JP2558357B2 - Barium titanate-based powder for semiconductor porcelain and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention has a barium titanate-based semiconductor having a remarkably positive temperature characteristic, a sufficiently low specific resistance, and an excellent withstand voltage and resistance temperature coefficient. The present invention relates to a powder which is a raw material of a porcelain composition and a method for producing the powder.

[Prior Art and Problems to Be Solved] Conventionally, barium titanate-based semiconductor porcelain is mainly composed of barium titanate, and a rare earth element such as Y, La, or Ce as a semiconducting agent, or Nb, Sb. It contains a trace amount of at least one kind, and has a characteristic that it has a low specific resistance at room temperature and shows a remarkable positive resistance-temperature characteristic when it exceeds a sudden resistance change point (Curie point).

Normally, the barium titanate-based semiconductor porcelain has a Curie point of approximately 12 due to the effect of its main component barium titanate.
It is around 0 ℃.

In order to shift the Curie point of such barium titanate-based semiconductor porcelain to a higher temperature side, it is known to partially replace Ba with Pb. It is also known that part of Ba is replaced with Sr or Ca, and part of Ti is replaced with Zr, Sn, etc., in order to shift the Curie point to the low temperature side or to improve electrical characteristics. I have.

Furthermore, by adding Mn, silica, alumina, copper oxide, etc. to barium titanate-based semiconductor porcelain, the resistance temperature change rate after exceeding the Curie point can be improved, and the characteristics of the semiconductor porcelain can be stabilized. Various attempts have been made. (Japanese Patent Publication 53-29386, Japanese Patent Publication 54-10110, Japanese Patent Publication 63-
By using the characteristics of the barium titanate-based semiconductor porcelain, it is used as a constant temperature heating element, a current limiting element, a temperature control element, and the like.

In the above-mentioned applications, the barium titanate-based semiconductor porcelain is often required to have a resistivity as low as possible, but in the conventional one, as the resistivity becomes lower, the resistance-temperature characteristic and the breakdown The voltage is extremely deteriorated. For example, if the specific resistance is about 5 Ω · cm, the gradient α (% / ° C) of the specific resistance and resistance temperature characteristics is only about 7, and the breakdown voltage is a low value of about 30 V / mm. Norimoto [Nishii: Electronic Ceramics, 88 May (1988) pp2
2 to 27] At present, barium titanate-based semiconductor ceramics having such a low specific resistance value have not been put into practical use.

[Means for Solving the Problems] In view of the present situation as described above, the present inventors have made earnest studies to solve the above-mentioned problems, and as a result, carbonates usually used as a raw material for barium titanate-based semiconductor porcelain. Or instead of oxide, BaTiO ₃ , Sr used as the main component
Of TiO ₃ , CaTiO ₃ , and PbTiO ₃ , at least BaTiO ₃ and SrTiO ₃
Has a fine and uniform primary particle produced by a specific method, and the specific resistance is sufficiently low as 8 Ω · cm or less by using the skeleton secondary particle in which oxalate having a large average particle diameter is calcined, and The present invention has been achieved by finding that a porcelain having a positive resistance temperature characteristic which is extremely excellent in other characteristics such as withstand voltage and resistance temperature characteristic can be obtained.

That is, the present invention is a skeleton secondary particle having open base holes in which primary particles of 0.2 μm or less are connected to each other, and the average size thereof is
Secondary particles of 150-250 μm and 50 μm or less
Barium titanate powder characterized by being 5 wt% or less, and Ba / Ti (molar ratio) = 1.02 to 1.05, BaCl ₂ : 10 wt
% When adding an aqueous solution containing titanium tetrachloride and barium chloride at a concentration of not more than 10% to the oxalic acid aqueous solution.
(Molar ratio) = 2.1 to 2.3, the concentration of the produced barium oxalate titanate tetrahydrate is set to 10 to 12 wt%, and the addition is carried out in a shower for 4 hours or more and the stirring peripheral speed is
Barium oxalate titanate obtained by maintaining the liquid temperature during addition at a constant temperature in the temperature range of 55 to 75 ° C for 2.5 m / sec or more is 700 to 900
A method for producing the above barium titanate powder, characterized by firing at ℃, and then a secondary particle having an open base hole in which primary particles having a size of 0.1 μm or less are connected to each other, and the average size thereof is 70
˜180 μm, and its BET specific surface area is 20 to 30 m ² / g, strontium titanate powder, and titanium tetrachloride having Sr / Ti (mol) = 1.2 or more and SrCl ₂ : 15 wt% or less When adding an aqueous solution containing strontium chloride and oxalic acid to an aqueous solution of oxalic acid, the concentration of oxalic acid / Ti = (molar ratio) = 2.1 to 2.3, and the concentration of strontium oxalate titanate pentahydrate produced is 10.0 to 14.0 wt%. Set, add in shower for 2 hours or more, and stirrer peripheral speed 3.0m / s
More than ec, strontium oxalate titanate obtained by keeping the liquid temperature during addition at a constant temperature in the temperature range of 60 to 80 ° C.
A method for producing the strontium titanate powder, which is characterized by firing at 0-900 ° C., and secondary particles having open pores in which primary particles of 0.2 μm or less are connected to each other and having an average size of 50-150 μm. And lead secondary particles of titanate characterized by having a secondary particle size of 20 μm or less in an amount of 5 wt% or less, and oxalic acid dissolved in oxalic acid after neutralizing titanium tetrachloride with ammonia Ti (molar ratio) = 2.1-2.3, TiO _2: when the 4 wt% or less of the aqueous solution is added to an aqueous solution of lead nitrate, Pb / T (molar ratio) = 1.01 to 1.03, generation oxalate titanate 4 tetrahydrate The concentration is set to 10 to 18 wt%, and the addition is shower-like, and the stirring peripheral speed is 2.0 m / s.
ec, lead oxalate titanate obtained by adding in 1 to 2 hours while maintaining a constant temperature at a liquid temperature of 45 to 55 ° C.
The method for producing the above-mentioned lead titanate powder, which is characterized by firing at 0 to 800 ° C., and BaTi in the invention using the above-mentioned powder.
At least one of the main components of O ₃ , SrTiO ₃ , CaTiO ₃ , and PbTiO ₃
BaTiO ₃ and SrTiO ₃ are composed of the above-mentioned powder, and the main component composition is BaTiO ₃ : 45 to 85 mol%, SrTiO ₃ : 1
20 mol%, CaTiO _3: 5 to 20 mol%, PbTiO _3: 1 to 20 mol%
Is a rare earth element such as Y, La, and Ce as a semiconducting agent with respect to the main component, and at least one of Nb and Sb is 0.1 to 0.3 mol%, and further Mn: 0.006 to 0.025 mol%, SiO ₂ : 0.1-1 mol%
Barium titanate-based semiconductor porcelain composition raw material powder, and BaTiO ₃ , SrTiO ₃ ,
Of the main components of CaTiO ₃ and PbTiO ₃ , at least BaTiO ₃ and Sr
TiO ₃ and PbTiO ₃ are the above-mentioned powders, and provide a raw material powder for a barium titanate-based semiconductor porcelain composition having the same composition.

