JPH02289426A - Powder for barium titanate-based semiconductor ceramics and its production - Google Patents

Abstract

PURPOSE:To obtain the raw material powder capable of producing a semiconductor ceramic composition having a remarkably positive temp. characteristic, sufficiently low resistivity and an excellent withstand voltage resistance temp. coefficient by forming the powder with secondary grains having open pores formed by the linkage of primary grains to one another and having specified grain diameter distribution and specific surface. CONSTITUTION:The BaTiO3 powder of the secondary grains (having 150-250mum average diameter and contg. <=5% grains having <=50mum diameter) having open pores formed by the linkage of the primary grains having <=0.2mum diameter to one another, the SrTiO3 powder of the secondary grains (having 70-180mum average diameter and 20-30m<2>/g BET specific surface) having open pores formed by the linkage of the primary grains having <=0.1mum diameter to one another, etc., are used as the powder for the barium titanate-based semiconductor ceramics. The molar ratio of Ba to Ti in the BaTiO3 is controlled to 1.02-1.05, an aq. soln. contg. <=10wt.% BaCl2 and TiCl4 is added to an oxalic acid soln. (where the molar ratio of oxalic acid to Ti is controlled to 2.1-2.3), and the precipitated barium oxalate titanate is calcined at 700-900 deg.C to produce the BaTiO3 powder.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is directed to a barium titanate-based semiconductor which has remarkable positive temperature characteristics, has sufficiently low specific resistance, and has excellent withstand voltage and temperature coefficient of resistance. This invention relates to a powder that is a raw material for a porcelain composition and a method for producing the same.

[Prior art and problems to be solved] Conventionally, barium titanate-based semiconductor porcelain has barium titanate as its main component, and rare earth elements such as Y, La, and Ce, among them Nb and Sb, are added as semiconducting agents. Contains a small amount of at least one kind, lowers the specific resistance at room temperature, and lowers the resistance sudden change point (
Curie point), it exhibits a significantly positive resistance-temperature characteristic.

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

In order to shift the Curie point of such barium titanate-based semiconductor ceramics to a high temperature side, it is known to replace a part of Ba with Pb. In addition, in order to shift the Curie point to a lower temperature side and improve electrical characteristics, a part of Ba is replaced with Sr or Ca, and a part of Ti is replaced with Zr or Sn.
It is also known to replace with

Furthermore, by adding Mn, silica, alumina, copper oxide, etc. to barium titanate-based semiconductor IF devices, it is possible to improve the rate of change in resistance temperature after exceeding the Curie point, stabilize the characteristics of semiconductor ceramics, etc. , various attempts have been made. (Tokuko Sho 53-29386, Sho 54-101
)0. (Japanese Patent Publication No. 63-28324, etc.) By utilizing the characteristics of such barium titanate-based semiconductor porcelain, it is used as a constant temperature heating element, a current limiting element, a temperature controlling element, etc.

In many of the above-mentioned applications, barium titanate-based semiconductor Mi devices are required to have as low a resistivity as possible, but with conventional products, as the resistivity decreases, the resistance-temperature characteristics and The breakdown voltage deteriorates extremely; for example, in the case of a resistor with a resistivity of about 5 Ω CI, the gradient α (Z/'C) of resistivity and resistance temperature characteristics is only about 7, and the breakdown voltage is about 30 V/mi. The value remains low [Moto Nishii: Electronic Ceramics, May 88 (1988) pp. 22-27] At present, barium titanate-based semiconductor porcelain with such a low resistivity value has not actually been put into practical use. It is.

[Means for Solving the Problems] In view of the current situation, the present inventors conducted intensive studies to solve the above problems, and as a result, carbonate, which is commonly used as a raw material for barium titanate semiconductor ceramics, was developed. or used as main component instead of oxide BaTiO
3. Out of SrTiO3, CaTiO3, and PbTiO3, at least BaTiO3 and SrTiO3 have fine and uniform primary particles produced by a specific method, and the use of temporary secondary particles obtained by calcining oxalate with a large average particle size. The inventors have discovered that it is possible to obtain an Mi device with a sufficiently low specific resistance of 8 Ω cm or less and excellent positive resistance-temperature characteristics in other properties such as withstand voltage and resistance-temperature characteristics, and have arrived at the present invention. It is something.

