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WO2016039253A1 - Procédé de fabrication d'une composition de céramique semi-conductrice, composition de céramique semi-conductrice et élément ctp - Google Patents

Procédé de fabrication d'une composition de céramique semi-conductrice, composition de céramique semi-conductrice et élément ctp Download PDF

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WO2016039253A1
WO2016039253A1 PCT/JP2015/075111 JP2015075111W WO2016039253A1 WO 2016039253 A1 WO2016039253 A1 WO 2016039253A1 JP 2015075111 W JP2015075111 W JP 2015075111W WO 2016039253 A1 WO2016039253 A1 WO 2016039253A1
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temperature
semiconductor ceramic
ceramic composition
composition
raw material
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到 上田
武司 島田
健太郎 猪野
雄太郎 寺門
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Proterial Ltd
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Hitachi Metals Ltd
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
    • C04B35/468—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient

Definitions

  • the present invention relates to a method for producing a semiconductor ceramic composition used for a PTC heater, a PTC thermistor, a PTC switch, a temperature detector, and the like, a semiconductor ceramic composition, and a PTC element including the semiconductor ceramic composition and an electrode.
  • BaTiO 3 -based semiconductor ceramic compositions have a Curie temperature of around 120 ° C. These semiconductor porcelain compositions need to shift the Curie temperature depending on the application. For example, it has been proposed to shift the Curie temperature by adding SrTiO 3 oxide to BaTiO 3 oxide, but in this case, the Curie temperature is shifted only in the negative direction and in the positive direction. Do not shift.
  • PbTiO 3 is a material that is currently in practical use and is known as an additive that shifts the Curie temperature in the positive direction.
  • lead is an element that causes environmental pollution, a lead-free semiconductor ceramic composition containing no lead is desired.
  • Patent Document 1 As a semiconductor porcelain composition that is lead-free and has a high Curie temperature, a part of Ba in the BaTiO 3 oxide is substituted with Bi—Na.
  • Patent Document 1 at least one of the composition formula [(BiA) x (Ba 1 -y R y) 1-x] [Ti 1-z M z] O 3 (A is Na, Li, K, R Is at least one of rare earth elements including Y, M is at least one of Nb, Ta, and Sb), and x, y, and z are 0 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 0.02, and 0 ⁇ z A semiconductor ceramic composition having crystal grains satisfying ⁇ 0.01 (where y + z> 0) is described.
  • Patent Document 1 describes, as a manufacturing method thereof, (BiA) TiO 3 -based first raw material and (BaR) [TiM] O 3 (R is at least one of rare earth elements including Y, M is Nb, Ta, A second raw material of each system is prepared, and the first raw material is calcined at 700 ° C. or higher and 950 ° C. or lower; The second raw material is calcined at 900 ° C. or higher and 1300 ° C. or lower, and the calcined materials are mixed to form a third raw material. The third raw material is heat-treated at 900 ° C. or higher and 1250 ° C. or lower, and then fired. It is described. However, there is no detailed description of the temperature lowering process.
  • Patent Document 2 describes that when firing a barium titanate-based semiconductor ceramic at a predetermined firing temperature, it is held at a set temperature that is lower than the firing temperature and at least 800 ° C. when the temperature is lowered. Thus, it is described that the specific resistance can be controlled and the withstand voltage characteristic and the resistance temperature characteristic can be reliably improved.
  • the semiconductor ceramic composition in which a part of Ba in the BaTiO 3 oxide described in Patent Document 1 is replaced with, for example, Bi—Na is effective in shifting the Curie temperature in the positive direction. If a sufficiently high temperature coefficient of resistance ⁇ cannot be obtained, the manufacturing method of Patent Document 2 is effective in improving the temperature coefficient of resistance ⁇ , but manufacturing of the above-described semiconductor ceramic composition substituted with Bi-Na. It has been found that the resistance temperature coefficient ⁇ cannot be improved when used as a method. Therefore, in order to improve the temperature coefficient of resistance ⁇ in a semiconductor ceramic composition in which a part of Ba in the BaTiO 3 oxide is substituted with Bi-Na, it is necessary to find a method for producing a semiconductor ceramic composition peculiar to this composition. is there.
