides, carbonates, and the like of A1, B1, M1, and M2. For example, the orientation of powder consisting A1B1O ₃ When added Xmol is added feedstock chemical composition formula 1: (1-s) such that _{A1 α1-x B1 1-X} O 3 -sM1M2O 3 Mixed.

The orientation powder is preferably added at a ratio of 0.1 mol or more and 10 mol or less, with the above general formula 1 as 100 mol. The ratio is more preferably 0.5 mol or more and 8 mol or less, and further preferably 1.0 mol or more and 6 mol or less. By adding these amounts, the piezoelectric constant d33 can be increased.

The orientation powder and the additive raw material are mixed to obtain a composition of general formula 1. Alkali metal-containing niobium oxide having a crystal structure of A1B1O ₃ Although it is known to express a high piezoelectric constant while there in a non-lead, by dispersing the further M1, perovskite type crystal structure consisting of M2 A higher piezoelectric constant can be obtained.

Furthermore, in order to obtain a higher piezoelectric constant d33, α1 indicating the ratio of the A1 site to the B1 site is set to a range of 1.02 <α1 ≦ 1.10. If it is 1.02 or less, an appropriate volatilization amount of the element at the A1 site cannot be obtained during firing. On the other hand, if α1 exceeds 1.10, a large amount of elements at the A1 site must be volatilized, and the firing is not stable. α1 is more preferably in the range of 1.030 ≦ α1 ≦ 1.055, and more preferably in the range of 1.035 ≦ α1 ≦ 1.045.

More specifically, in A1 _α1 B1O ₃ , A1 is represented by K _1-xy Na _x Li _y (0 <x <1, 0 <y <1), and B1 is Nb _1-z Q _z ( However, Q is at least one of transition metal elements other than Nb, and preferably represented by 0 ≦ z ≦ 0.3).
By including both K and Na as the alkali metal, it is possible to exhibit higher piezoelectric properties than when K or Na is included alone.
Moreover, Li can obtain the effect of increasing the Curie temperature and the effect of enhancing the piezoelectric characteristics by enhancing the firing property, and also exhibits the effect of improving the mechanical strength. However, if the Li content y exceeds 0.3, the firing density tends to decrease. For this reason, the content y of Li in the alkali metal is preferably 0 <y ≦ 0.3.
When z exceeds 0.3, it is difficult to obtain high piezoelectric characteristics.
The ranges of x, y, and z are more preferably 0.3 ≦ x ≦ 0.7, 0.05 ≦ y ≦ 0.2, and 0 ≦ z ≦ 0.2.

  M1 is at least one divalent element and preferably contains Ba. M2 is at least one tetravalent element and preferably contains Zr. Thereby, the piezoelectric constant d33 can be further increased. M2 is particularly preferably a composition containing Zr in an amount of 80 mass% or more.

Each raw material is mixed so that A1 _α1 B1O ₃ and M1M2O ₃ are contained in the piezoelectric ceramic at a ratio represented by the following general formula 1.
[General Formula 1: (1-s) A1 _α1 B1O ₃ −sM1M2O ₃ (0.05 <s ≦ 0.15)]
If the content ratio of M1M2O ₃ is in a range of 0.05 <s ≦ 0.15, it is possible to obtain a piezoelectric ceramic having a high piezoelectric constant d33 and high Curie temperature. On the other hand, if s is 0.05 or less, or if s exceeds 0.15, the piezoelectric constant d33 becomes small, and it becomes difficult to obtain the crystal-oriented piezoelectric ceramic of the present invention. A preferable range of s is 0.065 ≦ s ≦ 0.10.

In the step of adjusting the molding powder of (2), when the general formula 1 is 100 mol, it is selected from Mn, V, Cr, Fe, Co, Ni, Cu, Zn, Hf, Ta, and W. In addition, it is preferable to adjust to a composition containing at least 0.1 to 5 mol in total of at least one metal element. These elements increase sinterability. Moreover, in the manufacturing method of this invention, the effect which raises the piezoelectric constant d33 further is exhibited. The addition amount of these elements is preferably set to an amount of 0.1 mol% or more and 5 mol% or less, assuming that the composition of the general formula 1 is 100 mol%. Even if the manufacturing method of this invention is applied as it is less than 0.1 mol%, it is difficult to raise the piezoelectric constant d33 further. On the other hand, if it exceeds 5 mol%, a different phase other than the composition of general formula 2 described later is formed, and it is difficult to further increase the piezoelectric constant d33.

The (3) step will be described below. The third (3) step is a step of obtaining the oriented molded body by shaping the molding powder so that the crystal orientations of the orientation powders included in the molding powder are aligned. In FIG. 6, (S12) corresponds to the process.

