JPH0826727A - Production of perovskite material - Google Patents

Abstract

PURPOSE:To provide a method for producing a perovskite mateiral by which the cost can be reduced by an entirely novel reaction process and firing or heat treatment can be carried out at a temp. below the conventional firing temp. CONSTITUTION:A material mixture contg. one or more kinds of metal chlorides and one or more kinds of metal oxides is prepd. as starting material and roasted in a steam-contg. atmosphere to produce an intermediate product by at least a thermal decomposition reaction as a 1st-stage reaction while leaving at least part of the compds. as unreacted compds. The intermediate product is then brought into a solid phase reaction with the unreacted compds. as a 2nd-stage reaction by roasting in an oxidizing atmosphere to produce the objective perovskite material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a perovskite material.

[0002]

2. Description of the Related Art Perovskite compounds have the general formula ABO.
It is represented by ₃ , and as a typical one, B
aTiO ₃ , SrTiO ₃ , BaZrO ₃ , Pb (Mg
_{0.33 Nb 0.67) O 3, YBa} 2 Cu 3 Ox , and the like.

Perovskite compounds are widely used as various dielectric and piezoelectric materials for various electric and electronic parts such as multilayer ceramic capacitors.

Perovskite compounds such as BaTiO 3.
Conventionally, ₃ is generally manufactured by a solid phase method in which barium carbonate powder and titanium oxide powder are mixed and fired at about 1000 to 1200 ° C.

[0005]

However, in the above-mentioned conventional method for producing BaTiO ₃ , the barium carbonate powder is used, so that there is a problem that the production cost becomes high.

It is an object of the present invention to provide a method for producing a perovskite material which can reduce the cost by a completely new reaction process and can perform firing or heat treatment at a temperature lower than the conventional firing temperature. Is.

[0007]

The above objects are achieved by the present invention described in (1) to (3) below. (1) A mixed material containing at least one or more metal chlorides and at least one or more metal oxides is prepared, the mixed material is used as a starting material, and the reaction in the first stage is performed in an atmosphere in which water vapor is present. In the state where at least a part of the unreacted material remains, the intermediate is produced, and then as a second-step reaction, A method for producing a perovskite material, wherein an atmosphere is switched to an oxidizing atmosphere and roasting is performed, and the intermediate and the unreacted material are solid-phase reacted to produce a perovskite material. (2) The metal chloride is Ba, Ni, Cu, Ca, M
a divalent chloride of any one of g, Zn, Mn and Sr,
Trivalent chloride of any one of La, Y and Bi, Ti,
Tetravalent chloride of either Sn or Zr and Nb
Which is one or more pentavalent chlorides of
Pb, Ni, Cu, Co, Zn, Mn and Ca divalent oxide, La, Y, Mn and Bi trivalent oxide, Ti, Zr and Sn 4 The method for producing a perovskite material according to (1) above, which is one or more of a valent oxide and a pentavalent oxide of Nb. (3) The roasting temperature for the first-step reaction is 450 to
The method for producing a perovskite material according to (1) or (2) above, wherein the roasting temperature for the second-stage reaction is in the range of 800 ° C. and in the range of 500 to 1200 ° C.

[0008]

In the method of producing a perovskite material according to the present invention, since a mixture of metal chloride and metal oxide is used as a starting material, an inexpensive material can be used to produce a perovskite compound. The obtained perovskite compound also becomes inexpensive.

In the case of BaTiO ₃ , for example, BaCl ₂ and TiO ₂ can be used as raw materials according to the following reaction formula.

First, 2BaCl ₂ + 2TiO ₂ + 2H ₂ O → Ba ₂ TiO ₄
(Intermediate product) + TiO ₂ (unreacted product) + 4HCl thermal decomposition reaction and solid-phase reaction are carried out in an atmosphere of introducing steam, and then the atmosphere is changed to an oxidizing atmosphere, and Ba ₂ TiO ₄ (intermediate product) ) + TiO ₂ (unreacted material)
→ Solid-state reaction of 2BaTiO ₃ is performed to produce BaTiO ₃ .

On the market, BaCl ₂ is about 1/2 to ₃ of the price of BaCO ₃ , and therefore BaTi is
The production cost of O ₃ is about _1/3 to 5 as compared with the conventional one. Further, according to the production method of the present invention, the decomposition and synthesis of the starting material occurred at around 500 ° C, and low temperature firing at 1000 ° C or less became possible. Therefore, the obtained perovskite material has a specific surface area of 0.8 to 3.0 cm ² / g.
And the average particle size is small. Therefore, subsequent steps such as crushing can be omitted, the number of steps can be simplified, and the manufacturing cost can be reduced from this point as well. In the case of the conventional method of producing BaTiO ₃ using only the solid phase reaction using the above barium carbonate powder and titanium oxide powder as starting materials,
Since the starting material, particularly barium carbonate, is not decomposed at least up to around 600 ° C., the BaTiO ₃ single phase cannot be obtained unless the temperature is 1000 to 1200 ° C.