First, a method for producing various oxalate salts as a basic raw material of the present invention will be described. An important matter in these methods is to obtain an oxalate salt having a purity as high as possible,
The aim is to obtain one in which the molar ratio of Ba, Sr, Pb, Ca and Ti in the oxalate salt is as close to 1 as possible and there is no variation between crystals. Therefore, regarding the purity, the raw material oxalic acid,
Titanium tetroxide and Ba, Sr, Pb, Ca salts are not only as pure as possible, but acid-resistant plastic containers such as Teflon are preferable as the reaction container in order to avoid contamination from the reaction container. Oxalate has a metal impurity concentration of a few ppm or less, excluding alkaline earth, total 100 ppm
The following are preferred. As for the molar ratio, it is necessary to obtain as large as possible a crystal shape and a particle diameter which are uniform, and it has been found that they can be successfully produced by the following production method.

First, the production of barium oxalate titanate is described. The reaction is carried out by adding a solution in which titanium tetrachloride and barium chloride are dissolved to an aqueous solution in which oxalic acid is dissolved. The concentration of barium oxalate titanate tetrahydrate may be set to fall within the range of 10 to 12 wt%. Therefore, the water balance of both solutions may be any concentration as long as it is within the range of the set concentration, but the concentration of barium chloride in the solution is 10 wt% so that barium chloride does not precipitate in the solution of titanium tetrachloride and barium chloride.
Must be less than or equal to%.

Ba / Ti (molar ratio) needs to be set to 1.02 to 1.05, which is slightly larger than Ba. When Ba / Ti (molar ratio) is less than 1.02, the resulting oxalate has a Ba / Ti (molar ratio) of less than 0.998, which is not preferable.
If it is greater than 1.05, the resulting oxalate Ba / Ti
(Molar ratio) does not change much around 1.0, but unreacted Ba
Is not economical because it increases. Oxalic acid / Ti (molar ratio)
Is preferably set in the range of 2.1 to 2.3 from the viewpoint of yield and economy. Further, the concentration is preferably in the range of 10 to 12 wt% in view of the economical concentration, crystal shape, and the like, while suppressing precipitation of other salts.

Further, the addition conditions, stirring conditions, and temperature conditions greatly affect the size, shape, and particle size distribution of the resulting barium oxalate tetrahydrate tetrahydrate, and the addition should be made in a shower form over a wide range as much as possible. If they are not sufficiently dispersed at the time of addition, fine crystals will precipitate, and if not added slowly and little by little over 4 hours, similar phenomena will occur, and the physical properties of the final product will be degraded. The same is true for the stirring state, and it is necessary to perform the stirring at least at a peripheral speed of 2.5 m / sec, although the scale and shape of the container are slightly different.

Next is the temperature condition.Since the crystallization temperature and its fluctuation greatly affect the crystallization and become a major cause of the precipitation of microcrystals, it is necessary to maintain a constant temperature in the temperature range of 55 to 75 ° C. At a temperature lower than 55 ° C, crystals with poor crystallinity are formed, and the Ba / Ti (molar ratio) becomes a value smaller than 0.998. On the other hand, when the temperature is higher than 75 ° C, the crystallized crystals are unstable and Ba is contained in the crystal. If it is easy to come off and the time until filtration is long, Ba
/ Ti (molar ratio) is less than 0.998, which is not preferable.

