JP2006282434A - Method for manufacturing perovskite type compound oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a mixed dry material with little maldistribution and little aggregation by heating a slurry prepared by wet-blending metal oxides which are raw materials of a perovskite type compound oxide in the presence of a solvent such as water and by bringing pulse combustion gas into contact with the slurry. <P>SOLUTION: A method for manufacturing a perovskite type compound oxide having a composition represented by the formula: ABO<SB>3</SB>(where A and B each denote a metal element) is provided which includes a step of drying a slurry or solution of inorganic metal compounds by bringing pulse combustion gas into contact with it. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a perovskite complex oxide, and particularly to a lead zirconate titanate compound.

  Composite perovskite materials represented by lead zirconate titanate (hereinafter abbreviated as PZT) are used in a wide range of electronic parts as piezoelectric materials, and in recent years, in particular, with the improvement in performance, size and cost of parts. The PZT powder as a raw material is required to be fine and have high crystallinity.

  PZT can be produced by (1) a dry method in which the oxides or carbonates of the elements constituting PZT are separately weighed, mixed and pulverized, and calcined at a high temperature, and (2) PZT is constituted. (3) PZT, wherein alkali is added to a mixed solution in which a water-soluble compound of an element is dissolved in a predetermined ratio to obtain a mixed hydroxide precipitate, the precipitate is washed to remove impurities, and dried and calcined. A sol-gel method of hydrolyzing a composite compound solution obtained by mixing alkoxides of elements constituting acetylacetonate and acetylacetonate, and calcining the generated gel, (4) dissolving an aqueous solution compound of elements constituting PZT A method in which a carboxylic acid, for example, oxalic acid is added to the mixed solution to form a molecular compound, and the precipitate is washed to remove impurities and then dried, and then calcined. (5) An aqueous solution of elements constituting PZT Hydrogen peroxide is added to the compound to obtain a precursor aqueous solution, and this precursor aqueous solution is thermally decomposed. (6) A complex solution of the metal salt of the element constituting PZT and an amino acid is prepared and heated. Thus, a method of preparing and calcining powder is known. However, in the conventional powder manufacturing method, the composite composition oxide is separated at the time of drying after mixing the metal element compounds constituting the PZT before calcination, or the particle size is increased by aggregation at the time of drying. There were drawbacks.

  In order to solve these problems, for example, in Patent Document 1 and Patent Document 2, production of a composite oxide powder having a perovskite structure using a hydroxide or metal complex as a precursor of each oxide as a raw material Although the method has been described, there has been the disadvantage that the available metal compounds are limited.

JP-A-8-337423 JP 2003-252623 A

  In the present invention, each metal oxide that is a raw material of the perovskite complex oxide is wet-mixed in the presence of a solvent such as water, and then the slurry is heated and contacted with a pulse combustion gas, thereby reducing uneven distribution and aggregation. The object is to obtain a mixed dried product with a low content.

That is, the present invention relates to a method for producing a perovskite complex oxide having a composition represented by the general formula ABO ₃ (wherein A and B represent metal elements), and the method is applied to a slurry or solution of an inorganic metal compound. The present invention relates to a method for producing a perovskite complex oxide including a step of bringing a pulse combustion gas into contact with drying.

  The main component is preferably lead zirconate titanate.

The pulse combustion gas preferably has a frequency of 50 to 1000 Hz, a pressure amplitude of ± 0.2 kg / cm ² or more, a sound pressure of 100 to 200 dB, and a contact gas temperature of 100 to 1000 ° C.

  The present invention also relates to a perovskite complex oxide produced by the production method.

  PZT obtained by calcining and calcining the mixed dried product by a conventional manufacturing method because a mixed dried product with less uneven distribution and less agglomeration can be obtained by drying the wet mixed slurry of perovskite complex oxide in contact with pulse combustion gas. Compared with a mixed powder prepared by a system material or a stationary drying method which is a conventional drying method, electrical characteristics such as a relative dielectric constant are extremely good.

  The method for producing a perovskite composite oxide according to the present invention comprises heating a slurry or solution obtained by wet-mixing an inorganic compound such as a metal oxide, which is a raw material of a perovskite composite oxide, in the presence of a solvent such as water, and applying a shock wave. It is applied and dried.