A sheet in which the oriented powder 3 as shown in FIG. 8 is oriented in the additive raw material 4 by mixing a molding powder, a binder, a plasticizer, and a solvent into a slurry and forming a sheet-like molded body. A shaped oriented molded body 10 is obtained. In this state, the normal direction of the surface of the plate-like oriented powder is aligned substantially in the same direction as the normal direction of the sheet surface. Depending on the viscosity of the slurry and the thickness of the sheet to be molded, the degree of orientation of the orientation powder dispersed in the sheet-like molded body can be changed. As the oriented molded body, a laminated body in which sheet-like molded bodies are laminated can be used, and a laminated body in which electrodes are formed and laminated on the surface of the sheet-like molded body can also be used.

The step (4) will be described below. The step (4) is a step of firing the oriented molded body in an atmosphere having an oxygen partial pressure of 1 × 10 ⁻⁴ kPa or less. In FIG. 6, (S13) corresponds to the process.

In this baking step, A1 is volatilized from the composition of the general formula 1 of the molding powder, and the ratio α2 of the A1 site to the B1 site is 0.94 ≦ α2 <1 and α2 ≦ α1−0.045. To do. Specifically, the composition is represented by the general formula 2: (1-s) A1 _α2 B1O ₃ -sM1M2O ₃ (where 0.94 ≦ α2 <1 and α2 ≦ α1-0.045). Bake. When α2 is less than 0.94, a heterogeneous phase having a composition other than the general formula 2 is generated, so that a crystal-oriented piezoelectric ceramic having a high piezoelectric constant d33 cannot be obtained. In addition, when the composition is rich in A1 site, the withstand voltage of the material is lowered and polarization treatment cannot be performed, or crystal oriented piezoelectric ceramics having a high piezoelectric constant d33 cannot be obtained. Furthermore, α1 in the general formula 1 and α2 in the general formula 2 need to satisfy a relationship of α2 ≦ α1-0.045. In other words, the density and orientation degree after sintering can be obtained by intentionally volatilizing a large amount of the A1 site with respect to the composition of the molding powder and firing so that Δα which is the difference between α2 and α1 is 0.045 or more. As a result, crystal-oriented piezoelectric ceramics having an unprecedented high piezoelectric constant d33 can be obtained. If Δα exceeds 0.150, the characteristics are likely to deteriorate. α2 is more preferably in the range of 0.965 ≦ α2 ≦ 0.995, and more preferably in the range of 0.970 ≦ α2 ≦ 0.990. The relationship between α1 and α2 is more preferably α1−0.085 ≦ α2 ≦ α1−0.050, and more preferably α1−0.080 ≦ α2 ≦ α1−0.055.

For firing so that Δα is 0.045 or more, means for lowering the oxygen partial pressure of firing, means for increasing the firing time, means for raising the firing temperature, and the like can be appropriately combined.

Firing is performed in a reducing atmosphere with an oxygen partial pressure of 1 × 10 ⁻⁴ KPa or less. When this oxygen partial pressure is exceeded, the volatilization amount of A1 becomes small, Δα cannot be made 0.045 or more, and the obtained piezoelectric constant d33 is lowered. For example, the oxygen partial pressure can be adjusted by adjusting the supply amounts of water vapor and hydrogen.
The pressure of the atmosphere is preferably atmospheric pressure. Since a general furnace can be applied, manufacturing is easy.

The oxygen partial pressure is preferably 5 × 10 ⁻¹¹ kPa to 1 × 10 ⁻⁶ kPa. Since the relative density can be increased to 95% or more and the generation of oxygen defects can be sufficiently suppressed, a crystal-oriented piezoelectric ceramic having a higher piezoelectric constant d33 can be obtained.

  The firing temperature is preferably 900 ° C. or higher and 1300 ° C. or lower. When the temperature is less than 900 ° C. or exceeds 1300 ° C., the piezoelectric constant d33 of the obtained crystallographically-oriented ceramic is lowered. The temperature on the lower limit side of the firing is preferably 930 ° C. or higher. The temperature on the upper limit side of firing is preferably 1200 ° C. or lower, more preferably 1150 ° C. or lower.

  The firing time is preferably 0.5 hours or longer. If it is less than 0.5 hour, the volatilization amount of A1 becomes small, Δα cannot be made 0.045 or more, and the obtained piezoelectric constant d33 is lowered. Although an upper limit is not specifically limited, Since a manufacturing process will become long if it exceeds 24 hours, it is not preferable. More preferably, it is 1 hour or more and 20 hours or less.

This baking can be a two-stage baking pattern consisting of baking at a relatively low temperature (hereinafter referred to as pre-baking) and baking at a higher temperature than pre-baking (hereinafter referred to as main baking). When a laminated piezoelectric element is manufactured, peeling between the ceramic layer and the electrode layer can be suppressed by performing preliminary firing. The pre-baking temperature is preferably 800 ° C. or higher and 1190 ° C. or lower. The firing temperature is preferably 900 ° C. or higher and 1300 ° C. or lower.

