JPH0321486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing dielectric powder containing zirconium and lead.

Dielectric powder containing zirconium and lead is used in a wide range of fields as a raw material for functional ceramics such as dielectrics for capacitors, piezoelectrics, optoelectronic materials, semiconductors, and sensors.

(Prior Art) Conventionally, as a method for producing dielectric powder containing zirconium and lead, Japanese Patent Application Laid-Open No. 61-53119 discloses that (a) an oxide or (b) blending a lead compound into the powder obtained in step (a) to form a mixed powder; and heating the mixed powder at a temperature of 400 to 400°C.
An oxide powder containing at least two other metals in addition to lead is obtained through a two-step sequential bonding process consisting of a 1200°C calcining process, and the lead component is more concentrated on the outside than inside the powder particles. Disclosed is a method for producing a lead-containing oxide powder that has easy sinterability and excellent molding properties due to the presence of a large amount of lead.

(Problems to be Solved by the Invention) The lead-containing oxide powder obtained by the above-mentioned conventional method is excellent in that it has easy sinterability even under low-temperature firing; There is a problem with the uniformity of the composition when sintered, and the sintered density also seems to be a step further, and this is thought to be because the conventional zirconia raw material powder used as the raw material is extremely prone to agglomeration.

Note that it is often necessary to increase the zirconium content due to the properties of the dielectric, and in this case, there is a strong desire to improve the powder properties of the zirconia raw material.

Therefore, by modifying the zirconia raw material powder as the raw material to improve its dispersibility, it is possible to achieve high compositional uniformity without losing the characteristics of easy sinterability and excellent molding properties in the above-mentioned prior art. It is an object of the present invention to provide a method for producing a dielectric powder containing zirconium and lead, which is improved so as to obtain a high sintered density.

(Means for Solving the Problems) The inventors have developed a mixed solution (aqueous solution or alcohol solution; hereinafter the same applies) of at least one component other than zirconium constituting the dielectric powder in an appropriate amount (an appropriate amount but not the entire amount) and zirconium. ) is mixed with a precipitant to form a coprecipitate, and this coprecipitate is dried and calcined to form a fine powder (modified zirconia powder) with very little agglomeration and good dispersibility. The other components constituting the dielectric (lead is excluded or only a small amount) are mixed, calcined, and then crushed.The remaining components constituting the dielectric (lead A three-step process in which a dielectric powder is further added and calcined (mainly composed of The present invention was completed based on the knowledge that it could be obtained.

That is, the gist of the present invention is to add a precipitant to a mixed solution of zirconium and at least one other metal component among the metal components constituting the dielectric powder, to coprecipitate the metal components, and to prepare the coprecipitate. The modified zirconia powder A is further mixed with a powder B containing one or more metal components constituting the dielectric powder and calcined to obtain a mixed powder. and a step of further mixing and calcining a powder C made of one or more metal components including lead among the metal components constituting the dielectric powder into the mixed powder. This is a method for producing dielectric powder containing.

(Specific composition/effect) In addition to lead (Pb) and zirconium (Zr), the constituent components of the dielectric powder include Ba, Sr,
Ca, La, Ti, Mg, Sc, Hf, Th, W, Y, Nb,
Ta, Cr, Mo, Mn, Fe, Co, Ni, Cd, Al,
Examples include Sn, Zn, In, As, Bi, and Sb.

Now, in preparing zirconia modified powder A, first, zirconium oxychloride, zirconium oxynitrate, zirconium chloride, and zirconium nitrate are used as compounds for creating a zirconium solution (aqueous solution or alcohol solution), and metal zirconium It can also be used by dissolving it in an acid.

The amount of zirconium here is preferably the entire amount of zirconium components required to constitute the desired dielectric powder, or at least 50 atomic %, and if it is less than 50 atomic %, it is sufficient to ensure uniformity of the composition. This is because a suitable dielectric powder cannot be obtained.

Other metal components to be co-precipitated with the zirconium for the preparation of modified zirconia powder A include:
Among the metal components constituting the dielectric powder, those with a relatively large content, such as titanium, are preferable, and when such metal components are used, the agglomeration of the calcined powder of the coprecipitate is suppressed and the dispersibility is improved. Therefore, the mixability with powder B is improved, and the dielectric powder obtained using this powder is easy to sinter, and the uniformity of the zirconium component in the obtained sintered body is excellent.
The uniformity of the zirconium component can be measured by observation using EPMA or the like.

Regarding the other metal components mentioned above, it is better to use a portion of them as powder B than to use the entire amount that should constitute the dielectric powder for preparing the modified zirconia powder A. preferred in terms of gender.