That is, the present invention provides skeletal secondary particles having open pores in which primary particles of 0.2 μm or less are connected to each other, the average size of which is 150 to 250 μm, and 5 wt% or less of skeletal secondary particles of 50 μm or less. Barium titanate powder, and Ba/Ti (molar ratio)=1.02
~1.05, BaCl2: When adding water Ne containing titanium tetrachloride and barium chloride at a concentration of 10 wt% or less to an oxalic acid aqueous solution, oxalate pi (molar ratio) = 2
．． 1 to 2.3, the concentration of barium oxalate titanate tetrahydrate to be produced is set to be 10 to 12 wt%, and the addition is performed in a shower over a period of 4 hours or more, and the stirring peripheral speed is 2.
．． 5 m/see or more, the above-mentioned barium titanate powder is characterized in that barium oxalate titanate obtained by maintaining the liquid temperature during addition at a constant temperature in the temperature range of 55 to 75 °C is calcined at 700 to 900 °C. Next, the production method is to use skeletal secondary particles having open pores in which primary particles of 0.1 βm or less are connected to each other, the average size of which is 70 to 180 μm, and the BET specific surface area of 20 to 30 rrr/g. Strontium titanate powder, and Sr/T
i (-1: le) -1,2 or more, 5rCI2: 15
When adding an aqueous solution containing titanium tetrachloride and strontium chloride in wt% or less to an aqueous solution of oxalic acid, oxalic acid/Ti = (molar ratio) 2.1 to 2.3, strontium oxalate titanate 5 Water salt concentration power 10.0
~f4. owt%, the addition was carried out in a shower over a period of 2 hours or more, and the peripheral stirring speed was 3. Q■/see or more,
Strontium oxalate titanate obtained by maintaining the liquid temperature during addition at a constant temperature in the temperature range of 60 to 80 ° C.
The above-mentioned method for producing strontium titanate powder is characterized by firing at ~900°C, and the method further comprises forming secondary particles having open pores in which primary particles of 02 μm or less are connected to each other and having an average size of 50 to 150 μm. , and oxalic acid/Ti ( molar ratio) = 2.1 to 2.3, TiO2: 4
When adding wt% or less of an aqueous solution to an aqueous solution of lead nitrate, P
b/T (mole ratio) = 1.01 to 1.03, the concentration of lead oxalate titanate tetrahydrate to be produced was set to 10 = 18 wt%, and the addition was carried out in the form of a shower, with stirring at a circumferential speed of 2.0 m.
/see, the above titanic acid characterized in that the lead oxalate titanate obtained by adding it for 1 to 2 hours while maintaining the liquid temperature at a constant temperature of 45 to 55 ° C. is fired at 600 to 800 ° C. BaTi03. SrTiO3, CaTiO
3. Among the main components of PbTiO3, a small amount (also known as BaTiO
3. SrTiO3 is composed of the powder mentioned above, and its main component is BaTiO3: 45 to 85 mol%.
, SrTiO3: 1 to 20 mol%, CaTiO3
: 5 to 20 mol%, PbTiO3: 1 to 20 mol%, and Y, La, Ce as a semiconducting agent to the main component.
At least one of rare earth elements such as Nb and Sb is 0.1 to 0.3 mol%, further Mn: 0.006 to 0.025 mol%, Si
O2: Barium titanate-based semiconductor ceramic composition raw material powder characterized by a composition range of 0.1 to 1 mol%, and BaTiO3, SrTiO3, CaTiO3
, among the main components of PbTiO3, at least BaTiO
3. SrTiO3 and PbTi03 are made of the powders mentioned above, and raw material powder for a barium titanate semiconductor ceramic composition having a similar composition is provided.

First, we will describe the methods for producing various oxalates, which are the basic raw materials of the present invention.The important points in these methods are to obtain oxalates with as high a purity as possible, and to reduce the concentration of Ba, Sr, and The objective is to obtain a crystal in which the molar ratio of Pb, Ca and Ti is as close to 1 as possible and there is no variation between crystals. Therefore, in terms of purity, it is of course important that the raw materials, oxalic acid, titanium tetrachloride, and salts of Ba, Sr, Pb, and Ca, be as pure as possible.In order to avoid contamination from the reaction container, the reaction container must be made of acid-resistant material such as Teflon. A plastic container is preferable, and the finally obtained oxalate has a concentration of metal impurities other than alkaline earth metals of several ppm.
Below, a total of 100 pp- or less is preferable, and regarding the molar ratio, it is necessary to obtain particles with uniform crystal shape and particle size and as large as possible, but these can be successfully manufactured by using the following manufacturing method. Understood.

First, let's talk about the production of barium titanate oxalate.The reaction is carried out by adding a solution containing titanium tetrachloride and barium chloride to an aqueous solution containing oxalic acid. The concentration of barium oxalate titanate tetrahydrate may be set within the range of 10 to 12 wt%. Therefore, the water balance of both solutions may be at any concentration as long as it is within the set concentration range. However, in order to prevent barium chloride from precipitating in a solution of titanium tetrachloride and barium chloride, the concentration of barium chloride in the solution needs to be 10 wt % or less.

Ba/Ti (molar ratio) is 1.02 to 1, with 8a being slightly larger.
．． It is necessary to set it to 05. Ba/Ti (molar ratio)
If the power is smaller than 02, the Ba of the oxalate produced
/T i (molar ratio) is less than 0.998, which is undesirable, while Ba/T i (molar ratio) is 1.0.
If it is larger than 5, the Ba/T of the oxalate produced
i (molar ratio) does not change much around 1.0, but it is not economical because there is a large amount of unreacted Ba, oxalic acid/Ti
The molar ratio of (molar ratio) is 2 from the viewpoint of yield and economic efficiency
．． It is preferable to set the concentration in the range of 1 to 2.3, and the concentration is preferably in the range of 10 to 12 wt%, from the viewpoint of suppressing precipitation of other salts, economical concentration, crystal shape, etc.

Furthermore, the addition conditions, stirring conditions, and temperature conditions have a major influence on the crystal size, shape, and particle size distribution of the barium oxalate titanate tetrahydrate crystals that are formed, so addition should be done in a shower over as wide a range as possible. If it is not sufficiently dispersed during addition, fine crystals will precipitate, and if it is not added slowly and in small amounts over 4 hours or more, a similar phenomenon will occur, causing deterioration of the physical properties of the final product. The same applies to the stirring state, and although it differs slightly depending on the scale and shape of the container, it is necessary to perform stirring at a peripheral speed of at least 2.5 servings/sec.