The perovskite complex oxide of the present invention has a composition represented by the general formula ABO ₃ (wherein A and B represent metal elements). Here, examples of A include lead, cadmium, magnesium, calcium, strontium, barium, and lanthanum. Examples of B include titanium, zirconium, and manganese.

  Each metal oxide powder in the wet-mixed slurry may be a water-soluble salt such as hydroxide, chloride, nitrate, or a mixture thereof.

  The particle diameter of the particles containing the metal oxide, hydroxide and water-soluble salt mixture for forming the perovskite complex oxide in the slurry is preferably 0.01 to 50 μm, more preferably 0.05 to 50 μm, 0.1-20 micrometers is further more preferable and 0.3-15 micrometers is especially preferable. When the particle size is less than 0.01 μm, the particle size tends to increase due to aggregation even when pulse combustion drying is performed. On the other hand, if it exceeds 50 μm, the particle crushing effect by the pulse combustion gas is reduced, and the particle size after drying tends to increase.

  The solid content concentration of the raw material oxide particles constituting the perovskite complex oxide in the slurry is neutralized hydrate, neutralized coprecipitated hydrate, hydrolyzate, water-soluble salt, or their composites is dried. In terms of physical properties, it is preferably 5 to 60% by weight, more preferably 5 to 50% by weight. When the concentration is less than 5% by weight, the particle diameter after drying tends to be too fine to make collection difficult. On the other hand, if it exceeds 60% by weight, operations such as slurry transportation become difficult, the particle size after drying tends to be large, and the particle size distribution tends to be broad.

  In the raw metal compound of the perovskite-based composite oxide, for example, as a method of mixing the composite of lead oxide, zirconium oxide, titanium oxide particles, a predetermined amount of zirconium oxide, lead oxide, titanium oxide is weighed into a bead mill or a ball mill, It is preferable to add a solvent such as water, stir and mix for a predetermined time, and disperse and mix until a predetermined particle size is obtained.

  Examples of the solvent used in preparing the slurry include water, alcohol, water / alcohol mixed solution, methyl ethyl ketone / water mixed solution, and toluene. Among these, water or a water / alcohol mixed solution is preferable from the viewpoint of economy and safety.

  The raw metal compound for the perovskite complex oxide can be used as a solution in addition to being used in the form of a slurry. As a solvent used for the solution, a solvent for producing a fine particle slurry can be used.

  Examples of the inorganic metal compound used in the raw metal compound solution include hydroxides, chlorides, carbonates, sulfates, nitrates, and alkoxide compounds. Among these, water-soluble inorganic metal salts are preferable from the viewpoints of economy and safety. Examples of water-soluble inorganic metal salts include chlorides, sulfates, and nitrates. Specific examples of the aqueous solution of the inorganic metal salt include zirconium chloride aqueous solution, zirconyl sulfate aqueous solution, zirconyl nitrate aqueous solution, titanium tetrachloride aqueous solution, titanium trichloride aqueous solution, lead chloride aqueous solution, lead nitrate aqueous solution and the like.

  In the method for producing a perovskite complex oxide of the present invention, a drying method by contact with a pulse shock wave combustion gas is used as a drying method of the raw material powder. A shock wave refers to a state in which pressure, density, temperature, etc. repeats abrupt rise and fall in a compressive fluid, and ultrasonic waves, compressed liquid accompanying explosion, high-speed movement of an object, etc. can be used. Among these, ultrasonic vibration is preferable from the viewpoints of economy and safety. The heating means for the raw material liquid is not particularly limited. Means such as electric heating using a resistance heating element, gas heating by combustion of a combustible gas, and indirect heating via a self-jacket can be taken.

  As the means for applying and heating the shock wave, the contact with the pulse combustion gas is particularly preferable because both the application of the shock wave and the heating can be achieved simultaneously by a single means. Examples of the pulse combustion system that generates the pulse combustion gas include a drying apparatus described in Japanese Patent Application Laid-Open No. 8-40720. The system includes a pulse combustor, a drying chamber, a cyclone, and a bag filter.

