JP3804365B2 - Semiconductor ceramic and semiconductor ceramic element using the same - Google Patents

Description

【００２８】
【表２】

【００２９】
【表３】

【００３０】
次に、得られた粉末に純水を加えてジルコニアボールとともに２４時間湿式混合し、乾燥後、９００〜１２００℃で２時間仮焼した。この仮焼粉にバインダを加えて、ジルコニアボールとともに混合し、ろ過、乾燥後、円形板状に加圧成形し、１２００〜１６００℃で２時間、大気中で焼成して図１に示すような板状焼結体２を得た。この板状焼結体２の両主面に、白金ペーストを塗布し、１１００〜１４００℃で５時間大気中で焼き付けて外部電極３，４を形成し、板状の半導体セラミック素子１とした。
【００３１】
このようにして得られた負の抵抗温度特性を有する半導体セラミック素子１について、抵抗率とＢ定数の測定を行った。この結果を表１〜表３に示す（試料番号１−１〜試料番号１−３０参照）。比較のために、従来の半導体セラミック素子の測定結果も併せて記載している（表２の従来例１参照）。表１及び表２において、試料番号の右肩部に＊を付したものは突入電流制御用半導体セラミック素子としての特性が得られなかったものである。
【００３２】
抵抗率ρは２５℃で測定した値である。又、Ｂ定数は温度変化による抵抗変化を示す定数であり、温度Ｔ及びＴ₀における抵抗率をそれぞれρ（Ｔ），ρ（Ｔ₀）、自然対数をｌｎとすると、次式のように定義される。
Ｂ定数＝［ｌｎρ（Ｔ₀）−ｌｎρ（Ｔ）］／（１／Ｔ₀−１／Ｔ）
【００３３】
そして、このＢ定数が大きいほど、温度による抵抗変化が大きい。この式をもとに、Ｂ定数のＢ（−１０℃）とＢ（１４０℃）は、それぞれ以下のように定義される。

【００３４】
表１〜表３から明らかなように、主成分のＬａ_xＣｏＯ₃に副成分としてＣｒの酸化物を、元素に換算して、ランタンコバルト系酸化物のコバルト原子に対する比で、０．１〜１０ｍｏｌ％含有させ、かつ、Ｌｉ，Ｎａ，Ｋ，Ｒｂ，Ｃｓ，Ｂｅ，Ｍｇ，Ｃａ，Ｓｒ，Ｂａ，Ｎｉ，Ｃｕ及びＺｎの合計量を、各元素に換算して、ランタンコバルト系酸化物のコバルト原子に対する比で、０．００１〜０．５ｍｏｌ％とすることで、低温でのＢ定数が４０００Ｋ以下で、かつ高温でのＢ定数が従来例１より高い半導体セラミックを得ることができる。前記第１実施形態は、ランタンコバルト系酸化物がＬａ_0.95ＣｏＯ₃の場合である。一般式Ｌａ_xＣｏＯ₃（ただし、０．５００≦ｘ／（１＋ｙ）≦０．９９９）で表される範囲の半導体セラミックにおいても、同様の効果を得ることができる。
【００３５】
なお、従来例１の半導体セラミック素子は、以下のようにして製作した。Ｍｎ₃Ｏ₄，ＮｉＯ，ＣｕＯをそれぞれ重量比で７：２：１の割合で秤量し、純水、バインダ及びジルコニアボールとともにボールミルで５時間湿式混合した後、粉砕、ろ過、乾燥した。その後、前記第１実施形態と同じ形状の円形板状に加圧形成し、１２００℃で２時間大気中で焼成し、焼結体を得た。次に、この焼結体の両主面に銀パラジウム合金ペーストを塗布し、９００〜１１００℃で５時間、大気中で焼き付けて外部電極を形成し、半導体セラミック素子とした。
【００３６】
［第２実施形態］
第２実施形態は、前記第１実施形態と同様に、板状の半導体セラミック素子を例にして説明する。この板状の半導体セラミック素子は、以下のようにして製作される。
【００３７】
コバルトとクロムの合計に対するランタンのモル比率が０．９５となるように、ＣｏＣＯ₃，ＣＯ₃Ｏ₄，ＣｏＯ等のコバルトを含む化合物と、Ｌａ₂Ｏ₃，Ｌａ（ＯＨ）₃等のランタンを含む化合物を秤量した。その後、この秤量粉末に、Ｃｒ₂Ｏ₃又はＣｒＯ₃等のクロムを含む化合物と、次の表４、表５及び表６に示す添加元素を、酸化物等の形で、所定量秤量して添加した。なお、次の表４〜表６中の添加元素の量は、各元素に換算した量である。
【００３８】
【表４】