Next, regarding temperature conditions, the crystallization temperature and its temperature fluctuations have a great effect on crystallization and are a major cause of precipitation of microcrystals, so it is necessary to maintain a constant temperature within the temperature range of 55 to 75 degrees Celsius. If the temperature is lower than 55℃, crystals with poor crystallinity will be formed and the Ba/Ti (molar ratio) will be smaller than 0.998, while if the temperature is higher than 75℃, the crystals formed will be unstable and If the time until filtration is long, Ba/Ti (molar ratio) is 0.99.
It is not preferable because it becomes lower than 8.

The barium titanate oxalate crystals precipitated in this way have a Ba/Ti (molar ratio) of 0.998 to 1.00.
Within the range of 2, the inside of the crystal is also stoichiometrically uniform, the crystal grain size is uniform with an average of 100 μm or more, and there are few small crystals.

Next, regarding the production method of strontium oxalate titanate, compared to barium oxalate titanate, Sr/Ti (
Since the molar ratio) tends to be less than 1, the Sr of the preparation
/Ti (molar ratio) must be set to 1.2 or more.

If the setting Sr/T L (molar ratio) is smaller than 1.2,
Sr/T i (molar ratio) of the generated oxalate is 0.99
A value smaller than 8 is not preferable, but if it is too large, it is not economical, so it is usually set in the range of 1.2 to 1.3. The molar ratio of oxalic acid/Ti (molar ratio) is preferably set in the range of 2.1 to 2.3 from the viewpoint of yield and economic efficiency. , and the shape of the crystals, the concentration is 10 to 14 wt.
A range of % is preferred.

Furthermore, the addition conditions, stirring conditions, and temperature conditions have a major influence on the size, shape, and particle size distribution of the crystals of strontium oxalate titanate pentahydrate that are formed, so addition should be done in a shower over as wide a range as possible. If the addition is not sufficiently stirred and dispersed, fine crystals will precipitate, and
A similar phenomenon will occur if the Sr/Ti (molar ratio) of the crystals is not added slowly and in small amounts over a period of time to 0.9.
The same applies to the stirring conditions, which are less than 98, which is undesirable.Although the scale and shape of the container are slightly different, it is necessary to perform the stirring at at least a peripheral speed of 3.01/sec.

Next, regarding temperature conditions, the crystallization temperature and temperature fluctuations have a large effect on crystallization and are a major cause of precipitation of microcrystals, so we recommend a temperature of 60 to 80°C compared to barium titanate siloxate. It is necessary to maintain a constant temperature in a higher temperature range, and for the same reason as barium oxalate titanate, the Sr/Ti (molar ratio) is preferably smaller than 0.998 whether it is higher or lower than the above range. do not have.

The crystals of strontium titanate oxalate thus precipitated also have a Sr/Ti (molar ratio) of 0.998 to 1.
．． Within the range of 002, the inside of the crystal is also stoichiometrically uniform, the crystal grain size is uniform with an average of 70 μm or more, and there are few small crystals.

In the case of strontium oxalate titanate, the yield is as low as about 80 wt% at a reaction temperature of 60 to 80°C, so 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 that is subsequently precipitated changes depending on the cooling rate, the cooling rate must be within the range of 5°C/hr to 30°C/hr.

Furthermore, regarding the manufacturing method of lead oxalate titanate, if titanium tetrachloride is used in this case, lead chloride precipitates will be generated when the lead salt is dissolved, so it is difficult to produce lead titanate oxalate as in the case of barium titanate oxalate. method cannot be used, titanium tetrachloride is neutralized with -H ammonia to produce a titanium hydroxide gel,
After thorough filtration and washing, it becomes a solution by dissolving it in oxalic acid, and this solution can be used. In the case of lead oxalate titanate, Pb/Ti (molar ratio)
varies, so it is necessary to keep various conditions constant,
In order to obtain a complete solution and considering the yield during subsequent oxalate production, and under conditions where the molar ratio is close to 1, the oxalic acid/Ti (molar ratio) is 2.1 to 2.3, TiO2: 4w
It is necessary to keep it below t%. Considering the total water balance, the concentration of lead oxalate titanate produced is 10~
The concentration of the solution of Ti dissolved in oxalic acid and the concentration of lead nitrate may be set so that it is within this range.

Further, when the concentration of lead oxalate titanate is set to 10 to 18 wt%, it is possible to obtain uniform crystals with large particle size.

In order to obtain oxalate with a Pb/Ti (molar ratio) close to 1, the set Pb/Ti (molar ratio) should be 1.01 to 1.
03, setting Pb/T i (molar ratio)
is lower than 1.01, the Pb/T i (molar ratio) of oxalate decreases to 0.99 or less;
(molar ratio) is larger than 1.03, on the other hand, the molar ratio of oxalate is 1.01, which is too large. The same goes for the setting oxalic acid/Ti (molar ratio).The liquid temperature at the time of 0 reaction needs to be carried out in the range of 45 to 55°C, and outside this range the molar ratio will be lower than 0.99. Undesirable.

When obtaining lead oxalate titanate, the diffusion state in the liquid has a great influence on the crystalline state, so to ensure uniform and fast diffusion, addition is performed in a shower state, and the peripheral stirring speed is 2.0 μ/sec. It is necessary to do the above.