In the present invention, the (5) step may be performed after firing. The fifth (5) step is a step of reoxidation in an atmosphere having an oxygen partial pressure of more than 1 × 10 ⁻⁴ kPa. In FIG. 6, (S14) corresponds to the process. When this step is used, the oxygen partial pressure, the firing time, the firing temperature, and the reoxidation reoxidation are performed so that the composition after firing and reoxidation becomes the composition represented by the general formula 2. Adjust time and reoxidation temperature.

By reoxidation, oxygen defects in the crystal oriented ceramics can be further reduced, and the piezoelectric constant d33 of the crystal oriented ceramics can be increased. The reason for this is not clear, but by reoxidation in an atmosphere with an oxygen partial pressure of more than 10 ⁻⁴ kPa, oxygen is sufficiently supplemented by oxygen defects such as BaZrO _3-m , and tetragonal-rhombohedral This is thought to be due to the clear appearance of the structural phase boundary. As a result, it is estimated that a piezoelectric ceramic having a perovskite structure in which the number of moles of oxygen is optimized and the valence is balanced is obtained.

If it is the above-mentioned oxygen partial pressure, the atmosphere at the time of reoxidation may contain other inert gas, such as nitrogen and argon.
The atmosphere pressure during reoxidation is preferably atmospheric pressure. Since a general furnace can be applied, manufacturing is easy.

The temperature for reoxidation is preferably 500 ° C. or higher and 1200 ° C. or lower. If the temperature is 500 ° C. or higher, oxygen is sufficiently supplemented to oxygen defects, and polarization processing is facilitated, so that a high piezoelectric constant d33 can be obtained. Moreover, if the temperature of reoxidation is 1200 degrees C or less, ceramics can suppress excessive reoxidation. A more preferable range is 600 ° C. or higher and 1150 ° C. or lower. If the reoxidation temperature is 1100 ° C. or higher, A1 can be volatilized, and Δα can be adjusted.
The treatment time is preferably 0.5 hours or longer, and oxygen is sufficiently supplemented to oxygen defects. The upper limit is not particularly limited, but when the treatment time is longer than 24 hours, some of the elements constituting the piezoelectric ceramic may be volatilized. A more preferable range is 1 hour or more and 10 hours or less.

The obtained fired body has a composition represented by the general formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where 0.94 ≦ α2 <1 and α2 ≦ α1-0.045). To do. When α2 is less than 0.94 or exceeds 1, a high piezoelectric constant d33 cannot be obtained. Further, if the A1 element is not volatilized to a value where α2 becomes 0.045 or more smaller than α1, the density does not increase and a high piezoelectric constant d33 cannot be obtained.

As other steps, polarization processing (not shown) will be described.
The ceramic obtained by the above process exhibits excellent piezoelectric characteristics, but in order to further improve the piezoelectric characteristics, a polarization treatment for aligning the direction of spontaneous polarization in the ceramics can be performed. For the polarization treatment, a known polarization treatment generally used in the production of piezoelectric ceramics can be used. For example, an electrode is formed on the fired body, held at a temperature of room temperature to 200 ° C. with a silicone bath or the like, and a voltage of about 0.5 kV / mm to 6 kV / mm is applied.

The crystal-oriented piezoelectric ceramic obtained by the above manufacturing method has the general formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where A1 is at least one element selected from alkali metals, and B1 is a transition) It is at least one element of metal elements and includes Nb, M1 is a divalent element, M2 is a tetravalent element, and is expressed by 0.94 ≦ α2 <1, 0.05 <s ≦ 0.15). The piezoelectric constant d33 is 400 pC / N or more.

The crystal-oriented piezoelectric ceramic of the present invention can be made not only a bulk fired body but also a laminated piezoelectric element by forming and laminating electrodes. As the electrode, a noble metal such as Ag or a base metal such as Cu, Ni, or Al can be used.

Below, the measuring method of the composition of the general formula 1 of the molding powder and the general formula 2 after firing, the oxygen partial pressure, the degree of orientation, the piezoelectric constant d33 and the relative density, which are measured in the present invention, will be described.

[Composition] The composition of the general formula 1 of the molding powder and the general formula 2 after firing was specified by ICP-AES analysis (high frequency inductively coupled plasma emission spectroscopy). Each measured element amount (mass%) was converted into the form of general formula 1 or general formula 2, and s, α1, α2, etc. were obtained.

[Oxygen partial pressure] The oxygen partial pressure can be evaluated using an oxygen concentration meter having a commercially available YTZ (yttrium stabilized zirconia) sensor. The measurement method used was a method of extracting from the furnace using an alumina tube so that the atmosphere in the vicinity of the workpiece in the electric furnace that creates a gas atmosphere can be directly sampled. The oxygen partial pressure can be adjusted by a method of containing a certain amount of water vapor by bubbling or the like in a gas containing 0 to 4 mol% of hydrogen based on an inert gas such as nitrogen or argon. The oxygen partial pressure that can be generated at this time can be calculated from the following equations 1 and 2 using the hydrogen partial pressure PH ₂ and the water vapor partial pressure PH ₂ O. In Equation 1, ΔG _f is the standard production Gibbs energy of water vapor, R is a gas constant, and T is an absolute temperature.