  A pulse combustion gas is a combustion gas which normally pulsates at a cycle of 50 to 1000 times per second. This combustion gas is generated by a pulse combustor. The raw material liquid sent to the combustion gas atmosphere is instantly dried by being divided into fine droplets with a sharp particle size distribution by hot air drying effect and physical impact characteristics due to pulse action including sound pressure and pressure. . In addition, since it is dried instantaneously, the presence of a process usually concentrated by evaporation of the solvent causes significant aggregation of the dried powder, but the aggregation of the powder dried by this apparatus is suppressed. The other mechanisms are not clear, but a shock wave acts on the liquid column of the raw material liquid sprayed from a normal nozzle tip or rotating disk or the surface of the liquid droplet after the liquid column is split, In order for the liquid column to break up into equally sized droplets due to collisions between countless waves generated on the surface, or to re-divide the droplets into uniformly sized droplets, simply a nozzle, rotating disk, etc. It is presumed that fine droplets having a sharp particle size distribution that cannot be obtained when only the spray means are used are generated.

  At the same time, it is presumed that the aggregation of particles due to the surface tension of the solvent is suppressed by instantaneous drying. The perovskite complex oxide raw material obtained in this way is subject to partial metamorphism depending on the type of substance, but usually does not cause chemical changes in the components. Since the homogeneity of the composition is maintained, the pulse combustion system is effective as a means for applying shock waves and heating.

  The frequency of the pulse combustion gas is preferably 50 to 1000 Hz, more preferably 100 to 900 Hz, and still more preferably 125 to 550 Hz. If the frequency is less than 50 Hz, vibration disturbance due to low frequency may occur. Moreover, when the frequency exceeds 1000 Hz, there is a tendency that a sufficient drying effect cannot be obtained.

Pressure amplitude of the pulse combustion gas is preferably ± 0.2 kg / cm ² or more, more preferably ± 0.4 kg / cm ² or more, more preferably ± 0.6 kg / cm ² or more. When the pressure amplitude is less than ± 0.2 kg / cm ² , the fine droplets are not sufficiently divided, and the effect of dispersing the generated particles tends to be insufficient.

  The sound pressure of the pulse combustion gas is preferably 100 to 200 dB, more preferably 120 to 160 dB, and still more preferably 140 to 150 dB. When the sound pressure is less than 100 dB, there is a tendency that sufficient stirring action and drying action due to repeated pressure reduction action of air by sound waves in the vicinity of dispersed particles cannot be obtained. Moreover, if the sound pressure exceeds 200 dB, there is a tendency to require a large amount of cost for soundproofing measures.

  The contact gas temperature of pulse combustion gas becomes like this. Preferably it is 100-1000 degreeC, More preferably, it is 130-700 degreeC, More preferably, it is 150-500 degreeC. When the contact gas temperature is less than 100 ° C., the particles tend not to be sufficiently dried. When the contact gas temperature exceeds 1000 ° C., the particles tend to be easily knitted by heat.

  Stainless steel is preferably used as the device material for the pulse combustion system from the viewpoints of economy and maintainability, but when corrosive gas is generated as the raw material liquid or slurry is dried, Teflon (registered trademark) is used. It is also possible to coat the inside of the drying chamber with a resin such as the above or a ceramic having corrosion resistance. When coating with resin, the flow rate and temperature of the pulse combustion gas, the raw material liquid, the flow rate of the slurry, and the concentration of volatile components such as solvent, so that the drying chamber temperature is kept below the heat resistant temperature of the resin such as Teflon Can be set.

  Perovskite composite oxide is obtained by calcining, pulverizing, and granulating as necessary, by uniformly firing fine particles of perovskite composite oxide obtained by heating the raw material liquid or slurry and applying a shock wave. Can be manufactured. For example, PZT powder used as a piezoelectric material can be manufactured by calcining, pulverizing and granulating the PZT raw material powder particles described above. As a calcining device, an electric furnace, a vacuum firing furnace, a gas furnace, and an electromagnetic induction capable of controlling a firing temperature in the case of aiming at a heating rate, temperature, and particularly a non-oxide or metal-based inorganic raw material powder Although a heating furnace etc. are mentioned, it is not limited to these.

