JP2010083737A - Semiconductor porcelain composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor porcelain composition having uniform PTC characteristics in a semiconductor ceramic composition where a part of Ba in BaTiO<SB>3</SB>is substituted by Bi-Na. <P>SOLUTION: Variation of PTC characteristics is minimized by forming a first phase where a part of Ba in BaTiO<SB>3</SB>is substituted by Bi-Na and a second phase comprising oxides of mainly Ba and Ti. The composition with more stable and uniform characteristics can be supplied by further adding SiO<SB>2</SB>and controlling so that Si in the second phase exists at higher concentration than Si in the first phase. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

Conventionally, a composition in which various semiconducting elements are added to BaTiO ₃ has been proposed as a material exhibiting PTCR characteristics (Positive Temperature Coefficient of Resistivity). These compositions have a Curie temperature around 120 ° C. These 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 to BaTiO ₃ , but in this case, the Curie temperature is shifted only in the negative direction and not in the positive direction. Currently, PbTiO ₃ is known as an additive element that shifts the Curie temperature in the positive direction. However, since PbTiO ₃ contains Pb that causes environmental pollution, a material that does not use PbTiO ₃ has been demanded in recent years.

In BaTiO ₃ -based semiconductor ceramics, BaB of BaTiO ₃ that does not use PbTiO ₃ is used for the purpose of preventing a decrease in resistance temperature coefficient due to Pb substitution, reducing voltage dependency, and improving productivity and reliability. In the structure of Ba _1-2x (BiNa) _x TiO _{3 in} which a part of Bi is substituted with Bi-Na, a composition in which x is in the range of 0 <x ≦ 0.15 is selected from any one of Nb, Ta, and rare earth elements Alternatively, a BaTiO ₃ -based semiconductor ceramic manufacturing method in which one or more elements are added and sintered in nitrogen and then heat-treated in an oxidizing atmosphere has been proposed (Patent Document 1).

Patent Document 1 discloses, as an example, a composition in which 0.1 mol% of Nd ₂ O ₃ is added as a semiconducting element. However, when the valence of the composition is controlled, a trivalent cation is disclosed. Is added as a semiconducting element, the semiconducting effect is reduced due to the presence of monovalent Na ions. Therefore, there exists a problem that room temperature specific resistance becomes high.

A major feature of the PTC material is that the specific resistance value of the PTC material rapidly increases at the Curie point Tc (unit: ° C.) (jump characteristic = resistance temperature coefficient α), which is formed at the grain boundary. It is believed that this occurs because of increased resistance (resistance due to the Schottky barrier). Tc is defined as the temperature at which the specific resistance value is twice the specific resistance value at 25 ° C. Further, the temperature coefficient of resistance α is defined by the following equation. As a characteristic of the PTC material, one having a high jump characteristic of this specific resistance value is required.
(Here, the unit of α is Ω · cm, R ₁ is the maximum specific resistance, T ₁ is the temperature indicating R ₁ , Tc is the Curie point, and R _c is the specific resistance at T _c )

  A PTC material that does not contain Pb as in Patent Document 1 has a high room temperature specific resistance when it has excellent jump characteristics, and a low room temperature specific resistance when it has poor jump characteristics. There was a problem that it was not possible to achieve both resistance and excellent jump characteristics. In addition, the inferior jump characteristic has a problem that, when an electric current is passed through the material, the temperature variation near the Curie point increases and the stable temperature tends to be higher than the Curie point.

  In order to suppress fluctuations in the stable temperature and to facilitate material design, it is necessary to improve jump characteristics. For this purpose, it is conceivable to slightly increase the room temperature resistivity, but maintaining high jump characteristics and room temperature resistivity It is very difficult to achieve both suppression of the increase in the temperature, and it is usual that the room temperature specific resistance increases too much and exceeds the practical range.

In Patent Document 1, as an example, all elements constituting the composition such as BaCO ₃ , TiO ₂ , Bi ₂ O ₃ , Na ₂ O ₃ , and PbO as starting materials are mixed before calcination. , Calcining, molding, sintering, and heat treatment are disclosed, but in a composition in which a part of BaTiO ₃ is replaced with Bi-Na, all elements constituting the composition are subjected to pre-calcination. When mixed, in the calcination step, Bi is volatilized and a composition shift occurs in Bi-Na, thereby promoting the generation of a heterogeneous phase, resulting in an increase in room temperature resistivity and a Curie temperature variation.

  In order to suppress the volatilization of Bi, calcining at a low temperature may be considered, but although the volatilization of Bi is suppressed, a complete solid solution cannot be formed and desired characteristics cannot be obtained. There's a problem.

In order to solve the problems of the above-described conventional BaTiO ₃ -based semiconductor ceramics, the inventors can shift the Curie temperature in the positive direction without using Pb, and greatly increase the room temperature resistivity. [(A1 _0.5 A2 _0.5 ) _x (Ba _1-y Q _y ) _1-x ] TiO ₃ (A1 is a material obtained by substituting a part of BaTiO ₃ with Bi—Na. At least one selected from Na, Ka, Li, A2 is Bi, Q is at least one selected from La, Dy, Eu, Gd), 0 <x ≦ 0.2, 0.002 <y Semiconductor porcelain composition satisfying ≦ 0.01, and [(A1 _0.5 A2 _0.5 ) _x Ba _1-x ] [Ti _1-z M _z ] O ₃ (A1 is one of Na, Ka, and Li) At least one selected from (A2 is Bi, M is at least one selected from Nb, Ta, and Sb) A semiconductor ceramic composition that satisfies 0 <x ≦ 0.2 and 0 <z ≦ 0.01 is proposed (Patent Document 2) .

Furthermore, the inventors prepared a (BaQ) TiO ₃ composition and a (BiNa) TiO ₃ composition separately when manufacturing the semiconductor ceramic composition according to Patent Document 2, and the (BaQ) TiO ₃ composition was compared. (BiNa) TiO ₃ composition is relatively low temperature and calcined at the optimum temperature corresponding to each, thereby suppressing the volatilization of Bi in (BiNa) TiO ₃ composition, and the composition of Bi-Na A semiconductor porcelain composition having low room temperature resistivity and curie temperature variation can be prevented by preventing misalignment and suppressing the formation of heterogeneous phases, mixing, calcining, molding, and sintering. It was proposed that it be obtained (Patent Document 3).

Furthermore, when manufacturing the (BaQ) TiO3 composition of the calcined powder in Patent Document 3, the inventors calcined the raw materials TiO ₂ and BaCO _{3 so as} to remain slightly (Patent Document 4), or calcined. Semiconductor porcelain composition in which TiO ₂ and BaCO ₃ as raw materials are slightly added to (BaQ) TiO ₃ composition that is powder (Patent Document 5), room temperature resistivity is further reduced, and Curie temperature variation is suppressed Proposed to get things.
JP-A-56-169301 JP 2005-255493 A WO2006 / 118274A1 publication WO2008 / 050876A1 WO2008 / 050877A1 Publication

  The above-mentioned semiconductor ceramic composition proposed by the inventors has a low room temperature resistivity and excellent jump characteristics as compared with conventional materials, but it is suitable for various applications such as PTC thermistors, PTC heaters, and PTC switches. In order to provide it, it is necessary to stably obtain the same PTCR characteristics.