The lead oxalate titanate crystals precipitated in this way also
When the Pb/Ti (molar ratio) is within the range of 0.998 to 1.002, the inside of the crystal is stoichiometrically uniform, the crystal grain size is uniform at an average of 50 μm or more, and there are few small crystals. Become.

Regarding calcium titanate, which is one of the powder compositions of the present invention, in the same way as in producing strontium titanate, etc., the concentration of Ca/Ti (molar ratio), CaCl2, oxalic acid/Ti (molar ratio), The concentration of oxalate produced,
By setting the liquid temperature, addition method, stirring conditions, etc., it is possible to obtain calcium oxalate titanate having a Ca/T i (molar ratio) close to 1 and a similarly large crystal grain size.

Each oxalate obtained by the above method is in a form in which the protons of the organic acid are replaced by metals or metal oxides, and this is subjected to ordinary sintering in an atmosphere containing sufficient oxygen. By pre-calcining at a temperature slightly lower than the
Oxides such as TiO3, PbTiO3, and CaTiO3 are formed, but the crystalline state of the organic matter before decomposition has a large effect on the physical properties of the oxide after firing, such as particle size, particle size distribution, and molar ratio. Moreover, the above-mentioned physical properties greatly influence the electrical properties of the final sintered body.

The calcined body of oxalate obtained in the present invention has homogeneous and fine particles of about 0.2 μm or less that are lightly sintered to have a bonding force with each other and maintain the shape of the oxalate before decomposition. It has the structure of so-called skeleton particles, and the particles are uniformly distributed without uneven atomic distribution, and it is possible to obtain a sintered body using such a calcined body through the mixing and firing processes described later. As a result, the sintered body itself has a uniform &1IIa, and becomes a porcelain having a low resistivity, a high temperature coefficient of resistance, and a high withstand voltage.

First, to specifically describe the pre-calcination of barium oxalate titanate, strontium oxalate titanate, and calcium oxalate titanate, each of the obtained oxalates is dried at a temperature that does not allow crystal water to scatter. The resulting hydrated salt is calcined at a temperature that does not carbonize the 9QIJ and keeps the particles at an appropriate size.

Therefore, it is necessary to carry out firing in an atmosphere that is sufficiently supplied with oxygen in the furnace, but since organic acid salts may cause rapid decomposition and combustion, excessive oxygen is not necessary, and a moderate oxygen atmosphere is necessary. It is preferable to do so. Pre-firing temperature is 700~
The temperature is preferably 900°C. If it is lower than 700°C, oxidative decomposition will not proceed sufficiently and carbon etc. will remain, which is undesirable. On the other hand, if it is higher than 900"C, uneven grain growth will likely occur and local abnormalities will occur. Grain growth is often observed, which is not preferable.

For barium titanate and calcium titanate, the calcined body of oxalate obtained in this way is a skeletal secondary particle having open pores in which primary particles of 0.2 μm or less are connected to each other, and the size of the calcined body is The average particle size is 150 to 250 μm,
The calcined body has a uniform secondary particle size with a BET specific surface area of 6 to 1 Onf/g and 5 wt % or less of skeletal secondary particles of 50 μm or less.

In addition, for the calcined strontium titanate body, 0.1
) A skeletal secondary particle having open pores in which primary particles of Im or less are connected to each other and has an average size of 70 to 180 μm. In this case, the BET specific surface area of the calcined body produced by the oxalate production method Powder that exhibits excellent properties for sintered porcelain has a BET specific surface area of 20 to 30rd/g.
is within the range of

In the case of lead oxalate titanate, the oxidative decomposition temperature is lower than the above-mentioned oxalates, and the grain growth is faster, so the pre-calcination is 6
00 to 800°C is preferable, and temperatures lower than 600"C are not preferable because oxidative decomposition does not proceed sufficiently and carbon etc. remain. On the other hand, if the temperature is higher than 800"C,
In the calcined body of lead oxalate titanate obtained in this way, which is undesirable because uneven grain growth tends to occur and localized abnormal grain growth is often observed, the primary particles of 0.2 μm or less are mutually The particle size is 50 to 150 μm on average, the particle size of 20 μm or less is 5 wt% or less, and the BET specific surface area is 6 to 5 wt%.
The calcined body has a uniform secondary particle diameter of 10 m/g.

The oxalate calcined body obtained by the above method is used as a raw material, and is mixed and fired by the method described later. However, in this case, it is not necessarily necessary to use all oxalate calcined bodies. At least BaTiO3, SrTiO3
For this purpose, a calcined body of oxalate should be used.

In this case, the other PbTiO3 and CaTiO3 may be produced and used by the so-called ordinary solid phase method, and usually the respective raw material powders, for example, in the case of PbTi0:+, Pb3O
PbTiO3 produced by mixing, firing and pulverizing PbTiO3 and TiO2 and CaTiO3 produced in the same manner as above are mixed with an oxalate calcined body, but the oxalate calcined body and the average grain Both the diameter and the impurity concentration need to be similar, the average particle size needs to be 2 μm or less, and the metal impurities other than alkaline earth metals need to be less than Ioo pμm.

