JPS62207719A - Preparation of raw material powder of lead base perovskite type compound oxide ceramic containing niobium - Google Patents

Abstract

PURPOSE:To obtain easily the sinterable titled raw material powder having high perovskite content by forming coprecipitate of a specified metallic component and Nb, adding soln. of a Pb component and liquid for forming precipitate thereto, and calcining whole precipitate formed thereby. CONSTITUTION:Liquid for forming precipitate is added to aq. or alcoholic soln. of a Nb component and component A (at least one among Fe, Co, Ni, Mg, Mn, Zn, Cd, and In) to form coprecipitate of Nb and A component. Aq. soln. of Pb component is added to the slurry of the suspension, and the liquid for forming precipitate is added to the mixture. Formed precipitate is filtered dried and calcined at 400-1,000 deg.C after mixing, if necessary, with raw materials of ceramic. By this method, raw material powder for a perovskite type compound oxide ceramic contg. Nb expressed by PbAxNb1-xO3 is obtd. In the formula, x is 1/2 or 1/3. The raw material powder is fine particle and easily sinterable having characteristically high forming rate of perovskite.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ceramic raw material powder having a fine submicron particle size. especially,
A method for producing a raw material powder of a niobium-containing lead-based perovskite-type composite oxide having a particle size suitable for a multilayer capacitor and having easy sinterability is provided.

Generally, lead-based perovskite-type composite oxides are widely used as piezoelectric materials, but in recent years (1) they have a higher dielectric constant than conventionally used dielectric materials such as barium titanate, so It has a high dielectric capacity and is ideal for miniaturizing multilayer capacitors; (2) its low sintering temperature allows the use of silver, which is cheaper than palladium, which is conventionally used for internal electrodes; Since there are many types of dielectric materials, it is possible to develop many new materials for dielectric materials by varying the composition, and it is being actively researched and developed as a dielectric material.

The niobium-containing lead-based perovskite-type composite oxide described in the present invention (hereinafter referred to as the composition of the present invention) is a composition with the general formula containing the above elements of this lead-based perovskite-type composite oxide and niobium. It is.

Other pb-based perovskite complex oxides have the general formula P
bAxB1-xoa (where A=the above A component B=W
, Nb, and Ta (one or more selected from Ta, Nb, and Ta), and is usually put into practical use by being made into a solid solution with the ceramic composition of the present invention. The present invention can also be used as a precursor of this solid solution.

Conventional methods for producing lead-based perovskite composite oxide ceramic raw material powder include a dry method and a wet method.

The dry method is a method in which powders of oxides as constituent components are mixed according to their composition ratios, and this is calcined.

However, with this method, it is difficult to obtain raw material powder with a uniform composition;
There are also many pyrochlore phases.

Since it is necessary to increase the calcination temperature in order to increase the production rate of the perovskite phase, this causes the particles to become coarser, which has the drawback of making it difficult to easily sinter.

In the wet method, a mixed solution containing all of the constituent components is prepared, and a precipitate forming liquid such as an alkali is added to this to co-precipitate.
A common method is dry calcining. However, although this method makes it easy to obtain powder with excellent uniformity, due to its uniformity, it tends to coagulate during precipitate formation, drying, and calcination to form secondary particles, making the particles coarser and making them easier to burn. In addition, in this method, the concentration of the precipitate-forming solution is constant, so if the precipitate-forming ability of each component differs, for example, one component will form 100% precipitate, but other components will not. There are cases where 100% of the components do not precipitate, which has the disadvantage that it is difficult to obtain the desired composition.

The grain size of ceramics obtained using these raw material powders using these conventional techniques is 10μ or more, so when used in multilayer capacitors in particular, there is a limit to miniaturization and large capacity due to restrictions on layer thickness. This is where things happen.

Furthermore, when producing raw material powder for lead-based perovskite composite oxide ceramics, efforts are generally made to uniformly mix the constituent compounds. However, since the lead component is a very active element that moves at a relatively low temperature and reacts with Nb in a solid-phase reaction, it is necessary to place emphasis on uniform □ mixing because the precipitates of the A component and the Nb component. be.

If the lead component precipitate is mixed to the extent that it does not destroy the uniform precipitate mixture of A and Nb components, it will actively move between the solid phases during the calcination process, so that all the components will be sufficiently mixed. This makes it possible to achieve uniformity.