【００３９】
【表５】

【００４０】
【表６】

【００４１】
次に、得られた粉末に純水を加えてナイロンボールとともに１６時間湿式混合し、乾燥後、９００〜１２００℃で２時間仮焼した。この仮焼粉をジェットミルで粉砕し、酢酸ビニール系バインダを５ｗｔ％と純水を加えて、ナイロンボールとともに混合し、ろ過、乾燥後、円形板状に加圧成形し、１２００〜１６００℃で２時間、大気中で焼成して図１に示すような板状の焼結体２を得た。この焼結体２の両主面に、銀パラジウム合金ペーストを塗布し、９００〜１２００℃で５時間、大気中で焼き付けて外部電極３，４を形成し、板状の半導体セラミック素子１とした。
【００４２】
このようにして得られた負の抵抗温度特性を有する半導体セラミック素子１について、前記第１実施形態と同じ方法で、抵抗率とＢ定数の測定を行った。この結果を表４〜表６に示す（試料番号２−１〜試料番号２−３０参照）。比較のために、従来の半導体セラミック素子の測定結果も併せて記載している（表５の従来例２参照）。表４及び表５において、試料番号の右肩部に＊を付したものはＴＣＸＯ用半導体セラミック素子としての特性が得られなかったものである。
【００４３】
抵抗率ρは２５℃で測定した値である。又、Ｂ定数のＢ（−３０℃）とＢ（１４０℃）は、それぞれ以下のように定義される。

【００４４】
表４〜表６から明らかなように、主成分のＬａ_xＣｏＯ₃に副成分としてＣｒの酸化物を、元素に換算して、ランタンコバルト系酸化物のコバルト原子に対する比で、０．５〜１０ｍｏｌ％含有させ、かつ、Ｌｉ，Ｎａ，Ｋ，Ｒｂ，Ｃｓ，Ｂｅ，Ｍｇ，Ｃａ，Ｓｒ，Ｂａ，Ｎｉ，Ｃｕ及びＺｎの合計量を、各元素に換算して、ランタンコバルト系酸化物のコバルト原子に対する比で、０．００１〜０．５ｍｏｌ％とすることで、従来例２より比誘電率が低く、かつ、Ｂ定数が従来例２より高い半導体セラミックを得ることができる。
【００４５】
なお、従来例２の半導体セラミック素子は、Ｍｎ₃Ｏ₄，ＮｉＯ，ＣｕＯをそれぞれ重量比で７：２：１の割合で秤量する以外は、前記第２実施形態と同様の製造方法で製作した。
【００４６】
［第３実施形態］
第３実施形態は、積層型半導体セラミック素子を例にして説明する。この積層型半導体セラミック素子は、以下のようにして製作される。
【００４７】
コバルトとクロムの合計に対するランタンのモル比率が０．９５となるように、ＣｏＣＯ₃，ＣＯ₃Ｏ₄，ＣｏＯ等のコバルトを含む化合物と、Ｌａ₂Ｏ₃，Ｌａ（ＯＨ）₃等のランタンを含む化合物を秤量した。その後、この秤量粉末に、Ｃｒ₂Ｏ₃又はＣｒＯ₃等のクロムを含む化合物と、表７に示す添加元素（Ｃａ）を、酸化物等の化合物の形で所定量秤量して添加した。なお、表７中の添加元素の量は、各元素に換算した量である。
【００４８】
【表７】

【００４９】
次に、得られた粉末に純水を加えてナイロンボールとともに１６時間湿式混合し、乾燥後、９００〜１２００℃で２時間仮焼した。この仮焼粉をジェットミルで粉砕し、バインダ、分散剤及び水を加えて、ナイロンボールとともに１２時間湿式混合した後、ドクターブレード法によりセラミックグリーンシートに成形した。
【００５０】
次に、このグリーンシート上に、印刷法等の手法により白金ペーストを塗布し、内部電極を形成した。その後、内部電極がグリーンシートを介して対向するようにグリーンシートを積み重ね、さらに保護用グリーンシートを上下に配設して圧着し、グリーンシート積層体とした。
【００５１】
次に、このグリーンシート積層体を一定の寸法に切断し、１２００〜１４００℃で２時間焼成して図２に示す内部電極１２，１３を有した半導体セラミック焼結積層体１１を得た。その後、浸漬法により、焼結積層体１１の両端部に電極ペーストを付着させ、乾燥、焼付けを行って外部電極１４，１５を形成した。こうして、図２に示すような積層型半導体セラミック素子１０を得た。
【００５２】
このようにして得られた負の抵抗温度特性を有する積層型半導体セラミック素子１０をスイッチング電源に直列接続し、室温での破壊コンデンサ容量を測定した。この結果を表７に示す（試料番号３−１参照）。比較のために、従来の半導体セラミック素子の測定結果も併せて記載している（従来例３参照）。表７から明らかなように、第３実施形態の積層型半導体セラミック素子１０は、破壊コンデンサ容量が従来例３より大きくなっており、大電流にも適応できることが分かる。
【００５３】
なお、従来例３の半導体セラミック素子は、以下のようにして製作した。Ｍｎ₃Ｏ₄，ＮｉＯ，ＣｕＯをそれぞれ重量比で７：２：１の割合で秤量し、純水を加えてジルコニアボールとともに５時間湿式混合し、乾燥後、９００℃で２時間仮焼した。この仮焼粉に、バインダ、分散剤及び水を加えて、ジルコニアボールとともに５時間湿式混合した後、ドクターブレード法によりセラミックグリーンシートに成形した。
【００５４】
次に、このグリーンシート上に、印刷法等の手法により白金ペーストを塗布し、内部電極を形成した。その後、内部電極がグリーンシートを介して対向するように、かつ常温での抵抗値が第３実施形態と同じ数値になるように、グリーンシートを積み重ね、さらに保護用グリーンシートを上下に配設して圧着し、グリーンシート積層体とした。この後、前記第３実施形態と同様の製造方法で製作した。
【００５５】
［第４実施形態］
第４実施形態は、前記第３実施形態と同様に、積層型半導体セラミック素子を例にして説明する。この積層型半導体セラミック素子は、以下のようにして製作される。
【００５６】
コバルトとクロムの合計に対するランタンのモル比率が０．９５となるように、ＣｏＣＯ₃，ＣＯ₃Ｏ₄，ＣｏＯ等のコバルトを含む化合物と、Ｌａ₂Ｏ₃，Ｌａ（ＯＨ）₃等のランタンを含む化合物を秤量した。その後、この秤量粉末に、Ｃｒ₂Ｏ₃又はＣｒＯ₃等のクロムを含む化合物と、表８に示す添加元素（Ｎｉ）を、酸化物等の化合物の形で所定量秤量して添加した。なお、表８中の添加元素の量は、各元素に換算した量である。こうして得られた粉末を原料にして、前記第３実施形態と同様の製造方法により、図２に示すような積層型半導体セラミック素子１０を得た。
【００５７】
【表８】