  Since sintering conditions greatly affect the PTCR characteristics of the above-mentioned semiconductor ceramic composition, it is necessary to suppress variations in temperature and atmosphere existing in the sintering furnace in order to stably obtain jump characteristics. But this is not easy to achieve.

The present invention relates to a semiconductor ceramic composition in which a part of Ba in BaTiO ₃ is replaced with Bi-Na, and a jumping characteristic is ensured to some extent and a semiconductor ceramic composition having a required room temperature resistivity is stably obtained. Objective.

  The present invention provides a heating element system in which an ohmic electrode is provided on the semiconductor ceramic composition to form a heating element, which is assembled into a heating module, and a fluid is heated by a simple power supply method. For the purpose.

In order to achieve the above object, the inventors of the present invention, as a result of earnest research, combined the above-mentioned Patent Documents 3 and 4, 5 previously proposed by the inventors, that is, a (BaQ) TiO ₃ composition or Ba ( TiM) O ₃ composition (hereinafter referred to as “BT calcined powder”) and (BiNa) TiO ₃ composition (hereinafter referred to as “BNT” calcined powder) are prepared separately, and BT calcined powder and BNT calcined powder are prepared. We paid attention to the method of calcining the powder at the optimum temperature according to each (hereinafter referred to as “division calcining method”) and the addition of Si to the raw material of the BT calcined powder.

Then, in preparing the BT calcined powder in the divided calcining method, after adjusting so that BaCO ₃ and TiO ₂ partially remain in the BT calcined powder, the BT calcined powder and the BNT calcined powder are mixed. By sintering, a first phase in which part of Ba in BaTiO ₃ is replaced with Bi and Na, and a second phase containing Ba, Ti, and Na and containing Si at a higher concentration than the first phase. It was found to be generated.

  Knowing that the variation in PTCR characteristics can be reduced by controlling the amount of second phase generated as described above, and that the variation in PTCR characteristics can be further reduced by controlling the Si concentration in this second phase. The present invention has been completed.

  The first invention of the present application is characterized in that the first phase is an oxide mainly composed of Ba, Ti, Bi and Na, and the second phase is an oxide mainly composed of Ba and Ti. It is.

In the semiconductor ceramic composition of the present invention, a part of Ba constituting the first phase is replaced with La, and the composition formula of the first phase is represented by [(BiNa) _x (Ba _1-y La _y ) _1-x ]. It is expressed as TiO _3, and the molar ratio x and y is preferably a composition satisfying 0 <x ≦ 0.3 and 0 <y ≦ 0.02.

  In the semiconductor ceramic composition of the present invention, it is preferable that 1 ≦ a ≦ 15 [%] when the area ratio of the second phase to the total area on an arbitrary polished surface is represented by a.

  In the semiconductor ceramic composition of the present invention, at least the second phase of the first phase and the second phase contains Si, the concentration of Si contained in the first phase is b [wt%], and is contained in the second phase. When the concentration of Si is expressed as c [wt%], it is preferable that b <c.

  In the semiconductor ceramic composition of the present invention, the concentration c of Si contained in the second phase is preferably 0 <c ≦ 7 [wt%].

  According to a second aspect of the present invention, there is provided a heating element characterized in that an ohmic electrode is provided separately in at least two locations of the semiconductor ceramic composition of the first aspect of the present invention.

  A third invention of the present application is a heat generating module characterized in that the heating element of the second invention of the present application is sandwiched between metal electrodes and a current is passed through the metal electrode.

  The fourth invention of the present application is a fluid heating mechanism system using the heat generating module of the third invention of the present application, and the power supply circuit does not have a function of controlling supply power by means of adjusting voltage and phase. It is the heating mechanism system characterized by this.

According to the present invention, the jump characteristic α which is an evaluation index of the PTCR characteristic is 2 [% / ° C.] or more, the room temperature specific resistance ρ25 is less than 10 ⁴ Ω · cm, and the Curie temperature Tc is 130 ° C. or more. The semiconductor ceramic composition can be provided while reducing the variation Δρ in room temperature resistivity.

  In order to achieve the above-described effect, the semiconductor ceramic composition is interspersed with a second phase which is an oxide composed of Ba, Ti, and Na. This second phase stabilizes the grain boundary structure related to the mechanism of the development of PTCR characteristics, thereby reducing the variation in room temperature resistivity. Furthermore, by adding Si and controlling the Si concentration in the first phase and the second phase, the grain boundary structure can be further stabilized and the variation in the room temperature resistivity can be reduced.

  Further, according to the present invention, a temperature detection means such as a thermometer required for a normal electric heater, a comparison circuit with a set temperature, a supply power adjustment circuit, a thermal runaway and a safety in preparation for a fire accompanying it It becomes possible to omit the overheat detection mechanism, the power supply cutoff mechanism, and the like, and to realize a small and inexpensive heating mechanism system. Even when a conventional heating element using a semiconductor ceramic composition containing Pb is incorporated, it is possible to omit temperature detection means such as a thermometer, a comparison circuit with a set temperature, and a supply power adjustment circuit. However, since the semiconductor ceramic composition containing Pb has a characteristic that the resistance value decreases in a temperature range higher than about 200 ° C., an overheat detection mechanism and a power supply shut-off mechanism for safety in preparation for thermal runaway or fire accompanying it, etc. It may be necessary to provide. The heating mechanism system according to the present invention, which can also be omitted, has safety even though it is the simplest.

As the first phase of the semiconductor ceramic composition according to the present invention, any composition may be adopted as long as it contains a composition in which a part of BaTiO ₃ is replaced with Bi—Na, but the composition formula is [(BiNa) A composition represented by _x (Ba _1-y La _y ) _1-x ] TiO ₃ and satisfying 0 <x ≦ 0.3 and 0 <y ≦ 0.02 is preferable.

In the [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO ₃ composition, x represents the component range of (BiNa), and 0 <x ≦ 0.3 is a preferred range. If x is 0, the Curie temperature cannot be shifted to the high temperature side, and if it exceeds 0.3, the specific resistance at room temperature approaches 10 ⁴ Ωcm, which makes it difficult to apply to a PTC heater or the like.