Crystals of barium oxalate titanate precipitated in this way have a Ba / Ti (molar ratio) within the range of 0.998 to 1.002,
The inside of the crystal is also stoichiometrically uniform, with an average crystal grain size of 10
It is uniform at 0 μm or more, and has few small crystals.

Next, a method for producing strontium titanate oxalate is described. Since Sr / Ti (molar ratio) tends to be smaller than 1 as compared with barium oxalate, the charged Sr / Ti
(Molar ratio) must be set to 1.2 or more. Setting Sr / Ti
If (molar ratio) is less than 1.2, the oxalate Sr / Ti
(Molar ratio) is less than 0.998, which is not preferable. However, if it is too large, it is not economical, and it is usually set in the range of 1.2 to 1.3. The molar ratio of oxalic acid / Ti (molar ratio) is
It is preferable to set it in the range of 2.1 to 2.3 from the viewpoint of yield and economy. In addition, the concentration is 10 to 14 wt%, considering the economical concentration and the crystal shape, etc., while suppressing the precipitation of other salts.
Is preferred.

Further, it is the addition conditions, stirring conditions, and temperature conditions that greatly affect the size, shape, and particle size distribution of the resulting strontium oxalate titanate pentahydrate, and the addition is performed in a shower form over a wide range as much as possible. If not sufficiently stirred and dispersed at the time of addition, fine crystals will precipitate, and the same phenomenon will occur if the addition is not carried out little by little over 2 hours, and the Sr / Ti (molar ratio) of the crystals will be less than 0.998. It is not preferable. The same applies to the stirring conditions, and although the scale and shape of the container are slightly different, it is necessary to perform the stirring at least at a peripheral speed of 3.0 m / sec.

Next is the temperature condition.Since the crystallization temperature and fluctuations in the temperature greatly affect the crystallization and become a major cause of the precipitation of microcrystals, the temperature is 60 to 80 ° C, which is higher than that of barium oxalate titanate. It is necessary to maintain a constant temperature in a high temperature range, and for the same reason as for barium oxalate titanate, the Sr / Ti (molar ratio) value is less than 0.998 both above and below the above range, which is not preferable.

The crystals of strontium oxalate titanate precipitated in this manner also have a Sr / Ti (molar ratio) within the range of 0.998 to 1.002, the inside of the crystals is stoichiometrically uniform, and the average crystal grain size is 70 μm or more. They are all aligned and there are few small crystals.

In the case of strontium titanate oxalate, the yield is as low as about 80 wt% at the reaction temperature of 60 to 80 ° C., so that the yield can be increased to 90 wt% or more by cooling after the reaction. However, since the Sr / Ti (molar ratio) of the oxalate precipitated thereafter changes depending on the cooling rate, it is necessary to perform the cooling rate within the range of 5 ° C./hr to 30 ° C./Hr.

Furthermore, a method for producing lead oxalate titanate, in which case the use of titanium tetrachloride dissolves the lead salt,
The method used in the case of barium oxalate cannot be used to generate the precipitate of lead chloride, and titanium tetrachloride was neutralized once with ammonia to form a gel of titanium hydroxide, which was thoroughly filtered and washed. After dissolving in oxalic acid, a solution is obtained, and this solution can be used. For lead oxalate titanate, Pb / Ti (molar ratio) depending on conditions
Varies, so it is necessary to keep various conditions constant.
In order to obtain a complete solution and considering the yield at the time of oxalate formation later, and under conditions where the molar ratio is close to 1, oxalic acid
/ Ti (molar ratio) must be 2.1 to 2.3 and TiO ₂ : 4 wt% or less. Considering the total water balance, it is sufficient to set the concentration of the generated lead oxalate titanate to be 10 to 18 wt%, so that the concentration of the solution of Ti dissolved in oxalic acid and the concentration of lead nitrate are within the range. Should be set.

In addition, when the concentration of lead oxalate titanate is set to 10 to 18 wt%, a crystal having a large particle size and uniformity can be obtained.

In order to obtain an oxalate having a Pb / Ti (molar ratio) close to 1, the set Pb / Ti (molar ratio) needs to be 1.01 to 1.03, and the set Pb / Ti (molar ratio) is lower than 1.01. Pb / Ti (molar ratio) of oxalate and oxalate decreased to below 0.99, while set Pb / Ti
When the (molar ratio) is greater than 1.03, the molar ratio of the oxalate is conversely 1.01 which is too large. Set oxalic acid / T
The same applies to i (molar ratio). It is necessary to carry out the reaction at a liquid temperature in the range of 45 to 55 ° C., and outside of this range, the molar ratio is lower than 0.99, which is not preferable.

Also in the case of obtaining lead oxalate titanate, the diffusion state in the liquid has a great effect on the crystal state, and the addition is performed in the shower state so that the diffusion is as uniform and fast as possible, and the stirring peripheral speed is 2.0 m / sec or more. There is a need to do.

The thus-precipitated lead oxalate titanate crystal also had a Pb / Ti (molar ratio) within the range of 0.998 to 1.002, the inside of the crystal was stoichiometrically uniform, and the average crystal grain size was 50 μm.
As a result, the crystals are small and have few small crystals.