Next, to explain the composition of the present invention, the present invention comprises BaTi as the main component.3. SrTiO3, CaT
i03PbTi03 is BaTiO3: 45-85 mol%, SrTiO3: 1-20 mol%, CaTiO3
: 5 to 20 mol%, PbTi03: 1 to 20 mol%, and Y, La, C as a semiconducting agent.
At least one of rare earth elements such as e, Nb and Sb is 0.1 to 0.3 mol%, and Mn2 is 0.006
~0.025-mol%, SiO□: 0.1-1 mol% is added.

The main components of the present invention are BaTiO3, SrTiO3, and Ca.
The four-component ceramic of TiO3 and PbTiO3 is obtained by replacing a part of Ba in barium titanate with Ca, Sr, and Pb at the same time. Pb and Sr alone shift the Curie point to the high temperature side and low temperature side, respectively, and these Ca and Sr.

It is known that by including PB as the main component in a coexisting state, the withstand voltage value increases and the durability against large rush currents improves.However, in the conventional method, the specific resistance is 8 (
No material with excellent withstand voltage characteristics has been obtained with a voltage resistance of Ω·cm or less.

The main component of the present invention is BaTiO3: 45 to 85 mol%
, SrTiO3: 1 to 20 mol%, CaTi
It consists of O3: 5 to 20 mol% and PbTiO3: 1 to 20 mol%, but the main components are limited to the above ranges for the following reasons.

First, if BaTiO3 is less than 45%, it becomes difficult to make it into a semiconductor and the specific resistance becomes high. On the other hand, if it exceeds 85%, it is not preferable because the electrical characteristics deteriorate.

If the SrT i03 content is less than 1 mol%, the particles of the sintered body will become coarse, and the effect of improving electrical properties will not appear.
If it exceeds 0 mol %, partial grain growth will occur and electrical characteristics will deteriorate.

If CaTiO3 is less than 5 mol%, the withstand voltage characteristics are not excellent, and if it exceeds 20 mol%, the voltage withstand characteristics are deteriorated.

Regarding PbTiO3, if it is less than 1 mol%, the electrical properties will not be satisfactory, and if it exceeds 20 mol%,
During firing, PB scatters, making it difficult to sinter and make it difficult to convert into a semiconductor.

In addition, at this time, the main components Ba, Sr, Ca,
The total Pb and Ti molar ratio are 0.99 to 1
, 03, it is possible to produce porcelain that has almost no effect on the physical properties of the produced porcelain.

In order to manufacture barium titanate-based semiconductor ceramics, it is necessary to contain a small amount of a semiconducting agent, such as rare earth elements such as Y, La, and Ce, and Nb.

It is sufficient to add or contain at least one of the following in an amount of 0.1 to 0.3 mol%. If the amount added is less than 0.1 mol%, semiconductor formation will not be successful, and it will be more than 0.3 mol%. On the other hand, when adding
Preferably, it is added in the form of oxalate or oxide.

Furthermore, by adding Mn and SiO2 to the above composition, the resistance temperature characteristics can be improved.

In the present invention, compared to the solid phase method, trace amounts of Mn and Si are
Although the addition of O□ significantly improves the properties, it is thought that because the oxalate calcined body was used as the main raw material, the additive was dispersed very uniformly and the above effect was achieved.

In this case, the amount of Mn added is Mn + 0.006 to 0
．． 025 mol %, and these proportions are included in the porcelain.

By adding Mn, the rate of change in resistance temperature can be significantly increased in the positive resistance temperature characteristic exceeding the Curie point.

The temperature coefficient of resistance (
(hereinafter abbreviated as α value), but if Mn is less than 0.006 mol %, the α value becomes small and the withstand voltage characteristics deteriorate. On the other hand, if Mn is more than 0.025 mol%, the α value will increase, but the specific resistance at room temperature will increase, and when used at low voltage, it will not work, which is undesirable.
may be added in the form of oxalate or oxide.

Next is the addition of SiO2, the amount of which is SiO2
2: preferably in the range of 0.1 to 1 mol%.

By adding SiO□, it is possible to suppress changes in resistivity caused by slight fluctuations in the addition of the semiconducting agent, and to achieve a low resistivity value at room temperature.
．． If it is less than 1 mol%, grain growth tends to occur, voltage resistance characteristics deteriorate, and the α value becomes small, while if SiO□ is more than 1 mol%, the specific resistance becomes high, which is undesirable.
When adding SiO2, it is sufficient to use an oxide with a particle size as small as possible.

Weigh each raw material powder in the proportions described above, and use a ball mill pot made of plastic, etc., which is difficult to mix with metal impurities, and balls made of zirconia, etc., which are high in density and do not affect the electrical characteristics even if a small amount of impurities are mixed in. Use for mixing and crushing.

In this case, in order to increase the crushing effect, a liquid such as water or an aqueous solvent may be added. After this step, the liquid is removed and granulation is performed. Molding is performed at a pressure of Ot/cm3. After molding, perform steps 5 to b, and after firing at 1300 to 1400°C for 5 minutes to 2 hours, the temperature is lowered at the same rate as the temperature rise to obtain the porcelain of the present invention. . If the molding pressure is too low than the specified value, the specific resistance will increase, while if it is too high, the specific resistance will decrease, but the α value will drop, which is undesirable. Also, if the heating rate is too slow, the specific resistance will increase, while if it is too fast, the specific resistance will decrease. Regarding the firing temperature, if the temperature is too low or too high, the resistivity will increase, which is undesirable.