[0012]

Concrete Structure In the present invention, a perovskite material is produced by using a mixed material containing at least one kind of metal chloride and at least one kind of metal oxide as a starting material. Among the above raw materials, the metal chloride may be either solid or solution. When using a solid, the average particle size is 1
It is about 100 μm.

The perovskite compound obtained by the production method of the present invention is a complex oxide represented by the general formula ABO ₃ . In the above formula, both A and B are metals, and the metals include semimetals. More specifically,
A is one or more of Ba, Sr, Ca, Pb, Zn, Mg, Y, etc., and B is Ti, Zr, Nb, Mg, Mn,
It is preferable to be one or more of Cu and the like.

The perovskite material produced by the present invention is specifically BaTiO ₃ , SrTiO ₃ , Ca.
TiO ₃ , PbTiO ₃ , ZnTiO ₃ , MgTiO ₃
Titanate-based perovskite materials such as BaZrO ₃ ,
In addition to zirconate-based perovskite materials such as SrZrO ₃ , CaZrO ₃ , and PbZrO ₃ , Ba (ZrTi) O ₃ (hereinafter sometimes referred to as BZT) in which some of the A and B sites are replaced with other metals , Sr (ZrTi) O
₃ (hereinafter sometimes referred to as SrZT), Ca (Zr
Ti) O ₃ (hereinafter sometimes referred to as CaZT), P
b (ZrTi) O ₃ (hereinafter sometimes referred to as PZT), Pb (MgNb) O ₃ (hereinafter sometimes referred to as PMN), YBa ₂ Cu ₃ O _x (generally x is 6 to 7) , Pb (LaZrTi) O _{3 and the} like.

The composition ratio of metal chloride and metal oxide is preferably in the range of 99/1 to 30/70 in terms of molar ratio. If the amount of metal chloride is too large outside the above range, the temperature at which the target phase is formed becomes high. On the other hand, when the amount of the metal oxide is too large, unreacted oxide remains and it becomes difficult to make the target phase a single phase. Which component is chloride or oxide is completely free, and the degree of freedom in selecting raw materials is widened. This is a great advantage of the present invention.

Examples of the above metal chlorides include Ba,
Ni, Cu, Ca, Mg, Zn, Mn and Sr divalent metal chlorides, La, Y and Bi metal trivalent chlorides, Ti, Sn and Zr metal tetravalent metals. It is preferable to use chloride and pentavalent oxide of Nb.

Examples of the metal oxide include Pb,
Bivalent oxides of metals that are Ni, Cu, Co, Zn, Mn, and Ca, trivalent oxides of metals that are La, Y, Mn, and Bi, and tetravalent oxides of metals that are Ti, Sn, and Zr. It is preferable to use an oxide and a pentavalent oxide of Nb.

When the metal chloride is solid, the raw materials are mixed by weighing each raw material to a predetermined molar ratio and then mixing the raw materials with a vibration mill.

On the other hand, when the metal chloride solution is used, the metal chloride solution and other raw materials are weighed in a predetermined molar ratio, dissolved in water, and then water is evaporated with stirring to evaporate the mixed material. To get

The mixed material as described above undergoes a solid phase reaction simultaneously with the thermal decomposition reaction or only a thermal decomposition reaction by the first stage roasting in an atmosphere containing water vapor, and an intermediate product is obtained. As it is produced, unreacted material remains. For example, in the case of BaTiO ₃ , the raw material is, for example, Ba
With a mixture of Cl ₂ and TiO ₂ , first, Ba
Cl ₂ is decomposed, dechlorination is carried out, and at the same time, solid phase reaction is carried out to produce Ba ₂ TiO ₄ . That is,
The following reactions take place. 2BaCl ₂ + 2TiO ₂ + 2H ₂ O → Ba ₂ TiO ₄
(Intermediate product) + TiO ₂ (unreacted product) + 4HCl

Then, only the oxidizing atmosphere is switched to, the second stage roasting is carried out, and Ba ₂ TiO ₄ and Ti are added.
The solid phase reaction of O ₂ produces BaTiO ₃ , which is the target substance. That is, the following reaction is carried out. Ba ₂ TiO ₄ (intermediate product) + TiO ₂ (unreacted product)
→ 2BaTiO ₃

