JP5267505B2 - Semiconductor porcelain composition - Google Patents

Description

The present invention relates to a semiconductor ceramic composition having a positive resistance temperature, which is used for a PTC thermistor, a PTC heater, a PTC switch, a temperature detector, and the like.

Conventionally, compositions in which various semiconducting elements are substituted for BaTiO ₃ have been proposed as materials exhibiting positive PTCR. Since these compositions have a Curie temperature of around 120 ° C., it is necessary to shift the Curie temperature depending on the application.

For example, it has been proposed to shift the Curie temperature by adding SrTiO ₃ to BaTiO ₃ , but in that case, the Curie temperature is shifted only in the negative direction and not in the positive direction. Only PbTiO ₃ is used as an additive element to shift the Curie temperature in the positive direction. However, since PbTiO ₃ contains an element that causes environmental pollution, a material that does not use PbTiO ₃ has been demanded in recent years.

In BaTiO ₃ semiconductor porcelain, a part of BaTiO ₃ is added to Bi-- for the purpose of preventing decrease in temperature coefficient of resistance due to Pb substitution, reducing voltage dependence, and improving productivity and reliability. In the structure of Ba _1-2x (BiNa) _x TiO ₃ substituted with Na, in the nitrogen composition, one or more of Nb, Ta and rare earth elements is added to the composition in which x is in the range of 0 <x ≦ 0.15 There has been proposed a method of manufacturing a BaTiO ₃ -based semiconductor porcelain that is sintered in a furnace and then heat-treated in an oxidizing atmosphere.

Japanese Unexamined Patent Publication No. 56-169301

Patent Document 1 discloses a composition obtained by adding 0.1 mol% of Nd ₂ O ₃ as a semiconductor element to Ba _1-2x (BiNa) _x TiO ₃ (0 <x ≦ 0.15) as an example. However, the other Nb and Ta addition amounts are not described in the document, and it is not clear how to make them semiconductor.

Therefore, the inventors examined a composition system in which a part of Ba described in Patent Document 1 was substituted with Bi-Na. When performing valence control of the composition, a trivalent cation was used as a semiconducting element. When added, the effect of semiconductorization is reduced due to the presence of monovalent Na ions, and there is a problem that the resistivity at room temperature becomes high.On the other hand, 0.1 mol of Nd ₂ O ₃ is added as a semiconductor element. However, it has been found that sufficient semiconductorization for PTC applications cannot be realized.

This invention solves the above-mentioned problems of the conventional BaTiO ₃ based semiconductor ceramic composition, can shift the Curie temperature in the positive direction without using Pb, and greatly reduces the resistivity at room temperature. An object of the present invention is to provide a semiconductor ceramic composition.

The inventors focused on valence control when a part of Ba is substituted with Bi-Na or the like in the BaTiO ₃ based semiconductor ceramic composition, and the content of additive elements for optimal valence control. As a result of diligent research, while replacing a part of Ba with A1 element (at least one of Na, K, Li) and A2 element (Bi), and further substituting Ba with a specific amount of Q element, an optimal atom It was found that the valence can be controlled and the resistivity at room temperature can be greatly reduced.

Further, the inventors replaced a part of Ba with an A1 element (at least one of Na, K, Li) and an A2 element (Bi), and also replaced a part of Ti with a specific amount of M element. The inventors have found that the same effect as described above can be obtained, and further, in this case, have found that there is an advantage that the valence can be controlled with a smaller amount of substitution than the amount of substitution with the above-mentioned Q element. completed.

That is, in the present invention, the composition formula is [(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O ₃ (where A1 is one or more of Na, K, Li, A2 represents Bi and M represents one or more of Nb, Ta, and Sb), and x and z satisfy 0 <x ≦ 0.2, 0 <z ≦ 0.01, more preferably 0 <z ≦ 0.005. This is a semiconductor porcelain composition.

