JP2008007397A - Method for producing bulk lead zirconate titanate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing bulk lead zirconate titanate without using an organic binder. <P>SOLUTION: The method for producing the bulk lead zirconate titanate comprises: a process for obtaining a raw material powder by mixing a powder of lead zirconate titanate and a powder of amorphous lead zirconate titanate niobate; and a process for sintering the raw material powder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing bulk lead zirconate titanate.

  As a method for producing bulk lead zirconate titanate, there is known a method in which powder of lead zirconate titanate is mixed with an organic binder such as polyvinyl alcohol, and then molded and fired. For example, Japanese Patent Application Laid-Open No. 2005-290494 discloses a technique for mixing a ceramic powder, a polymer aqueous solution as a binder, and a foaming agent to form a bulk foam and sintering it to obtain a bulk ceramic. It is disclosed.

However, in such a conventional method, it is difficult to completely remove the organic binder, which may adversely affect the characteristics of ceramics such as piezoelectricity and insulation.
JP 2005-290494 A

  The present invention is to provide a production method capable of obtaining bulk lead zirconate titanate without using an organic binder.

The method for producing bulk lead zirconate titanate according to the present invention is as follows.
Mixing raw powder of lead zirconate titanate and amorphous lead zirconate titanate niobate powder to obtain raw powder;
Sintering the raw material powder;
including.

  According to the manufacturing method of the present invention, an organic binder such as polyvinyl alcohol is used by mixing and sintering a powder of lead zirconate titanate and a powder of amorphous lead zirconate titanate niobate, for example. And bulk lead zirconate titanate can be obtained.

  In the production method of the present invention, the lead zirconate titanate niobate may be used in a proportion of 5 to 25% by weight with respect to the raw material powder.

In the production method of the present invention, said lead zirconate titanate niobate is represented by the formula _{Pb (Zr, Ti) 1-} x Nb x O 3, it is 0.05 ≦ x ≦ 0.3 in the formula Can do.

  In the production method of the present invention, the lead zirconate titanate niobate can further contain 0.5 mol% or more of Si, or Si and Ge.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1. Manufacturing Method of Bulk Lead Zirconate Titanate The manufacturing method of bulk lead zirconate titanate according to the present embodiment includes the steps shown in FIG. FIG. 1 is a flowchart showing the manufacturing method of this embodiment.

(1) Weighing and mixing raw materials First, lead zirconate titanate (Pb (Zr, Ti) O ₃ ; hereinafter also referred to as “PZT”) powder and amorphous lead zirconate titanate niobate (Pb (Pb ( Zr, Ti) _1-x Nb _x O ₃ (hereinafter also referred to as “PZTN”) is weighed so that both of them become a predetermined amount (step S1). Thereafter, PZT powder and amorphous PZTN (hereinafter also referred to as “α-PZTN”) powder are mixed to obtain a raw material powder (step S2). The particle size of the PZT and α-PZTN powder is not particularly limited, but may be, for example, 1 to 100 μm.

  In the present embodiment, α-PZTN is preferably used in a proportion of 5 to 25% by weight with respect to the raw material powder. When the proportion of α-PZTN is within this range, bulk PZT having good characteristics can be obtained without using an organic binder. That is, α-PZTN has a function of a binder with respect to the crystal powder of PZT because atoms are easy to move, that is, in a soft state. Furthermore, since PZTN has the same perovskite structure as PZT, α-PZTN is easily crystallized by dragging the crystallinity of PZT, so that the sintering temperature can be made lower than in the case of PZTN alone. Furthermore, since PZTN is excellent in piezoelectric characteristics, ferroelectric characteristics, and insulating properties, it does not adversely affect the characteristics of bulk PZT, and more excellent characteristics can be added. When a conventional organic binder is used, it is difficult to completely remove the organic binder, which may have some influence on the bulk PZT. In this embodiment, α-PZTN is used as the binder. Because it works, this problem does not occur. α-PZTN and PZTN will be described in detail later.

(2) Sintering Next, the raw material powder is sintered. A known method can be used for sintering. For example, the raw material powder can be put in a mold and sintered by a vacuum hot press method. Sintering can be performed at 800 ° C to 1200 ° C. In this way, the bulk PZT of this embodiment can be obtained.

  Next, α-PZTN and PZTN used in the present embodiment will be described in more detail.

Α-PZTN used in the present embodiment becomes a perovskite type PZTN through a sintering process. When PZTN is represented by the formula Pb (Zr, Ti) _1-x Nb _x O ₃ , it preferably satisfies 0.05 ≦ x ≦ 0.30, more preferably 0.1 ≦ x ≦ 0.3. Niobium can be included in proportions.