In the [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO ₃ composition, y represents a component range of La, and 0 <y ≦ 0.02 is a preferred range. If y is 0, the composition does not become a semiconductor, and if it exceeds 0.02, the resistivity at room temperature increases, such being undesirable. The valence is controlled by changing the value of y. In a system in which a part of Ba is replaced with Bi-Na, when the valence of the composition is controlled, a trivalent cation is made into a semiconductor. When added as an element, there is a problem that the effect of semiconductorization is lowered due to the presence of monovalent Na ions and volatilization of Bi, and the resistivity at room temperature is increased. Therefore, a more preferable range is 0.002 ≦ y ≦ 0.02. Note that 0.002 ≦ y ≦ 0.02 is 0.2 mol% to 2.0 mol% in terms of mol%. Incidentally, in the above-mentioned Patent Document 1, 0.1 mol% of Nd ₂ O ₃ is added as a semiconductor element. However, it is considered that sufficient semiconductorization for PTC use cannot be realized.

In the above-described _{[(BiNa) x (Ba 1} -y La y) 1-x] TiO 3, the ratio of Bi and Na is 1: 1 to the basic. In the composition formula, it can be expressed as [(Bi _0.5 Na _0.5 ) _x (Ba _1-y R _y ) _1-x ] TiO ₃ . The reason why “the ratio of Bi and Na is based on 1: 1” is clearly described in the above because Bi is volatilized in the calcination process and the ratio of Bi and Na may not be 1: 1. . Accordingly, the ratio of Bi and Na is 1: 1 at the time of blending the raw materials, but the case where the ratio is not 1: 1 in the sintered body is also included in the present invention.

  The present invention is characterized in that in the semiconductor ceramic composition having the above configuration, the area ratio of the second phase to the total area on an arbitrary polished surface is 1 ≦ a ≦ 15 [%] when represented by a. And

  The above-mentioned second phase is scattered in the sintered body, and it is desirable that 1 ≦ a ≦ 15% when the area ratio other than the entire area of the cross section of the sintered body is represented by a. If it exceeds 15%, the room temperature resistivity cannot be obtained stably stably, and it is difficult to apply it to a PTC heater or the like. On the other hand, if it is less than 1%, it is difficult to stably obtain a temperature coefficient of resistance of 2.0 [% / K] or more while keeping the room temperature specific resistance low.

  In the semiconductor ceramic composition having the above-described configuration, b <c [wt%] when the concentration of Si contained in the first phase is represented by b and the concentration of Si contained in the second phase is represented by c. Featuring a semiconductor porcelain composition.

In the second phase, BNT having a melting point of about 1200 ° C. becomes a liquid phase during sintering, and Ti and Na remain by volatilization of Bi, and these and unreacted BaCO ₃ and TiO contained in the BT calcined powder It is generated when ₂ reacts. Therefore, the second phase in the semiconductor porcelain composition of the present invention is characterized in that in the EDX composition analysis, the Bi concentration is a very small amount of less than 0.1 wt%, and Ti is contained in a higher composition ratio than Ba. .

  The second phase has an effect of collecting Si contained in the semiconductor ceramic composition before sintering into the second phase itself during sintering. This is thought to be because BNT, which became liquid during sintering, volatilizes and stabilizes Bi while taking up Si. Since the second phase is uniformly scattered in the semiconductor ceramic composition having the first phase as the main phase, an appropriate concentration of Si, which can more stably obtain the PTCR characteristics, is obtained. It can be contained in two phases.

  The concentration of Si contained in the first phase and the second phase is higher in the second phase than in the first phase due to the property of incorporating Si during the sintering process of the second phase. Therefore, when the concentration of Si contained in the first phase is represented by b and the concentration of Si contained in the second phase is represented by c, b <c [wt%]. When the raw material composition, calcination conditions, a series of steps up to mixing and pulverization are ideally controlled, the Si content in the first phase may be below the detection limit.

  The present invention provides a semiconductor ceramic composition having the above-described structure, wherein the concentration c of Si contained in the second phase is 0 <c ≦ 7 [wt%], more preferably 0 <c ≦ 5 [wt%]. Characterized composition.

When the Si concentration c contained in the second phase is 0 [% wt], the room temperature specific resistance cannot be obtained stably stably, and it becomes difficult to provide a PTC heater with uniform characteristics, which is not preferable. Further, when 7 [% wt] <c, the room temperature specific resistance is 10 ⁴ Ω · cm or more, which is not preferable because it is difficult to apply to a PTC heater or the like.

  The present invention is characterized in that the heating element is provided with an ohmic electrode separated into at least two or more of the semiconductor ceramic composition having the above-described configuration. When only two electrodes are provided, it can be used as a heat source with a constant output. When three or more electrodes are provided, the heat source can be substantially changed by changing the combination of electrodes through which current flows. It becomes possible to switch the rated power.

When an Ag electrode or an Au electrode is provided in the semiconductor ceramic composition of the present invention, resistance is generated at the semiconductor-metal interface, and the combined resistivity exceeds 10 ⁴ Ω · cm. This is thought to be because the semiconductor-metal interface is in Schottky connection, and the interface resistance can be almost eliminated by using an Ag-Zn electrode that forms an ohmic connection. Accordingly, it is possible to provide a heating element having a PTC characteristic with a low room temperature specific resistance.

  In order to efficiently transmit the generated heat to the fluid and heat the fluid, it is most desirable to sandwich the heating element with a metal electrode that supplies electric power and diffuse the heat to the metal electrode. By increasing the area of the metal electrode, heat can be efficiently transferred to a fluid such as gas or liquid.

  In a heating mechanism system incorporating a heating element using the semiconductor ceramic composition of the present invention, a temperature detection means such as a thermometer, a comparison circuit with a set temperature, a supply power adjustment circuit, a thermal runaway, a fire, etc. Therefore, an overheat detection mechanism and a power supply cutoff mechanism associated therewith can be omitted, and a simple on / off switch may be inserted and directly connected to an AC or DC power source.

First, in the present invention, Si is added (Ba _1-x La _x ) TiO ₃ (0 <x ≦ 0...) In the production of a semiconductor ceramic composition in which a part of BaTiO ₃ is replaced with Bi—Na. 02) and BNT calcined powder made of (Bi _0.5 Na _0.5 ) TiO ₃ calcined powder are prepared separately, and the BT calcined powder and BNT calcined powder are respectively prepared. A split calcining method is used in which calcining is performed at an appropriate temperature.

  By using the above-mentioned divided calcination method, it is possible to prevent the composition shift of Bi-Na due to the volatilization of Bi of the BNT calcined powder in the calcination process and to suppress the generation of a different phase in the calcination process. A semiconductor ceramic composition having uniform PTCR characteristics can be obtained by mixing BT calcined powder and BNT calcined powder, molding and sintering.