Similarly, other perovskite compound ABO ₃ is also produced by solid-state reaction of an intermediate product such as A ₂ BO ₄ , A ₃ B ₂ O ₇ or the like, which is an A oxide, with BO ₂ . For example, in the case of a titanate-based perovskite material, a mixed material of titanium oxide and a chloride of another metal is used as a starting material, and the target perovskite material is SrTiO ₃ , C
aTiO ₃ , PbTiO ₃ , ZnTiO ₃ , MgTiO
_{If it is 3} , the first step of roasting is Sr ₃ Ti ₂ O ₇ , Ca ₃ Ti ₂ O ₇ , PbO, Zn ₂ which are intermediates, respectively.
TiO ₄ and MgO are produced, and TiO ₂ which is an unreacted product
Remains, and the second stage roasting causes the above-mentioned intermediate and unreacted matter to undergo a solid phase reaction to produce the desired titanate-based perovskite material. When Pb or Mg is used as a material, as described above, the pyrolysis is performed in the first stage roasting, and the pyrolyzed metal is dechlorinated to produce a metal oxide. No phase reaction occurs. In the case of a zirconate-based perovskite material, a mixed material of titanium oxide and a chloride of another metal is used as a starting material, and the target perovskite material is BaZrO ₃ , SrZrO ₃ , CaZrO ₃ , PbZ.
If rO ₃ is used, Ba ₂ ZrO ₄ , Sr ₃ Zr ₂ O ₇ and Ca ₃ Zr ₂ which are intermediates in the first stage roasting, respectively.
O ₇ and PbO are produced, unreacted ZrO ₂ remains, and the second stage roasting causes a solid-phase reaction between the intermediate and unreacted product, resulting in the desired zirconate-based perovskite material. Is generated. When PbCl ₂ is used as the material, as described above, it is only thermally decomposed by the first-stage roasting, and the thermally decomposed Pb is dechlorinated to generate PbO.
No solid phase reaction occurs. Also in the case of the composite perovskite material, the same intermediate product as above and an unreacted substance such as a metal oxide are obtained by the first stage roasting, and these are solid-phase reacted by the second stage roasting. Then, the desired perovskite material is obtained.

The roasting in the first step varies depending on the intended product or the material to be used, but is 450 to 800 ° C. in an atmosphere composed of a non-oxidizing gas or an oxidizing gas and steam.
It is preferable that the temperature is within the range of 5 to 120 minutes. If the temperature is lower than the above range, dechlorination will not proceed and it will be difficult to synthesize an intermediate product. On the other hand, when the amount exceeds the above range, the roasting temperature in the second step for obtaining the target phase becomes high and the roasting time becomes long. The reason for setting the first-stage roasting time as described above is to perform sufficient dechlorination and obtain the intended intermediate product. Further, it is preferable that the steam introduced has a steam pressure of 200 to 760 mmHg and the higher the steam pressure. As the non-oxidizing gas, nitrogen gas, argon gas or the like can be used,
It is preferably substantially oxygen-free. Air or oxygen can be used as the oxidizing gas, and the oxygen content is preferably 15% or more.

In the second-stage roasting, the atmosphere is switched to the atmosphere containing only the oxidizing gas, and the solid-phase reaction proceeds. As the oxidizing gas, air, oxygen or the like can be favorably used as in the above case. This roasting is preferably performed in the temperature range of 500 to 1200 ° C. for about 1 to 50 hours.
If the temperature is below this range, it becomes difficult to produce the desired product, while if the temperature is above the range, sintering occurs and grain growth proceeds. Further, the reason why the second-stage roasting time is set as described above is to promote the solid-phase reaction to synthesize the target substance.

For the first-stage roasting, any roasting method may be used so long as the hermeticity of the furnace used is good, for example, spray roasting method, fluidized roasting method and rotary kiln. It can be preferably carried out by the method used, the method using a tunnel kiln, or the like.

In the spray roasting method, the chloride aqueous solution containing an oxide is adjusted in concentration, and the chloride aqueous solution containing an oxide prepared in a roasting furnace is sprayed from the top of the furnace, and the flow of spray droplets and high This is a method in which spray roasting is performed so that the gas flow of the heating medium is countercurrent, and the oxide powder produced by this roasting reaction is taken out from the furnace bottom.