In conventional technology, the manufacturing method of the raw material powder lacks consideration for the behavior of each component during solid phase reaction, and all the components are uniformly mixed, resulting in a pyrochlore phase, which is a compound of lead and niobium. The production rate of perovskite was increased, and the production of perovskite phase was suppressed. Due to this, the calcination degree must be increased to a high temperature in order to increase the formation of the perovskite phase, resulting in a vicious cycle in which the particles of the raw material powder also become coarse.

An object of the present invention is to eliminate the drawbacks of conventional methods for producing raw material powder for a zero-start composition, and to produce a composition of the present invention having a desired composition ratio of fine particles, easy sinterability, and a high production rate of perovskite phase. The object of the present invention is to provide a method for producing raw material powder.

In order to achieve the above object, the present inventors have conducted extensive research on the method of precipitating with a precipitate-forming liquid such as potash, or when adding and mixing a compound powder equivalent to lead precipitate into a coprecipitate slurry. Since it is a double precipitation operation, the concentration of the precipitate component forming liquid can be adjusted to the conditions suitable for precipitate formation at each stage, and the composition of the precipitate component can be made as desired. It was determined that there was no formation of secondary particles.

When calcining the precipitate obtained in this way, it is possible to lower the calcining temperature, so the raw material powder is fine particles of submicron size, which makes it easy to sinter. From this, it was found that the grain size of ceramics obtained by molding and firing this powder can be reduced by wI, making it ideal for laminated capacitors as well as disc-shaped capacitors. Based on these findings, the present invention has been completed.The gist of the present invention is that, in the method for producing the raw material powder of the composition of the present invention, component A and an aqueous or alcoholic solution of Nb are mixed, and a precipitate forming liquid is added thereto. After producing a co-precipitate of component A and Nb, add the remaining pb acid component aqueous solution and add a precipitate forming solution to this to produce a pb precipitate, or add this pb precipitate and equivalent P
Add compound b to the coprecipitate slurry, or precipitate all components obtained by either method at 400-1000°C.
It is characterized by being calcined at

In addition, the precipitate created by such precipitation is
Since the Pb component is precipitated in a coprecipitate of Nb and A components, the perovskite production rate in the calcination process is high, so the calcination temperature can be lowered. As a result, a fine-grained, easily sinterable raw material powder can be obtained.

In addition, as a practical dielectric material, a solid solution of the composition of the present invention and another pb-based perovskite type composite oxide is often used. In this case, the raw material powder of the other pb-based perovskite composite oxide is mixed with the precipitate of the composition of the present invention and calcined to form a solid solution, or the precipitate of the composition of the present invention is mixed with the precipitate of the composition of the present invention. A precipitate is generated during the process of obtaining a material, and a precipitate containing the entire composition of the practical material is obtained.
This may be calcined to form a solid solution.

In addition, in order to control the sinterability and electrical properties of ceramics obtained using the raw material powder when producing the raw material powder in the present invention, trace components such as Mn02S 102 + B are added.
Compounds such as i203 may also be added. in this case,
It is also possible to add it uniformly by coprecipitating it into an aqueous solution during any manufacturing process. In addition, it may be added by a dry or wet method after preparing the raw material powder according to the present invention.

In the present invention, the component compounds used for preparing the solution include component hydroxides, oxychlorides, carbonates, oxynitrates, sulfates, nitrates, acetates, formates, oxalates, chlorides, Examples include oxides, ammonium salts, and sodium salts.

If these are not soluble in water, examples of precipitate-forming liquids that can be made soluble by adding organic acids, mineral alkalis, etc. include ammonia, ammonium carbonate, caustic alkali, soda carbonate, ammonium oxalate, and oxalate. Examples include solutions of organic reagents such as and amines.

You can choose from these.

In order to generate precipitation of the constituent components, it is preferable to perform the precipitation while stirring the liquid.

Alternatively, the liquid after the formation of a certain precipitate may be removed, and the type and concentration of the precipitate forming liquid may be changed to those suitable for the remaining components before precipitation.

Water is usually used to wash the precipitate, but if an alcohol such as ethanol is used, good results can be obtained by suppressing the coagulation of the precipitate in the subsequent drying and calcination steps.

The present invention has the following excellent effects.

(1) In the uniform coprecipitate of A component and Nb component, p
B) Because it has a structure that disperses precipitates,
Since the uniformity of (A component, Nb component) is higher than that of A (Pb component), the production rate of perovskite phase during calcination is high. By doing this, the calcination temperature can be lowered, so that a fine particle raw material powder can be obtained, and the grain size of the ceramic obtained by sintering this is fine, making it ideal for multilayer capacitors. obtain.