In order to obtain the semiconductor porcelain composition according to the present invention using the above-described divided calcination method, the following three methods can be employed. (1) When preparing BT calcined powder in the divided calcining method, a method of preparing BaCO ₃ and TiO ₂ to partially remain in the BT calcined powder (hereinafter referred to as “residual method”), (2 ) A method of adding BaCO ₃ and / or TiO ₂ to the BT calcined powder and / or BNT calcined powder produced by the divided calcining method (hereinafter referred to as “addition method”), (3) When the BT calcined powder and the BNT calcined powder prepared in this manner are sintered, the BT and BNT are sintered without completely solid solution (hereinafter referred to as “incomplete sintering method”). This will be described in order below.

(1) Residual method In the divided calcining method, when preparing the BT calcined powder, BaCO ₃ , TiO ₂ and La ₂ O ₃ which is a raw material powder of a semiconducting element, and SiO ₂ for stabilizing the characteristics are used. Mixed raw material powder is prepared by mixing. In the residual method, this mixed raw material powder is calcined at 900 ° C. or less, and (Ba _1-x La _x ) TiO ₃ is not completely formed, and some BaCO ₃ and TiO ₂ remain in the calcined powder. Is.

By mixing the BT calcined powder in which BaCO ₃ and TiO ₂ are partially left by the residual method and the separately prepared BNT calcined powder, the mixed calcined powder is molded and sintered, whereby the BaTiO ₃ according to the present invention is formed. A semiconductor ceramic composition having a first phase in which a part of Ba is substituted with Bi-Na and a second phase that is an oxide composed of Ba, Ti, and Na can be obtained.

In order to change the remaining amount of BaCO ₃ and TiO _{2 in} the BT calcined powder, in the step of preparing the BT calcined powder, the calcining temperature is changed at 900 ° C. or less, the calcining time is changed, Alternatively, the residual amount of BaCO ₃ and TiO _{2 in} the BT calcined powder can be changed by changing the blending composition of the BT calcined powder, thereby controlling the amount of the second phase generated.

In the above-mentioned residual method, when the calcining temperature exceeds 900 ° C., (Ba _1-x La _x ) TiO ₃ is excessively formed, and BaCO ₃ and TiO ₂ cannot be left, which is not preferable. The calcining time is preferably 0.5 hours to 10 hours, and more preferably 2 to 6 hours.

The residual amounts of BaCO ₃ and TiO ₂ in the BT calcined powder are (Ba _1-x La _x ) TiO ₃ , BaCO ₃ and TiO ₂ being 100 mol% in total, and BaCO ₃ is 30 mol% or less, TiO _2. Is preferably 30 mol% or less.

The reason why the residual amount of BaCO ₃ is set to 30 mol% or less is that when it exceeds 30 mol%, the second phase is excessively generated and the room temperature resistivity is increased. Further, CO ₂ gas is generated in the sintering process, and cracks are generated in the sintered body, which is not preferable. The reason why the residual amount of TiO ₂ is set to 30 mol% or less is that when it exceeds 30 mol%, the second phase is excessively generated and the variation in the room temperature specific resistance becomes large.

The upper limit of the remaining amount of BaCO ₃ and TiO ₂ is 60 mol% in total of 30 mol% of BaCO _{3 and} 30 mol% of TiO ₂ , and the lower limit exceeds 0, but when BaCO ₃ exceeds 20 mol%, TiO ₂ is less than 10 mol% This is not preferable because the second phase is excessively generated and the variation in the room temperature resistivity increases. Similarly, when TiO ₂ exceeds 20 mol% and BaCO ₃ is less than 10 mol%, it is also not preferable. Therefore, when one of BaCO ₃ or TiO ₂ exceeds 20 mol%, it is preferable to adjust the calcining temperature, temperature, blending composition, etc. so that the other is 10 mol% or more.

The step of preparing BNT calcined powder composed of (Bi _0.5 Na _0.5 ) TiO ₃ calcined powder mixed with BT calcined powder in which part of BaCO ₃ and TiO ₂ remain is the raw material powder. A mixed raw material powder is prepared by mixing Na ₂ CO ₃ , Bi ₂ O ₃ , and TiO ₂ . At this time, if Bi ₂ O ₃ is added excessively (for example, exceeding 5 mol%), a heterogeneous phase is generated during calcination, and the room temperature specific resistance becomes high, which is not preferable.

Next, the mixed raw material powder is calcined. The calcining temperature is preferably in the range of 700 ° C to 950 ° C. The calcining time is preferably 0.5 hours to 10 hours, more preferably 2 hours to 6 hours. If the calcining temperature is less than 700 ° C. or the calcining time is less than 0.5 hour, unreacted Na ₂ CO ₃ or decomposed NaO reacts with the water in the atmosphere or in the case of wet mixing, resulting in a composition shift And undesirably variations in characteristics occur. On the other hand, if the calcining temperature exceeds 950 ° C. or the calcining time exceeds 10 hours, the volatilization of Bi proceeds, the composition shifts, and the generation of heterogeneous phases is promoted.

In the step of preparing each calcined powder described above, pulverization may be performed according to the particle size of the raw material powder when the raw material powder is mixed. The mixing and pulverization may be either wet mixing / pulverization using pure water or ethanol, or dry mixing / pulverization. However, it is preferable to perform dry mixing / pulverization because the compositional deviation can be further prevented. In the above description, BaCO ₃ , Na ₂ CO ₃ , TiO _{2 and the} like are exemplified as the raw material powder, but other Ba compounds and Na compounds may be used.

As described above, BT calcined powder and BNT calcined powder in which part of BaCO ₃ and TiO ₂ remain are prepared separately, and each calcined powder is blended in a ratio described later, and then mixed. Mixing may be either wet mixing using pure water or ethanol, or dry mixing. However, it is preferable to perform dry mixing because the compositional deviation can be further prevented. Further, depending on the particle size of the calcined powder, pulverization after mixing, or mixing and pulverization may be performed simultaneously. The average particle size of the mixed calcined powder after mixing and pulverization is preferably 0.5 μm to 2.5 μm.

The mixing ratio of BT calcined powder and BNT calcined powder must be adjusted according to the operating temperature of the element. In order to control the Tc at 120 to 180 ° C. and provide a PTCR element having a low room temperature specific resistance, the composition of the semiconductor ceramic composition was expressed as [(BiNa) _x (BaLa) _1-x ] TiO ₃ . It is sometimes preferable to mix so that 0 <X ≦ 0.3.

The mixed calcined powder obtained by the process of mixing the BT calcined powder and the BNT calcined powder is molded by a desired molding means. If necessary, the mixed calcined powder may be granulated by a granulator before molding. The molded body density after molding is preferably 2.5 to 3.5 g / cm ³ .

  Sintering can be performed in the air, in a reducing atmosphere, or in an inert gas atmosphere having a low oxygen concentration. In particular, sintering is preferably performed in a nitrogen or argon atmosphere having an oxygen concentration of less than 1%. The sintering temperature is preferably 1250 ° C to 1360 ° C. The sintering time is preferably 1 hour to 8 hours, and more preferably 4 hours to 6 hours. Any of them is not preferable because the room temperature resistivity increases or the jump characteristic decreases as it deviates from preferable conditions.