The porcelain of the present invention produced by the method described above has a density of 5
．． 2 to 5.6 g/cra3, specific resistance value 8 (Ω・cm
) or less, α value is 9 (!/”C) or more, and withstand voltage is 60 (
V/am> or more, low specific resistance and high withstand voltage (and α
This results in an excellent barium titanate-based semiconductor Mi device with a high value.

In this way, the reason why it has excellent electrical properties due to the use of materials manufactured from oxalate as the main component is that the purity of the raw materials is the total metal content excluding alkaline earth elements. Since the elemental content is very high at less than 100μm, it is easy to control the properties by adding trace elements, and the effect of improving the properties is large.The structure in the porcelain has a dalein size of less than 10μm and an average size of approximately 5μm. It is thought that this is because the withstand voltage characteristics were improved due to the uniform microstructure consisting of sintered bodies with regular grain sizes.

Furthermore, since the oxalate calcined body, which is the main component, is a skeleton particle in which fine and uniform primary particles with appropriate strength are combined, the skeleton particles are sequentially crushed and mixed during mixing and crushing, so it is very mixable. As a result, each atom is uniformly dissolved in solid solution during sintering, and when made into porcelain, the distribution of atoms becomes more uniform, and there are no local changes in the characteristics within the porcelain, and the overall characteristics are uniform. However, as a result of actually examining various conditions to obtain the most optimal conditions for the selection of raw materials, manufacturing method, mixing and crushing method, sintering method, etc. of the present invention,
The overall effect was that we were able to obtain porcelain with such outstanding electrical properties.

These are extremely useful as constant temperature heating elements, current limiting elements, temperature control elements, and the like.

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

Example 1 Ti (DH) was placed in a rubber-lined tank A with a capacity of 5 d.
) Ti solution 650 containing 27.6 wt% Ti ions in terms of 4 and 32.8 wt% Cl ions in terms of HCI.
Kg, barium chloride dihydrate 389g and pure water 29g
80Kg was slowly mixed to form a solution for addition. On the other hand, in rubber-lined tank B with a capacity of 7 d, oxalic acid 4
Dissolve 29 kg in 2055 kg of pure water and lower the temperature to 60 kg.
The temperature was raised to and maintained at that temperature.

At this time, Ba/Ti (molar ratio) = 1.03, oxalic acid/
T1 (molar ratio) = 2.2, BaCl2: 8.25
It was wt%.

The solution was added from tank A to tank B using a charge pump, and the solution was added by making about 200 holes at the tip of a vibrator and adding the solution to the liquid surface in a shower-like manner.

Stirring at this time was performed by rotating a stirring blade having two flat blades at 50 rμm, and the peripheral stirring speed at this time was 2.9 m/sec.
The addition time was 4 hours.

Further, the set concentration of barium titanate oxalate produced at this time was 1) wt%.

After the addition was completed, the reaction solution was filtered and washed using a centrifuge, and then dried at 50° C. to obtain 592 kg of barium titanate oxalate crystals. The yield at this time was 88.3
In wt%, its Ba/Ti (mole ratio) was 0.999.

The resulting powder was placed in a porcelain crucible and heated to 900" in air.
The barium titanate calcined powder was obtained by calcining with Cl2hr. The obtained powder has metal impurities other than alkaline earth metals of 10ρp1 or less, an average particle size of 200 μm, and 5.
Particles with a diameter of 0 μm or less were about 2 wt%. Figure 2 shows a scanning electron micrograph (SEN photograph) of the powder obtained at this time, and Figure 3 shows a transmission electron microscope photograph (TEM photograph) in which a portion of the powder was collected and the appearance of the primary particles was observed. show.

Example 2 Ti(
Ti solution 51 containing 39.9 wt% Ti ions in terms of OH)4 and 31.9 wt% CI ions in terms of HCI
6 kg of strontium chloride hexahydrate, 516 kg of strontium chloride hexahydrate, and 1590 g of pure water were slowly mixed to prepare a solution for addition.

On the other hand, in a rubber-lined tank B with a capacity of 7 d, 429 kg of oxalic acid was dissolved in 2147 g of pure water, and the temperature was set to 7 d.
The temperature was raised to 5°C and maintained at that temperature.

At this time, Sr/Ti (molar ratio) = 1.25, oxalic acid/Ti (molar ratio) -2,2,5rC12 = 12.0 w
It was t%.

The solution was added from tank A to tank B using a charge pump, and about 200 holes were provided at the tip of a pipe, and the solution was added to the liquid surface in a shower-like manner.

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

After the addition was completed, the reaction solution was cooled to room temperature at a rate of 20°C/hr, filtered and washed with a centrifuge, and further
By drying at ℃, 600 kg of crystals of strontium titanate oxalate pentahydrate were obtained. Sr/T i (molar ratio) of this oxalate = 0.999, yield is 93
%.

The obtained powder was placed in a porcelain crucible and heated to 900°C in air.
, for 2 hours to obtain calcined strontium titanate powder. The obtained powder contained all metal impurities other than alkaline earth metals of 10 pμm or less, the average particle diameter of secondary particles was 150 μm, and the secondary particles of 50 μm or less were 2.5 wt%.
, BET specific surface area is 26. On? /g.