Examples of the precipitant include inorganic substances such as ammonia, ammonium carbonate, and caustic alkali, and organic substances such as oxalic acid, ammonium, amines, and oxine.

The calcining temperature of the obtained coprecipitate is preferably 700 to 1300°C. At temperatures lower than 700℃, significant aggregation occurs;
When the temperature exceeds 1300℃, the particles tend to become coarse.

The calcined body is preferably ground to a particle size of 1 μm or less using a grinding device such as a ball mill described below.

Next, regarding powder B, the metal component used therein is the entire remaining amount of the metal components constituting the dielectric powder, excluding the portion used for preparing zirconia modified powder A and the portion scheduled to be used as powder C.

The form of the metal component is an elemental metal or a compound. The compounds include inorganic compounds such as oxides, carbonates, basic carbonates, nitrates and hydroxides, organic acid salts such as oxalates and formates, or mixed crystals thereof.

These metals or metal compounds are preferably ones that do not leave impurities such as halogens such as chlorine, sulfur, and phosphorus after calcination. Specific examples include SrCO ₃ , Sr(CH ₃ COO) ₂・1/2H ₂ O, Sr
( _NO3 ) ₂ , Sr(OH) ₂・_8H2O , SrO, _CaCO3 , Ca
(OH) ₂ , CaO, Ba( _CH3COO ) ₂ , _BaCO3 , Ba
(HCOO) ₂ , Ba(OH) ₂・8H ₂ O, BaC ₂ O ₄・H ₂ O,
BaO, _BaCl2 , _BaO2 , Mg, Mg(OH) ₂ ,
MgC ₂ O ₄・2H ₂ O, MgO, Mn(CH ₃ COO) ₂・
4H ₂ O, MnCO ₃ , Mn (HCOO) ₂・H ₂ O, Mn
( _NO3 ) ₂ , Mn, Zn, ZnO, Zn( _CH3COO ) ₂・
2H ₂ O, Ni, Ni (CH ₃ COO) ₂ , 4H ₂ O, NiCO ₃・
2Ni(OH) ₂・4H ₂ O, Ni(HCOO) ₂・2H ₂ O, NiO,
Ni ₂ O ₃ , CO, CO (CH ₃ COO) ₂・4H ₂ O, CoO,
Y, _Y2O3 , In, _In2O3 , Nb _{, Nb2O5 ,} Ta _,
Ta ₂ O ₅ , Al, Al ₂ O ₃ , Al(OH) ₃ , Fe, FeC ₂ O ₄・
Examples include simple metals and metal compounds such as 2H ₂ O, Fe ₂ O ₃ , Fe ₃ O ₄ , Zr, ZrO ₂ , Ti, and TiO ₂ , and these powders preferably have a particle size of 1 μm or less.

Modified zirconia powder A and powder B may be mixed by a common method using a mortar or ball mill, and wet mixing using liquids such as water, alcohol, acetone, chlorocene, etc., especially highly volatile liquids is preferable to dry mixing. is more efficient and preferable. It is also desirable to mix thoroughly.

Sufficient mixing is necessary to improve the uniformity of the composition and increase the efficiency of the solid phase reaction during calcination after mixing, and is particularly important for improving the electrical properties of the sintered body made using the obtained powder. It has a big impact. For example, if wet mixing is performed using a ball mill, the mixing time is preferably 5 to 30 hours;
If it is shorter than 5 to 30 hours, mixing will be insufficient and there will be problems with uniformity, but 5 to 30 hours is sufficient.
It is neither necessary nor efficient if it exceeds the time limit.

As for the material of the equipment used for mixing, it is preferable to use an organic material such as nylon as it prevents metal impurities from entering, a ball mill using zirconia balls is also preferable, and alumina is preferable if the composition does not include aluminum impurities. It may be quality.

The resulting mixture is then calcined or heated to carry out a solid phase reaction.

The calcination temperature after mixing varies depending on the composition of the mixture, and is particularly related to the shrinkage start temperature and diffusion coefficient of the mixture, but in general, the reaction efficiency is low at temperatures lower than 700℃, while at temperatures lower than 1300℃ At high temperatures, powders tend to form solid agglomerates, resulting in poor reactivity of the resulting powder. Therefore, the calcination temperature is
Preferably 700-1300°C, more preferably 900-1300°C
The temperature is 1100℃.

Calcination is not limited to one time, but may be performed two or more times. When calcination is performed two or more times, crushing and mixing are performed before the next calcination to improve uniformity and prevent agglomeration.

Powder C is mainly composed of a metal component whose main component is lead.