【００５８】
このようにして得られた負の抵抗温度特性を有する積層型半導体セラミック素子１０について、静電容量とＢ定数の測定を行った。この結果を表８に示す（試料番号４−１参照）。比較のために、従来の半導体セラミック素子の測定結果も併せて記載している（従来例４参照）。表８から明らかなように、第４実施形態の積層型半導体セラミック素子１０は、静電容量が従来例４より小さくなっており、温度補償の精度を向上させることができる。なお、従来例４の半導体セラミック素子は、前記従来例３と同様の製造方法により製作した。
【００５９】
［他の実施形態］
なお、本発明に係る半導体セラミック及びそれを用いた半導体セラミック素子は前記実施形態に限定するものではなく、その要旨の範囲内で種々に変更することができる。例えば、前記第１及び第２実施形態では、ランタンコバルト系酸化物がＬａ_xＣｏＯ₃の場合について説明したが、Ｌａの一部をＰｒ、Ｎｄ、Ｓｍ等の他の希土類元素やＢｉ等の元素と置換したランタンコバルト系酸化物の場合についても同様の効果が得られる。
【００６０】
また、半導体セラミック素子は円形板状のものや積層型のものに限定されるものではなく、円筒型素子、角形チップ素子など、他の形状の半導体セラミック素子にも適用することができる。さらに、半導体セラミック素子の外部電極として、銀パラジウム合金や白金を用いたが、銀、パラジウム、クロムもしくはそれらの合金などの電極材料を用いても同様の特性を得ることができる。
【００６１】
【発明の効果】
以上の説明からも明らかなように、本発明によれば、ランタンコバルト系酸化物からなる主成分に、副成分としてＣｒの酸化物と、Ｌｉ，Ｎａ，Ｋ，Ｒｂ，Ｃｓ，Ｂｅ，Ｍｇ，Ｃａ，Ｓｒ，Ｂａ，Ｎｉ，Ｃｕ，及びＺｎのうち少なくとも１種の酸化物を含有させることにより、比誘電率が低く、かつ高温でのＢ定数を４０００Ｋ以上維持しながら、低温でのＢ定数が４０００Ｋ未満の負の抵抗温度特性を有する半導体セラミックを得ることができる。
【００６２】
従って、この半導体セラミックを用いることにより、突入電流が大きい回路や高い電流制御が要求される回路に対応することができる、ＴＣＸＯ回路にあっては高精度の補償に対応できる負の抵抗温度特性を有する半導体セラミック素子を得ることができる。つまり、本発明に係る半導体セラミック素子は、スイッチング電源の突入電流防止用の他に、モータの起動遅延、レーザプリンタのドラム保護、ハロゲンランプの保護などの一般回路や電球など、電圧印加初期に、過大な電流が流れる機器の突入電流防止用の素子として、あるいは、ＴＣＸＯ用の温度補償用素子や一般的な温度補償、温度検知素子として広く使用できる。
【図面の簡単な説明】
【図１】本発明に係る半導体セラミック素子の一実施形態を示す斜視図。
【図２】本発明に係る半導体セラミック素子の別の実施形態を示す断面図。
【符号の説明】
１…半導体セラミック素子
２…焼結体（半導体セラミック）
３，４…外部電極
１０…積層型半導体セラミック素子
１１…積層体
１２，１３…内部電極
１４，１５…外部電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor ceramic having negative resistance temperature characteristics and a semiconductor ceramic element using the same, and in particular, for inrush current control such as a switching power supply or for temperature compensation of an element such as a crystal oscillator and for starting a motor. And a semiconductor ceramic element using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there are semiconductor ceramic elements (hereinafter referred to as NTC elements) having a negative resistance temperature characteristic (hereinafter referred to as negative characteristics) in which the resistance value at normal temperature is high and the resistance value decreases with increasing temperature. The NTC element is used in various applications such as a temperature compensated crystal oscillator, inrush current control, motor start delay, and halogen lamp protection.
[0003]
For example, a temperature compensated crystal oscillator (hereinafter referred to as TCXO) used as a frequency source in an electronic device such as a communication device includes a temperature compensation circuit and a crystal resonator. A device in which the temperature compensation circuit is directly connected to the crystal resonator in the oscillation loop is called a direct type TCXO, and the temperature compensation circuit is indirectly connected to the crystal resonator outside the oscillation loop. Is called indirect TCXO.
[0004]
In the direct type TCXO, at least two NTC elements are used for temperature compensation of the oscillation frequency of the crystal resonator. One NTC element is used for temperature compensation at room temperature (25 ° C.) or lower, and has a low resistance of about 30 to 150Ω at room temperature. The other NTC element is used for temperature compensation at room temperature or higher, and a high resistance element having a resistance value of about 2000 to 3000Ω at room temperature is used.
[0005]
Further, in a switching power supply and a lighting circuit for a halogen lamp, an overcurrent flows at the moment when the switch is turned on. In order to prevent this, an NTC element for inrush current control is used as an element that absorbs the initial inrush current. When the power switch is turned on, the NTC element absorbs the initial inrush current and controls the overcurrent flowing through the circuit. Thereafter, the NTC element rises in temperature due to self-heating to become low resistance, and reduces power consumption in a steady state.
[0006]
Furthermore, in the gear device motor configured to start supplying the lubricating oil after the motor is started, it is preferable that the gear is gradually rotated at a high speed after the current is supplied. Further, even in a lapping machine that grinds the surface of a porcelain by rotating a grindstone, it is preferable to gradually rotate the lapping machine at a high speed after starting the drive motor. An NTC element for delaying motor activation is used as an element for delaying the rotation start time of a gear or a grindstone for a predetermined time when the motor is activated. Since the resistance value of this NTC element is high when the motor is started, the motor terminal voltage becomes low and the start of the motor is delayed. Thereafter, when the temperature of the NTC element rises due to self-heating and becomes low resistance, the motor terminal voltage increases and the motor is started. In steady state, the motor rotates normally.
[0007]
Conventionally, spinel oxides composed of transition metal elements such as manganese, cobalt, nickel and copper have been used for semiconductor ceramics having negative resistance temperature characteristics constituting these NTC elements.
[0008]
[Problems to be solved by the invention]
By the way, in TCXO, in order to temperature-compensate the oscillation frequency with high accuracy, it is preferable that the NTC element has a large resistance value temperature dependency (hereinafter referred to as a B constant). In general, a spinel oxide composed of a transition metal element has a positive correlation between the resistivity at room temperature and the B constant, so that a high B constant can be obtained if the resistivity at room temperature is high. Therefore, the spinel oxide composed of a transition metal element is suitable for an NTC element that requires a high resistance and a high B constant at room temperature, that is, an NTC element used for temperature compensation at room temperature or higher. However, it is not suitable for an NTC element that requires a low resistance and a high B constant at room temperature, that is, an NTC element used for temperature compensation below room temperature. For example, by making the NTC element a laminated structure in which a plurality of internal electrodes are laminated, it is possible to keep the resistance value of the NTC element low even if a high resistivity material is used. However, using a laminated structure increases the capacitance of the NTC element, and eventually it is difficult to obtain satisfactory temperature compensation accuracy.
[0009]
Further, when an NTC element is used for inrush current control, the resistance value must be small in a temperature rising state due to self-heating. However, when a conventional spinel oxide is used, the B constant generally tends to decrease as the resistivity decreases. Therefore, it cannot be said that the resistance value in the temperature rising state is sufficiently small. Therefore, as a method of sufficiently reducing the resistance value at high temperature, for example, when the NTC element is plate-shaped, a method of increasing its area or reducing its thickness is employed. However, increasing the area of the NTC element is contrary to the miniaturization of the element and maintaining the strength, the thickness of the NTC element cannot be extremely reduced. Further, by making the NTC element a laminated structure in which a plurality of internal electrodes are laminated, the resistance value of the NTC element can be kept low even when a material having a high resistivity and a high B constant is used. However, since the distance between the facing internal electrodes is small, the allowable overcurrent is not so large.
[0010]
By the way, the rare earth transition metal element-based oxide has a negative resistance temperature characteristic in which the resistance decreases in a temperature rising state at a high temperature. G. Bhide and D.W. S. It is known from the work of Rajoria et al. The characteristics of the LaCoO ₃ -based NTC element are as follows. H. Wlakov and O.W. O. According to research by Shiwarea, it is generally known that LaCoO ₃ has a lower resistance than GdCoO ₃ .
[0011]
However, this LaCoO ₃ -based NTC element has a low resistivity at room temperature, but has a B constant of less than 2000K. Therefore, since the LaCoO ₃ -based NTC element is used for inrush current control, adjusting its resistance value so that the inrush current can be controlled increases the power consumption in a steady state.
[0012]
In order to solve this problem, as reported in Japanese Patent Application No. 9-208310, the inventors have added a B oxide constant to a main component composed of a lanthanum cobalt-based oxide to thereby obtain a B constant. It has been found that it can be increased to 4000K or more. According to this, by controlling the addition range of the Cr oxide, the low and high temperature B constants can be individually controlled. Therefore, by using different materials mainly composed of lanthanum cobalt-based oxides, it is necessary to increase the high temperature B constant, for inrush current suppression, for motor start-up delay, for halogen lamp protection, and for the low temperature B constant. It can be used for various purposes such as a use for TCXO that needs to be improved.
[0013]
Further, by using a material in which Cr oxide is added to a main component made of a lanthanum cobalt-based oxide as the material of the stacked NTC element, even if the number of internal electrodes is smaller than the conventional one, the same level as the conventional one is obtained. A stacked NTC element having a resistance value is obtained. Therefore, the capacitance of the stacked NTC element can be made smaller than before. Furthermore, since the distance between the internal electrodes can be increased, the allowable overcurrent can be further increased as compared with the conventional case.
[0014]
By the way, when a composition in which a Cr oxide is added to the main component of the lanthanum cobalt-based oxide is used as an NTC element for inrush current control, the B constant at a high temperature can be increased to 4500K. However, the B constant at low temperature also shows a value of 4000K or more.
[0015]
In addition, a composition in which an oxide of Cr is added to the main component made of this lanthanum cobalt-based oxide has a high relative dielectric constant, and therefore has a large capacitance.
[0016]
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor ceramic having a small resistance value in a temperature rising state and having an appropriate resistance value in a low temperature environment, and a semiconductor ceramic element using the same. Another object of the present invention is to provide a semiconductor ceramic suitable for applications in which a small capacitance is desired and a semiconductor ceramic element using the same.
[0017]
[Means and Actions for Solving the Problems]
In order to achieve the above-mentioned object, the semiconductor ceramic according to the present invention is obtained by converting the oxide of Cr as a subcomponent into a main component composed of a lanthanum cobalt-based oxide and converting it into an element to the cobalt atom of the lanthanum cobalt-based oxide. ratio, containing 0.1 to 10 mol%, and, Li, Na, K, Rb , Cs, be, Mg, Ca, Sr, Ba, Ni, at least one oxide of Cu and Zn, each In terms of elements, the lanthanum cobalt-based oxide is contained in a total amount of 0.001 to 0.5 mol% in terms of the ratio to the cobalt atom .
[0018]
With such a composition, a semiconductor ceramic having a low resistivity at room temperature, a high B constant and a low relative dielectric constant can be obtained. Note that when the total amount of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn exceeds 0.5 mol%, the B constant becomes small. The amount is selected in the range of 0.001 to 0.5 mol%.
[0019]
Further, when the lanthanum cobalt-based oxide is represented by the general formula La _x CoO ₃ , x is 0.500 ≦ x / (1 + y) ≦ 0.999 (where y is the content of Cr oxide converted to an element) The range is selected. This is because when x / (1 + y) exceeds 0.999, unreacted lanthanum oxide (La ₂ O ₃ ) in the sintered body reacts with moisture in the atmosphere and expands, so that the semiconductor ceramic collapses. This is because it is not practical. On the other hand, if it is less than 0.500, the resistivity of the semiconductor ceramic increases, but the B constant becomes too small.
[0020]
In the present invention, in addition to La _x CoO ₃ , lanthanum cobalt-based oxides are the same for semiconductor ceramics in which part of La is substituted with other rare earth elements such as Pr, Nd, Sm, and elements such as Bi. An effect can be obtained.
[0021]
The semiconductor ceramic element according to the present invention includes any one of the semiconductor ceramics having the above-described characteristics and an external electrode provided on the surface of the semiconductor ceramic. Alternatively, the semiconductor ceramic having the above-described characteristics and an internal electrode are stacked to form a laminated body, and an external electrode electrically connected to the internal electrode is provided on the surface of the laminated body.
[0022]
The semiconductor ceramic element is suitably used for inrush current control, motor start delay, halogen lamp protection, and temperature compensated crystal oscillator, but can also be used for other temperature compensation circuits and temperature detection circuits. When used for inrush current control, motor start delay, and halogen lamp protection, the resistance value in the temperature rising state is reduced, power consumption is reduced, and a large current can be accommodated. When used for a temperature-compensated crystal oscillator, the capacitance can be reduced to suppress impedance reduction, and high-precision compensation can be handled.
[0023]
Here, the Cr amount in the present invention or the total amount of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn is the ratio of the lanthanum cobalt-based oxide to the cobalt atom. (Cr / Co, etc.)
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a semiconductor ceramic according to the present invention and a semiconductor ceramic element using the same will be described below.
[0025]
[First Embodiment]
In the first embodiment, a plate-shaped semiconductor ceramic element will be described as an example. This plate-like semiconductor ceramic element is manufactured as follows.
[0026]
A compound containing cobalt such as CoCO ₃ , CO ₃ O ₄ , and CoO and a lanthanum such as La ₂ O ₃ and La (OH) ₃ so that the molar ratio of lanthanum to the total of cobalt and chromium is 0.95. The containing compound was weighed. Thereafter, a compound containing chromium such as Cr ₂ O ₃ or CrO ₃ and an additive element (Ni, Li, Na, K, Pb, etc.) shown in the following Tables 1, 2 and 3 are converted into compounds such as oxides. A predetermined amount was weighed and added. In addition, the amount of the additive element in Tables 1 to 3 is an amount converted to each element.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
[Table 3]

