JP3829431B2 - Semiconductor ceramic with positive resistance temperature characteristics - Google Patents
Semiconductor ceramic with positive resistance temperature characteristics Download PDFInfo
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- JP3829431B2 JP3829431B2 JP25530197A JP25530197A JP3829431B2 JP 3829431 B2 JP3829431 B2 JP 3829431B2 JP 25530197 A JP25530197 A JP 25530197A JP 25530197 A JP25530197 A JP 25530197A JP 3829431 B2 JP3829431 B2 JP 3829431B2
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Description
【発明の属する技術分野】
本発明は、正の抵抗温度特性を有する半導体セラミックに関する。
【従来の技術】
従来より、定温発熱ヒータや、カラーテレビの消磁用部品、あるいは過電流保護などに使用される素子には、正の抵抗温度特性（以下、ＰＴＣ特性とする）を有する半導体セラミックが用いられており、特に、抵抗変化温度（以下、キュリー点とする）以上になると急激に高抵抗化するというＰＴＣ特性を有するＢａＴｉＯ3系の半導体セラミックが広く用いられている。
このような用途に使用されるＰＴＣ特性を有する半導体セラミックには、特に、その抵抗値がある特定温度でなるべく急激に上昇することが望まれており、この課題に対応するものとしてＢａＴｉＯ3中にＭｎを添加して抵抗値の上昇率を高めた半導体セラミックなどが実施されていた。
一方、従来のＢａＴｉＯ3中にＭｎを添加した半導体セラミックとは別に、「日本セラミックス協会１９９２年会（題目：Ｂｉ4Ｔｉ3Ｏ12系セラミックスの半導体化及び比抵抗温度特性）」（鄒・岡田・本間、日本セラミックス協会、１９９２）にあるように、抵抗変化比が高いＢｉ−Ｔｉ−Ｏ系の半導体セラミックが提案されている。
【発明が解決しようとする課題】
しかしながら、近年、進歩を続ける電子機器に十分に満足するように、ＰＴＣ特性を有する半導体セラミックに対してＰＴＣ特性のさらなる改善が求められている。
このような状況において、従来のＢｉ−Ｔｉ−Ｏ系の半導体セラミックは、抵抗変化比が高いものの、キュリー点が２７０℃付近と高いため、半導体セラミック素子の電極やケースなどを高い温度にまで耐えられるようにしておく必要があるという問題があった。
本発明は、キュリー点前後の抵抗変化比が従来のＢｉ−Ｔｉ−Ｏ系の半導体セラミックの水準を維持しており、かつ、キュリー点がＢｉ−Ｔｉ−Ｏ系の半導体セラミックのもの（約２７０℃）より低いＰＴＣ特性を有する半導体セラミックを提供することにある。
【課題を解決するための手段】
本発明のＰＴＣ特性を有する半導体セラミックは、比抵抗１ｋΩ・cm以上の材料を主成分とし、前記材料中に、副成分としてＢｉ−Ｓｎ合金を分散させてなり、前記Ｂｉ−Ｓｎ合金中に含まれるＢｉとＳｎとの組成比Ｓｎ／Ｂｉ（原子比）が０．３〜０．８の範囲であることを特徴とする。
このような組成にすることによって、キュリー点前後の抵抗変化比を２０００以上とすることができ、キュリー点を２ 0 ０℃以下と低くし、半導体素子の信頼性を高めることができる。
【発明の実施の形態】
本発明のＰＴＣ特性を有する半導体セラミックの主成分として用いられる材料は、好ましいものとして、Ｔｉ−Ｎｂ−Ｏ系、Ｂａ−Ｔｉ−Ｎｂ−Ｏ系、Ｂｉ−Ｔｉ−Ｎｂ−Ｏ系等が挙げられるが、特にこれらに限定するものではなく、比抵抗が１ｋΩ・cm以上であれば、アルミナやジルコニアなどのセラミックでもよいし、この他ガラスなどの無機材料でもよい。また、エポキシ樹脂やフェノール樹脂等の熱硬化性樹脂、ポリイミドやポリアミド等の熱可塑性樹脂等の有機材料も用いることができる。