Niobium (Nb) is approximately the same size as titanium (Ti) (the ionic radius is the same, and the atomic radius is the same), is twice the weight, and atoms from the lattice are also affected by collisions between atoms due to lattice vibration. It is hard to come off. Also, the valence is +5 and stable, and even if Pb is lost, the valence of Pb loss can be compensated by Nb ⁵⁺ . Further, even if Pb loss occurs during crystallization, it is easier to enter small Nb than large O loss.

In addition, since Nb also has a +4 valence, Ti ⁴⁺ can be sufficiently replaced. Furthermore, Nb is actually considered to have a very strong covalent bond and Pb is difficult to escape (H. Miyazawa, E. Natori, S. Miyashita; Jpn. J. Appl. Phys. 39 (2000). 5679).

  When PZT contains Nb at a specific ratio, adverse effects due to Pb deficiency are eliminated, and the composition controllability is excellent. As a result, PZTN has extremely good piezoelectric characteristics, ferroelectric characteristics, insulation, and the like as compared with normal PZT.

  Until now, Nb doping to PZT has been mainly performed in the Zr-rich rhombohedral region, but the amount is 0.2-0.025 mol% (J. Am. Ceram. Soc, 84). (2001) 902; Phys. Rev. Let, 83 (1999) 1347) and so on. It is considered that the reason why Nb could not be doped in a large amount as described above was that the crystallization temperature increased to 800 ° C. or more when Nb was added at, for example, 10 mol%.

Therefore, it is preferable to add PbSiO ₃ silicate to the PZTN precursor composition at a ratio of 0.5 to 10 mol%, for example. Thereby, the crystallization energy of PZTN can be reduced. That is, when PZTN is used as the material of the ferroelectric layer, the crystallization temperature of PZTN can be reduced by adding PbSiO ₃ silicate together with Nb. In addition, silicate and germanate can be mixed and used instead of silicate. The inventors of the present application have confirmed by Raman spectrum analysis that silicon, after acting as a sintering agent, constitutes a part of the crystal as an A site ion. That is, when silicon was added to lead titanate, a change was observed in the Raman vibration mode E (1TO) of the A site ion. The change in the Raman vibration mode was observed when the Si addition amount was 8 mol% or less. Therefore, it was confirmed that Si was present at the A site of the perovskite with a slight addition of Si.

  As described above, in this embodiment, PZTN preferably contains 0.5 mol% or more of Si, or Si and Ge, more preferably 0.5 to 10 mol% of Si, or Si and Ge. it can.

  Next, a method for producing α-PZTN used in the present embodiment will be described. α-PZTN can be obtained through the following steps. First, a PZTN precursor composition solution is prepared alkaline. Next, an oxidizing substance is mixed into the precursor composition solution. Through such a process, α-PZTN particles are precipitated in the precursor composition solution. The particles thus obtained can be recovered and used as α-PZTN powder. These steps will be described in more detail.

(1) Preparation of PZTN precursor composition (solution) The precursor composition is a thermally decomposable organometallic compound containing Pb, Zr, Ti or Nb, or a hydrolyzable organometallic containing Pb, Zr, Ti or Nb. It contains at least one compound, its partial hydrolyzate and / or polycondensate, at least one polycarboxylic acid and polycarboxylic acid ester, and an organic solvent.

  In the precursor composition, an organic metal compound containing each component metal of the material to be a composite metal oxide, or a partial hydrolyzate and / or polycondensate thereof are mixed so that each metal has a desired molar ratio. Further, it can be prepared by dissolving or dispersing them using an organic solvent such as alcohol. It is preferable to use an organometallic compound that is stable in a solution state.

  In the present embodiment, usable organometallic compounds are those that can be hydrolyzed or oxidized to produce metal oxides derived from the metal organic compounds, and each metal alkoxide, organometallic complex, And an organic acid salt.

  As the thermally decomposable organometallic compound containing each of the constituent metals of the composite metal oxide, for example, organometallic compounds such as metal alkoxides, organic acid salts, and β-diketone complexes can be used. As the hydrolyzable organometallic compound containing the constituent metals of the composite metal oxide, organometallic compounds such as metal alkoxides can be used. The following are mentioned as an example of an organometallic compound.

  Examples of the organometallic compound containing Pb include lead acetate and lead octylate. Examples of organometallic compounds containing Zr or Ti include these alkoxides, acetates, octylates and the like.

  Examples of the organometallic compound containing Nb include niobium octylate and lead niobium octylate. Niobium octylate has a structure in which Nb is covalently bonded to two atoms and an octyl group is present in the other part.