[0030]
Next, pure water was added to the obtained powder, wet-mixed with zirconia balls for 24 hours, dried, and calcined at 900 to 1200 ° C. for 2 hours. A binder is added to the calcined powder, mixed with zirconia balls, filtered, dried, pressed into a circular plate shape, fired at 1200 to 1600 ° C. for 2 hours in the atmosphere, and as shown in FIG. A plate-like sintered body 2 was obtained. A platinum paste was applied to both main surfaces of the plate-like sintered body 2 and baked in the atmosphere at 1100 to 1400 ° C. for 5 hours to form external electrodes 3 and 4, thereby obtaining a plate-like semiconductor ceramic element 1.
[0031]
With respect to the semiconductor ceramic element 1 having negative resistance-temperature characteristics obtained as described above, the resistivity and the B constant were measured. The results are shown in Tables 1 to 3 (see sample numbers 1-1 to 1-30). For comparison, the measurement results of a conventional semiconductor ceramic element are also shown (see Conventional Example 1 in Table 2). In Tables 1 and 2, the sample number with an asterisk (*) indicates that the characteristics as a semiconductor ceramic element for inrush current control were not obtained.
[0032]
The resistivity ρ is a value measured at 25 ° C. The B constant is a constant indicating a resistance change due to a temperature change, and is defined as follows when the resistivity at temperatures T and T ₀ is ρ (T), ρ (T ₀ ), and the natural logarithm is ln. Is done.
B constant = [lnρ (T ₀ ) −lnρ (T)] / (1 / T ₀ −1 / T)
[0033]
As the B constant increases, the resistance change due to temperature increases. Based on this equation, the B constants B (−10 ° C.) and B (140 ° C.) are respectively defined as follows.