また、上記材料中に分散しているＢｉ−Ｓｎ合金の分散状態は、特に数値的に限定するものではないが、できるだけ一様に分散している状態であることが好ましい。また、上記Ｂｉ−Ｓｎ合金の平均粒径は、大きすぎるとＰＴＣ特性が低下し、小さすぎると酸化されて高抵抗化するという理由から、０．１μｍ〜１００μｍであることが好ましい。また、上記Ｂｉ−Ｓｎ合金の添加量は、多すぎるとＰＴＣ特性が低下し、少なすぎると高抵抗化するという理由から、上記材料１００重量部に対して、５０重量部〜１５０重量部であることが好ましい。
次に、本発明を実施例に基づき、さらに詳しく説明するが、本発明はかかる実施例のみに限定されるものではない。
【実施例】
本発明の半導体材料を以下のように作製した。まず、主成分となる材料として、（Ｔｉ1-xＮｂx）Ｏ2（０≦ｘ≦０．００１）を用意した。なお、材料（Ｔｉ1-xＮｂx）Ｏ2は、ｘの値を変動させることによって、比抵抗を変動させることができる。この材料に、副成分として、平均粒径を２０μｍとしたＳｎ−Ｂｉ合金粉末を重量比で１：１の割合となるように調合した後、ＰＳＺボールとともに５時間水中で粉砕混合し、混合粉を得た。
得られた混合粉にバインダーを混合し、１２ｍｍφ×１ｍｍｔに乾式プレス成形して成形体とし、この成形体をＨ2／Ｎ2雰囲気中において１３００℃で還元焼成し、焼結体を得た。
このとき、Ｂｉ−Ｓｎ比の原子比と、（Ｔｉ1-xＮｂx）Ｏ2の単独の比抵抗とを変動させて各試料とし、キュリー点と、キュリー点の前後５０℃での抵抗比である抵抗変化比とを測定し、その結果を表１に示した。なお、表中の※印は本発明の範囲外であることを示す。また、表中の評価欄の○印は良好、△印は実用上差し支えなし、×印は実用上問題有りであることをそれぞれ示す。
【表１】
表１に示すように、比抵抗１ｋΩ・cm以上の材料中にＢｉ−Ｓｎ合金を添加した半導体セラミックは、キュリー点が低く、かつ、抵抗変化比が高いことが確認できる。
ここで、本発明のＰＴＣ特性を有する半導体セラミックにおいて、主成分となる材料の比抵抗を１ｋΩ・cm以上としたのは、試料番号９のように、材料の比抵抗が１ｋΩ・cmより小さい場合には、材料の抵抗変化比Ｒ高温／Ｒ低温が１０００より小さくなり、好ましくないからである。
また、Ｓｎ−Ｂｉ合金のＳｎ、Ｂｉの組成比Ｓｎ／Ｂｉを０．３〜０．８の範囲に限定したのは、試料番号１のように、Ｓｎ／Ｂｉが０．１より小さい場合には、抵抗上昇温度が２００℃を越えてしまい、好ましくないからである。
また、試料番号６のように、Ｓｎ／Ｂｉが０．８より大きい場合には、抵抗変化比Ｒ高温／Ｒ低温が２０００より小さくなり、好ましくないからである。
（実施例２）主成分となる材料としてＡｌ2Ｏ3粉末を用意し、実施例１と同様にして成形体を得た。
そして、得られた成形体をＨ2／Ｎ2雰囲気中において１４００℃で還元焼成し、焼結体を得た。
このとき、Ａｌ2Ｏ3単独の比抵抗を１．２×１０11Ω・cm、Ｂｉ／Ｓｎ＝０．５に固定して実施例１と同じく特性評価を行った。それぞれの値は、キュリー点が１５０℃、抵抗変化比が３２００となり、本発明の課題を解決するにあたり、十分な特性値であることを確認した。
【発明の効果】
本発明の正の抵抗温度特性を有する半導体セラミックは、比抵抗１ｋΩ・cm以上の材料を主成分とし、その材料中に、副成分としてＢｉ−Ｓｎ合金を分散させてなり、前記Ｂｉ−Ｓｎ合金中に含まれるＢｉとＳｎとの組成比Ｓｎ／Ｂｉ（原子比）が０．３〜０．８の範囲にしているので、キュリー点前後の抵抗変化比を２０００以上とすることができ、かつ、キュリー点を２ 0 ０℃以下と低くいＰＴＣ特性を有する半導体セラミックとすることができる。BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor ceramic having positive resistance temperature characteristics.