Example 3 TiC14: A 10 wt% solution was cooled to below 40°C and neutralized with an ammonium aqueous solution until the pH reached 7 to obtain gel-like titanium hydroxide, which was then filtered and washed with pure water. do. The gel after washing was immediately dissolved with oxalic acid, and after measuring the concentration of Ti ions, the concentration of Ti ions was 2.4 wt% with pure water and oxalic acid.
Oxalic acid bis (molar ratio) was adjusted to 2°15, and 2,378 kg of this solution was transferred to rubber-lined tank A with a capacity of 7 M as an addition solution. On the other hand, 402 kg of lead nitrate and 1 kg of pure water were placed in a rubber-lined tank B with a capacity of 5 fff.
086 kg was added to form a solution. At this time, Pb/Ti (molar ratio) was 1.02, and the set concentration of lead oxalate titanate to be produced was 16.0 wt%.

The solution was added from tank A to tank B using a charge pump, and about 200 holes were provided at the tip of a pipe, and the solution was added to the liquid surface in a shower-like manner.

For stirring at this time, a stirring blade having two flat blades was used, and the peripheral stirring speed at this time was 2.0 .mu./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 further dried at 50°C to obtain lead oxalate titanate tetrahydrate. Yield is 97.0w
t%, Pb/Ti (molar ratio) of lead oxalate titanate is 0
．． It was 998.

The obtained powder was placed in a porcelain crucible and heated to 600 ml in air.
' Calcined with Cl2hr to obtain calcined powder of lead titanate.

The obtained powder contained all metal impurities other than alkaline earth metals of 10 ppm or less, and the average particle size of the secondary particles was 140 pm.
Secondary particles with a diameter of 150 μm or less were 3 int%.

Examples 4 to 19 Main component raw materials include BaTiO3, SrTiO3, P
For bTiO3, the oxalate calcined powder produced in Examples 1 to 3 was used, and for CaTi0a, CaCO3 and Ti were used.
Manufactured from O2 by a solid phase method, all metal impurities other than alkaline earth metals are lop μm or less, and the average particle size is 0.5
Powder of μm was used.

Next, lanthanum oxide, manganese oxalate, and silicic anhydride were used as trace components, and for lanthanum oxide and silicic anhydride, particles having a particle size of 10 μm or less were used. These raw materials were blended in a composition ratio as shown in Table 1, a binder was added, a 50 Il polyethylene ball mill pot and a zirconia ball were used, an alcohol solvent was added, and the mixture was heated for 24 hours. Timed mixing was performed.

After dehydrating and drying this and granulating it, the molding pressure was 1000 kg/
- It was formed into a disk shape. This was further fired at 1350° C. for 2 hours to obtain a disc-shaped sintered body with a diameter of 13×φ and a thickness of 2.5@×. An In-Ga alloy electrode was provided on the amphibian surface of the obtained semiconductor porcelain, and this was used as a sample.

For these samples, the Curie point, resistivity value, α value,
The withstand voltage value was measured. The results are shown in Table 1.

Comparative Examples 1 to 9 In each method of Examples 1 to 3, oxalates were produced by changing only one condition, calcined in the same manner, and the calcined powder was used. Example 4~
Porcelain was manufactured using the same composition and method as No. 19, and its electrical properties were measured.

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

Comparative Examples 1O to 24 The same operations as in Examples 4 to 19 were performed, except that the raw material composition was set to the proportions shown in Table 3. Table 3 shows the physical properties of the obtained porcelain.

Comparative Example 25.26 As a raw material, its main components include BaCO3, CaCO3,
5rC03, Pb30,, TiO2, la203 as a semiconductor agent, MnCO3, SiO as an additive
After blending 2 to give the porcelain composition shown in Table 3, the same operations as in Examples 4 to 19 were performed.

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

In the above-mentioned characteristics, the withstand voltage is the voltage that is gradually increased after a voltage is applied to the sample, and indicates the maximum applied voltage value before the sample breaks down.

Figure 1 shows the resistance-temperature characteristics of the porcelains obtained in Example 10, Example 18, and Example 19. Both resistivity and temperature characteristics can be maintained at low specific resistance and high α value.

[Effects of the Invention] The raw material powder of the present invention is a secondary particle having a unique shape consisting of fine primary particles with a uniform particle size, and barium titanate obtained by sintering using this raw material The system semiconductor ceramic composition can be used in a wide range of applications such as current limiting elements, temperature control elements, constant temperature heating elements, etc., and has a specific resistance value of 8 (Ω・C■) or less and an α value of 9. (χ/
'C) As shown above, it exhibits excellent electrical properties such as low resistance and high withstand voltage of 60 (V/mm) or more, as well as a high α value, so it is particularly suitable as a current limiting element for low voltages. It can be applied to various uses.

[Brief explanation of the drawing]

FIG. 1 is a resistance temperature characteristic diagram of the barium titanate-based semiconductor ceramic composition of the present invention, and FIG. 2 is an SEN photograph showing the particle structure of a calcined barium titanate oxalate body.
FIG. 3 is a TEN photograph showing the particle structure of the powder similar to FIG. 2. Patent Applicant Central Glass Co., Ltd. Procedural Amendment 1. Case description 2, title of the invention 3. Person making the amendment: Patent Application No. 225061, 1999. Barium titanate powder for semiconductor porcelain and its manufacturing method 4. Agent address: 8-3 Horinouchi-chome, Suginami-ku, Tokyo. 607 No. 8,
Contents of amendment (1) On page 31, line 1 of the specification, ``The yield is 88.3%,
The Ba/Ti (molar ratio) is 0.999 J [yield is 85.3%, Ba/Ti (molar ratio) is 0.
．． Corrected to 999 J. R-1-4iWI liquid 51 on page 31, line 15 of the specification
The description "6 Kg, -m-" is corrected to "r----Ti solution 449 Kg, -1-". (3) Table 2 on page 39 of the specification is amended as shown in the attached sheet.