In the above fluidized roasting method, the concentration of an aqueous chloride solution containing an oxide is adjusted, and the adjusted aqueous chloride solution containing an oxide is sprayed into a fluidized bed roasting furnace of a fluidized bed maintained at a constant temperature. This is a method of spray roasting so that the flow of spray droplets and the flow of gas of the high-temperature heat medium are in the same direction, and the oxide powder produced by this roasting reaction is taken out from the furnace top.

The method using a rotary kiln is that a large iron cylinder lined with heat-resistant brick is tilted slightly and heated from the bottom of the kiln / iron cylinder laid on the turning device, while the raw materials are put from the top and rotated. According to the method, the material is moved to the highest temperature in the lower part and the raw material is fired or heat treated.

As the rotary kiln, for example, FIG.
The structure shown in FIGS.

In the figure, reference numeral 1 indicates a rotary kiln, and this rotary kiln 1 includes a rotary furnace main body 2. The rotary furnace main body 2 has a cylindrical furnace core tube 3, into which the raw material is introduced from one end 4,
Heat treatment is performed. Then, the generated perovskite material is taken out from the other end 5. The furnace core tube 3 is
The one end 4 side into which the raw material is charged is on the top side, and the other end 5 side from which the perovskite material is taken out is the bottom side.
It is tilted in the range of ~ 30 degrees. Therefore, the flow angle of the rotary kiln 1 is in the range of 10 to 30 degrees. Further, the furnace core tube 3 is preferably set to have a rotation speed in the range of 3 to 30 rpm.

Sealing plugs 6a and 6b for sealing the inside of the furnace core tube are provided at one end and the other end of the furnace core tube 3, respectively. A raw material charging pipe 7 for charging a raw material into the furnace core tube 3 and a HCl generated when the perovskite material is generated, in the sealing plug 6a on the one end 4 side.
A recovery pipe 8 for recovering etc. is attached. A metering pump or metering feeder 9 for metering the material into the furnace core tube 3 is disposed in the middle of the material feeding pipe 7.

On the other hand, the sealing plug 6b on the other end 5 side is provided with a take-out pipe 10 for taking out the perovskite material produced in the furnace to the outside of the furnace, and an atmosphere introducing pipe 11 for introducing an atmosphere into the furnace. It is installed. Further, as shown particularly well in FIG. 2, inside the furnace core tube 3, a glass peeling member arranged along the upper edge of the inner wall of the furnace core tube and fixed so as not to move together with the furnace core tube. A bar 12 is provided. The peeling rod 12 is arranged at an interval of 3 to 30 mm from the inner wall surface of the furnace core tube 3 and has a function of scraping off the generated perovskite material attached to the inner wall surface from the inner wall. .

According to the rotary kiln having the above structure,
A perovskite material can be satisfactorily produced by using the above mixed raw material.

The tunnel kiln is a tunnel-shaped kiln furnace for continuously firing (heat-treating) ceramic products and the like. The method using this kiln is such that the temperature rises from the inlet to the preheating chamber and heating chamber,
This is a method in which a trolley carrying a material to be baked moves at a constant speed in a cooling chamber, an outlet, and the inside of which the temperature is low, and baking (heat treatment) is performed at a constant heating and cooling speed.

The introduction of water vapor into the various furnaces described above introduces either a non-oxidizing gas or an oxidizing gas which constitutes a part of the atmosphere as a carrier gas. In addition, air or oxygen can be used as the oxidizing gas such as argon gas.

The second stage roasting is carried out using the above tunnel furnace and rotary kiln because the hermeticity is unnecessary. As the atmosphere, only the oxidizing gas is used as described above.

The temperature raising / lowering rate is not particularly limited, but is 3 to.
It is preferably about 60 ° C./min. This is the same for both the first and second stages of roasting.

The perovskite material obtained by the production method of the present invention is substantially a single phase of the target phase. But,
The phase other than the target may be contained in the range of less than 50%.

The perovskite material obtained by the production method of the present invention preferably has a good dispersity as a material and a large specific surface area (preferably 0.8 to 3.0 m ² / g). The dispersity as the above material is indicated by a CV value, which is as small as possible for each element and is preferably less than 25.0.

[0040]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

The metal chlorides and metal oxides shown in Table 1 are shown in Table 1.
Each of the predetermined molar ratios shown in (1) and (2) were mixed in a vibration mill for 2 hours to obtain mixed samples. In addition, metal oxides were added to the metal chloride solution at the respective predetermined molar ratios shown in Table 1, and 100
The mixed solution was stirred while evaporating water in the metal chloride solution at 0 ° C. to obtain a mixed sample.