(2) Since double precipitates are generated without co-precipitating all of the constituent components, these precipitates are in a mutually dispersed state, and there is less formation of secondary particles during dry calcination as in conventional coprecipitation. . Therefore, a material with high bulk density and easy sinterability can be obtained.

(3) Since double precipitation is performed, the type and concentration of the precipitant suitable for each component can be selected, so that the raw material powder of the desired composition can be easily obtained.

Example 1 N b 20 s ・X H20 (Mitsui Metal Mining Co., Ltd.') 0
．． 04 mol and Fe(NOa) a"9H20 (Wako Tsumugi Yakuhin) O, Oa mol were dissolved in an aqueous solution of 0.32 mol of oxalic acid (Ube Industries), and this Fe-Nb mixture was dissolved in 20
Add nitrogen-ammonia gas (1:1) into 0-water
The mixture was injected at a rate of f/gin and gradually added dropwise over about 2 hours with stirring while maintaining the pH at 8 to 8.5. The obtained precipitate was subjected to the filtered water method, and the precipitate was dispersed in 500 d of water to obtain PbO (
0.16 mol of Dainippon Paint) was added and mixed and stirred. It was then filtered and dried, and calcined by heating at 700° C. for 2 hours in an aluminum crucible. This calcined product was wet-pulverized with pure water in a polyethylene ball mill containing zirconia balls. The obtained calcined powder was shown to be Pb(Fe+Nb,)03 having perovskite crystals by X-ray diffraction.

Further, the average particle diameter was as fine as 0.2 IIm as seen from an electron micrograph. The X-ray diffraction diagram is shown in Figure 1.

Comparative Example 1 Commercially available PbO (Dainippon Toyo), Fe203 (Tone Sangyo)
, 20g of Nb (1 liter of each powder of Mitsui Metal Mine) was
They were blended to have a composition of Fe + Nb + ) Oa, wet mixed overnight in a ball mill containing zirconia balls in acetone, and then dried. Thereafter, calcining was performed in the same manner as in Example 1. The obtained calcined powder was found to be a mixture of perovskite crystals and pyrochlore crystals by X-ray diffraction. The X-ray diffraction diagram is shown in Figure 2.

Examples 2, 3 NbC1g0.08mol and CoC12o,04mol (
Wako Tsumugi) Dissolve in 300 d of tt ethanol, and add this Nb-Co ethanol solution to 200 tt of water, 3N
-NaOH was injected and added dropwise over about 2 hours while stirring while maintaining the pH at 8 to 9 to form a coprecipitate of Nb and Co.

Furthermore, while keeping the pH at 8 to 9, Pb (NOs) 2
100 d of a 0.12 mol (Wako Tsumugi) aqueous solution was added dropwise over 1 hour to obtain a mixed precipitate of niobium-cobalt-lead. Thereafter, P b (CO+ Nb + ) Oa was obtained in the same manner as in Example 1. This X-ray diffraction diagram showed a perovskite crystal structure, and the average particle diameter was found to be 0.157 m by electron microscopy.

Example 4 A coprecipitate of Nb and Fe was obtained in the same manner as in Example 1 (N
b0.28 mol, Fed, 28 mol), and further, this precipitate was filtered and washed with water, dispersed in 500 d of water, and PbO powder 0.
56 mol was added, mixed and stirred. Then filtered and dried to remove Pb.
:Fe:Nb=2:1:1 mixed precipitate dried product was obtained. Separate C (ammonium tungstate aqueous solution (H
Disperse 0.1 mol of 2WOa (Wako Tsumugi) in 80 parts of water, and when boiling, give 4.2% NH and 200 parts of water (Wako Tsumugi)
■Prepared by adding λ (hereinafter referred to as AT solution) 3
00d (0.08 mol as W), under stirring, add lead nitrate (Wako Tsumugi) aqueous solution 240++Ij (0.24 mol as
Pb) is added dropwise to precipitate pbwo. Next, 260 parts (0
, 38 mol) to precipitate the remaining Pb2+. Aqueous solution of ferric nitrate (Wako Tsumugi, special grade) (hereinafter referred to as Fe(NOa)s aqueous solution) was added to this reaction slurry under stirring.
, 550 d (0,16 mol asFe) and 4.2% N
At the same time, 240 ml of H3 water was added dropwise, and Fe(O
H) Precipitate 3. After the completion of precipitation, the mixture was stirred for 30 minutes, filtered, and the cake was washed with water. This cake was dried at 100° C. to obtain a mixed precipitate of Pb:Fe:W=3:2:1. After wet mixing the two together with acetone in a ball mill, the mixture was calcined at 700° C. for 2 hours. The calcined product is wet-pulverized in a ball mill and P b (Fe,
Nb, ) 0.7 (Fe, W, ) 0.3 03 powder was obtained. This X-ray diffraction diagram shows perovskite structure comparative example 2 PbOO, 3 mol, Fe2030.165 mol, Nb2
060.0525 mol and WO 30.03 mol were wet mixed in acetone for 24 hours in a ball mill. 100 after filtration
℃ overnight, calcined at 800℃ for 2 hours, and wet-pulverized in a ball mill to obtain Pb (Fe+Nt)t.
)0.7 (Fe+W, )o, 30a compound was obtained. This X-ray diffraction diagram shows a mixture of perovskite structure and pyrochlore structure, and the average particle diameter is 1.3. Met.