As for the calcium titanate, which is one of the powder compositions of the present invention, Ca / Ti (molar ratio), CaCl ₂ concentration, oxalic acid / Ti
(Molar ratio), the concentration of the resulting oxalate, the temperature of the liquid, the method of addition, and the conditions of stirring, etc.
It is possible to obtain calcium oxalate titanate having a (molar ratio) close to 1 and a similarly large crystal grain size.

Each oxalate obtained by the above method,
The protons of the organic acid are replaced with metals or metal oxides.The organic matter is oxidized by pre-baking it in an atmosphere with sufficient oxygen and at a temperature slightly lower than the temperature at which normal baking is performed. Decomposes, BaTiO ₃ , SrTiO ₃ ,
Although it becomes an oxide in the form of PbTiO ₃ and CaTiO ₃ , the crystalline state of the organic matter before decomposition at this time has a great influence on the physical properties such as the particle size, particle size distribution and molar ratio of the oxide after firing. In addition, the above physical properties have a great influence on the electrical properties of the final sintered body.

The calcined body of the oxalate obtained in the present invention is a so-called oxalate shape in which uniform and fine particles of about 0.2 μm or less are lightly sintered and have a binding force to each other and retain the shape of the oxalate before decomposition. It has a structure of skeletal particles and the particles are evenly distributed without deviation of atomic distribution.When using such a calcined body as described later, it is possible to obtain a sintered body by a firing process. The sintered body itself also has a uniform structure, and has a low specific resistance, a high temperature coefficient of resistance, and a high withstand voltage.

First, the calcination of barium oxalate, strontium oxalate, and calcium oxalate is specifically described.Each oxalate obtained is dried at a temperature at which water of crystallization does not scatter. Although it is a hydrated salt, it is calcined at such a temperature that the organic matter is not carbonized and the particles remain in an appropriate size. Therefore, the firing must be performed in an atmosphere in which oxygen is sufficiently supplied.However, organic acid salts may cause rapid decomposition and combustion, so that excessive oxygen is not necessary. It is preferred to do so. The calcination temperature is preferably from 700 to 900 ° C. If the calcination temperature is lower than 700 ° C, oxidative decomposition does not proceed sufficiently and carbon and the like remain, which is not preferable. 900 ° C
If it is higher, uneven grain growth is likely to occur, and local abnormal grain growth is often observed, which is not preferable.

The calcined oxalate thus obtained is a secondary particle of barium titanate or calcium titanate having open pores in which primary particles of 0.2 μm or less are connected to each other, and the average size thereof is Particle size is 150-250μm, 50μm
The following secondary particles are 5 wt% or less, BET specific surface area is 6-10
A calcined body having a uniform secondary particle diameter of m ² / g is obtained.

For the strontium titanate calcined body, 0.1%
A secondary particle of a skeleton having open pores in which primary particles having a size of μm or less are connected to each other and having an average size of 70 to 180 μm. In this case, the BE of the calcined body produced by the method for producing an oxalate salt is used.
The powder whose T specific surface area is greatly changed and the sintered porcelain exhibits excellent characteristics has a BET specific surface area in the range of 20 to 30 m ² / g.

In the case of lead oxalate titanate, the temperature of oxidative decomposition is lower than that of the oxalate described above, and grain growth is easy.
The temperature is preferably from 600 to 800 ° C., and if the temperature is lower than 600 ° C., the oxidative decomposition similarly does not proceed sufficiently and carbon and the like remain, which is not preferable. On the other hand, when the temperature is higher than 800 ° C., uneven grain growth tends to occur, and local abnormal grain growth is often observed, which is not preferable. The thus obtained calcined body of lead oxalate titanate is also a secondary particle of a skeleton having open pores in which primary particles of 0.2 μm or less are connected to each other, and the size thereof is 50 to 50 on average.
The calcined body has a uniform secondary particle diameter of 150 μm, 5% by weight or less of secondary particles having a shape of 20 μm or less, and a BET specific surface area of 6 to 10 m ² / g.

The oxalate calcined body obtained by the above method is used as a raw material, and the mixture and firing are performed by the method described below. In this case, it is not always necessary to use the calcined oxalate body. Instead, a calcined body of oxalate may be used for at least BaTiO ₃ and SrTiO ₃ .

In this case, other PbTiO ₃ , CaTiO ₃ may be produced and used by a so-called ordinary solid phase method, usually each raw material powder, for example in the case of PbTiO ₃ Pb ₃ O ₄ and TiO ₂ are mixed, Firing,
CaTiO ₃ produced by the same method as PbTiO ₃ produced by crushing will be used as a mixture with the calcined oxalate body. It is necessary that the average particle diameter is 2 μm or less, and the metal impurities other than the alkaline earth metal are 100 ppm or less.

Next, the composition of the present invention will be described. In the present invention, BaTiO ₃ , SrTiO ₃ , CaTiO ₃ and PbTiO ₃ as the main components are BaTi ₃ .
O _3: 45 to 85 mol%, SrTiO _3: 1~20 mol%, CaTiO _3: 5~20
Mol%, PbTiO ₃ : 1 to 20 mol%, while at least one of rare earth elements such as Y, La, and Ce, Nb, and Sb as a semiconducting agent, 0.1 to 0.3 mol%, and Mn. : 0.006-0.02
The composition is such that 5 mol% and SiO ₂ : 0.1 to 1 mol% are added.