  • an object of the present invention is to provide a manufacturing method capable of improving the temperature coefficient of resistance ⁇ in a semiconductor ceramic composition having a composition in which a part of Ba is substituted with, for example, Bi—Na. It is another object of the present invention to provide a semiconductor ceramic composition obtained by the manufacturing method, and a PTC element including the semiconductor ceramic composition and an electrode.
  • the present invention relates to a method for producing a semiconductor ceramic composition having a composition in which a part of Ba in a BaTiO 3 oxide is substituted with Bi and A (A is at least one element of an alkali metal and contains Na as an essential element). After firing at a temperature of over 1350 ° C, the temperature starts to drop at a rate of 150 ° C / h or less, and then changes to a temperature drop rate of over 150 ° C / h between 1150 ° C and 1350 ° C. It has a temperature lowering process. Semiconductor porcelain compositions obtained by these production methods are characterized in that the amount of Na at grain boundaries of crystal grains is 3 mol% or more.
  • the semiconductor ceramic composition the composition formula of the crystal grains is [(BiA) x (Ba 1 -y R y) 1-x] [Ti 1-z M z] O 3
  • A is at least one alkali metal
  • the element is essential and contains Na
  • R is represented by at least one of rare earth elements including Y
  • M is represented by at least one of Nb, Ta, and Sb
  • x, y, and z are 0 ⁇ x ⁇ Those satisfying 0.2, 0 ⁇ y ⁇ 0.02, and 0 ⁇ z ⁇ 0.01 can be employed.
  • PTC elements can be obtained by forming electrodes on these semiconductor ceramic compositions.
  • the method for producing a semiconductor ceramic composition of the present invention can obtain a semiconductor ceramic composition having a high resistance temperature coefficient ⁇ . If an electrode is formed on this semiconductor ceramic composition, a PTC element having an excellent resistance temperature coefficient ⁇ can be obtained.
  • the present invention relates to a lead-free semiconductor ceramic composition having a composition in which a part of Ba in a BaTiO 3 oxide is substituted with Bi and A (A is an element of at least one alkali metal and contains Na as an essential element).
  • a temperature pattern in which the temperature decreasing rate is changed in the temperature decreasing process as shown in FIG. 1 during baking that is, after baking at a temperature exceeding 1350 ° C., the temperature starts decreasing at a temperature decreasing rate of 150 ° C./h or less.
  • a temperature lowering process is applied to change the temperature decreasing rate to over 150 ° C / h between 1150 ° C and 1350 ° C.
  • the temperature coefficient of resistance ⁇ can be increased.
  • the resistance temperature coefficient ⁇ is increased by increasing the amount of Na at the grain boundary of the crystal grains (hereinafter referred to as grain boundary Na amount). The reason for this is presumed to be that the concentration of Na at the grain boundary increases the grain boundary level and increases the Schottky barrier at the grain boundary. And it was discovered that the resistance temperature coefficient ⁇ can be kept large by keeping Na at the grain boundary in the temperature lowering process.
  • the amount of Na at the grain boundary decreases. While Bi is volatilized, Na supply from the grain boundary to the grain boundary occurs and the grain boundary Na amount increases, but when Bi stops volatilizing thereafter, the amount of Na moving from the grain boundary to the triple point is increased. As the amount increases, the amount of Na at the grain boundary decreases.
  • the temperature range in which the amount of Na increases is on the high temperature side, and the temperature range in which the amount of Na decreases decreases on the lower temperature side. It was found that the boundary between both temperature ranges was between 1150 °C and 1350 °C.
  • the temperature range on the high temperature side is over 150 ° C / h when the temperature is lowered at a rate of 150 ° C / h or less to collect and increase Na at the grain boundaries over time and then move to the low temperature range.
  • the temperature is lowered at a rate of Na, the time for Na to move from the grain boundary to the heterogeneous phase can be shortened, and Na movement can be suppressed.
  • a semiconductor porcelain composition having a larger amount of Na present at the grain boundaries than that produced by the conventional production method could be obtained.
  • the firing is performed at a temperature higher than 1350 ° C.
  • the temperature is preferably 1400 ° C. or higher.
  • the firing temperature is preferably 1500 ° C. or less.