[Orientation degree] The degree of orientation was measured by the Lotgering method. Specifically, it calculated | required from the result of XRD using the Cu-K alpha ray. XRD evaluation was performed in the range of 2θ: 5 ° to 80 ° on the surface of the fired body ground. From the XRD evaluation, the degree of orientation f was calculated from the following Lotgering numbers 3 and 4. Here, P is the remanent polarization value of the piezoelectric ceramic, ΣI {h00} is the sum of all integrated intensities of diffraction peaks derived from {h00}, and ΣI {hkl} is the integrated intensities of all observed diffraction peaks. The sum is shown. P ₀ is the remanent polarization value of the non-oriented piezoelectric ceramic, and a fired body was prepared without using the orientation powder, and was calculated from Equation 3 in the same manner as described above.

[Piezoelectric constant d33] After the polarization treatment, the piezoelectric constant d33 is measured. For the polarization treatment, an Ag electrode was formed on the ceramic by sputtering, and a 4.0 kV / mm DC electric field was applied for 10 minutes at 413 K (140 ° C.). The piezoelectric constant d33 was measured with a d33 meter (manufactured by Institute of Speech, Chinese Academy of Sciences).

[Relative Density] First, the true density was calculated, and the ratio of the actually measured density (measured by the Archimedes method) to the true density was expressed as%, assuming that the true density was 100%. The true density was calculated by calculating the mass of the perovskite-type unit cell from the charged composition, and calculating the volume of the unit cell from the measurement result of XRD (X-Ray Diffraction) of the fired product, and dividing the mass of the unit cell. The thing was adopted as the true density.

When the crystal-oriented piezoelectric ceramic is a laminated piezoelectric material, it is difficult to measure the relative density because another material such as an internal electrode exists between the layers of the ceramics. Therefore, the relative density can be obtained by measuring the porosity instead. The porosity φ can be calculated from the equation φ = Sp / S as the cross-sectional area S of the ceramic and the area Sp of the void existing on the cross-sectional area, and can also be calculated from the laminated piezoelectric material. Since the value obtained by dividing the value of porosity φ from 100 (%) is the same value as the relative density, whether the porosity φ is 1.5% or more and 5% or less can be further increased as the crystal oriented piezoelectric ceramic of the present invention. It is possible to determine whether it is preferable.

Example 1
First, in the manufacturing steps (S1 to S10) shown in FIG. 1, (1): A1 and B1 (where A1 is at least one element selected from alkali metals, and B1 is at least one element of a transition metal element) And a step of preparing an oriented powder having a perovskite type compound structure and having the same internal crystal orientation. Details are described below.

General ^{_{formula: (Bi 2 O 2) 2+}} (Bi 0.5 A m-1.5 Nb m O 3m + 1) in ^2-, A becomes the Na, and _{m = 5 Bi 2.5 Na 3.5 Nb} 5 O The raw materials of Bi ₂ O ₃ , Na ₂ CO ₃ and Nb ₂ O ₅ were weighed so as to be ₁₈ (S1).
These raw materials were mixed by a ball mill. Ethanol was used as a solvent and zirconia balls were used as a medium, and mixed for 24 hours at a rotation speed of 94 rpm. The media and raw materials were taken out from the ball mill container and dried in the air at 130 ° C. Thereafter, the media and the raw material were separated by a sieve (S2).
The separated raw material was mixed with 100% by mass of NaCl as the first flux with respect to the raw material, and then dry mixed for 10 minutes with a coarse pulverizer (S3).
The raw material after the addition of the first flux was held in the atmosphere at 850 ° C. for 1 hour, and then subjected to two stages of first heating held at 1100 ° C. for 2 hours to obtain a first intermediate fired body. The temperature increase and decrease were about 200 ° C./h (S4).
In order to remove the component of the first flux from the obtained first intermediate fired body, it was immersed in warm water of 95 ° C. to 100 ° C. and left for 3 hours. Thereafter, the step of stirring and dehydrating in warm water for 60 minutes was repeated three times. As a result, a first crystal powder composed of the general formula: Bi _2.5 Na _3.5 Nb ₅ O ₁₈ was obtained (S5).

  FIG. 2 is a SEM observation photograph of the first crystal powder. It can be confirmed that the crystals are plate-like.

FIG. 3 shows the X-ray diffraction result of the first crystal powder, and FIG. 4 shows the result of specifying the compound using the X-ray diffraction result. The X-ray diffraction of the present invention used a Cu Kα radiation source.
Most of the crystals obtained are represented by the general formula: Bi _2.5 Na _3.5 Nb ₅ O ₁₈ . However, the general _formula: In addition to _{Bi 2.5 Na 3.5 Nb 5 O 18} , ^{_{formula: (Bi 2 O 2) 2+}} (Bi 0.5 A m-1.5 Nb m O 3m + 1) 2- In this case, a compound of Bi _2.5 Na _0.5 Nb ₂ O ₉ where m = 2 and Bi _2.5 Na _2.5 Nb ₄ O ₁₅ where m = 4 can also be confirmed.