The four-component porcelain of the main components of the present invention, BaTiO ₃ , SrTiO ₃ , CaTiO ₃ , and PbTiO ₃ , uses a part of Ba of barium titanate as Ca, S
It is a substitution at the same time with r and Pb. Pb and Sr individually shift the Curie points to the high temperature side and the low temperature side, respectively.By including these Ca, Sr, and Pb in the main component in the coexisting state, the withstand voltage value becomes high, and the inrush voltage is large. It is known that the durability against electric current is improved, but in the conventional method, one having a specific resistance of 8 (Ω · cm) or less and excellent withstand voltage characteristics has not been obtained.

The main components of the present invention are: BaTiO ₃ : 45 to 85 mol%, SrTiO ₃ : 1
20 mol%, CaTiO _3: 5 to 20 mol%, PbTiO _3: 1 to 20 mol%
However, the main component was limited to the above range for the following reason.

First, if BaTiO ₃ is less than 45%, it becomes difficult to form a semiconductor and the specific resistance becomes high. On the other hand, if it exceeds 85%, the electrical characteristics are deteriorated, which is not preferable.

If the amount of SrTiO ₃ is less than 1 mol%, the particles of the sintered body become coarse, and the effect of improving the electrical characteristics does not appear.
If it exceeds, partial grain growth occurs and electrical characteristics are degraded.

If the content of CaTiO ₃ is less than 5 mol%, the withstand voltage characteristics are not excellent, and if it exceeds 20 mol%, the withstand voltage characteristics are deteriorated.

When the content of PbTiO ₃ is less than 1 mol%, the electrical characteristics are not satisfactory. When the content exceeds 20 mol%, Pb is scattered at the time of sintering, so that sintering is difficult, and it is difficult to form a semiconductor.

At this time, if the total of Ba, Sr, Ca, Pb as the main components and the molar ratio of Ti are adjusted within the range of 0.99 to 1.03, the physical properties of the manufactured porcelain are hardly affected. Can be manufactured.

In order to manufacture barium titanate-based semiconductor porcelain,
It is necessary to contain a small amount of a semiconducting agent, and at least 1 of rare earth elements such as Y, La, and Ce, and Nb, is used as the semiconducting agent.
The seed may be added and contained in an amount of 0.1 to 0.3 mol%. Addition amount
If the amount is less than 0.1 mol%, semiconductor formation will not be successful, and if the amount is more than 0.3 mol%, the specific resistance will be increased, which is not preferable. In the case of addition, it is preferable to add in the form of an oxalate or an oxide.

Furthermore, by adding Mn, SiO ₂ to the above composition,
The resistance temperature characteristic can be improved.

In the present invention, compared to the solid phase method, a small amount of Mn, SiO ₂
However, since the oxalate calcinated body is used as the main raw material, it is considered that the additive is very uniformly dispersed and the above-mentioned effect is exhibited.

In this case, the amount of Mn added is Mn: 0.006 to 0.025 mol%
Then, these ratios are included in the porcelain. By adding Mn, the resistance temperature change rate can be remarkably increased in the positive resistance temperature characteristic exceeding the Curie point.

There is a temperature coefficient of resistance (hereinafter abbreviated as α value) as a parameter representing the above characteristics, but when Mn is less than 0.006 mol%, the α value becomes small and the withstand voltage characteristic deteriorates. On the other hand, when Mn is more than 0.025 mol%, the α value is increased, but the specific resistance at room temperature is increased, and when used at a low voltage, it does not operate, which is not preferable. Mn may be added in the form of oxalate or oxide.

Next is the addition of SiO ₂ , the amount of which is SiO ₂ : 0.1
The range of 1 mol% is preferable.

The addition of SiO ₂ suppresses the change in the specific resistance caused by a slight change in the addition of the semiconducting agent, and tries to obtain a low specific resistance value at room temperature. When SiO ₂ is less than 0.1 mol%, It easily grows, the withstand voltage characteristic deteriorates, and the α value becomes small. On the other hand, when SiO ₂ is more than 1 mol%, the specific resistance becomes high, which is not preferable. The addition of SiO ₂ is
An oxide having as small a particle size as possible may be used.

Each raw material powder is weighed in the ratio as described above, and a ball mill pot made of plastic or the like, which is hard to mix with metal impurities, has a high density and a ball such as zirconia that does not affect the electrical characteristics even when a small amount is mixed as an impurity. Use to mix and disintegrate.

In this case, a liquid such as water or an organic solvent may be added to enhance the crushing effect. After this step, remove the liquid,
Granulation is performed and molding is performed under a pressure of 0.3 to 1.0 t / cm ³ . After the molding, the temperature is raised at 5 to 10 ° C./min, and after baking at 1300 to 1400 ° C. for 5 minutes to 2 hours, the temperature is lowered at the same rate as the temperature rising to obtain the porcelain of the present invention. If the molding pressure is lower than a predetermined value, the specific resistance increases. On the other hand, if the molding pressure is too high, the specific resistance decreases, but the α value decreases. On the other hand, if the rate of temperature rise is too slow, the specific resistance increases, while if it is too fast, the specific resistance decreases but the α value also decreases, which is not preferable. Regarding the firing temperature, if the temperature is too low or too high, the specific resistance increases, which is not preferable.