Furthermore, the present invention is the semiconductor ceramic composition characterized in that Si oxide is added in an amount of 3.0 mol% or less and Ca oxide is added in an amount of 4.0 mol% or less in each of the semiconductor ceramic compositions having the above configuration.
The present invention is also the semiconductor ceramic composition having a Curie temperature of 120 ° C. or higher and a room temperature resistivity of 318 Ωcm or lower in each of the semiconductor ceramic compositions having the above-described configuration.

According to the present invention, in the BaTiO ₃ based semiconductor ceramic composition, the Curie temperature can be increased without using Pb that causes environmental pollution, and the resistivity at room temperature is greatly reduced. Can be provided.

The BaTiO ₃ based semiconductor ceramic composition according to the present invention has a resistivity characteristic that the resistivity is sufficiently low at a room temperature and a range until a predetermined temperature is reached, and the resistivity rapidly increases in a target temperature range. It is most suitable for applications such as thermistors, PTC heaters, PTC switches, temperature detectors, especially automotive heaters.

A feature of the present invention is that the Curie temperature is shifted in the positive direction by substituting a part of Ba with an A1 element (at least one of Na, K, Li, that is, one or more) and an A2 element (Bi). In addition, in order to optimally control the valence disturbed by the substitution of the A1, A2 element, a part of Ba is substituted with a specific amount of Q element (at least one of La, Dy, Eu, Gd), [ (A1 _0.5 A2 _0.5 ) _x (Ba _1-y Q _y ) _1-x ] TiO ₃ composition, or a part of Ti is substituted with a specific amount of M element, and [(A1 _0.5 A2 _0.5 ) _x The composition is Ba _1-x ] [Ti _1-z M _z ] O ₃ .

The reasons for limiting each composition are as follows.
[(A1 _0.5 A2 _0.5 ) _x (Ba _1-y Q _y ) _1-x ] In the TiO ₃ composition, A1 is at least one of Na, K, Li, A2 is Bi, Q is La, Dy, Eu, Gd Is at least one kind. Preferably, A1 is Na and Q is La.

In the above composition formula, x represents a component range of A1 + A2, and 0 <x ≦ 0.2 is a preferable range. If x is 0, the Curie temperature cannot be shifted to the high temperature side, and if it exceeds 0.2, the resistivity at room temperature exceeds 10 ³ Ωcm, which is not preferable.

In the above composition formula, y represents a component range of Q, and 0.002 ≦ y ≦ 0.01 is a preferable range. If y is less than 0.002, the valence control of the composition is insufficient, and the resistivity at room temperature exceeds 10 ³ Ωcm. On the other hand, if y exceeds 0.01, the composition becomes an insulator, and the resistivity at room temperature exceeds 10 ³ Ωcm. Preferably, 0.005 ≦ y ≦ 0.01, and the resistivity at room temperature can be further reduced. The above 0.002 ≦ y ≦ 0.01 is 0.2 mol% to 1.0 mol% in terms of mol%.

[(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O _{3 In the} composition, A1 is at least one of Na, K, Li, A2 is Bi, M is Nb, Ta, Sb. At least one kind. Preferably, A1 is Na and M is Nb.

In the above composition formula, x represents a component range of A1 + A2, and 0 <x ≦ 0.2 is a preferable range. If x is 0, the Curie temperature cannot be shifted to the high temperature side, and if it exceeds 0.2, the resistivity at room temperature exceeds 10 ³ Ωcm, which is not preferable. Z represents the component range of M, and 0 <z ≦ 0.01 is a preferable range. If z is 0, the valence cannot be controlled, the composition does not become a semiconductor, and if it exceeds 0.01, the resistivity at room temperature exceeds 10 ³ Ωcm, which is not preferable. More preferably, 0 <z ≦ 0.005. The above 0 <z ≦ 0.01 is 0 to 1 mol% (not including 0) in terms of mol%.