  • the temperature drop from the holding temperature above 1350 ° C is performed at a temperature drop rate of 150 ° C / h or less. If the temperature decreasing rate here exceeds 150 ° C./h, the resistance temperature coefficient ⁇ does not increase and becomes less than 4.5% / ° C.
  • the temperature lowering rate is preferably 120 ° C./h or less.
  • the temperature drop rate is changed in the range of 1150 °C to 1350 °C. If the temperature drop rate is changed below 1150 ° C or above 1350 ° C, the effect of increasing the resistance temperature coefficient ⁇ is difficult to obtain. Specifically, the resistance temperature coefficient ⁇ cannot be 4.5% / ° C. or more.
  • the timing for changing the temperature drop rate is more preferably set in a range of 1180 ° C. or higher and 1320 ° C. or lower.
  • the cooling rate after changing the cooling rate is over 150 ° C / h. At 150 ° C./h or less, the effect of increasing the resistance temperature coefficient ⁇ is difficult to obtain, and the resistance temperature coefficient ⁇ does not exceed 4.5% / ° C.
  • the temperature lowering rate here is more preferably 180 ° C./h or more. Further, it is preferable that the temperature lowering rate is higher than 150 ° C./h until it is cooled to 800 ° C.
  • the atmosphere at the time of firing is not particularly limited, but can be, for example, the atmosphere or a reducing atmosphere, or an inert gas atmosphere with a low oxygen concentration. It is particularly preferable to carry out in an atmosphere having an oxygen concentration of less than 1 vol%. If the oxygen concentration is less than 1 vol%, the effect of reducing the room temperature resistivity can also be obtained.
  • the holding time at the firing temperature is preferably 1 hour or more and 10 hours or less. If the holding time is less than 1 hour, firing may be insufficient. On the other hand, when the holding time exceeds 10 hours, Na concentrated in the grain boundary diffuses from the grain boundary, forms another phase that is not a tetragonal crystal between the crystals, and as a result, the temperature coefficient of resistance ⁇ is There is a possibility of becoming smaller.
  • the holding time is more preferably 2 hours or longer and 6 hours or shorter.
  • the present invention a known production method can be applied to the production process before firing.
  • the present invention will be described by showing an example of a manufacturing process before firing, but the present invention is not limited to this manufacturing method.
  • Step 1 a manufacturing method having the following steps (Step 1) to (Step 5) as shown in FIG. 2 can be adopted.
  • Step 1 (BiA) TiO 3 system (A is at least one element of an alkali metal and contains Na essential), and (BaR) [TiM] O 3 (R is a rare earth containing Y) Prepare at least one of the elements, M is at least one of Nb, Ta, and Sb) series second raw materials, (Step 2)
  • the first raw material is calcined at 700 ° C. or higher and 950 ° C. or lower
  • the second raw material is calcined at 900 ° C. or higher and 1300 ° C. or lower
  • Step3 Mix each calcined material to make the third raw material, (Step4) Molding, (Step 5) Firing at a temperature exceeding 1350 ° C.
  • This manufacturing method will be described below.
  • the (BiA) TiO 3 -based first raw material is prepared by mixing A 2 CO 3 , Bi 2 O 3 , and TiO 2 as raw material powders.
  • the (BiA) TiO 3 -based first raw material refers to a raw material for forming the (BiA) TiO 3 oxide.
  • the (BaR) [TiM] O 3 -based second raw material is a raw material powder of BaCO 3 , TiO 2 , R, M, for example, an R element oxide such as La 2 O 3 , Nb 2 O 5, etc. It is made by mixing the M element oxide. R and M are used as semiconducting elements.
  • the (BaR) [TiM] O 3 -based second raw material refers to a raw material for forming the (BaR) [TiM] O 3 oxide. These raw materials are prepared so as to have a final semiconductor ceramic composition.
  • This composition is composed of [(BiA) x (Ba 1-y R y ) 1-x ] [Ti 1-z M z ] O 3 (A is an element of at least one alkali metal and Na is essential.
  • R is at least one of rare earth elements including Y
  • M is at least one of Nb, Ta, and Sb
  • x, y, and z are 0 ⁇ x ⁇ 0.2 and 0 ⁇ y ⁇ 0.02. And those satisfying 0 ⁇ z ⁇ 0.01 are preferable.