It is preferable that the entire amount or at least 50 atomic % of lead constituting the dielectric powder be included in the powder C from the viewpoint of sinterability of the dielectric. The remaining amount of lead is used in the preparation of modified zirconia powder A or incorporated into powder B.

Components other than lead in powder C are modified zirconia powder A and powder B among the metal components constituting the dielectric powder.
This is the total amount left over from the amount used. Generally speaking, it is preferable to use all of the components other than lead in modified zirconia powder A and powder B, and to use only the lead component in powder C, in view of the reactivity of the dielectric powder, but if necessary to improve the properties of the dielectric, In addition to lead, other metal components may be added to the powder C.

In addition to metallic lead, lead components include lead oxide, lead carbonate, basic lead carbonate, lead hydroxide, lead nitrate, lead oxalate, lead formate, lead chloride, and lead fluoride.

In Powder C, control of the lead content in the powder composition is extremely important. That is, the amount of the lead compound to be added is the stoichiometric amount of the powder composition, or preferably an excess amount of 8 at % or less of the stoichiometric amount.

The reason for this is that the final sintered density does not improve if the excess amount is greater than 8 at %. moreover,
When polarization is performed, such as with piezoelectric materials, the amount of lead compounds added is limited to a stoichiometric amount or 3.5 at. An excess of is preferred.

Next, in the case of powder C, mixing may be carried out in the same manner as the mixing of modified zirconia powder A and powder B.

The mixture is then calcined, preferably under a lead atmosphere, in a hermetically sealed condition to prevent evaporation of the lead, as is generally done when calcining lead-containing oxides.

The calcination temperature is 400 to 1000℃, preferably 600℃.
~900℃; below 400℃, the solid phase reaction of the mixed powder is insufficient, while above 1000℃, agglomerated powder tends to form, the particle size of the powder becomes uneven, and the final sintered density is sufficiently high. This is because not only the reactivity of the obtained powder decreases, but also the sinterability decreases.

Further, the powder obtained by calcining may be further crushed or classified.

(Example) Example 1 Titanium tetrachloride aqueous solution (0.76 mol/concentration) 0.5
and zirconium oxynitrate aqueous solution (0.84mol/
(Concentration) 1.81 and use this mixed aqueous solution as a precipitate forming agent.
The mixture was gradually added to the solution while stirring to obtain a hydroxide coprecipitate of zirconium and titanium. After washing and drying this, it was calcined at a temperature of 1100℃ and the composition was (Zr _0.8
Deformed zirconia powder A, which is Ti _0.2 ) O ₂ , was obtained.

This modified zirconia powder A represented by (Zr _0.8 Ti _0.2 )O ₂ has a mixed composition {(Mg1/3Nb2/3)} _0.3 Ti _0.4 Zr _0.3 }O with TiO ₂ , MgO and Nb ₂ O ₅ as powder B. ₂
After mixing in a ball mill for 10 hours, the mixture was calcined and crushed at a temperature of 900 to 1000°C to obtain a mixed powder. Next, this mixed powder was mixed with PbO and powder C so that the composition would be Pb {(Mg1/3Nb2/3) _0.3 Ti _0.4 Zr _0.3 }O ₃ , mixed in a ball mill for 1 hour, and then heated at a temperature of 740℃. It was calcined for 1 hour.

The average particle size of the dielectric powder containing zirconium and lead thus obtained was 0.3 μm.

This dielectric powder was used as a sintering raw material powder and was molded into a disk shape at a molding pressure of 1000 kg/cm ² and at a temperature of 1200°C.
It was sintered for 1 hour.

The density of the obtained sintered body was measured by an underwater displacement method (Archimedes method) and was found to be 7.94 g/cm ³ , which was a high density.

In addition, after polishing the sintered body, we measured the composition distribution of zirconium in the sintered body using EPMA.
It turned out to be very evenly distributed.

Comparative Example 1 Obtained by performing the same treatment as in Example 1, except that commercially available ZrO ₂ powder was used in place of modified zirconia powder A with the (Zr _0.8 Ti _0.2 )O ₂ composition used in Example 1. The density of the sintered body was measured using the same method as in Example 1, and found to be 7.78 g/cm ³ , which was a relatively low density.

In addition, after polishing the sintered body, we measured the composition distribution of zirconium in the sintered body using EPMA.
It was found that zirconium was partially segregated.

Example ₂ CoO, _{TiO 2 and}
Composition of Nb ₂ O ₅ as powder B {(Co1/3Nb2/3) _0.2
They were blended in a ratio of Zr _0.4 Ti _0.4 }O ₂ and mixed in a ball mill for 10 hours, then calcined at a temperature of 900 to 1000°C and crushed to obtain a mixed powder.