Na ₂ CO ₃ was used as the first additive, and an amount such that Na and Nb were 1: 1 after the reaction was added. These were mixed by a ball mill. Ethanol was used as a solvent and zirconia balls were used as media, and the mixture was mixed at 94 rpm for 4 hours. The mixture was taken out from the ball mill container and dried in an atmosphere of 130 ° C. Thereafter, the media was separated by a sieve (S6).
To the separated raw material, 100 mass% of NaCl as the second flux was mixed with the first crystal powder, and dry-mixed for 10 minutes with a coarse pulverizer (S7).
The mixed material composed of the first crystal powder, the first additive, and the second flux was subjected to second heating that was held at 950 ° C. for 8 hours in the atmosphere to obtain a second intermediate fired body. The temperature increase and decrease were about 200 ° C./h (S8).
In order to reduce the second flux component from the second intermediate fired body, it was immersed in warm water of 95 ° C. to 100 ° C. and left for 3 hours. Thereafter, the step of stirring and dehydrating in warm water for 60 minutes was repeated three times (S9).
Thereafter, pickling was performed to remove the Bi component from the second intermediate fired body. The to-be-processed object obtained by process S9 was put in the pickling liquid which mixed pure water and nitric acid by the ratio of about 3: 1-10: 1, and was stirred. Thereafter, the supernatant liquid in which the Bi component was melted was removed. Further, the pickling solution was added, stirred, and the supernatant was removed repeatedly. Thereafter, the residue was dried to obtain oriented powder made of NaNbO ₃ (S10).
FIG. 5 is a SEM observation photograph of the oriented powder. The aspect ratio (ratio of plate thickness to maximum diameter) of the obtained oriented powder was about 10.

Next, in the manufacturing step (S11) shown in FIG. 6, (2): An additive raw material is mixed into the oriented powder, and the general formula 1: (1-s) A1 _α1 B1O ₃ -sM1M2O ₃ (however, A1 Is at least one element selected from alkali metals, B1 is at least one element of transition metal elements and contains Nb, M1 is a divalent element, M2 is a tetravalent element, and 1.02 <Α1 ≦ 1.10, 0.05 <s ≦ 0.15) A step of adjusting to a molding powder having a composition satisfying was performed.

In this example, the additive material was prepared as follows. The chemical composition is 0.92 (K _0.490 Na _0.500-X Li _0.050 ) Nb _1-X O with respect to the oriented powder Xmol made of NaNbO ₃ (in this example, X = 0.01). The raw materials of K ₂ CO ₃ , Na ₂ CO ₃ , Li ₂ CO ₃ , Nb ₂ O ₅ , BaCO ₃ and ZrO ₂ were weighed so as to be ₃ + 0.08BaZrO ₃ . Thereafter, ball mill mixing was performed in an ethanol solvent for 16 hours. At this time, a zirconia ball having a diameter of 5 mm was used as a medium, and the rotation speed was 100 rpm. After the mixed raw material was separated from the media, it was dried in the atmosphere at 130 ° C. The dried raw material was passed through a 500-mesh sieve and then placed in a zirconia mortar and baked at 1050 ° C. for 3 hours in the air. The fired raw material was pulverized again with a ball mill for 16 hours, and the average particle size was adjusted to 0.8 μm.
An oriented powder Xmol (X = 0.01) made of NaNbO ₃ is added to the obtained additive raw material, and 0.92 corresponding to s = 0.08 and α1 = 1.04 in the above general formula 1. was _{(K 0.490 Na 0.500 Li 0.050)} NbO consisting ₃ + 0.08BaZrO 3 composition. Furthermore, with this composition as 100 mol, MnO ₂ was added and mixed so that Mn would be 1 mol (S11).

Next, in the manufacturing step (S12) of FIG. 6, (3): a step of obtaining an oriented compact by molding the molding powder so that the crystal orientations of the orientation powders included in the molding powder are aligned. did.
First, in order to make the molding powder into a slurry, ethanol was added in an amount of 200 to 300 mass% with respect to the molding powder and butanol was added in an amount of 50 to 100 mass% with respect to the molding powder. A plasticizer was also added. In this example, 5 to 15 mass% of dioctyl phthalate was added as a plasticizer to the mixture. A binder was also added. In this example, 5 to 15 mass% of polyvinyl butyral was added as a binder to the mixture. The slurry thus obtained was formed into a sheet (S12).

Next, in the manufacturing step (S13) of FIG. 6, the step of firing the oriented molded body in an atmosphere having an oxygen partial pressure of 1 × 10 ⁻⁴ kPa or less was performed.
By mixing nitrogen containing 0.01 to 2% of hydrogen and water vapor, the atmosphere in the furnace was reduced to an oxygen partial pressure adjusted to 2.0 × 10 ⁻⁷ kPa and 4 at 1140 ° C. Firing was performed under the condition of maintaining the time (S13).