  • both the first raw material and the second raw material may be pulverized according to the particle size of the raw material powder when the raw material powder is mixed.
  • the raw material powder may be mixed by either wet mixing using pure water or ethanol or dry mixing. However, when dry mixing is performed, compositional deviation is more easily prevented.
  • a 2 CO 3 , Bi 2 O 3 , TiO 2, etc. another A compound, Bi compound, or Ti compound may be used as the first raw material.
  • other Ba compounds and Ti compounds may be used for the second raw material in addition to BaCO 3 , TiO 2 and the like.
  • the calcination of the (BiA) TiO 3 -based first raw material in (Step 2) will be described in detail.
  • the calcining temperature of the first raw material is 700 ° C. or higher and 950 ° C. or lower. If the calcining temperature is less than 700 ° C, unreacted A 2 CO 3 , Bi, Ti and unreacted A 2 O react with the moisture in the furnace atmosphere or in the case of wet mixing, and generate heat, resulting in a composition.
  • the PTC characteristic tends to become unstable due to deviation from the desired value.
  • the volatilization of Bi proceeds, causing a composition shift and promoting the generation of a different phase.
  • the calcination time is preferably 0.5 hours or more and 10 hours or less.
  • the calcination time is less than 0.5 hours, the obtained PTC characteristics are likely to be unstable for the same reason as when the calcination temperature is less than 700 ° C.
  • the calcining time exceeds 10 hours, the generation of a heterogeneous phase is easily promoted for the same reason as when the calcining temperature exceeds 950 ° C. More preferably, it is 1 hour or more and 8 hours or less.
  • the calcination of the first raw material is preferably performed in the air. In order to suppress Bi volatilization, the calcining temperature of the first raw material is preferably lower than the calcining temperature of the second raw material.
  • the calcining temperature of the second raw material is 900 ° C. or higher and 1300 ° C. or lower.
  • the calcining time is preferably 0.5 hours or more. If the calcining time is less than 0.5 hours, it causes a composition shift.
  • the upper limit is not particularly limited, but it is preferable that the upper limit is 100 hours or less because solid solution with the (BiA) TiO 3 calcined powder to be mixed later can be promoted.
  • the calcination of the second raw material is preferably performed in the air.
  • Step 3 After the first and second calcined powders are blended in a predetermined amount, they are mixed to obtain a third raw material. Mixing may be either wet mixing using pure water or ethanol or dry mixing. Further, depending on the particle size of the calcined powder, pulverization may be performed after mixing, or mixing and pulverization may be performed simultaneously.
  • the average particle size of the calcined powder after mixing and pulverization is preferably 0.5 ⁇ m to 7.0 ⁇ m. Furthermore, 0.8 ⁇ m to 5.0 ⁇ m is preferable, and 1.0 ⁇ m to 4.0 ⁇ m is more preferable.
  • the third raw material has a composition formula of [(BiA) x (Ba 1-y R y ) 1-x ] [Ti 1-z M z ] O 3 (A is at least one element of an alkali metal and Na Wherein R is at least one of rare earth elements including Y, M is at least one of Nb, Ta, and Sb), and x, y, and z are 0 ⁇ x ⁇ 0.2 and 0 ⁇ y ⁇ 0.02. , 0 ⁇ z ⁇ 0.01 is preferably satisfied. In order to obtain this composition, it is preferable to adjust the first and second raw materials. Hereinafter, the reasons for defining the preferred composition formula will be described.
  • ⁇ Curie temperature can be set to 130 ° C to 200 ° C by setting the range of x to more than 0 and 0.2 or less. If x exceeds 0.2, it is not preferable because a different phase is easily formed.
  • the range of x is more preferably 0.03 or more and 0.1 or less.
  • both R and M are not necessarily required, and at least one of them may be used.
  • the value of y in R may be 0, but 0 ⁇ y ⁇ 0.02 is a preferred range.
  • y When y is 0, the composition is not sufficiently semiconductive. If it exceeds 0.02, the room temperature resistivity tends to increase.
  • the valence can be controlled by changing the value of y.