The porcelain of the present invention manufactured by the above method has a density of
5.2 to 5.6g / cm ³ , low specific resistance of 8 (Ω · cm) or less, α value of 9 (% / ° C) or more, and withstand voltage of 60 (V / mm) or more, high withstand voltage Further, it becomes an excellent barium titanate-based semiconductor ceramic having a high α value.

As described above, the reason why the raw material produced from oxalate as the main component has excellent electrical characteristics is that the purity of the raw material is the total metal excluding alkaline earth elements. Since the elements are very high (100ppm or less), the characteristics can be easily controlled by adding trace elements, and the effect of improving the characteristics is great. The grain size of the porcelain structure is 10μm or less and the average size is about 5μm.
It is conceivable that the withstand voltage characteristics were improved due to the uniform microstructure consisting of a sintered body with a controlled grain size.

Furthermore, since the oxalate calcined body of the main component is a skeleton particle in which fine and uniform primary particles having an appropriate strength are combined, the skeleton particles are sequentially crushed and mixed at the time of mixing and crushing, so that the mixing property is very high. As a result, each atom is uniformly solid-soluted during sintering, and the distribution of atoms becomes more uniform when made into porcelain, and there is no local change in the characteristics in the porcelain, and the whole shows uniform characteristics. However, in actuality, as a result of examining various conditions such that selection and manufacturability of raw materials of the present invention, mixing crushing method, sintering method, and the like are optimal conditions, the overall effect is as follows. It was possible to obtain a porcelain having outstanding electrical characteristics.

These are extremely useful for applications such as constant temperature heating elements, current limiting elements, and temperature controlling elements.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the Examples.

Example 1 Ti (OH) was added to a tank A made of gum lining with a capacity of 5 m ^3.
27.6 wt% Ti ion in terms of ₄ and 32.8 wt% Cl in terms of HCl
650 kg Ti solution containing ions, barium chloride dihydrate 389
Kg and 2980 Kg of pure water were slowly mixed to prepare a solution for addition. On the other hand, the rubber-lined tank B the capacity 7m ^3,
429 Kg of oxalic acid was dissolved in 2055 Kg of pure water, and the temperature was raised to 60 ° C and maintained at that temperature.

At this time, Ba / Ti (molar ratio) was 1.03, oxalic acid / Ti (molar ratio) was 2.2, and BaCl ₂ was 8.25 wt%.

The addition of the solution from the tank A to the tank B was performed by a charge pump, and the addition was performed by providing about 200 holes at the end of the pipe and adding the solution to the liquid surface in a shower.

The stirring at this time was performed by rotating a stirring blade having two flat blades at 50 rpm, and the stirring peripheral speed at this time was 2.9 m / sec. The solution during the reaction was maintained at 60 ° C,
The addition time was 4 hours.

The set concentration of barium oxalate titanate produced at this time was 11 wt%.

After the addition was completed, the reaction solution was filtered by a centrifuge, washed, and dried at 50 ° C. to obtain 592 kg of barium oxalate titanate crystals. The yield at this time was 85.3 wt%,
Its Ba / Ti (molar ratio) was 0.999.

The resulting powder is placed in a porcelain crucible and 900 in air.
Calcination was performed at 2 ° C. for 2 hours to obtain a barium titanate calcined powder.
The resulting powder contained 10 ppm or less of metal impurities other than alkaline earth, had an average particle diameter of 200 μm, and contained about 2 wt% of particles of 50 μm or less. A scanning electron micrograph (SEM photograph) of the powder obtained at this time is shown in Fig. 2, and a transmission electron micrograph (TEM photograph) of a part of the powder is observed and observed in Fig. 3. Show.

Example 2 In a tank A made of rubber lining having a capacity of 5 m ³ , Ti (OH)
₄ converted to 39.9wt% Ti ion, HCl converted to 31.9wt% Cl
Ti solution containing ion 449Kg, strontium chloride 6
A solution for addition was prepared by slowly mixing 516 kg of water salt and 1590 kg of pure water. On the other hand, a tank B made of rubber lining with a capacity of 7 m ^3.
Dissolve 429 Kg of oxalic acid in 2147 Kg of pure water and keep the temperature at 75 ° C.
And maintained at that temperature.

At this time, Sr / Ti (molar ratio) = 1.25, oxalic acid / Ti (molar ratio) = 2.2, and SrCl ₂ = 12.0 wt%.

The addition of the solution from the tank A to the tank B was performed by a charge pump, and the addition was performed by providing about 200 holes at the end of the pipe and adding the solution to the liquid surface in a shower.

The stirring at this time used a stirring blade having two flat blades, and the stirring peripheral speed at this time was 4.1 m / sec. The solution during the reaction was maintained at 75 ° C., and the addition time was 2.5 hours.
The set concentration of strontium oxalate titanate generated at this time was 12 wt%.

After completion of the addition, the reaction solution was cooled to room temperature at a rate of 20 ° C./hr, filtered and washed with a centrifuge, and dried at 50 ° C. to obtain strontium oxalate 5
600 kg of crystals of hydrate salt were obtained. The oxalate salt had an Sr / Ti (molar ratio) of 0.999 and a yield of 93 wt%.

The resulting powder is placed in a porcelain crucible and 900 in air.
Calcination was performed at 2 ° C. for 2 hours to obtain a strontium titanate calcined powder. The resulting powder has a metal impurity other than alkaline earth of 10 ppm or less, and the average particle size of the secondary particles is 150 μm.
m, 2.5 wt% of secondary particles of 50 μm or less, BET specific surface area of 2
6.0 m ² / g.