  As another sintering process, in an atmosphere having a temperature of 1290 ° C. to 1360 ° C. and an oxygen concentration of less than 1%, (1) it is executed with a sintering time of less than 4 hours, or (2) Formula: ΔT ≧ 25t (t = Sintering time (hr), ΔT = cooling rate after sintering (° C / hr)), and then cooling after sintering is performed at a cooling rate satisfying the above formula. As a result, it is possible to obtain a semiconductor ceramic composition having an improved resistance temperature coefficient in a high temperature region (Curie temperature or higher) while keeping the room temperature resistivity low.

(2) Addition method In the addition method, in order to prepare BT calcined powder, BaCO ₃ , TiO ₂ and La ₂ O ₃ which is a raw material powder of a semiconducting element are mixed to prepare a mixed raw material powder, and calcined To do. The calcining temperature is preferably 1000 ° C. or higher. A calcining temperature of less than 1000 ° C. is not preferable because a complete single phase of (Ba _1-x La _x ) TiO ₃ is not formed. If a complete single phase is not formed, unreacted BaCO ₃ and TiO ₂ remain, and since it is assumed that BaCO ₃ powder and / or TiO ₂ powder is added, it is difficult to predict the amount of addition. However, some BaCO ₃ or TiO ₂ remains acceptable. A preferable calcination temperature is 1000 ° C to 1300 ° C. The calcining time is preferably 0.5 hours to 10 hours, and more preferably 2 to 6 hours.

  In the addition method, the step of preparing the BNT calcined powder, the step of mixing (pulverizing) the BT calcined powder and the BNT calcined powder, and the like are the same as the residual method described above.

The addition method is characterized by adding SiO ₂ , BaCO ₃ and / or TiO ₂ to the BT calcined powder, BNT calcined powder or mixed calcined powder prepared as described above. By forming and sintering the mixed calcined powder after addition, a part of BaTiO ₃ according to the present invention is substituted with Bi—Na, and a semiconductor ceramic composition having a second phase can be obtained.

The amount of BaCO ₃ and / or TiO ₂ added is such that the total amount of (Ba _1-x La _x ) TiO ₃ and SiO ₂ , BaCO ₃ and / or TiO ₂ is 100 mol%, and BaCO ₃ is 30 mol% or less. it is preferred TiO ₂ is not more than 30 mol%. By changing the amount of addition, the area ratio of the second phase can be controlled. In particular, according to the addition method, since the addition amount can be adjusted accurately, the jump characteristic can be controlled with extremely high accuracy.

The reason why the amount of BaCO ₃ added is 30 mol% or less is that when it exceeds 30 mol%, the second phase is excessively generated and the variation in the room temperature resistivity increases. Further, CO ₂ gas is generated in the sintering process, and cracks are generated in the sintered body, which is not preferable. The reason why the amount of TiO ₂ added is set to 30 mol% or less is that when it exceeds 30 mol%, the second phase is excessively generated and the variation in the room temperature resistivity increases.

When both BaCO ₃ and TiO ₂ are contained, the upper limit of the addition amount is 30 mol% BaCO _{3 and} 30 mol% TiO ₂ , and the lower limit exceeds 0%. However, when BaCO ₃ exceeds 20 mol%, TiO 2 _{This is because when 2} is less than 10 mol%, the second phase is excessively generated and the variation in the room temperature specific resistance becomes large. The case where TiO ₂ exceeds 20% mol and BaCO ₃ is less than 10 mol% is also not preferable. Therefore, when one of BaCO ₃ or TiO ₂ exceeds 20% mol, the other is preferably made 10 mol% or more.

In the addition method, when SiO ₂ addition is not performed after preparation of a complete single-phase BT calcined powder, BaCO ₃ , TiO ₂ , La ₂ O at the time of initial raw material mixing, as in the case of the residual method described above. ₃ and SiO ₂ for stabilizing the properties need to be added. The addition amount of SiO ₂ is preferably more than 0 mol% and less than 3 mol%. This is because the variation in room temperature resistivity increases outside this range. In particular, when 3 mol% or more is added, the room temperature resistivity becomes 10 ⁴ Ω · cm or more, which is not preferable.

As described above, it is preferable that a complete single phase with (Ba _1-x La _x ) TiO ₃ is formed as the BT calcined powder, but a complete single phase is formed. Replacing a part of the BT calcined powder with BT calcined powder in which BaCO ₃ and TiO ₂ remain by the above-mentioned residual method, and further adding a predetermined amount of SiO ₂ , BaCO ₃ and / or TiO ₂ Thus, the addition amount can be changed.

In the addition method, as described above, after preparing the BT calcined powder and the BNT calcined powder separately, the BT calcined powder or the BNT calcined powder or a mixed calcined powder thereof is mixed with SiO ₂ , BaCO ₃ and / or TiO ₂ is added. Next, each calcined powder is mixed in a predetermined amount and then mixed. Mixing may be either wet mixing using pure water or ethanol, or dry mixing. However, it is preferable to perform dry mixing because the compositional deviation can be further prevented. Further, depending on the particle size of the calcined powder, pulverization after mixing, or mixing and pulverization may be performed simultaneously. The average particle size of the mixed calcined powder after mixing and pulverization is preferably 0.5 μm to 2.5 μm.

  The steps such as molding and sintering after the step of mixing the BT calcined powder and the BNT calcined powder are the same as the above-described residual method.

(3) Incomplete sintering method In the incomplete sintering method, a step of preparing BT calcined powder, a step of preparing BNT calcined powder, a step of mixing (pulverizing) BT calcined powder and BNT calcined powder, For the molding step, any of the above-described residual method and addition method can be employed.

In the incomplete sintering method, when the mixed calcined powder of BT calcined powder and BNT calcined powder is sintered, the BT calcined powder and BNT calcined powder may be sintered without completely dissolving them. It is a feature. Thereby, a part of Ba of BaTiO ₃ according to the present invention is substituted with Bi—Na, and a semiconductor ceramic composition having a second phase can be obtained.

  Although the sintering temperature and sintering time in the incomplete sintering method vary depending on the calcining temperature of the BT calcined powder, for example, when the calcining temperature of the BT calcined powder is 700 ° C. to 1200 ° C., the sintering temperature is 1250 ° C to 1380 ° C and the sintering time is preferably 2.5 hours or less. However, the preferable sintering time when the sintering temperature is relatively low (for example, 1300 ° C.) may be 3.5 hours or less, and preferable sintering when the sintering temperature is relatively high (for example, 1380 ° C.). The time will be 2 hours or less. If the sintering temperature is high (for example, 1400 ° C. or higher), or if the sintering time is long (for example, 5 hours or longer), the BT calcined powder and BNT calcined powder are completely Since it dissolves, it is not preferable.