[0034]
As is apparent from Tables 1 to ₃ , the oxide of Cr as a minor component in La _x CoO _{3 as the} main component is converted into an element in terms of the ratio of the lanthanum cobalt-based oxide to the cobalt atom. 10 mol%, and the total amount of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn is converted into each element, and the lanthanum cobalt oxide By setting the ratio to 0.001 to 0.5 mol% with respect to the cobalt atom, a semiconductor ceramic having a B constant at a low temperature of 4000 K or less and a B constant at a high temperature higher than that of Conventional Example 1 can be obtained. In the first embodiment, the lanthanum cobalt oxide is La _0.95 CoO ₃ . The same effect can be obtained even in a semiconductor ceramic in a range represented by the general formula La _x CoO ₃ (where 0.500 ≦ x / (1 + y) ≦ 0.999).
[0035]
The semiconductor ceramic element of Conventional Example 1 was manufactured as follows. Mn ₃ O ₄ , NiO, and CuO were weighed in a weight ratio of 7: 2: 1, respectively, wet-mixed with pure water, a binder, and zirconia balls for 5 hours in a ball mill, then pulverized, filtered, and dried. Thereafter, it was press-formed into a circular plate having the same shape as in the first embodiment, and fired in the atmosphere at 1200 ° C. for 2 hours to obtain a sintered body. Next, a silver palladium alloy paste was applied to both main surfaces of the sintered body and baked in the atmosphere at 900 to 1100 ° C. for 5 hours to form external electrodes, thereby obtaining semiconductor ceramic elements.
[0036]
[Second Embodiment]
The second embodiment will be described by taking a plate-shaped semiconductor ceramic element as an example, similarly to the first embodiment. This plate-like semiconductor ceramic element is manufactured as follows.
[0037]
A compound containing cobalt such as CoCO ₃ , CO ₃ O ₄ , and CoO and a lanthanum such as La ₂ O ₃ and La (OH) ₃ so that the molar ratio of lanthanum to the total of cobalt and chromium is 0.95. The containing compound was weighed. Thereafter, a predetermined amount of a compound containing chromium such as Cr ₂ O ₃ or CrO ₃ and the additive elements shown in the following Table 4, Table 5 and Table 6 are weighed into this weighed powder in the form of an oxide or the like. Added. In addition, the quantity of the additional element in the following Table 4-Table 6 is the quantity converted into each element.
[0038]
[Table 4]