  In the raw material composition of this embodiment, alcohol can be used as the organic solvent. When alcohol is used as the solvent, both the organometallic compound and the polycarboxylic acid or polycarboxylic acid ester can be dissolved well. Although it does not specifically limit as alcohol, Monovalent alcohols, such as butanol, methanol, ethanol, and propanol, or a polyhydric alcohol can be illustrated. Examples of such alcohols include the following.

Monohydric alcohols;
As propanol (propyl alcohol), 1-propanol (boiling point 97.4 ° C), 2-propanol (boiling point 82.7 ° C),
As butanol (butyl alcohol), 1-butanol (boiling point 117 ° C.), 2-butanol (boiling point 100 ° C.), 2-methyl-1-propanol (boiling point 108 ° C.), 2-methyl-2-propanol (melting point 25.4) ℃, boiling point 83 ℃),
As pentanol (amyl alcohol), 1-pentanol (boiling point 137 ° C.), 3-methyl-1-butanol (boiling point 131 ° C.), 2-methyl-1-butanol (boiling point 128 ° C.), 2,2 dimethyl-1 -Propanol (boiling point 113 ° C), 2-pentanol (boiling point 119 ° C), 3-methyl-2-butanol (boiling point 112.5 ° C), 3-pentanol (boiling point 117 ° C), 2-methyl-2-butanol (Boiling point 102 ° C.),
Polyhydric alcohols;
Ethylene glycol (melting point −11.5 ° C., boiling point 197.5 ° C.), glycerin (melting point 17 ° C., boiling point 290 ° C.).

  In the precursor composition, the polycarboxylic acid or polycarboxylic acid ester can be divalent or higher. The following can be illustrated as polycarboxylic acid used for this invention. Examples of the trivalent carboxylic acid include Trans-aconitic acid, trimesic acid, and examples of the tetravalent carboxylic acid include pyromellitic acid and 1,2,3,4-cyclopentanetetracarboxylic acid. Polycarboxylic acid esters include divalent dimethyl succinate, diethyl succinate, dibutyl oxalate, dimethyl malonate, dimethyl adipate, dimethyl maleate, diethyl fumarate, trivalent tributyl citrate, 1,1 , 2-ethanetricarboxylic acid triethyl, tetravalent 1,1,2,2-ethanetetracarboxylic acid tetraethyl, 1,2,4-benzenetricarboxylic acid trimethyl and the like.

  In the precursor composition, the divalent carboxylic acid ester can be preferably at least one selected from succinic acid esters, maleic acid esters and malonic acid esters. Specific examples of these esters include dimethyl succinate, dimethyl maleate, and dimethyl malonate.

  The polycarboxylic acid or polycarboxylic acid ester can have a higher boiling point than the organic solvent. When the boiling point of the polycarboxylic acid or the polycarboxylic acid ester is higher than that of the organic solvent, the reaction of the raw material composition can be performed more rapidly as described later.

  The molecular weight of the polycarboxylic acid ester may be 150 or less. If the molecular weight of the polycarboxylic acid ester is too large, the film tends to be damaged when the ester volatilizes during heat treatment, and a dense film may not be obtained.

  The polycarboxylic acid ester may be a liquid at room temperature. If the polycarboxylic acid ester is solid at room temperature, the liquid may gel.

  The composite metal oxide obtained by the precursor composition described above can preferably contain Nb in the range of 0.05 ≦ x <1, more preferably in the range of 0.1 ≦ x ≦ 0.3. The composite metal oxide may contain 0.5 mol% or more, more preferably 0.5 mol% or more and 5 mol% or less of Si, or Si and Ge.

  The PZTN contained in the bulk PZT in the present embodiment contains Nb at a specific ratio, thereby eliminating the adverse effects due to Pb loss and having excellent composition controllability.

  The amount of polycarboxylic acid or polycarboxylic acid ester used depends on the composition of PZTN. For example, the total molar ion concentration of the metal for forming PZTN and the molar ion concentration of the polycarboxylic acid (ester) is preferably 1 ≧ (the molar ion concentration of the polycarboxylic acid (ester)) / (the total molar ion concentration of the metal in the raw material solution). It can be.

  Here, the number of moles of polycarboxylic acid or polycarboxylic acid ester is a valence. That is, in the case of a divalent polycarboxylic acid or polycarboxylic acid ester, one molecule of polycarboxylic acid or polycarboxylic acid ester corresponds to 0.1 mol of polycarboxylic acid or polycarboxylic acid ester per 1 mol of metal in the raw material solution. 5 moles is 1: 1.

(2) Preparation of pH of precursor composition First, the pH of the precursor composition is adjusted to be alkaline. The pH of the precursor composition is preferably adjusted to pH 10 or more, more preferably pH 10 or more and 13 or less. At this time, as the pH adjuster, a known ant potency substance can be used. As such an alkaline substance, for example, ammonia solution, dimethylaminomethanol, diethylaminomethanol, dimethylaminoethanol, diethylaminoethanol and the like can be used.