Example 5 After adding and mixing 0.25 wt% MnO□ to the compounds obtained in Examples 1, 4 and Comparative Example 1.2 using a ball mill, a 5 wt% polyvinyl alcohol aqueous solution (8 wt% polyvinyl alcohol) was added and granulated. The obtained granules were press-molded at a pressure of 1 ton/c+/ to form a green molded body, and then the green molded body was subjected to thermal decomposition of polyvinyl alcohol at 400°C for 3 hours in an electric furnace, and then heated to a predetermined temperature (700°C). ~110
0) and fired for 2 hours to obtain a sintered body. The weight and dimensions of this sintered body were measured to determine the sintered density at a predetermined temperature. In addition, the grain diameter of the surface was measured using an optical microscope. Check out the results! 0 Figure 5 shown in 15°6,
6 shows that the compound of the present invention has excellent sinterability compared to the comparative example and has fine grains for the same level of sintering degree. Next, Table 1 shows the electrical properties of the above sintered body sample at the temperature at which the sintered density begins to saturate. For those coated on both sides, the dielectric constant at one Curie point and at one Curie point was measured by measuring the temperature change in capacitance from room temperature to 150°C. The capacitance, dielectric constant, and dielectric loss tangent were measured using the Yokogawa Hewlett-Packard LF Impedance Analyzer (419).
2A) using lKH2, and the resistivity was measured using a Yokogawa Hewlett-Buckard Picoammeter (414OB).
It was determined from the current value after 1 minute of application of DC 25V. It can be seen from Table 1 that the compound obtained according to the present invention has a lower sintering temperature, V & fine dagrain properties, and equivalent electrical properties than the oxide calcined product.

[Brief explanation of drawings]

FIG. 1 is based on Example 1, and the 31st! I is an X-ray diffraction diagram of a niobium-containing lead-based perovskite type composite oxide produced by the method of the present invention obtained in Example 4. FIG. 2 is an X-ray diffraction diagram of a niobium-containing lead-based perovskite-type composite oxide obtained in Comparative Example 1 and FIG. FIG. 5 shows the relationship between the sintering temperature, sintered density, and grain diameter of Example 1 and Comparative Example 1 in Example 5. 6th
The figure shows the relationship between the sintering temperature, sintered density, and grain diameter of Example 4 and Comparative Example 2 in Example 5. λθ 31st drawing paper [stock] Spoon breather (=C) 1st. ,lz

Claims (1)

[Claims] Lead-based perovskite-type composite oxide ceramics containing niobium represented by the general formula PbAxNb_1_-_xO_3 (where X = 1/2 or 1/3, A = Fe, Co,
When producing a raw material powder of one or more selected from Ni, Mn, Mg, Zn, Cd, and In, a precipitate forming solution is added to an aqueous or alcohol solution in which the entire amount of Nb and A components are dissolved. After obtaining a coprecipitate of Nb and A components, a slurry of this precipitate suspended in water or an alcoholic medium is mixed with an aqueous lead solution to form a precipitate of a lead compound using a precipitate forming liquid. A precipitate generation step characterized by mixing the precipitate with a lead compound powder equivalent to the precipitate, and the precipitate obtained by filtering and drying the precipitate alone or with other raw materials for lead-based perovskite-type composite oxide ceramics. The mixture is 400 to 10
A method for producing a niobium-containing lead-based perovskite-type composite oxide ceramic raw material powder, characterized by comprising a step of calcining at 00°C.