  • the valence control of the composition is performed in a system in which a part of Ba in the BaTiO 3 oxide is substituted with Bi and A, the addition of a trivalent cation as a semiconducting element results in a monovalent effect.
  • a more preferable range is 0.002 ⁇ y ⁇ 0.02.
  • R is at least one element selected from rare earths including Y (Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Tb, Tm, Yb, Lu), Since excellent PTC characteristics can be obtained, R and La are particularly preferable as R.
  • the value of z in M may be 0, but 0 ⁇ z ⁇ 0.01 is a preferable range.
  • z When z is 0, the valence cannot be controlled and the composition is not easily made into a semiconductor.
  • z exceeds 0.01 the room temperature resistivity tends to increase or the Curie temperature tends to decrease.
  • a more preferable range is 0.001 ⁇ z ⁇ 0.005.
  • Nb is particularly preferable as M for obtaining excellent PTC characteristics.
  • the ratio of Bi and A should be 1: 1. However, even when this ratio is 1: 1 at the time of compounding, Bi is volatilized by the calcination or firing process, and the ratio of Bi and A is shifted, so the sintered body is 1: 1. It is included in this invention also when there is no.
  • An allowable range of Bi: A 0.78 to 1.55: 1 is acceptable, and an increase in heterogeneous phase can be suppressed within this range, so that an increase in room temperature resistivity and a change with time can be suppressed.
  • a site: B site 0.9 to 1.0: 1, more preferably 0.990 to 1.000: 1.
  • the effect of reducing the change with time and the effect of improving the resistance temperature coefficient ⁇ can be expected.
  • Si raw materials and Ca raw materials can be used as sintering aids.
  • Si and Ca may be included in the above composition formula.
  • Step 4 Mold the mixture. You may granulate a mixture with a granulator as needed before shaping
  • the compact density after molding is preferably 2.5 to 4.2 g / cm 3, more preferably 2.5 to 3.5 g / cm 3 .
  • the third raw material is heat-treated at 900 ° C. to 1250 ° C. before molding.
  • the composition of the first calcined powder and the second calcined powder can be made uniform.
  • the homogenized state is close to the state immediately before the crystal grains are grown, and the crystal grains can be grown without significant change in the composition by subsequent firing. Easy to change.
  • Y is segregated out of the crystal grains, thereby obtaining a semiconductor ceramic composition in which the change with time is small.
  • the temperature of the heat treatment is preferably set to a temperature at which the diffraction line peaks of the X-ray diffraction of both compositions are in the same position, that is, a solid solution state by this step.
  • a temperature at which the diffraction line peaks of the X-ray diffraction of both compositions are in the same position that is, a solid solution state by this step.
  • Bi is not sufficiently diffused. If it exceeds 1250 ° C, the melting point of (BiA) TiO 3 system is around 1250 ° C, so Bi will evaporate into the furnace atmosphere, or part of it will sinter and stick to the mortar for heat treatment. There are problems that become difficult and accelerate the deterioration of the mortar.
  • a more preferable heat treatment temperature is 1000 ° C. or higher and 1200 ° C. or lower.
  • the heat treatment time is preferably 0.5 hours or more and 20 hours or less.
  • the time is shorter than 0.5 hours, the solid solution of the (BaR) [TiM] O 3 type calcined powder and the (BiA) TiO 3 type calcined powder is not stable, and the obtained PTC characteristics are not stable.
  • the volatilization of Bi increases and the composition shift tends to occur.
  • the heat treatment time is preferably 1 hour or more and 12 hours or less, more preferably 1.5 hours or more and 6 hours or less.
  • the heat treatment of the third raw material is preferably performed in the atmosphere.
  • Step 5 is as described above, and the description is omitted.
  • the semiconductor ceramic composition of the present invention is obtained by the above production method, and a part of Ba in the BaTiO 3 -based oxide is Bi and A (A is at least one element of an alkali metal and contains Na as an essential component).
  • the crystal grain boundary refers to a boundary surface between two different tetragonal crystal grains (BaTiO 3 -based oxides) 1a and 1b as shown in FIG.
  • the amount of grain boundary Na was measured at the center of the cross section of the boundary surface with a scanning transmission electron microscope (STEM) at a field of view of 100,000 times. Details of the measurement method will be described later.