Next, PbO was added to this mixed powder as powder C, and the composition was
Pb{(Co1/3Nb2/3) _0.2 Zr _0.4 Ti _0.4 }O ₃ was added to the mixture in a ratio of Pb{(Co1/3Nb2/3) 0.2 Zr 0.4 Ti 0.4 }O 3 , mixed for 1 hour in a ball mill, and then calcined at a temperature of 740° C. for 1 hour.

The average particle size of the dielectric powder containing zirconium and lead thus obtained was 0.3 μm.

Pressure to form this dielectric powder as a sintering raw material powder
It was formed into a disk shape at 1000Kg/cm ² and sintered at a temperature of 1150°C for 1 hour.

The density of the obtained sintered body was measured by the method described above, and the density was 7.98 g/cm ³ .

In addition, after polishing the sintered body, we measured the composition distribution of zirconium in the sintered body using EPMA.
It turned out to be very evenly distributed.

Example 3 Modified zirconia powder A with the composition (Zr _0.8 Ti _0.2 )O ₂ produced in Example 1 was made with TiO ₂ and Nb ₂ O ₅ as powder B, and the atomic ratio of Nb, Zr, and Ti was 1:4:4.5. After mixing in a ball mill for 10 hours, the mixture was calcined and crushed at a temperature of 900 to 1000°C to obtain a mixed powder. Next, a mixed powder of PbO and CoO is added to this mixed powder as powder C, and the composition is Pb{(Co1/3Nb2/3) _0.
15 Zr _0.4 Ti _0.45 }O ₃ , mixed in a ball mill for 1 hour, and then calcined at a temperature of 740° C. for 1 hour.

The average particle size of the dielectric powder containing zirconium and lead thus obtained was 0.3 μm.

This dielectric powder is used as a sintering raw material powder under compacting pressure.
It was formed into a disk shape at 1000Kg/cm ² and sintered at a temperature of 1150°C for 1 hour.

The density of the obtained sintered body was measured by the method described above, and it was found to be 7.96 g/cm ³ , which was a high density.

In addition, after polishing the sintered body, we measured the composition distribution of zirconium in the sintered body using EPMA.
It turned out to be very evenly distributed.

Example 4 A lead nitrate aqueous solution (1.01 mol/concentration) and a zirconium oxynitrate aqueous solution (0.84 mol/concentration) were prepared.
Pb and Zr were mixed in an atomic ratio of 1:9.
This mixed solution was dropped into a coprecipitation tank maintained at pH 6 to 8 with aqueous ammonia to obtain a coprecipitate. After washing and drying this, it was calcined at a temperature of 1000°C to obtain modified zirconia powder A.

This modified zirconia powder A is TiO ₂ powder B.
Mix Zr and Ti in an atomic ratio of 1:1, mix in a ball mill for 10 hours, and then heat to a temperature of 900~
A mixed powder was obtained by calcining and crushing at 1000°C.

This mixed powder has a composition of Pb with PbO as powder C.
(Zr _0.5 Ti _0.5 )O ₃ was mixed in a ball mill for 1 hour, and then calcined at a temperature of 750°C for 1 hour.

The average particle size of the dielectric powder containing zirconium and lead thus obtained was 0.3 μm.

This dielectric powder was used as a sintering raw material powder and formed into a disk shape at a compacting pressure of 1000 kg/cm ² and at a temperature of 1150°C.
It was sintered for 1 hour.

The density of the obtained sintered body was measured by the method described above and was found to be 7.90 g/cm ³ , indicating a high density.

In addition, after polishing the sintered body, we measured the composition distribution of zirconium in the sintered body using EPMA.
It turned out to be very evenly distributed.

(Effects of the Invention) According to the method of the present invention, a dielectric powder containing ruconium and lead that has a highly dispersible zirconium component and is easily sintered can be obtained, so a dielectric sintered body using this powder as a raw material can be obtained. During the production of the sintered body, the liquid phase sintering mechanism accelerates sintering, making it possible to achieve high density through low-temperature sintering. Compositional uniformity can also be ensured.

Claims (1)

[Scope of Claims] 1. Among the metal components constituting the dielectric powder, a precipitant is added to a mixed solution consisting of zirconium and at least one other metal component to coprecipitate the metal components, and this coprecipitation a step of drying and calcining the body to obtain a modified zirconia powder A, and further mixing the modified zirconia powder A with a powder B containing one or more metal components constituting the dielectric powder and calcining the mixture. It is characterized by comprising the steps of obtaining a powder, and further mixing a powder C made of one or more metal components including lead among the metal components constituting the dielectric powder into this mixed powder, and calcining the mixture. A method for producing dielectric powder containing zirconium and lead.