  Next, an oxidizing substance is mixed into the precursor composition. As the oxidizing substance, known substances can be used. As the oxidizing substance (acidic substance), for example, hydrogen peroxide, organic acids such as citric acid, inorganic acids such as hydrochloric acid, and the like can be used. When an oxidizing substance is added to the precursor composition in this way, α-PZTN particles are precipitated in the precursor composition solution. When these particles are collected and dried, α-PZTN powder is obtained. The α-PZTN powder can be used as it is as a sintering material, but can be further pulverized as required.

  According to the present embodiment, bulk PZT can be obtained without using an organic binder such as polyvinyl alcohol, for example, by using a mixture of PZT powder and α-PZTN powder as raw material powder. . This bulk PZT does not contain impurities such as an organic binder and has excellent bulk crystal characteristics. Further, the bulk PZT is excellent in piezoelectric characteristics, ferroelectric characteristics, insulation, and the like, and includes PZTN, and has better characteristics than the PZT alone.

  The bulk PZT according to the present embodiment can be used for various applications, and can be suitably applied to, for example, a piezoelectric motor, a SAW device, a gyro, and the like.

2. Examples Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

  The sample of the Example was obtained by the following method.

(1) Production of α-PZTN A precursor composition for obtaining α-PZTN powder includes first to third raw material solutions containing at least one of Pb, Zr, Ti, and Nb; It was obtained by mixing dimethyl succinate as an acid ester and n-butanol as an organic solvent. The mixed solution is obtained by dissolving the sol-gel raw material and dimethyl succinate in n-butanol at a ratio of 1: 1.

As the first raw material solution, a solution obtained by dissolving a polycondensation product for forming a PbZrO ₃ perovskite crystal with Pb and Zr in an n-butanol solvent in an anhydrous state was used.

As the second raw material solution, a solution obtained by dissolving a condensation polymer for forming PbTiO ₃ perovskite crystals of Pb and Ti in an n-butanol solvent in an anhydrous state was used.

As the third raw material solution, a solution obtained by dissolving a condensation polymer for forming PbNbO ₃ perovskite crystals with Pb and Nb in an n-butanol solvent in an anhydrous state was used.

When a ferroelectric layer made of PbZr _0.33 Ti _0.47 Nb _0.2 O ₃ (PZTN) is formed using the first, second and third raw material solutions, (first raw material solution) ) :( second raw material solution) :( third raw material solution) = 33: 47: 20. Further, for the purpose of lowering the crystallization temperature of the ferroelectric layer, as a fourth raw material solution, a solution obtained by dissolving a condensation polymer for forming PbSiO ₃ crystals in an n-butanol solvent in an anhydrous state is 2 It added to the said mixed solution in the ratio of mol%, and the precursor composition was obtained.

  An aqueous ammonia solution was added to the precursor composition obtained by the above method to adjust the pH of the precursor composition to 13. Subsequently, 40% hydrogen peroxide solution was added to the precursor composition to adjust the pH to about 7. Then, particles were precipitated in the precursor composition. The particles were collected and dried to obtain a powder. The average particle size of the powder particles was about 100 μm. Furthermore, when the obtained powder was analyzed by the XRD method, it was confirmed that the powder was α-PZTN.

(2) Production of bulk PZT The α-PZTN powder obtained in (1) and the PZT powder were mixed at a weight ratio of 1: 4 to obtain a raw material powder. The ratio of the α-PZTN powder to the raw material powder was 20% by weight. The average particle size of the PZT powder was about 500 μm.

  Subsequently, the raw material powder was put into a mold and sintered by a vacuum hot press method. Sintering was performed at 850 ° C. In this way, bulk PZT of this example was obtained.

The flowchart figure which shows the manufacturing method of bulk PZT.

Claims (4)

Mixing raw powder of lead zirconate titanate and amorphous lead zirconate titanate niobate powder to obtain raw powder;
Sintering the raw material powder;
A method for producing bulk lead zirconate titanate, comprising: In claim 1,
The said lead zirconate titanate niobate is a manufacturing method of bulk lead zirconate titanate used in the ratio of 5 to 25 weight% with respect to the said raw material powder. In claim 1 or 2,
The lead zirconate titanate niobate is represented by the formula _{Pb (Zr, Ti) 1-} x Nb x O 3, is 0.05 ≦ x ≦ 0.3 in said formula, bulk lead zirconate titanate Manufacturing method. In claim 3,
The lead zirconate titanate niobate further includes 0.5 mol% or more of Si, or Si and Ge, and is a method for producing bulk lead zirconate titanate.

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