Example 3 A 10 wt% TiCl ₄ solution was cooled to 40 ° C. or lower, neutralized to pH 7 with an aqueous ammonium solution to obtain gel titanium hydroxide, which was then filtered and purified with pure water. To wash. The gel after washing is immediately dissolved by oxalic acid,
After measuring the concentration of Ti ion, the concentration of Ti ion was 2.4 wt% with pure water and oxalic acid, and oxalic acid / Ti (molar ratio) = 2.
Adjusted to 15, 2378Kg of this solution as a solution for addition volume 7m
^The solution was transferred to the rubber-lined tank A of No. ³ . On the other hand, in a rubber-lined tank B with a capacity of 5 m ³ , 402 kg of lead nitrate and pure water
1086 Kg was added to make a solution. Pb / Ti (molar ratio) at this time =
1.02, set concentration of generated lead oxalate titanate: 16.0wt
%Met.

The addition of the solution from the tank A to the tank B was performed by a charge pump, and the addition was performed by providing about 200 holes at the end of the pipe and adding the solution to the liquid surface in a shower.

For stirring at this time, a stirring blade having two flat blades was used, and the stirring peripheral speed at this time was 2.0 m / sec. The solution during the reaction was maintained at 50 ° C., and the addition time was 2.0 hours.

After the addition was completed, the solution was filtered and washed, and dried at 50 ° C. to obtain lead oxalate titanate tetrahydrate. The yield is 97.0wt%,
Pb / Ti (molar ratio) of lead oxalate titanate was 0.998.

The obtained powder is placed in a porcelain crucible and placed in air for 600
Calcination at 2 ° C. for 2 hours gave a calcined powder of lead titanate. The resulting powder is free of any metallic impurities other than alkaline earths.
10ppm or less, the average particle diameter of the secondary particles 140μm, 50μm
The following secondary particles were 3 wt%.

As examples 4-19 main ingredient _{material, BaTiO 3, SrTiO 3, PbTiO} 3 is used oxalate calcined powder prepared according to Example 1 to 3, CaTi
As O ₃ , a powder produced from CaCO ₃ and TiO ₂ by a solid-phase method and containing 10 ppm or less of metal impurities other than alkaline earth and having an average particle size of 0.5 μm was used.

Next, lanthanum oxide, manganese oxalate, and silicic acid anhydride were used as the minor components, but for lanthanum oxide and silicic acid anhydride, particles having a particle size of 10 μm or less were used. Each of these raw materials was blended so as to have a composition ratio as shown in Table 1, a binder was added, 50 polyethylene ball mill pots and zirconia balls were used, and an alcohol solvent was added for 24 hours. Wet mixing was performed.

This was dehydrated and dried, granulated, and then molded into a disc at a molding pressure of 1000 kg / cm ² . Further, this was fired at 1350 ° C. for 2 hours to obtain a disk-shaped sintered body having a diameter of 13 mmφ and a thickness of 2.5 mm. An electrode of an In-Ga alloy was provided on both main surfaces of the obtained semiconductor ceramic, and this was used as a sample. Curie points, specific resistance values, α values, and withstand voltage values were measured for these samples. The results are shown in Table 1.

Comparative Examples 1 to 9 In each method of Examples 1 to 3, oxalate was produced by changing only one condition, calcined in the same manner, and the calcined powder was used. Example 4
The porcelain was manufactured with the same composition and method as those of ~ 19 and its electrical characteristics were measured.

 Table 2 shows the conditions and electrical characteristics at that time.

Comparative Examples 10 to 24, except that the composition of the raw materials was set to the ratio shown in Table 3,
The same operation as in Examples 4 to 19 was performed. Table 3 shows the physical properties of the obtained porcelain.

Comparative Examples 25 and 26 As raw materials, the main components were BaCO ₃ , CaCO ₃ , SrCO ₃ and P.
_{b 3 O 4, TiO 2,} La 2 O 3 as the semiconductor-forming agent, after Additives formulated so as to be ceramic composition showing a MnCO _3, SiO ₂ in Table 3, exactly the same as in Example 4 to 19 The operation was performed.

Table 3 shows the composition of each component and the physical properties of the obtained porcelain in this comparative example.

In the above-mentioned characteristics, the withstand voltage indicates the maximum applied voltage value before the destruction of the sample by gradually increasing the voltage after applying the voltage to the sample.

FIG. 1 shows the resistance temperature characteristics of the porcelains obtained in Example 10, Example 18 and Example 19, and as can be seen from the figure, the Curie points can be set variously and All of the resistance temperature characteristics can have a low specific resistance and a high α value.

[Effects of the Invention] The raw material powder of the present invention is secondary particles having a unique shape composed of fine primary particles having a regular particle size, and barium titanate obtained by sintering using this raw material. The system-based semiconductor porcelain composition can be used in a wide range of applications such as a current limiting element, a temperature control element, and a constant temperature heating element, and at the same time, has a specific resistance value of 8 (Ω · cm) or less and an α value of 9 ( % /
℃) and withstand voltage of 60 (V / mm) or more, low resistance, high withstand voltage, and high α value. It can be applied to.