In the case of the above [(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O ₃ composition, Ti is replaced with M element in order to perform valence control. The addition of elements (preferably addition amount 0 <z ≦ 0.005) is intended to control the valence of the Ti site, which is a tetravalent element, so the above-mentioned [(A1 _0.5 A2 _0.5 ) _x (Ba _1-y Q _y ) _The valence control can be performed with a smaller amount than the amount of addition of the Q element (0.002 ≦ y ≦ 0.01) in the _1-x ] TiO ₃ composition, and the internal strain of the composition according to the present invention can be reduced. .

[(A1 _0.5 A2 _0.5 ) _x (Ba _1-y Q _y ) _1-x ] TiO ₃ composition and [(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O ₃ By adding 3.0 mol% or less of Si oxide and 4.0 mol% or less of Ca oxide in the composition, the sinterability at low temperature can be improved. In any case, adding more than the above-mentioned limited amount is not preferable because the composition does not show semiconducting properties.

An example of a method for producing a semiconductor ceramic composition according to the present invention will be described below.
(1) Prepare oxide powders of each element, weigh them and mix them.
(2) The mixture is further mixed in pure water or ethanol and then dried to obtain a mixed powder.
(3) The mixed powder is calcined at 900 to 1100 ° C. for 2 to 6 hours.
(4) The calcined body is pulverized in pure water or ethanol and then dried.
(5) After the pulverized powder is granulated using PVA or the like, it is molded by a single screw press.
(6) The molded body is subjected to binder removal treatment at 300 ° C. to 700 ° C., and then sintered at 1200 ° C. to 1450 ° C. for 2 to 6 hours in the air or in a reducing atmosphere.

Example 1
BaCO ₃ and TiO ₂ as main raw materials, La ₂ O ₃ , Dy ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₃ , sintered as semiconducting elements SiO ₂ and CaO as auxiliaries, (Na ₂ CO ₃・ Bi ₂ O ₃・ TiO ₂ ), (K ₂ CO ₃・ Bi ₂ O ₃・ TiO ₂ ), (Li ₂ CO ₃・Each powder of Bi ₂ O ₃ · TiO ₂ ) was prepared. Each powder was blended as shown in Tables 1 to 6, mixed in pure water and then dried to obtain a mixed powder having an average particle size of 0.6 to 1.2 μm.

Next, the mixed powder was calcined at 900 to 1100 ° C. for 2 to 6 hours depending on the composition. The calcined powder obtained was pulverized in pure water until the average particle size became 0.8 to 1.5 μm, and then the pulverized powder was dried. Next, PVA was added to the dry powder, mixed, and granulated by a granulator.

The obtained granulated powder was molded to a molding density of 2 to ³ g / cm ³ with a uniaxial press machine. The obtained molded body was debindered at 300 ° C. to 700 ° C. and then sintered at 1300 ° C. to 1360 ° C. for 4 hours in an atmosphere having an oxygen concentration of 75% to obtain a sintered body.

The obtained sintered body was processed into a plate shape of 10 mm × 10 mm × 0.1 mm to obtain a test piece. When the resistance of the obtained test piece was measured, a change in resistance value was measured in a range from room temperature to 200 ° C. The measurement results are shown in Tables 1 to 6.

When No. 1 to 29 in Table 1 is a [(A1 _0.5 Bi _0.5 ) _x Ba _1-x ] [Ti _1-z Nb _z ] O ₃ composition,
When No. 30 to 56 in Table 2 are [(A1 _0.5 Bi _0.5 ) _x Ba _1-x ] [Ti _1-z Sb _z ] O ₃ composition,
When No57 to 86 in Table 3 are [(A1 _0.5 Bi _0.5 ) _x (Ba _1-y La _y ) _1-x ] TiO ₃ composition,
When No. 87 to 102 in Table 4 are [(A1 _0.5 Bi _0.5 ) _x (Ba _1-y Gd _y ) _1-x ] TiO ₃ composition,
When Nos. 103 to 118 in Table 5 are [(A1 _0.5 Bi _0.5 ) _x (Ba _1-y Eu _y ) _1-x ] TiO ₃ composition,
Nos. 119 to 134 in Table 6 show the case of [(A1 _0.5 Bi _0.5 ) _x (Ba _1-y Dy _y ) _1-x ] TiO ₃ composition.