  The calcining temperature needs to be a temperature at which conversion to the target compound, such as a chemical reaction or solid solution, is achieved, and further, the particle diameter of the generated particles, the degree of aggregation, and the like are in a preferable range. It chooses suitably so that it may become. For example, when PZT fine particle powder is obtained from zirconium oxide, titanium oxide, and lead oxide mixed powder, the temperature is preferably 600 to 1000 ° C, more preferably 700 to 900 ° C. If it is lower than 600 ° C., the solid solution of zirconium oxide and lead oxide tends to be insufficient. On the other hand, when the temperature exceeds 1000 ° C., the generated particles grow too much, and it takes time for pulverization after calcination, and there is a risk of contamination being mixed during pulverization.

  Perovskite complex oxides are arranged so that oxide ions and cations of the same size as the oxide ions gather to form a cubic close-packed structure, and the smaller cation is the oxide ion. Is a compound having a basic structure in an octahedral structure vacancy formed by As a method for identifying a crystal structure, a method by X-ray diffraction is generally used.

  The perovskite complex oxide of the present invention is used for applications such as ultrasonic components, earphones, pickups, high-frequency filters, piezoelectric ignition devices, pressure sensors, electronic components, fuel cells and catalyst materials.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
Each powder of lead oxide, zirconium oxide, titanium oxide and manganese oxide is weighed so that Pb / Zr / Ti / Mn = 1.0 / 0.46 / 0.47 / 0.07 (molar ratio) and dried. Water was added so that the solid content concentration was 45%, and the mixture was pulverized and mixed in a planetary pot mill to prepare a slurry.

The prepared slurry was subjected to pulse combustion drying under conditions such that the drying inlet temperature was 170 to 190 ° C and the outlet temperature was 70 ° C. As the pulse combustion drying device, High Palcon (registered trademark) 2.5 type manufactured by Partec Co., Ltd. was used. The pulse combustion gas generated by the pulse combustion apparatus had a frequency of 550 Hz, a pressure amplitude of ± 0.8 kg / cm ² , a sound pressure of 145 dB, and a contact gas temperature of 240 ° C. The dried product was put in a crucible and calcined at 850 ° C. for 2 hours.

The calcined powder was pulverized for about 45 minutes with a Leica machine, and the pulverized powder was molded by applying a pressure of 0.7 ton / cm ² with a uniaxial press. The molded body was sintered at 1230 ° C. for 2 hours and processed into a size of 17 × 4.4 × 1.2 mm to obtain a sample piece.

  Electrodes were attached to the obtained sample pieces, subjected to polarization treatment, and piezoelectric characteristics were evaluated by the following methods.

Measurement Method The calcined powder was pulverized for 45 minutes with a lycra machine, and the pulverized powder was molded with a uniaxial press at a pressure of 0.7 ton / cm ² . The compact was fired at 1230 ° C. for 2 hours and processed to a size of 17 × 4.4 × 1.2 mm to obtain a sample piece. An electrode was attached to the obtained sample piece for polarization treatment, and the relative dielectric constant and dielectric loss (tan δ) at 1 kHz were measured with an impedance analyzer (HP, model number: 4194A). Further, the frequency characteristics were measured, and the piezoelectric characteristics (electromechanical coupling constant K31, piezoelectric constant d31) were obtained by the resonance / antiresonance method (resonance / antiresonance method: opposite to the resonance frequency at which the impedance is minimized at a certain frequency). The above-mentioned piezoelectric characteristics are obtained using the maximum anti-resonance frequency value).

In general, the capacitance (C (PF)) of a capacitor is expressed by equation (1).
C = ε _r · S / (36π · t) (1)
S: Electrode area (mm)
t: Dielectric thickness (mm)
ε _r : relative permittivity

Moreover, the composition produced this time is a composition used for the material for high-power piezoelectric ceramics, and the mechanical energy density accumulated in this material is represented by the following formula (2).
U = 8 / π ² S ₁₁ ^E × Q _m ² d ₃₁ ² / E ² (2)
E: Drive electric field (V / m)
Q _m : Mechanical quality factor (sharpness of vibration at resonance point)
d ₃₁ : Piezoelectric constant (amount of strain of the element with respect to electrolysis) (pC / N)
S ₁₁ : Elastic compliance (softness of material) (m ² / N)

D ₃₁ can be expressed by the following formula (3).
d ₃₁ = k ₃₁ √ (ε ₃₃ ^T · S ₁₁ ^E ) (3)
k ₃₁ : electromechanical coupling coefficient (%)
ε ₃₃ ^T : Relative permittivity of the element

Comparative Example 1
A pulverized and mixed slurry of metal oxide powder having the same composition as in Example 1 was prepared, and the slurry was poured into an enamel bat and put in a high-temperature dryer at 120 ° C. to evaporate water.