  As described above, by controlling the sintering temperature and sintering time, the solid solubility of the BT calcined powder and the BNT calcined powder can be changed, thereby controlling the area ratio of the second phase. Can do.

When an Ag electrode or Au electrode is used as an electrode applied to the semiconductor ceramic composition, resistance is generated at the semiconductor-metal interface, and the combined specific resistance exceeds 10 ⁴ Ω · cm. This is thought to be because the semiconductor-metal interface is in Schottky connection, and the interface resistance can be almost eliminated by using an alloy electrode of Ag and Zn that forms an ohmic connection. Accordingly, it is possible to provide a heating element having a PTC characteristic with a low resistivity at room temperature.

  The metal electrode efficiently transmits the generated heat to the fluid to heat the fluid and at the same time has a role of supplying electric power. Therefore, it is desirable to use a metal or alloy mainly composed of aluminum or copper. In order to make the electrical connection good and uniform, it is often effective to insert a flexible spacer between the metal electrode and the heating element using the semiconductor porcelain composition of the present invention. is there. Examples of such a spacer material include a graphite sheet and a conductive resin sheet in which metal particles are dispersed. In some cases, it is also effective to use a conductive adhesive.

  In a heating mechanism system incorporating a heating element using the semiconductor ceramic composition of the present invention, a temperature detection means such as a thermometer, a comparison circuit with a set temperature, a supply power adjustment circuit, a thermal runaway, a fire, etc. Therefore, an overheat detection mechanism and a power supply cutoff mechanism associated therewith can be omitted, and a simple on / off switch may be inserted and directly connected to an AC or DC power source. However, in order to prevent overloading of the operation power supply detection circuit connected to the display device so that the operating state of the heating mechanism system can be easily understood for the operator, the temperature display circuit, the battery and the generator, etc. The current detection circuit may be provided as appropriate.

[Example 1]
Raw material powders of BaCO ₃ , TiO ₂ , and La ₂ O ₃ were prepared, blended so as to be (Ba _0.994 La _0.006 ) TiO _3, and mixed with pure water. The obtained mixed raw material powder was calcined in the atmosphere at 900 ° C. for 4 hours to prepare BT calcined powder. The calcination at this temperature becomes the aforementioned residual method.

_{Na 2 CO 3, Bi 2 O} 3, to prepare a raw material powder of TiO _2, was blended so as to _{(Bi 0.5 Na 0.5) TiO 3} , were dry mixed. The obtained mixed raw material powder was calcined in the air at 800 ° C. for 2 hours to prepare BNT calcined powder.

Mix the prepared BT calcined powder and BNT calcined powder in the molar ratio shown in Table 1 and mix them with a pot mill using pure water as a medium until the central particle size of the mixed calcined powder becomes 1.0 μm to 2.0 μm. After being pulverized, it was dried. After adding and mixing PVA to the pulverized powder of the mixed calcined powder, it was granulated by a granulator. The obtained granulated powder was molded at 8 MPa with a uniaxial press, and the molded body was debindered at 700 ° C. and then sintered at 1340 ° C. for 4 hours in a nitrogen atmosphere to obtain a sintered body. . As the atmosphere during sintering, nitrogen whose oxygen concentration was controlled to be less than 1% was constantly introduced to form a nitrogen atmosphere. The rate of temperature increase / decrease was 200 ° C. In Table 1, the numbers in parentheses of the BNT addition amount and the La addition amount are x and y when the first phase is expressed as [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO _3. Is the value of

The obtained sintered body is processed into a plate shape of 10 mm × 10 mm × 1 mm to produce a test piece, and after forming an ohmic electrode, each test piece is subjected to a specific resistance in a range from room temperature to 270 ° C. with a resistance measuring instrument. The temperature change of the value was measured, and the room temperature specific resistance, the Curie temperature, and the resistance temperature coefficient were obtained. Further, the distribution of the room temperature resistivity was obtained from 50 samples prepared under the same conditions, and the difference between the maximum value and the minimum value was obtained as the resistivity variation Δρ. The results are shown in Table 1. In Table 1, those marked with * next to the sample number are comparative examples. In the examples, the temperature coefficient of resistance α was obtained by the following equation. α = (lnR ₁ −lnR _c ) × 100 / (T ₁ −T _c ) R ₁ is the maximum specific resistance, R _c is the specific resistance at T _c , T ₁ is the temperature indicating R ₁ , and T _c is the Curie temperature is there.

  FIG. 1 shows an example of an SEM observation image of the sintered body of sample number 1-5. The observation field is a surface obtained by polishing the cross section of the sintered body with diamond abrasive grains having an average particle diameter of 1 μm. The black contrast scattered in the image is the second phase. A white contrast smaller than the second phase scattered in the image means that the holes appear brighter due to the edge effect. The second phase appears as a black contrast because the composition of the second phase contains almost no Bi and the amount of secondary electrons generated in the second phase is less than that of the first phase in which BNT is dissolved in BT. is there. This shows that the second phase is easily distinguishable from the first phase.

  Moreover, the image processing of the observation image obtained with the scanning electron microscope (SEM) in the plane of the obtained sintered body is performed, the number of dots corresponding to the second phase is counted, and the number of dots per dot is counted. The area was divided by the total area of the image-processed portion to obtain the area ratio a (%) of the second phase. The results are shown in Table 1.

As is clear from Table 1, the Curie temperature and the area ratio of the second phase can be increased by increasing the ratio of the BNT addition amount. Further, when the addition amount of BNT is 0 mol% (Sample 1-1), a high Curie temperature and a second phase cannot be obtained. On the other hand, if the amount of BNT is more than 30 mol% (Sample 1-9), the room temperature resistivity becomes about 10 ⁴ Ω · cm and Δρ becomes 200, which is not preferable. Therefore, by controlling the amount of BNT to be 0 <x ≦ 0.3 and a to be 0 <a ≦ 15 [%], a low specific resistance product can be stably produced.

[Example 2]
The addition amount of BNT calcined powder and the addition amount of La are the values shown in Table 2, and the BT calcining temperature, sintering temperature, and sintering time are the room temperature specific resistance of the sintered body obtained in the same manner as in Example 1. Variations in Curie temperature, resistance temperature coefficient, and room temperature resistivity were obtained. The results are shown in Table 2. In Table 2, those marked with * next to the sample number are comparative examples. In Table 2, the numbers in parentheses for the BNT addition amount and the La addition amount are x and y when the first phase is expressed as [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO _3. Is the value of

From Table 2, it can be seen that the room temperature resistivity can be decreased by increasing the amount of La added. However, it is not preferable that the amount added exceeds 3 mol% (Sample 2-6) because the room temperature specific resistance exceeds 10 ⁴ Ω · cm. An addition amount of 0 mol% (Sample 2-1) is not preferable because α is 2 or less. Therefore, the amount of La added is preferably larger than 0 and 2 mol% or less (Samples 2-2 to 2-5).