Comparative Example 1
In Tables 1 to 6, those marked with * in the No. column are comparative examples. That is, No. 1 to 4 in Table 1, No. 11, No. 30, No. 31, No. 44 in Table 2, No. 57, No. 58 in Table 3, No. 87, No. in Table 4. 88, No. 103 and No. 104 in Table 5, and No. 119 and No. 120 in Table 5 are comparative examples.

Example 2
BaCO ₃ and TiO ₂ as main raw materials, La ₂ O ₃ and Nb ₂ O ₅ as semiconducting elements, and (Na ₂ CO ₃ · Bi ₂ O ₃ · TiO ₂ ) as Curie temperature shifters were prepared. Each powder was blended as shown in Tables 7 to 8, mixed in pure water and then dried to obtain a mixed powder having an average particle size of 0.6 to 1.2 μm.

Next, the mixed powder was calcined at 900 to 1100 ° C. for 2 to 6 hours depending on the composition. The calcined powder obtained was pulverized in pure water until the average particle size became 0.8 to 1.5 μm, and then the pulverized powder was dried. Next, PVA was added to the dry powder, mixed, and granulated by a granulator.

The obtained granulated powder was molded to a molding density of 2 to ³ g / cm ³ with a uniaxial press machine. The obtained molded body was debindered at 300 ° C. to 700 ° C. and then sintered at 1380 ° C. to 1450 ° C. for 4 hours in an atmosphere having an oxygen concentration of 75% to obtain a sintered body.

The obtained sintered body was processed into a plate shape of 10 mm × 10 mm × 0.1 mm to obtain a test piece. The resistance change of the obtained test piece was measured in the range from room temperature to 200 ° C. by resistance measurement. The measurement results are shown in Tables 7-8.
When No. 135 to 144 in Table 7 is a [(A1 _0.5 Bi _0.5 ) _x Ba _1-x ] [Ti _1-z Nb _z ] O ₃ composition,
Nos. 145 to 154 in Table 8 show the case of [(A1 _0.5 Bi _0.5 ) _x (Ba _1-y La _y ) _1-x ] TiO ₃ composition.

Comparative Example 2
In Tables 7 to 8, those marked with * in the No. column are comparative examples. That is, No. 135 and No. 136 in Table 7 and No. 145 and No. 146 in Table 8 are comparative examples.

As is apparent from Tables 1 to 8, it can be seen that the semiconductor ceramic composition according to the present invention can increase the Curie temperature and significantly reduce the resistivity at room temperature without using Pb.

According to the present invention, the Curie temperature can be raised without using Pb that causes environmental pollution, and the resistivity at room temperature can be greatly reduced, so that the PTC thermistor, PTC heater, PTC switch, temperature Detectors can be used. It is particularly suitable for applications where there is a concern about the influence on the human body, such as an automotive heater.

Claims (4)

The composition formula is [(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O ₃ (where A1 is one or more of Na, K, Li, A2 is Bi, M is Nb, Ta, or Sb), wherein x and z satisfy 0 <x ≦ 0.2 and 0 <z ≦ 0.01. 2. The semiconductor ceramic composition according to claim 1, wherein z satisfies 0 <z ≦ 0.005. 3. The semiconductor ceramic composition according to claim 1, wherein Si oxide is added at 3.0 mol% or less and Ca oxide is added at 4.0 mol% or less. The semiconductor ceramic composition according to any one of claims 1 to 3, which has a Curie temperature of 120 ° C or higher and a room temperature resistivity of 318 Ωcm or lower.