  • This semiconductor ceramic composition has crystal grains having a composition in which a part of Ba in the BaTiO 3 oxide is substituted with Bi and Na.
  • the composition formula is [(BiA) x (Ba 1-y R y ) 1-x ] [Ti 1-z M z ] O 3
  • A is at least one element of an alkali metal and Na is essential.
  • R is represented by at least one of rare earth elements including Y
  • M is represented by at least one of Nb, Ta, and Sb
  • x, y, and z are 0 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 0.02, Those having crystal grains satisfying 0 ⁇ z ⁇ 0.01 are preferable.
  • the reason for limiting each numerical value is the same as the reason for the composition formula described in the third raw material, and a description thereof will be omitted.
  • a PTC element can be formed by processing the semiconductor ceramic composition of the present invention into a plate shape and providing electrodes on both sides of the plate.
  • the PTC element includes a semiconductor ceramic composition and an electrode formed on the semiconductor ceramic composition.
  • known means can be adopted, but a means for baking after applying the electrode paste is low in cost.
  • the measurement of the amount of Na at the crystal grain boundary, the evaluation method of the temperature coefficient of resistance ⁇ , the room temperature specific resistance R 25 , and the composition analysis of the crystal grains were performed as follows.
  • the temperature coefficient of resistance ⁇ was calculated by measuring the resistance-temperature characteristics while raising the temperature of the semiconductor ceramic composition to 260 ° C.
  • the Curie temperature T C was the temperature at which the resistivity becomes twice the room temperature resistivity R 25.
  • the room temperature resistivity R 25 ( ⁇ cm) of the semiconductor ceramic composition was measured at 25 ° C. by a four-terminal method.
  • composition analysis of crystal grains Using an atomic resolution analytical electron microscope (model number JEM-ARM200F) manufactured by JEOL, the inside of the crystal grains was subjected to elemental analysis by STEM-EDX. The measurement conditions were the same as the measurement of the grain boundary Na amount.
  • a (BiA) TiO 3 -based first material and a (BaR) [TiM] O 3 -based second material were prepared as raw materials (Step 1).
  • raw material powder of Na 2 CO 3 , Bi 2 O 3 , TiO 2 was prepared as the first raw material of (BiA) TiO 3 system, and the molar ratio Bi / Na Bi / Na of 1.05 ( Bi 0.525 Na 0.500 ) TiO 3 was blended and dry mixed.
  • a raw material powder of BaCO 3 , TiO 2 , and La 2 O 3 was prepared as the second raw material of the (BaR) [TiM] O 3 system, blended so as to be (Ba 0.994 La 0.006 ) TiO 3, and pure Mixed with water.
  • the first raw material was calcined at 700 ° C. to 950 ° C. and the second raw material was calcined at 900 ° C. to 1300 ° C. (Step 2).
  • the obtained first raw material was calcined in the air at 800 ° C. for 2 hours to prepare a (BiA) TiO 3 -based calcined powder.
  • the second raw material was calcined in the atmosphere at 1200 ° C.
  • This third raw material was heat-treated at 900 ° C. or higher and 1250 ° C. or lower. Specifically, this raw material was heat-treated at 1150 ° C. for 4 hours in the air.
  • the third raw material treated at this temperature has a diffraction line of (BaR) [TiM] O 3 -based calcined powder and (BiA) TiO 3 -based calcined powder as measured by X-ray diffraction. It was. Thereafter, Ba 6 Ti 17 O 40 , Y 2 O 3 and CaCO 3 were added in this example. Ba 6 Ti 17 O 40 has the effect of stabilizing the firing conditions. Y 2 O 3 has the effect of suppressing changes over time. CaCO 3 has the effect of a sintering aid.
  • the third raw material was 100 mol%, the addition amount of Ba 6 Ti 17 O 40 was 0.6 mol%, the addition amount of Y 2 O 3 was 1 mol%, and the addition amount of CaCO 3 was 2 mol%.
  • Step 4 PVA was added, mixed, and granulated.
  • the obtained granulated powder was molded with a single screw press machine and subjected to binder removal treatment by heating at 700 ° C. for 10 hours.
  • Step 5 After that, it was fired (Step 5).
  • the temperature was lowered under each temperature drop condition shown in Table 1 to obtain a sintered body.