[Example 3]
Raw material powders of BaCO ₃ , TiO ₂ , and La ₂ O ₃ are prepared, blended so as to be (Ba _0.994 La _0.006 ) TiO _3, and further added to (Ba _0.994 La _0.006 ) TiO ₃ . On the other hand, SiO ₂ powder was added to the amount shown in Table 3 and mixed with pure water. The obtained mixed raw material powder was calcined in the atmosphere at the temperature shown in Table 3 for 4 hours to prepare BT calcined powder.

BNT calcined powder was prepared in the same manner as in Example 1, mixed, molded, sintered and processed so that BNT was 8 mol%, and test pieces were prepared, and PTCR characteristics were evaluated. Table 3 shows variations in room temperature specific resistance, Curie temperature, resistance temperature coefficient, and room temperature specific resistance of the obtained sintered body. In Table 3, an asterisk (*) beside the sample number is a comparative example. In Table 3, the numbers in parentheses of the BNT addition amount and the La addition amount are x and y when the first phase is expressed as [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO _3. Is the value of

From Table 3, the variation Δρ in room temperature resistivity ρ25 can be reduced to 10 Ω · cm or less by setting the SiO ₂ addition amount to 0.97% mol or more and 3.77 mol% or less (Samples 3 to 3-5). You can see that However, an addition amount of 3.77 mol% is not preferable because the room temperature resistivity exceeds 10 ⁴ Ω · cm.

Si concentration b [wt%] in the first phase and Si concentration c [wt%] in the second phase when the SiO ₂ addition amount is 0.97 mol% or more and 3.77 mol% or less (Samples 3 to 3-5). Note that b <c. As described above, this is presumably because Si was collected by the liquid phase-solid phase reaction during the second phase sintering. Further, when paying attention to the value of c, good characteristics can be stably obtained by controlling so that 0 <c ≦ 5 wt%.

When the calcining temperature is 950 ° C. and the SiO ₂ addition amount is 8.41 mol% (Sample 3-6), ρ25 exceeds 10 ⁴ Ω · cm, which is not preferable. At this time, b> c, and since the calcining temperature was increased, the remaining amount of BaCO ₃ and TiO ₂ decreased, the amount of second phase formed decreased, and the collection of Si during sintering was insufficient. It is thought. Therefore, it is desirable that c <b.

  Table 4 shows the results of the composition analysis of the first phase and the second phase of the sintered body of sample number 1-5. It can be seen that the second phase does not contain Bi. For composition analysis, a scanning electron microscope S-2300 (manufactured by Hitachi, Ltd.) was used. Point analysis is performed at an acceleration voltage of 20 kV (X-ray generation region is about 1 μm in diameter from the center of the beam), and composition analysis is performed using an energy dispersive (EDX) semiconductor X-ray detector, Ba, Ti, Bi, Na, Si and O were analyzed elements. However, when the above-mentioned element peak was not clearly seen in the X-ray spectrum, it was excluded from the analysis.

  Since the surface of the sintered semiconductor ceramic composition was rough, it was processed using a surface grinder or a slicer. It is also effective to perform burr and chamfering by barrel polishing as appropriate. The processing was performed also for the purpose of adjusting the dimensions to keep the dimensional accuracy at a predetermined value when the semiconductor ceramic composition was attached to a circuit board as a small element or incorporated in a heating mechanism system.

  Next, the processed semiconductor ceramic composition is mounted on a tray, and electrodes are formed by screen printing. It is desirable to devise a mechanism such as a spring mechanism for aligning the semiconductor ceramic composition in one direction on the tray so that the semiconductor ceramic composition mounted on the tray is correctly aligned and fixed at a predetermined position. First, silver fine particles and zinc fine particles are mixed, and a paste adjusted with an organic binder, a dispersant and an organic solvent is printed and dried to form an ohmic electrode at a desired position. It is often effective to mix a small amount of glass, oxide, or the like in order to enhance the adhesion to the semiconductor ceramic composition. Zinc sometimes contains cadmium having similar chemical properties as a trace impurity, but from the viewpoint of environmental pollution, it is desirable that the cadmium content of harmful substances is small. On the surface of the ohmic electrode, a paste prepared by using silver fine particles as a main component and adjusting with an organic binder, a dispersant and an organic solvent is printed and dried to form a surface electrode. A small amount of glass, oxide, or the like can also be mixed with the surface electrode to obtain an effect of improving adhesion and denseness.

  After forming a two-layer electrode in this way, the electrode is sintered in a sintering furnace. Depending on the combination of the material of the semiconductor porcelain composition, the material of the ohmic electrode, and the material of the surface electrode, it may be desirable to separate the electrode sintering into two times. In other words, after the ohmic electrode is once sintered, the surface electrode is printed and the second sintering is performed. Thereby, the mutual diffusion of the ohmic electrode and the surface electrode is suppressed, and the respective characteristics can be sufficiently exhibited. Furthermore, depending on the material of the semiconductor porcelain composition, the material of the ohmic electrode, and the material of the surface electrode, the atmosphere during sintering may be adjusted in order to exhibit its characteristics. In particular, the electrode adhesion strength can be adjusted by adjusting the oxygen concentration. In some cases, electrical characteristics can be improved. In order to adjust the oxygen concentration, it is easiest to change the ratio by mixing air and nitrogen gas. The thickness after sintering of the ohmic electrode and the surface electrode formed by the printing and sintering methods is usually easily controlled to about 5 to 20 μm. These electrodes can be formed not only by printing and sintering, but also by thin film methods such as vacuum deposition, ion plating, sputtering, and plating. Since electrodes may adhere to undesired parts when forming by the thin film method, processing using a surface grinder or slicer is performed after electrode formation, and the electrodes attached to undesired parts are removed. It is reasonable to process it so that it also doubles.

  When a semiconductor porcelain composition is used as a heating element, the structure and arrangement of the electrodes are basically such that two electrodes are paired at a position separated via the semiconductor porcelain composition. However, sometimes it is also effective as an applied design to be provided separately in three or more places. FIG. 2 shows an example in which the heating element 10 is formed by providing the semiconductor ceramic composition 1 of the present invention with strip electrodes having a width w (2 mm) at three positions with a distance d (10 mm). In this example, the distance between the electrode 1a and the electrode 1b was 10 mm, and the DC resistance at that time was 20Ω. The distance between the electrode 1a and the electrode 1c was 22 mm, and the DC resistance at room temperature was 40Ω. Since either direct current or alternating current may be applied between the electrode 1a and the electrode 1b, a current of 2.6A and power consumption of 52W were measured when a voltage of 20V was applied and left for 3 minutes or longer and the self-heating was stabilized. On the other hand, when a voltage of 20 V was similarly applied between the electrode 1a and the electrode 1c, the current in the stable state was reduced to 1.3 A and the power consumption was reduced to 26 W. Furthermore, when the central electrode 1b was used as a common electrode and the same voltage (voltage having the same phase and the same amplitude in the case of alternating current) 20V was applied to the electrodes 1a and 1c, the current was 5.2A and the power consumption was 104W. . In any of the above cases, the temperature in the stable state was almost constant according to the Curie temperature of the material, irrespective of the electric power. As described above, if the electrodes are provided separately in two or more places, or three places in the example of FIG. 2, the power consumption can be changed in several stages by appropriately selecting the electrodes to which the voltage is applied. It can be selected with a simple external switch or the like according to the load condition of the user and the degree of necessity of heating desired.