[0039]
[Table 5]

[0040]
[Table 6]

[0041]
Next, pure water was added to the obtained powder, wet mixed with nylon balls for 16 hours, dried, and calcined at 900 to 1200 ° C. for 2 hours. This calcined powder is pulverized by a jet mill, 5 wt% of vinyl acetate binder and pure water are added, mixed with nylon balls, filtered, dried, and then pressed into a circular plate shape at 1200 to 1600 ° C. The plate-like sintered body 2 as shown in FIG. 1 was obtained by firing in the air for 2 hours. A silver-palladium alloy paste was applied to both main surfaces of the sintered body 2 and baked in the atmosphere at 900 to 1200 ° C. for 5 hours to form the external electrodes 3 and 4. Thus, a plate-shaped semiconductor ceramic element 1 was obtained. .
[0042]
With respect to the semiconductor ceramic element 1 having negative resistance temperature characteristics obtained as described above, the resistivity and B constant were measured by the same method as in the first embodiment. The results are shown in Tables 4 to 6 (see Sample No. 2-1 to Sample No. 2-30). For comparison, the measurement results of a conventional semiconductor ceramic element are also shown (see Conventional Example 2 in Table 5). In Tables 4 and 5, the sample number marked with * on the right shoulder indicates that the characteristics as a semiconductor ceramic element for TCXO were not obtained.
[0043]
The resistivity ρ is a value measured at 25 ° C. The B constants B (−30 ° C.) and B (140 ° C.) are respectively defined as follows.