  • the obtained sintered body is processed into a plate of 10 mm x 10 mm x 1.0 mm to produce a test piece, a base metal ohmic electrode is applied, and a cover electrode mainly composed of Ag is further applied at 180 ° C. After drying, the electrode was formed by baking at 600 ° C. for 10 minutes to obtain a PTC element.
  • Table 1 shows the measurement results of the temperature lowering rate from the holding temperature during firing, the temperature for changing the temperature lowering rate, the temperature falling rate after the change, the resistance temperature coefficient ⁇ , the room temperature specific resistance R 25 , and the grain boundary Na amount. Note that the sample number of the comparative example is indicated with *.
  • the measured values of the temperature coefficient of resistance ⁇ , the room temperature specific resistance R 25 , and the amount of grain boundary Na are average values of a plurality of prepared samples. The number of samples was 6 or more.
  • No. 1 is a comparative semiconductor porcelain composition in which the temperature was lowered uniformly at 100 ° C./h without changing the temperature lowering condition from the past, but its resistance temperature coefficient ⁇ was as low as 4.42% / ° C.
  • No. 2 is a comparative semiconductor porcelain composition in which the temperature drop rate was changed at 1100 ° C, but the increase in resistance temperature coefficient ⁇ was slight compared to No. 1, which was as low as 4.44% / ° C, respectively. It was.
  • Nos. 3 and 4 are semiconductor porcelain compositions of the examples in which the temperature drop rate was changed at 1200 ° C. and 1300 ° C.
  • the temperature drop rate was 300 ° C./h, but the temperature coefficient of resistance ⁇ was The number increased significantly compared to No. 1 and increased to 5.31% / ° C and 5.15% / ° C, respectively, exceeding 4.5% / ° C.
  • No. 5 is a semiconductor ceramic composition of an example in which the temperature change rate is 1200 ° C. and the subsequent temperature drop rate is 200 ° C./h. Similar to Nos. 3 and 4, the temperature coefficient of resistance ⁇ increased to 4.93% / ° C, which was 4.5% / ° C or higher.
  • No. 6 is a comparative semiconductor porcelain composition in which the temperature was lowered slower than No. 5 at a rate of temperature decrease of 50 ° C./h. In this case, the temperature coefficient of resistance ⁇ decreased to 4.33% / ° C. and became 4.5% / ° C. or less.
  • composition formula was [(BiA) x (Ba 1-y R y ) 1-x ] [Ti 1-z M z ] O 3 (A is at least one of Na, Li and K and contains Na, R is at least one of rare earth elements including Y, M is at least one of Nb, Ta and Sb), x, y and z satisfied 0 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 0.02, and 0 ⁇ z ⁇ 0.01.
  • FIG. 5 is a diagram schematically showing measurement points when a line analysis of the No. 3 sample in Table 1 having a large resistance temperature coefficient ⁇ is performed by STEM-EDX. Each measurement point is the position of a round point on a line drawn in the center lateral direction. The magnification is 100,000 times.
  • FIG. 6 shows the Na concentration when the line analysis is performed. Na is segregated around the position of the grain boundary (measured value on the horizontal axis 5).
  • FIG. 7 is a diagram schematically showing measurement points when a line analysis is performed on the No. 1 sample of Table 1 having a small resistance temperature coefficient ⁇ by STEM-EDX as in FIG.
  • FIG. 8 shows the Na concentration when the line analysis is performed. Na is not segregated at the grain boundary. From this result, it is considered that the presence of Na at the grain boundary is greatly involved in the increase of the temperature coefficient of resistance ⁇ .
  • FIG. 10 shows the results of measuring the weight loss of the semiconductor porcelain composition at high temperatures.
  • the amount of Na in the semiconductor ceramic composition was not substantially changed before and after the temperature was raised, so the weight loss shown here is considered to be caused by evaporation of Bi, not Na.
  • the volatilization of Bi starts from around 1150 ° C., and the volatilization of Bi becomes remarkable from around 1200 ° C.
  • the cooling rate from the firing temperature above 1350 ° C. to 1150 ° C. is increased to increase the treatment time in that temperature range. Shortened. As a result, a semiconductor ceramic composition having a high resistance temperature coefficient ⁇ could be obtained.