[Brief description of drawings]

FIG. 1 is a resistance temperature characteristic diagram of a barium titanate-based semiconductor ceramic composition of the present invention, and FIG. 2 is an SEM photograph showing a particle structure of a barium oxalate titanate calcinated body, and FIG. 3 is a TEM photograph showing the particle structure of the same powder as in FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-146710 (JP, A) JP 62-283816 (JP, A)

Claims (8)

(57) [Claims] 1. A secondary particle having a shape of open pores in which primary particles having a diameter of 0.2 μm or less are connected to each other and having an average particle size of 150.
~ 250μm, 5wt of secondary particles of 50μm or less
% Or less, barium titanate powder. 2. Ba / Ti (molar ratio) = 1.02 to 1.05, BaCl ₂ : 10w
When adding an aqueous solution containing titanium tetrachloride and barium chloride at a concentration of t% or less to the oxalic acid aqueous solution,
i (molar ratio) = 2.1 to 2.3, and the concentration of the produced barium oxalate titanate tetrahydrate is set to 10 to 12 wt%,
The barium oxalate titanate obtained by maintaining the liquid temperature during the addition in the shower for 4 hours or more and maintaining the stirring peripheral speed at 2.5 m / sec or more and the liquid temperature during the addition at a constant temperature range of 55 to 75 ° C is 700 ~ 9
The method for producing barium titanate powder according to claim 1, wherein the barium titanate powder is fired at 00 ° C. 3. A skeleton secondary particle having open pores in which primary particles having a diameter of 0.1 μm or less are connected to each other, and the size thereof is 70 to 70 μm.
Strontium titanate powder having a BET specific surface area of 180 μm and a BET specific surface area of 20 to 30 m ² / g. 4. When adding an aqueous solution containing titanium tetrachloride and strontium chloride in an amount of Sr / Ti (mol) of 1.2 or more and SrCl ₂ : 15 wt% or less, to the aqueous solution of oxalic acid, oxalic acid / Ti =
(Mole ratio) = 2.1-2.3, the concentration of strontium oxalate titanate pentahydrate to be formed is set to 10.0-14.0wt%, and the addition is performed in a shower for 2 hours or more and the stirring peripheral speed
Strontium oxalate titanate obtained by maintaining the liquid temperature during addition at a constant temperature in the temperature range of 60 to 80 ° C. for 3.0 m / sec or more,
The method for producing a strontium titanate powder according to claim 3, wherein the firing is performed at 700 to 900 ° C. 5. A shaped secondary particle having open pores in which primary particles having a size of 0.2 μm or less are connected to each other and having an average size of 50 to 150.
Lead titanate powder, characterized in that secondary particles having a size of 20 μm or less are 5 wt% or less. 6. Titanium tetrachloride is neutralized with ammonia, then filtered and washed, and an aqueous solution of oxalic acid / Ti (molar ratio) = 2.1 to 2.3 and TiO ₂ : 4 wt% or less dissolved in oxalic acid is an aqueous solution of lead nitrate. Pb / Ti (molar ratio) = 1.01 to 1.03, and the concentration of the produced lead oxalate titanate tetrahydrate is 10 to 18 wt%, and the addition is shower-like and the stirring peripheral speed is 2.0 m. / s
ec, lead oxalate titanate obtained by adding in 1 to 2 hours while maintaining a constant temperature at a liquid temperature of 45 to 55 ° C.
The method for producing lead titanate powder according to claim 5, wherein the firing is performed at 0 to 800 ° C. 7. Among the main components of BaTiO ₃ , SrTiO ₃ , CaTiO ₃ , and PbTiO ₃ , at least BaTiO ₃ is the barium titanate powder according to claim (1) or (2), and SrTiO ₃ is claim (3). Alternatively, it is composed of the strontium titanate powder described in (4), and the composition of the main components is BaTiO ₃ : 45 to 85 mol%, SrTiO ₃ : 1 to 2
0 mol%, CaTiO ₃ : 5 to 20 mol%, PbTiO ₃ : 1 to 20 mol% and Y, La, rare earth elements such as Ce as a semiconducting agent with respect to the main component, at least Nb, Sb A raw material powder for a barium titanate-based semiconductor porcelain composition, characterized in that one kind has a composition range of 0.1 to 0.3 mol%, Mn: 0.006 to 0.025 mol%, and SiO ₂ : 0.1 to 1 mol%. 8. Among the main components of BaTiO ₃ , SrTiO ₃ , CaTiO ₃ , and PbTiO ₃ , at least BaTiO ₃ is the barium titanate powder according to claim (1) or (2), and SrTiO ₃ is claim (3). Alternatively, the strontium titanate powder according to (4) and PbTiO ₃ are composed of lead titanate according to claim (5) or (6), and the main component composition is BaTiO ₃ : 45 to 85 mol%, SrTiO ₃ : 1 ~ 2
0 mol%, CaTiO ₃ : 5 to 20 mol%, PbTiO ₃ : 1 to 20 mol% and Y, La, rare earth elements such as Ce as a semiconducting agent with respect to the main component, at least Nb, Sb A raw material powder for a barium titanate-based semiconductor porcelain composition, characterized in that one of them has a composition range of 0.1 to 0.3 mol%, Mn: 0.006 to 0.025 mol%, and SiO ₂ : 0.1 to 1 mol%.