[0042]

[Table 1]

100 g of each of the mixed crystal samples obtained here
Then, the pyrolysis reaction and the solid-phase reaction were simultaneously advanced in a batch furnace. An atmosphere having a water vapor pressure of 760 mmHg was continuously introduced and circulated in the furnace using nitrogen or air as a carrier gas. In this state, the temperature was raised at 3 ° C./min, the temperature and the holding time shown in Table 1 were maintained, and the first-stage roasting was performed to obtain an intermediate product and an unreacted product as described above.

After that, the atmosphere was switched to air or oxygen only, the temperature was raised again at 3 ° C./min, and the temperature was held at the holding temperature and holding time shown in Table 1, and after the second stage roasting was performed. Then, the furnace was cooled to obtain the samples of the respective examples. In addition, BaTiO 3
Regarding ₃ as the target product, only the first stage of roasting was used as a comparative sample.

The crystal type, the specific surface area (m ² / g), and the CV value showing the dispersity of the CMA elemental analysis of the material obtained by the electron probe microanalyzer (EPMA) were examined. . The crystal type was specified by qualitative analysis by X-ray diffraction method. The specific surface area was measured by the BET one-point method with 0.5 g of each sample set in a cell. The CV value was measured as follows. First, 10 g of the obtained perovskite material was taken, filled in a mold, and molded into a disc shape at a pressure of 20 MPa / m ² . Regarding the particle distribution of each element of the material of the obtained disk-shaped molded body,
An image was obtained using EPMA under the following conditions, and the number of counts per spot size of particles containing each element was measured.

Conditions Acceleration voltage (V _acc ): 20 kV Detection current (I _abs ): 10 ^-7 A Measurement magnification: 250 μm × 160 μm Beam spot size: 1 μm ² Number of pixels: 50,000 points

From the obtained measured values, the standard deviation was divided by the sample mean, that is, the coefficient of variation (CV value) was obtained.

The results are shown in Tables 1 and 2.

[0049]

[Table 2]

As can be seen from these tables, the perovskite material produced according to the present invention satisfactorily produces the target phase, has a large specific surface area, and has a good dispersibility as a material. Also, the perovskite materials shown in the above table, such as PbTiO ₃ , ZnTiO ₃ , and MgTi.
O ₃ , SrZrO ₃ , CaZrO ₃ , PbZrO ₃ and composite perovskite materials such as BZT, SrZT,
Similar experiments were carried out for CaZT and Pb (LaZrTi) O ₃ , and the target perovskite material having the same desirable characteristics as above was obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a rotary kiln used in a method for producing a perovskite material according to the present invention.

FIG. 2 is a lateral sectional view of the rotary kiln.

[Explanation of symbols]

 1 Rotary Kiln 2 Rotating Furnace Main Body 3 Furnace Core Tube 4 One End of Furnace Core Tube 5 Other End of Furnace Core Tube 6a, 6b Sealing Plug 7 Raw Material Input Pipe 8 HCl Recovery Pipe 9 Quantitative Feeder 10 Perovskite Material Removal Pipe 11 Atmosphere Introduction Pipe 12 peeling stick

Claims (3)

[Claims] 1. A mixed material containing at least one or more metal chlorides and at least one or more metal oxides is prepared, the mixed material is used as a starting material, and steam is present in the first stage reaction. Roasting in an atmosphere,
At least the thermal decomposition reaction of the thermal decomposition reaction and the solid-phase reaction is caused to generate an intermediate in the state where at least a part of the unreacted material remains, and then, as the second stage reaction, the atmosphere is an oxidizing atmosphere. A method for producing a perovskite material, wherein the perovskite material is produced by solid-state reaction between the intermediate and the unreacted material by switching to roasting. 2. The metal chloride is Ba, Ni, Cu,
Divalent chloride of any one of Ca, Mg, Zn, Mn and Sr, trivalent chloride of any of La, Y and Bi, tetravalent chloride of any of Ti, Sn and Zr and Nb Which is one or more pentavalent chlorides, and the metal oxide is any of divalent oxides of Pb, Ni, Cu, Co, Zn, Mn and Ca, and La, Y, Mn and Bi. Trivalent oxides, Ti, Zr and Sn
2. The method for producing a perovskite material according to claim 1, which is one or more of the tetravalent oxide and the pentavalent oxide of Nb. 3. The roasting temperature for the first-step reaction is in the range of 450 to 800 ° C., and the roasting temperature for the second-step reaction is in the range of 500 to 1200 ° C. A method for producing the perovskite material according to claim 1 or 2.