  • FIG. 11 shows the analysis results obtained by examining the amount of Bi and Na in the sample by changing the temperature drop rate between 1150 ° C. and room temperature. The amount of Bi and Na is not affected by changing the temperature drop rate below 1150 °C. From this, it can be seen that it is important not to change the temperature decrease rate below 1150 ° C but to change the temperature decrease rate to an appropriate rate above 1150 ° C.
  • FIG. 12 shows data of a comparative example in which the temperature was lowered from the firing temperature (1440 ° C.) at 300 ° C./h and the temperature lowering rate was not changed as it was (12 samples were fired simultaneously in the same lot).
  • the average value of resistance temperature coefficient ⁇ is as large as 5.92, but the variation (maximum value – minimum value) of resistance temperature coefficient ⁇ exceeded 1.5% / ° C, which proved difficult to apply in mass production.
  • the sample produced by the manufacturing method of this example (sample 3 in Table 1) has a variation in resistance temperature coefficient ⁇ (maximum value ⁇ minimum value) of 1.0% / ° C. or less.
  • the manufacturing method which can improve resistance temperature coefficient (alpha) is provided in the semiconductor ceramic composition which has a composition which substituted a part of Ba with Bi-Na, for example. Moreover, the semiconductor ceramic composition obtained by the manufacturing method, and the PTC element provided with the semiconductor ceramic composition and an electrode are provided.

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Abstract

　L'objectif de la présente invention est de fournir un procédé de fabrication, le coefficient de résistance thermique α pouvant être amélioré dans une composition céramique semi-conductrice présentant une composition dans laquelle une partie de Ba est substituée par Bi-Na par exemple. L'invention concerne un procédé de fabrication d'une composition de céramique semi-conductrice présentant une composition dans laquelle une partie de Ba dans un oxyde à base de BaTiO3 est substituée par Bi et A (A étant au moins un type d'élément de métal alcalin comprenant nécessairement Na), le procédé étant caractérisé en ce qu'il présente un procédé de réduction de température pour une cuisson à une température de plus de 1350°C et il commence ensuite la réduction de température à une vitesse de réduction de la température à 150°C/h ou moins, puis il passe à une vitesse de réduction de la température de plus de 150°C/h dans une plage de température de 1150°C à 1350°C.
PCT/JP2015/075111 2014-09-10 2015-09-03 Procédé de fabrication d'une composition de céramique semi-conductrice, composition de céramique semi-conductrice et élément ctp Ceased WO2016039253A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007097462A1 (fr) * 2006-02-27 2007-08-30 Hitachi Metals, Ltd. Composition de ceramique semiconductrice
WO2008038538A1 (fr) * 2006-09-28 2008-04-03 Murata Manufacturing Co., Ltd. Composition de porcelaine semiconductrice de titanate de baryum et dispositif ptc utilisant celle-ci
JP2009155145A (ja) * 2007-12-26 2009-07-16 Hitachi Metals Ltd 半導体磁器組成物
JP2010030875A (ja) * 2008-06-30 2010-02-12 Hitachi Metals Ltd セラミックス焼結体および圧電素子
WO2013157649A1 (fr) * 2012-04-20 2013-10-24 日立金属株式会社 Composition de céramique semi-conductrice, son procédé de fabrication et un élément à coefficient positif de température (ptc)

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007097462A1 (fr) * 2006-02-27 2007-08-30 Hitachi Metals, Ltd. Composition de ceramique semiconductrice
WO2008038538A1 (fr) * 2006-09-28 2008-04-03 Murata Manufacturing Co., Ltd. Composition de porcelaine semiconductrice de titanate de baryum et dispositif ptc utilisant celle-ci
JP2009155145A (ja) * 2007-12-26 2009-07-16 Hitachi Metals Ltd 半導体磁器組成物
JP2010030875A (ja) * 2008-06-30 2010-02-12 Hitachi Metals Ltd セラミックス焼結体および圧電素子
WO2013157649A1 (fr) * 2012-04-20 2013-10-24 日立金属株式会社 Composition de céramique semi-conductrice, son procédé de fabrication et un élément à coefficient positif de température (ptc)

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