[0044]
As is apparent from Tables 4 to 6, in the main component La _x CoO ₃ , the oxide of Cr as a subcomponent is converted into an element, and the ratio of the lanthanum cobalt-based oxide to the cobalt atom is 0.5 to 10 mol%, and the total amount of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn is converted into each element, and the lanthanum cobalt oxide By making the ratio to cobalt atoms 0.001 to 0.5 mol%, a semiconductor ceramic having a relative dielectric constant lower than that of Conventional Example 2 and a B constant higher than that of Conventional Example 2 can be obtained.
[0045]
The semiconductor ceramic device of Conventional Example 2 was manufactured by the same manufacturing method as in the second embodiment except that Mn ₃ O ₄ , NiO, and CuO were weighed at a weight ratio of 7: 2: 1. .
[0046]
[Third Embodiment]
In the third embodiment, a multilayer semiconductor ceramic element will be described as an example. This multilayer semiconductor ceramic element is manufactured as follows.
[0047]
A compound containing cobalt such as CoCO ₃ , CO ₃ O ₄ , and CoO and a lanthanum such as La ₂ O ₃ and La (OH) ₃ so that the molar ratio of lanthanum to the total of cobalt and chromium is 0.95. The containing compound was weighed. Thereafter, a compound containing chromium such as Cr ₂ O ₃ or CrO ₃ and an additive element (Ca) shown in Table 7 were weighed in a predetermined amount in the form of a compound such as an oxide and added to the weighed powder. In addition, the quantity of the additional element in Table 7 is the quantity converted into each element.
[0048]
[Table 7]

[0049]
Next, pure water was added to the obtained powder, wet mixed with nylon balls for 16 hours, dried, and calcined at 900 to 1200 ° C. for 2 hours. The calcined powder was pulverized with a jet mill, added with a binder, a dispersant and water, wet-mixed with nylon balls for 12 hours, and then formed into a ceramic green sheet by a doctor blade method.
[0050]
Next, platinum paste was applied onto the green sheet by a printing method or the like to form internal electrodes. Thereafter, the green sheets were stacked such that the internal electrodes were opposed to each other with the green sheets interposed therebetween, and protective green sheets were arranged vertically and pressure-bonded to obtain a green sheet laminate.
[0051]
Next, this green sheet laminate was cut to a certain size and fired at 1200 to 1400 ° C. for 2 hours to obtain a semiconductor ceramic sintered laminate 11 having internal electrodes 12 and 13 shown in FIG. Thereafter, an electrode paste was attached to both ends of the sintered laminate 11 by dipping, followed by drying and baking to form external electrodes 14 and 15. Thus, a multilayer semiconductor ceramic element 10 as shown in FIG. 2 was obtained.
[0052]
The thus obtained multilayer semiconductor ceramic element 10 having negative resistance temperature characteristics was connected in series to a switching power supply, and the breakdown capacitor capacity at room temperature was measured. The results are shown in Table 7 (see sample number 3-1). For comparison, the measurement results of a conventional semiconductor ceramic element are also shown (see Conventional Example 3). As can be seen from Table 7, the laminated semiconductor ceramic element 10 of the third embodiment has a larger breakdown capacitor capacity than that of the conventional example 3, and can be applied to a large current.
[0053]
The semiconductor ceramic element of Conventional Example 3 was manufactured as follows. Mn ₃ O ₄ , NiO, and CuO were weighed in a weight ratio of 7: 2: 1, added with pure water, wet-mixed with zirconia balls for 5 hours, dried, and calcined at 900 ° C. for 2 hours. A binder, a dispersant, and water were added to the calcined powder, and wet mixed with zirconia balls for 5 hours, and then formed into a ceramic green sheet by a doctor blade method.
[0054]
Next, platinum paste was applied onto the green sheet by a printing method or the like to form internal electrodes. Thereafter, the green sheets are stacked so that the internal electrodes face each other through the green sheets, and the resistance value at room temperature is the same as that of the third embodiment, and further, the protective green sheets are arranged vertically. And pressed to form a green sheet laminate. Thereafter, it was manufactured by the same manufacturing method as in the third embodiment.
[0055]
[Fourth Embodiment]
As in the third embodiment, the fourth embodiment will be described by taking a laminated semiconductor ceramic element as an example. This multilayer semiconductor ceramic element is manufactured as follows.
[0056]
A compound containing cobalt such as CoCO ₃ , CO ₃ O ₄ , and CoO and a lanthanum such as La ₂ O ₃ and La (OH) ₃ so that the molar ratio of lanthanum to the total of cobalt and chromium is 0.95. The containing compound was weighed. Thereafter, a compound containing chromium such as Cr ₂ O ₃ or CrO ₃ and an additive element (Ni) shown in Table 8 were weighed in a predetermined amount in the form of a compound such as an oxide and added to the weighed powder. In addition, the quantity of the additional element in Table 8 is the quantity converted into each element. Using the powder thus obtained as a raw material, a multilayer semiconductor ceramic element 10 as shown in FIG. 2 was obtained by the same manufacturing method as in the third embodiment.
[0057]
[Table 8]