[Prior art]
Conventionally, semiconductor ceramics having positive resistance temperature characteristics (hereinafter referred to as PTC characteristics) have been used for constant temperature heating heaters, color television demagnetization parts, or elements used for overcurrent protection. In particular, BaTiO 3 -based semiconductor ceramics having a PTC characteristic of rapidly increasing in resistance when the resistance change temperature (hereinafter referred to as Curie point) is reached are widely used.
The semiconductor ceramic having PTC characteristics used in such applications, in particular, has become desirable to increase the resistance value is possible rapidly at a specific temperature, in BaTiO 3 as corresponding to this challenge Semiconductor ceramics and the like in which Mn is added to increase the rate of increase in resistance value have been implemented.
On the other hand, apart from the conventional semiconductor ceramic in which Mn is added to BaTiO 3 , the “Japan Ceramic Society 1992 (Title: Bi 4 Ti 3 O 12 ceramics made into semi-conductor and resistivity temperature characteristics)” (Sakai / Okada -Bi-Ti-O-based semiconductor ceramics having a high resistance change ratio have been proposed as described in Honma, Japan Ceramic Society, 1992).
[Problems to be solved by the invention]
However, in recent years, there has been a demand for further improvement of PTC characteristics for semiconductor ceramics having PTC characteristics so as to be fully satisfied with the progress of electronic devices.
Under such circumstances, the conventional Bi—Ti—O based semiconductor ceramic has a high resistance change ratio, but has a high Curie point of around 270 ° C., so that the electrodes and cases of the semiconductor ceramic element can withstand high temperatures. There was a problem that it was necessary to be able to.
In the present invention, the resistance change ratio before and after the Curie point maintains the level of the conventional Bi-Ti-O based semiconductor ceramic, and the Curie point is of the Bi-Ti-O based semiconductor ceramic (about 270). It is to provide a semiconductor ceramic having a lower PTC characteristic.
[Means for Solving the Problems]
Semiconductor ceramic having PTC characteristics of the present invention is mainly composed resistivity 1 k [Omega · cm or more materials, the material, Ri Na by dispersing Bi-Sn alloy as the minor component, in the Bi-Sn alloy The composition ratio Sn / Bi (atomic ratio) between Bi and Sn contained is in the range of 0.3 to 0.8 .
By using such a composition, the resistance change ratio across the Curie point can be 2000 or more, and the Curie point as low as 2 0 0 ° C. or less, it is possible to enhance the reliability of the semiconductor device.
DETAILED DESCRIPTION OF THE INVENTION
Preferred examples of the material used as the main component of the semiconductor ceramic having PTC characteristics according to the present invention include Ti—Nb—O, Ba—Ti—Nb—O, and Bi—Ti—Nb—O. However, the present invention is not particularly limited thereto, and may be ceramic such as alumina or zirconia or other inorganic material such as glass as long as the specific resistance is 1 kΩ · cm or more. Moreover, organic materials, such as thermosetting resins, such as an epoxy resin and a phenol resin, and thermoplastic resins, such as a polyimide and a polyamide, can also be used.
Further, the dispersion state of the Bi—Sn alloy dispersed in the material is not particularly limited numerically, but is preferably dispersed as uniformly as possible. The average particle diameter of the Bi—Sn alloy is preferably 0.1 μm to 100 μm because the PTC characteristics are lowered if it is too large, and if it is too small, it is oxidized to increase the resistance. Moreover, the addition amount of the Bi-Sn alloy is 50 parts by weight to 150 parts by weight with respect to 100 parts by weight of the material because the PTC characteristic is lowered when the amount is too large and the resistance is increased when the amount is too small. It is preferable.
Next, the present invention will be described in more detail based on examples, but the present invention is not limited to only such examples.