Next, in the manufacturing step (S14) of FIG. 6, the step of (5): reoxidizing the fired body in an atmosphere with an oxygen partial pressure exceeding 1 × 10 ⁻⁴ kPa was performed.
The atmosphere in the furnace was an oxidizing atmosphere prepared so as to have an oxygen partial pressure of 2.1 × 10 ¹ kPa. The reoxidation temperature was 1000 ° C., and the holding time was 3 hours.

The obtained fired body is obtained from 0.092 (K _0.428 Na _0.500 Li _0.050 ) NbO ₃ + 0.08BaZrO ₃ corresponding to s = 0.08 and α2 = 0.978 in the general formula 2. And a composition containing 1 mol of Mn, where the composition of the general formula 2 is 100 mol.

Table 1 shows the temperature, holding time, and oxygen partial pressure of the atmosphere in the firing and reoxidation steps.
Further, Table 2 shows s and α1 in the obtained general formula 1, and α2 and Δα in the general formula 2 of the fired body, the piezoelectric constant d33, the degree of orientation, and the relative density.

In the method for producing a crystal-oriented piezoelectric ceramic of Example 1, α1 is 1.040 in General Formula 1 of the molding powder. Further, in the general formula 2 of the fired body, α2 is 0.978 and Δα is 0.062, and α2 in the general formula 2 is 0.94 ≦ α2 <1 and α2 which are the conditions of the production method of the present invention. ≦ α1−0.045 (Δα ≧ 0.045). The crystal-oriented piezoelectric ceramic thus obtained has a piezoelectric constant d33 of 587 pC / N. Further, the degree of orientation is as high as 93% and the relative density is as high as 98.6%.

(Example 2)
The influence of the change of Δα on the piezoelectric constant d33 was examined.
A crystal-oriented piezoelectric ceramic was produced in the same manner as in Example 1 except that α1 was set to 1.050 in the general formula 1 of the molding powder.
Hereinafter, only the step of producing an additive material different from that in Example 1 will be described.

The additive raw material is 0.92 (K _0.500 Na _0.500-X Li _0.050 ) with respect to the oriented powder Xmol (in this example, X = 0.01) made of NaNbO _3. The raw materials of K ₂ CO ₃ , Na ₂ CO ₃ , Li ₂ CO ₃ , Nb ₂ O ₅ , BaCO ₃ and ZrO ₂ were weighed so as to be Nb _1-X O ₃ + 0.08BaZrO ₃ .
Thereafter, ball mill mixing was performed in an ethanol solvent for 16 hours. At this time, a zirconia ball having a diameter of 5 mm was used as a medium, and the rotation speed was 100 rpm. After the mixed raw material was separated from the media, it was dried in the atmosphere at 130 ° C. The dried raw material was passed through a 500-mesh sieve and then placed in a zirconia mortar and baked at 1050 ° C. for 3 hours in the air. The fired raw material was again pulverized in a ball mill for 16 hours, so that the average particle size was 0.8 μm.

An oriented powder Xmol (X = 0.01) made of NaNbO ₃ is added to the obtained additive raw material, and 0.92 corresponding to s = 0.08 and α1 = 1.05 in the above general formula 1. was _{(K 0.500 Na 0.500 Li 0.050)} NbO consisting ₃ + 0.08BaZrO 3 composition. Furthermore, the composition as 100 mol, Mn was added and mixed MnO ₂ so that 1 mol. (S11)

Table 1 shows the temperature, holding time, and oxygen partial pressure of the atmosphere in the firing and reoxidation steps.
Further, Table 2 shows s and α1 in the obtained general formula 1, and α2 and Δα in the general formula 2 of the fired body, the piezoelectric constant d33, the degree of orientation, and the relative density.

In the method for producing the crystal-oriented piezoelectric ceramic of Example 2, α1 is 1.050 in the general formula 1 of the molding powder. Moreover, in General formula 2 of a sintered body, α2 is 0.969 and Δα is 0.081. All of these are within the scope of the present invention. The obtained crystal-oriented piezoelectric ceramics had a piezoelectric constant d33 of 400 pC / N or more, which was the same as that of a lead-free piezoelectric material. Further, the ceramics had a high degree of orientation of 89% or more and a relative density of 98.7% or more. In addition, the value of α2 tends to decrease as the value of α1 increases, that is, as the composition of the molding powder becomes A1 site rich, the volatilization during firing of A1 increases, and the composition after firing becomes A1 site poor. It has become.

(Comparative Example 1)
The influence on the piezoelectric constant d33 when Δα was less than 0.045 was examined.
A crystal-oriented piezoelectric ceramic was produced in the same manner as in Example 1 except that the firing time was 1 hour.
Only the firing step different from that in Example 1 will be described below.