Claims (8)

[Claims] (1) A skeletal secondary particle with open pores in which primary particles of 0.2 μm or less are connected to each other, and the average particle size is 150 to 150.
A barium titanate powder having a particle size of 250 μm and containing 5 wt % or less of secondary particles having a size of 50 μm or less. (2) Ba/Ti (molar ratio): 1.02 to 1.05, B
aCl_2: When adding an aqueous solution containing titanium tetrachloride and barium chloride at a concentration of 10 wt% or less to an oxalic acid aqueous solution, oxalic acid/Ti (molar ratio) = 2.1 to 2.3,
The concentration of barium oxalate titanate tetrahydrate produced is 10
The concentration was set to ~12wt%, and the addition was carried out in a shower-like manner.
Performed for 4 hours or more and stirred at a peripheral speed of 2.5 m/sec.
As mentioned above, the barium oxalate titanate obtained by maintaining the liquid temperature during addition at a constant temperature in the temperature range of 55 to 75 °C was 700 to 90 °C.
The method for producing barium titanate powder according to claim 1, wherein the barium titanate powder is fired at 0°C. (3) Substantial secondary particles having open pores in which primary particles of 0.1 μm or less are connected to each other and have an average particle size of 70 to 1
80 μm, and its BET specific surface area is 20 to 30
Strontium titanate powder, characterized in that it has a mass of m^2/g. (4) Sr/Ti (mol) = 1.2 or more, SrCl_2
: When adding an aqueous solution containing 15 wt% or less of titanium tetrachloride and strontium chloride to an aqueous solution of oxalic acid,
Oxalic acid/Ti: (molar ratio): 2.1 to 2.3, the concentration of strontium oxalate titanate pentahydrate produced is 10
．． Set to 0 to 14.0 wt%, add in shower form, 2
Strontium oxalate titanate, which was obtained by stirring at a peripheral speed of 3.0 m/sec or more and maintaining the liquid temperature during addition at a constant temperature in the temperature range of 60 to 80°C, was
The method for producing strontium titanate powder according to claim 3, wherein the strontium titanate powder is fired at a temperature of 900°C to 900°C. (5) Formative secondary particles with open pores in which primary particles of 0.2 μm or less are connected to each other, with an average size of 50 to 150
μm, and 5wt of skeletal secondary particles of 20 μm or less
% or less. (6) Titanium tetrachloride was neutralized with ammonia, filtered and washed, and dissolved in oxalic acid (molar ratio) =
2.1-2.3, TiO_2: When adding an aqueous solution of 4 wt% or less to an aqueous solution of lead nitrate, Pb/Ti (molar ratio) =
1.01 to 1.03, the concentration of lead oxalate titanate tetrahydrate to be produced is set to be 10 to 18 wt%, and addition is performed in a shower manner, stirring peripheral speed is 2.0 m/sec, and liquid temperature is 45 to 1.
Lead oxalate titanate obtained by adding over 1 to 2 hours while maintaining a constant temperature at 55 ° C.
The method for producing lead titanate powder according to claim 5, characterized in that the firing is performed at 0°C. (7) BaTiO_3, SrTiO_3, CaTiO_
3. Among the main components of PbTiO_3, at least BaTi
O_3 is the barium titanate powder according to claim (1) or (2), and SrTiO_3 is the barium titanate powder according to claim (3) or (4).
It consists of the strontium titanate powder described above, and its main component composition is BaTiO_3: 45 to 85 mol%.
, SrTiO_3: 1 to 20 mol%, CaTiO_3:
5 to 20 mol%, PbTiO_3: 1 to 20 mol%, and at least one of rare earth elements such as Y, La, Ce, Nb, and Sb is added as a semiconducting agent to the main component.
1 to 0.3 mol%, further Mn: 0.006 to 0.025 mol%, SiO_
2: Raw material powder for barium titanate-based semiconductor ceramic composition, characterized by having a composition range of 0.1 to 1 mol%. (8) BaTiO_3, SrTiO_3, CaTiO_
3. Among the main components of PbTiO_3, at least BaTi
O_3 is the barium titanate powder according to claim (1) or (2), and SrTiO_3 is the barium titanate powder according to claim (3) or (4).
The strontium titanate powder described above, PbTiO_3, is composed of lead titanate according to claim (5) or (6), and the main component thereof has a composition of BaTiO_3: 45 to 85 mol%.
, SrTiO_3: 1 to 20 mol%, CaTiO_3:
5 to 20 mol%, PbTiO_3: 1 to 20 mol%, and at least one of rare earth elements such as Y, La, Ce, Nb, and Sb is added as a semiconducting agent to the main component.
1 to 0.3 mol%, further Mn: 0.006 to 0.025 mol%, SiO_
2: Raw material powder for barium titanate-based semiconductor ceramic composition, characterized by having a composition range of 0.1 to 1 mol%.