  In the subsequent steps, sample pieces were produced by the same method as in Example 1, and the piezoelectric characteristics were evaluated according to the method.

Example 2
Each powder of lead carbonate, zirconium carbonate, titanium oxide, and manganese oxide was weighed so that Pb / Zr / Ti / Mn = 1.0 / 0.46 / 0.45 / 0.09 (molar ratio). The same operation as in Example 1 was performed to prepare a sample piece, and the piezoelectric characteristics were evaluated according to the above method.

Comparative Example 2
A pulverized and mixed slurry of metal oxide powder having the same composition as in Example 2 was prepared, a sample piece was prepared by the same method as in Comparative Example 1, and the piezoelectric characteristics were evaluated according to the above method.

Example 3
Weigh each powder of lead chloride, zirconium oxychloride, titanium tetrachloride, and manganese chloride so that Pb / Zr / Ti / Mn = 1.0 / 0.46 / 0.45 / 0.09 (molar ratio). Thereafter, the same operation as in Example 1 was performed to prepare a sample piece, and the piezoelectric characteristics were evaluated according to the above method.

Comparative Example 3
A pulverized and mixed slurry of metal oxide powder having the same composition as in Example 3 was prepared, a sample piece was prepared by the same method as in Comparative Example 1, and the piezoelectric characteristics were evaluated according to the above method.

  The piezoelectric characteristics of each example and comparative example are shown in Table 1.

Example 4
Each powder of lead oxide, zirconium oxide, titanium oxide and manganese oxide is weighed so that Pb / Zr / Ti / Mn = 1.0 / 0.46 / 0.45 / 0.09 (molar ratio) and dried. Water was added so that the solid content concentration was 45%, and the mixture was pulverized and mixed in a planetary pot mill to prepare a slurry.

The prepared slurry was subjected to pulse combustion drying in the same manner as in Example 1. The dried powder was molded into a coin mold having a diameter of 30 mm and calcined at 850 ° C. for 2 hours. When the diameter after calcination was measured, it was 24.6 mm. Further, the density of the obtained molded body was 4.62 g / cm ³ .

Comparative Example 4
A pulverized and mixed slurry of metal oxide powder having the same composition as in Example 1 was prepared, and the slurry was calcined in the same manner as in Comparative Example 1. The dried product was pulverized in a mortar, and the powder was formed into a coin shape having a diameter of 30 mm and calcined at 850 ° C. for 2 hours. It was 32.0 mm when the diameter after calcination was measured. Further, the density of the obtained molded body was 2.49 g / cm ³ .

  In general, the higher the density after calcination, the more the reaction of each mixed composition proceeds. Therefore, when the pulverized mixed slurry of metal oxide powder is contact-dried with pulse combustion gas, it is clear that the raw inorganic compound It can be seen that the reaction between each other was promoted and an easily sinterable powder could be prepared. This is because, when contact-dried with a pulse combustion gas, the reactivity of the raw material inorganic compound particles is reduced compared to the conventional stationary drying method, and the dispersion state of the particles is kept uniform. It is thought that it was because of.

  According to the utilization example of the present invention, it is possible to provide a PZT-based composite oxide powder that is suitably used for an oxide piezoelectric material, particularly a piezoelectric ceramic.

Claims (4)

A method for producing a perovskite composite oxide having a composition represented by the general formula ABO ₃ (wherein A and B represent metal elements), wherein a pulse combustion gas is brought into contact with a slurry or solution of an inorganic metal compound. The manufacturing method of the perovskite type complex oxide including the process made to dry. The method for producing a perovskite complex oxide according to claim 1, wherein the main component is lead zirconate titanate. The perovskite complex oxide according to claim 1 or 2, wherein the pulse combustion gas has a frequency of 50 to 1000 Hz, a pressure amplitude of ± 0.2 kg / cm ² or more, a sound pressure of 100 to 200 dB, and a contact gas temperature of 100 to 1000 ° C. Method. A perovskite complex oxide produced by the production method according to claim 1, 2 or 3.