In the production step (S13) shown in FIG. 6, the atmosphere in the furnace is changed to an oxygen partial pressure of 2.0 × 10 ⁻⁷ kPa by mixing nitrogen containing 0.1 to 2% of hydrogen and water vapor. The reducing atmosphere prepared as described above was fired under the condition of holding at 1140 ° C. for 1 hour (S13).

Table 1 shows the temperature, holding time, and oxygen partial pressure of the atmosphere in the firing and reoxidation steps.
Further, Table 2 shows s and α1 in the obtained general formula 1, and α2 and Δα in the general formula 2 of the fired body, the piezoelectric constant d33, the degree of orientation, and the relative density.

In the method for producing the crystal-oriented piezoelectric ceramic of Comparative Example 1, α1 is 1.040 in the general formula 1 of the molding powder, and α2 is 0.996 in the general formula 2 of the fired body, which is within the scope of the present invention. Δα is 0.044, which is outside the range of α2 ≦ α1-0.045 (Δα ≧ 0.045), which is the condition of the present invention. The thus obtained crystal-oriented piezoelectric ceramic has a piezoelectric constant d33 as low as 94 pC / N. Further, the degree of orientation was 44% and the relative density was 97.2%, which were low values.

(Examples 3 to 5)
In the firing step, this step is divided into two-stage firing (pre-firing + main firing), and the pre-firing firing temperature is 900 ° C. (Example 3), 1000 ° C. (Example 4), 1050 ° C. ( Example 5).
Only the firing process different from that in Example 1 will be described below.

In the production process (S13) shown in FIG. 6, in Example 3, the atmosphere in the furnace was mixed with oxygen containing 4 to 10 ^-11 kPa by mixing nitrogen containing 0.1-2% hydrogen and water vapor. Reduced to a pressure of 2.0 × 10 ⁻⁷ kPa after pre-baking at 900 ° C. for 4 hours and cooling to room temperature. The main calcination was performed under an atmosphere and maintained at 1140 ° C. for 4 hours.
Moreover, in Example 4, the atmosphere in the furnace was adjusted to an oxygen partial pressure of 2 × 10 ⁻⁹ kPa, pre-baked at 1000 ° C. for 4 hours, cooled to room temperature, The firing was performed under the condition that the atmosphere was a reducing atmosphere prepared so as to have an oxygen partial pressure of 2.0 × 10 ⁻⁷ kPa, and maintained at 1140 ° C. for 4 hours.
In Example 5, the atmosphere in the furnace was adjusted so as to have an oxygen partial pressure of 1 × 10 ⁻⁸ kPa, pre-baked at 1050 ° C. for 4 hours, cooled to room temperature, The firing was performed under the condition that the atmosphere was a reducing atmosphere prepared so as to have an oxygen partial pressure of 2.0 × 10 ⁻⁷ kPa, and maintained at 1140 ° C. for 4 hours.

Table 3 shows the temperature, holding time, and oxygen partial pressure of the atmosphere in the preliminary firing, main firing, and reoxidation steps.
Table 4 shows s and α1 in the obtained general formula 1, and α2 and Δα in the general formula 2 of the fired body, pre-baking temperature, piezoelectric constant d33, degree of orientation, and relative density.

In the method for producing crystal-oriented piezoelectric ceramics of Examples 3 to 5, α1 is 1.040 in the general formula 1 of the molding powder. Moreover, in General formula 2 of a sintered body, α2 is in the range of 0.972 to 0.977. Moreover, (DELTA) (alpha) is the range of 0.062-0.68. All of these ranges are within the scope of the present invention. The obtained crystal-oriented piezoelectric ceramics had a piezoelectric constant d33 of 576 pC / N, 545 pC / N, and 558 pC / N, and were the same as the lead-free piezoelectric material. Further, this ceramic had a high degree of orientation of 95% or more and a relative density of 97.9% or more.

(Comparative Example 2) As in Example 3, in the firing process, this process is divided into two stages of firing (preliminary firing + main firing), but the piezoelectric constant when Δα is less than 0.45. The effect on d33 was examined.
A crystal-oriented piezoelectric ceramic was produced in the same manner as in Example 3 except that α1 was 1.20 in the general formula 1 of the molding powder.
Hereinafter, only the step of producing an additive material different from Example 3 will be described.

The additive raw material was produced as follows. The chemical composition is 0.92 (K _0.470 Na _0.500-X Li _0.050 ) Nb _1-X O with respect to the oriented powder Xmol made of NaNbO ₃ (in this example, X = 0.01). The raw materials of K ₂ CO ₃ , Na ₂ CO ₃ , Li ₂ CO ₃ , Nb ₂ O ₅ , BaCO ₃ and ZrO ₂ were weighed so as to be ₃ + 0.08BaZrO ₃ .
Thereafter, ball mill mixing was performed in an ethanol solvent for 16 hours. At this time, a zirconia ball having a diameter of 5 mm was used as a medium, and the rotation speed was 100 rpm. After the mixed raw material was separated from the media, it was dried in the atmosphere at 130 ° C. The dried raw material was passed through a 500-mesh sieve and then placed in a zirconia mortar and baked at 1050 ° C. for 3 hours in the air. The fired raw material was again pulverized in a ball mill for 16 hours, so that the average particle size was 0.8 μm.
An oriented powder Xmol (X = 0.01) made of NaNbO ₃ is added to the obtained additive raw material, and 0.92 corresponding to s = 0.08 and α1 = 1.02 in the above general formula 1. was _{(K 0.470 Na 0.500 Li 0.050)} NbO consisting ₃ + 0.08BaZrO 3 composition. Furthermore, with this composition as 100 mol, MnO ₂ was added and mixed so that Mn would be 1 mol (S11).