【Example】
The semiconductor material of the present invention was produced as follows. First, (Ti 1−x Nb x ) O 2 (0 ≦ x ≦ 0.001) was prepared as a main component material. The specific resistance of the material (Ti 1-x Nb x ) O 2 can be varied by varying the value of x. To this material, Sn-Bi alloy powder having an average particle size of 20 μm as a minor component was prepared so as to have a weight ratio of 1: 1, and then pulverized and mixed in water together with PSZ balls for 5 hours. Got.
The obtained mixed powder was mixed with a binder, and dry press-molded to 12 mmφ × 1 mmt to obtain a molded body. This molded body was reduced and fired at 1300 ° C. in an H 2 / N 2 atmosphere to obtain a sintered body.
At this time, the atomic ratio of the Bi—Sn ratio and the single specific resistance of (Ti 1-x Nb x ) O 2 were varied to obtain each sample, and the Curie point and the resistance ratio at 50 ° C. before and after the Curie point The resistance change ratio was measured and the results are shown in Table 1. In addition, * mark in a table | surface shows that it is outside the scope of the present invention. Further, in the evaluation column in the table, ○ marks indicate good, Δ marks indicate that there is no practical problem, and × marks indicate that there is a problem in practical use.
[Table 1]
As shown in Table 1, it can be confirmed that a semiconductor ceramic in which a Bi—Sn alloy is added to a material having a specific resistance of 1 kΩ · cm or more has a low Curie point and a high resistance change ratio.
Here, in the semiconductor ceramic having the PTC characteristic of the present invention, the specific resistance of the material as the main component is set to 1 kΩ · cm or more when the specific resistance of the material is smaller than 1 kΩ · cm as in sample number 9. This is because the resistance change ratio R high temperature / R low temperature of the material is less than 1000, which is not preferable.
In addition, the Sn / Bi composition ratio Sn / Bi of the Sn—Bi alloy is limited to the range of 0.3 to 0.8 when the Sn / Bi is smaller than 0.1 as in the sample number 1. This is because the resistance rise temperature exceeds 200 ° C., which is not preferable.
Also, as in sample number 6, when Sn / Bi is larger than 0.8, the resistance change ratio R high temperature / R low temperature becomes smaller than 2000, which is not preferable.
(Example 2) Al 2 O 3 powder was prepared as a main component material, and a molded body was obtained in the same manner as in Example 1.
Then, reduction firing at 1400 ° C. In the resulting molded product H 2 / N 2 atmosphere to obtain a sintered body.
At this time, the characteristic evaluation was performed in the same manner as in Example 1 with the specific resistance of Al 2 O 3 alone fixed at 1.2 × 10 11 Ω · cm and Bi / Sn = 0.5. Each value has a Curie point of 150 ° C. and a resistance change ratio of 3200, and it was confirmed that the characteristic values are sufficient for solving the problems of the present invention.
【The invention's effect】
The semiconductor ceramic having a positive resistance-temperature characteristics of the present invention, a main component resistivity 1 k [Omega · cm or more materials, in the material, Ri Na by dispersing Bi-Sn alloy as the minor component, the Bi-Sn Since the composition ratio Sn / Bi (atomic ratio) between Bi and Sn contained in the alloy is in the range of 0.3 to 0.8, the resistance change ratio before and after the Curie point can be 2000 or more, and it may be a semiconductor ceramic having PTC characteristics have a Curie point as low as 2 0 0 ° C. or less.
Claims (1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25530197A JP3829431B2 (en) | 1997-09-19 | 1997-09-19 | Semiconductor ceramic with positive resistance temperature characteristics |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25530197A JP3829431B2 (en) | 1997-09-19 | 1997-09-19 | Semiconductor ceramic with positive resistance temperature characteristics |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1197210A JPH1197210A (en) | 1999-04-09 |
| JP3829431B2 true JP3829431B2 (en) | 2006-10-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25530197A Expired - Fee Related JP3829431B2 (en) | 1997-09-19 | 1997-09-19 | Semiconductor ceramic with positive resistance temperature characteristics |
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| Country | Link |
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| JP (1) | JP3829431B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2016136321A1 (en) * | 2015-02-25 | 2016-09-01 | 株式会社村田製作所 | Composite material and manufacturing method thereof |
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- 1997-09-19 JP JP25530197A patent/JP3829431B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| JPH1197210A (en) | 1999-04-09 |
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