[0058]
The multilayer semiconductor ceramic element 10 having negative resistance temperature characteristics obtained in this way was measured for capacitance and B constant. The results are shown in Table 8 (see sample number 4-1). For comparison, the measurement results of a conventional semiconductor ceramic element are also shown (see Conventional Example 4). As is apparent from Table 8, the multilayer semiconductor ceramic element 10 of the fourth embodiment has a smaller capacitance than that of the conventional example 4 and can improve the accuracy of temperature compensation. The semiconductor ceramic element of Conventional Example 4 was manufactured by the same manufacturing method as that of Conventional Example 3.
[0059]
[Other Embodiments]
In addition, the semiconductor ceramic which concerns on this invention, and the semiconductor ceramic element using the same are not limited to the said embodiment, It can change variously within the range of the summary. For example, in the first and second embodiments, the case where the lanthanum cobalt-based oxide is La _x CoO ₃ has been described. However, a part of La is part of other rare earth elements such as Pr, Nd, Sm, and elements such as Bi. The same effect can be obtained in the case of the lanthanum cobalt-based oxide substituted.
[0060]
Further, the semiconductor ceramic element is not limited to a circular plate or laminated type, and can be applied to other shapes of semiconductor ceramic elements such as a cylindrical element and a square chip element. Further, although silver palladium alloy or platinum is used as the external electrode of the semiconductor ceramic element, similar characteristics can be obtained by using an electrode material such as silver, palladium, chromium, or an alloy thereof.
[0061]
【The invention's effect】
As apparent from the above description, according to the present invention, the main component composed of the lanthanum cobalt-based oxide, the oxide of Cr as a subcomponent, and Li, Na, K, Rb, Cs, Be, Mg, By containing at least one oxide of Ca, Sr, Ba, Ni, Cu, and Zn, the B constant at a low temperature is maintained while maintaining a B constant at 4000 K or higher at a low dielectric constant and at a high temperature. A semiconductor ceramic having a negative resistance temperature characteristic of less than 4000K can be obtained.
[0062]
Therefore, by using this semiconductor ceramic, the TCXO circuit can cope with a circuit with a large inrush current and a circuit that requires high current control. A semiconductor ceramic element having the same can be obtained. In other words, the semiconductor ceramic element according to the present invention, in addition to preventing the inrush current of the switching power supply, the start delay of the motor, the drum protection of the laser printer, the general circuit such as the protection of the halogen lamp, the light bulb, etc. It can be widely used as an element for preventing an inrush current of an apparatus through which an excessive current flows, or as a temperature compensating element for TCXO, a general temperature compensating element, or a temperature detecting element.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a semiconductor ceramic element according to the present invention.
FIG. 2 is a cross-sectional view showing another embodiment of a semiconductor ceramic element according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor ceramic element 2 ... Sintered body (semiconductor ceramic)
3, 4 ... External electrode 10 ... Multilayer semiconductor ceramic element 11 ... Laminated body 12, 13 ... Internal electrodes 14, 15 ... External electrode

Claims (9)

In the main component composed of lanthanum cobalt-based oxide, 0.1 to 10 mol% of Cr oxide as a sub-component is converted into element in terms of the ratio of lanthanum cobalt-based oxide to cobalt atoms , and Li , Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn , each element is converted into each element and converted to each cobalt atom of the lanthanum cobalt-based oxide. A semiconductor ceramic characterized by containing 0.001 to 0.5 mol% in total. The content of the sub component Cr oxide is 0.5 to 10 mol% in terms of the element relative to the main component, in terms of elements, in terms of the lanthanum cobalt-based oxide , and Li, Na , K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Cu and Zn, the content of at least one oxide is converted into each element with respect to the main component, and the lanthanum cobalt type 2. The semiconductor ceramic according to claim 1, wherein the ratio of the oxide to cobalt atoms is 0.001 to 0.5 mol% in total. The lanthanum cobalt-based oxide is La _x CoO ₃ (where 0.500 ≦ x / (1 + y) ≦ 0.999, and y is the content of Cr oxide in terms of element). The semiconductor ceramic according to claim 1 or 2.   A semiconductor ceramic element comprising the semiconductor ceramic according to claim 1 and an external electrode provided on a surface of the semiconductor ceramic.   A semiconductor ceramic according to any one of claims 1 and 2 and an external electrode provided on a surface of the semiconductor ceramic, and any one of inrush current control, motor starting, and halogen lamp protection A semiconductor ceramic element characterized by being used as one.   A semiconductor ceramic element comprising the semiconductor ceramic according to claim 2 and an external electrode provided on a surface of the semiconductor ceramic, wherein the semiconductor ceramic element is used for temperature compensated crystal oscillation.   A semiconductor ceramic according to any one of claims 1 to 3 and an internal electrode are stacked to form a laminated body, and an external electrode electrically connected to the internal electrode is provided on the surface of the laminated body. A semiconductor ceramic element characterized by the above.   A semiconductor ceramic according to any one of claims 1 and 2 and an internal electrode are stacked to form a laminated body, and an external electrode electrically connected to the internal electrode is provided on the surface of the laminated body to enter A semiconductor ceramic element used as one of current control, motor start-up and halogen lamp protection.   The semiconductor ceramic according to claim 2 and an internal electrode are stacked to form a laminated body, and an external electrode electrically connected to the internal electrode is provided on the surface of the laminated body to be used for temperature compensated crystal oscillation. A semiconductor ceramic element characterized by the above.

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