In the method for producing the crystal-oriented piezoelectric ceramic of Comparative Example 2, α1 is 1.020 in the general formula 1 of the molding powder, α2 is 0.985, and Δα is 0.035 in the general formula 2 of the fired body. This is outside the range of α2 ≦ α1-0.045 (Δα ≧ 0.045), which is the condition of the production method of the present invention. The crystal-oriented piezoelectric ceramic thus obtained has a piezoelectric constant d33 as low as 288 pC / N. Also, the degree of orientation is as low as 7%.

1: pseudo-perovskite layer, 2: (Bi ₂ O ₂ ) ²⁺ layer, 3: oriented powder, 4: additive raw material, 10: sheet-like molded product, a: oriented crystal, b: non-oriented crystal, 11: ceramics Layer, 12: electrode layer

Claims (7)

(1): A perovskite type compound structure containing A1 and B1 (wherein A1 is at least one element selected from alkali metals, and B1 is at least one element of transition metal elements and contains Nb). A step of preparing an oriented powder having an internal crystal orientation and (2): an additive raw material is mixed with the oriented powder, and a general formula 1: (1-s) A1 _α1 B1O ₃ —sM1M2O ₃ (where A1 is at least one element selected from alkali metals, B1 is at least one element of transition metal elements and contains Nb, M1 is a divalent element, and M2 is a tetravalent element. And a step of adjusting the molding powder to a composition satisfying 1.02 <α1 ≦ 1.10, 0.05 <s ≦ 0.15), and (3): each of the molding powder contained in the molding powder. Molded so that the crystal orientation of oriented powder is aligned. And obtaining an oriented molded body, (4): the orientation moldings, oxygen partial pressure and a step of firing under the following atmosphere 1 × 10 -4 ^kPa, and calcination of the (4) In the process, A1 is volatilized, and the composition represented by the general formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where 0.94 ≦ α2 <1 and α2 ≦ α1-0.045) A method for producing a crystal-oriented piezoelectric ceramic to obtain a fired body. After the firing step (4), (5): having a step of reoxidation in an atmosphere having an oxygen partial pressure of more than 1 × 10 ⁻⁴ kPa, and A1 in the steps (4) and (5) Volatilization is performed to obtain a fired body having a composition represented by the general formula 2: (1-s) A1 _α2 B1O ₃ -sM1M2O ₃ (where 0.94 ≦ α2 <1 and α2 ≦ α1-0.045). The manufacturing method of the crystal orientation piezoelectric ceramic of Claim 1. The A1 is represented by K _1-xy Na _x Li _y (0 <x <1, 0 <y <1), and the B1 is Nb _1-z Q _z (where Q is a transition metal element other than Nb) The M1 is Ba, and the M2 is at least one element of Group 4A and contains Zr. A method for producing crystal-oriented piezoelectric ceramics. In the step of adjusting the molding powder of (2), when the general formula 1 is 100 mol, it was selected from Mn, V, Cr, Fe, Co, Ni, Cu, Zn, Hf, Ta and W The method for producing a crystal-oriented piezoelectric ceramic according to any one of claims 1 to 3, wherein the composition is adjusted to a composition containing 0.1 to 5 mol in total of at least one metal element. General formula 2: (1-s) A1 _α2 B1O ₃ —sM1M2O ₃ (where A1 is at least one element selected from alkali metals, and B1 is at least one element of transition metal elements and contains Nb) , M1 is a divalent element, M2 is a tetravalent element, 0.94 ≦ α2 <1, 0.05 <s ≦ 0.15), and a piezoelectric constant d33 of 400 pC / N or more Oriented piezoelectric ceramics. The A1 is represented by K _1-xy Na _x Li _y (0 <x <1, 0 <y <1), and the B1 is Nb _1-z Q _z (where Q is a transition metal element other than Nb) The crystal-oriented piezoelectric element according to claim 5, wherein M 1 is Ba, and M 2 is at least one element of Group 4A and contains Zr. Ceramics. When the general formula 2 is 100 mol, a total of at least one metal element selected from Mn, V, Cr, Fe, Co, Ni, Cu, Zn, Hf, Ta, and W is 0.1. The crystal-oriented piezoelectric ceramic according to claim 5 or 6, which is contained in an amount of -5 mol.

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