  In the semiconductor ceramic composition of the present invention, a heating element 11 having electrodes 2a, 2b, and 2c provided with electrodes having a structure and arrangement different from those of the above example in three locations was manufactured. This will be described with reference to FIG. The size of the sintered ceramic porcelain composition 2 is 10 mm × 23 mm and the thickness is 0.7 mm. The electrode 2a and the electrode 2c were each formed to be a square having a side (W) of 10 mm and to be aligned on the same plane with a gap D (3 mm). The electrode 2b was formed over almost the entire surface opposite to the electrode 2a and the electrode 2c with a flat-plate semiconductor ceramic composition interposed therebetween.

  The heating element was fixed so as to be sandwiched between metal heat radiation fins that also served as electrodes. The structure of the radiation fin at this time will be described with reference to FIG. The electrode 2a formed on one surface of the heating element 11 is in thermal and electrical contact with the power supply electrode 20a, and the electrode 2c is in thermal and electrical contact with the power supply electrode 20c and formed on the other surface. The formed electrode 2b is assembled to be in thermal and electrical contact with the power supply electrode 20b to form the heat generating module 20. The power supply electrodes 20a, 20b, and 20c are thermally connected to the radiation fins 20a1, 20b1, and 20c1, respectively. Heat generated in the heating element 11 is transmitted in the order of the electrodes 2a, 2b, 2c, the power supply electrodes 20a, 20b, 20c, and the radiation fins 20a1, 20b1, 20c1, and is mainly released from the radiation fins 20a1, 20b1, 20c1 into the atmosphere. The An insulator 20d provided between the power supply electrodes 20a and 20c achieves electrical insulation between them. When the power supply is connected between the power supply electrode 20a and the power supply electrode 20b, or between the power supply electrode 20c and the power supply electrode 20b, the power consumption is reduced, and both the power supply electrode 20a and the power supply electrode 20c are connected. When connected between the power supply electrodes 20b, the power consumption becomes large, and the power consumption can be changed in two stages. In this way, the heat generating module is capable of switching the heating capacity in accordance with the load condition of the power supply device and the degree of necessity of heating desired.

  An example in which a heating mechanism system is manufactured by connecting the heating module capable of switching the heating capacity to a power source will be described with reference to FIG. The power supply to be prepared may be either DC / AC. The power supply electrode 20a and the power supply electrode 20c of the heat generating module 20 are connected in parallel to one electrode of the power supply 30c via separate switches 30a and 30b, respectively, and the power supply electrode 20b is connected to the other electrode of the power supply 30c as a common terminal. The heating mechanism system 30 is connected. If either one of the switches 30a and 30b is turned on, the heating capacity can be reduced to reduce the load of the power source, and if both are turned on, the heating capacity can be increased. Since a circuit for adjusting the phase and amplitude of the power supply is not required, a heating mechanism system capable of easily switching the heating capacity can be realized. Since the temperature in the stable state converges uniformly at the Curie temperature of the semiconductor porcelain composition, a temperature detection mechanism, a comparison mechanism with the target temperature, a heating power adjustment circuit, etc. are unnecessary, so a heating mechanism system can be realized very easily. Can do. It is possible to provide a heating mechanism system that is suitable and safe for warming a liquid by flowing air between fins shown in FIG. 5 or connecting a tubular metal through which a liquid such as water passes.

  The semiconductor ceramic composition obtained by the present invention is most suitable as a material for PTC thermistors, PTC heaters, PTC switches, temperature detectors and the like.

It is a photograph which shows the observation image by the scanning electron microscope (SEM) of the semiconductor ceramic composition by this invention. It is an example of the element when a large number of electrodes are provided as an application of the method of using the semiconductor ceramic composition according to the present invention, particularly when a total of three places are provided on one side. It is an example of the element when a large number of electrodes are provided as an application of the method of using the semiconductor ceramic composition according to the present invention, particularly when a total of three locations are provided on both sides. The schematic diagram of the heat generating module of the form which provided the electrode in the semiconductor ceramic composition by this invention, and was inserted | pinched and fixed to the metal radiation fin which served as the electrode. The schematic diagram of the heating mechanism system which connected the power supply to the heat generating module of FIG.

Explanation of symbols

1, 2 Semiconductor porcelain compositions 1a, 1b, 1c, 2a, 2b, 2c Electrodes 10, 11 Heating element 20 Heating modules 20a, 20b, 20c Power supply electrodes 20a1, 20b1, 20c1 Radiation fins 20d Insulator 30 Heating mechanism system 30a, 30b Switch 30c Power supply

Claims (8)

A semiconductor ceramic composition characterized in that the first phase is an oxide mainly composed of Ba, Ti, Bi and Na, and the second phase is an oxide mainly composed of Ba and Ti. A part of Ba constituting the first phase is replaced with La, and the composition formula of the first phase is represented as [(BiNa) _x (Ba _1-y La _y ) _1-x ] TiO _3, and the molar ratio x and The semiconductor ceramic composition according to claim 1, wherein y satisfies 0 <x ≦ 0.3 and 0 <y ≦ 0.02. 3. The semiconductor ceramic composition according to claim 1, wherein an area ratio of the second phase with respect to the total area on an arbitrary polished surface is 1 ≦ a ≦ 15 [%]. At least the second phase of the first phase and the second phase contains Si, the concentration of Si contained in the first phase is b [wt%], and the concentration of Si contained in the second phase is c [wt%]. The semiconductor ceramic composition according to claim 1, wherein b <c. 5. The semiconductor ceramic composition according to claim 4, wherein the concentration c of Si contained in the second phase is 0 <c ≦ 7 [wt%]. 6. A heating element, wherein an ohmic electrode is provided separately in at least two places of the semiconductor ceramic composition according to claim 1. 7. A heat generating module, wherein the heat generating element according to claim 6 is sandwiched between metal electrodes, and a current is passed through the metal electrodes. 8. A fluid heating mechanism system using the heat generating module according to claim 7, wherein the power supply circuit does not have a function of controlling supply power by means for adjusting a voltage or a phase.