JPH0258302A - Manufacture of positive temperature coefficient semiconductor porcelain - Google Patents

Abstract

PURPOSE:To easily perform a low specific resistance of 5OMEGA.cm or less without increasing a PTC thermistor in size by mixing raw material powder containing powder of titanium oxide raw material of a specific chemical composition, calcining the mixture of powder, molding it and firing it in the atmosphere. CONSTITUTION:A PTC element having high oxygen defective concentration in bulk and low resistance is formed of titanium oxide material powder containing reduced oxide of titanium reduced in advance by selectively reducing the bulk without reducing grain boundaries for controlling PTC characteristics. Powder having chemical composition represented by TiO2-x in which x is 0.02 or less or power having chemical composition to become TiO2-x by calcination is employed as the titanium oxide material of material powder. Thus, reduced oxide of titanium such as TiO, Ti2O3, Ti3O4, etc., are employed solely or in mixture as the titanium oxide material. TiO2 may be employed in mixture with the reduced oxide of the titanium. If the x is less than 0.03, its specific resistance cannot be reduced to 5OMEGA.cm or less, and its reduction in the specific resistance becomes insufficient. If the x exceeds 1, since metallic properties are generated, it is not desired. Additional matter for making it semiconductor or positive temperature coefficient additional matter can be contained in the material powder.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a method for manufacturing a special semiconductor porcelain (PTC thermistor) characterized by barium titanate. The present invention relates to a method for manufacturing a positive characteristic semiconductor La device that can obtain a desired resistance value in a compact shape, expands the degree of freedom in design, and is expected to reduce costs due to miniaturization of applied products.

INDUSTRIAL APPLICATION This invention is utilized for the overcurrent protection device (blower resistor) of a motor or a transformer, a motor starting element, a temperature sensor, a self-temperature control heating element, etc.

[Prior Art] The conventional general method for manufacturing positive characteristic semiconductor porcelain uses barium carbonate (BaCO3) and titanium dioxide (TO2) as main raw materials, and adds semiconducting elements such as Y, La, and Nb to them. This is a method in which the barium titanate (Bacho 103) powder obtained by calcining is carried out to carry out an in-phase reaction, and the resultant barium titanate (Bacho 103) powder is pulverized, molded using the powder, and then fired in the atmosphere.

Also, attempts have been made to produce semiconductor ceramics using the coprecipitation method or the alkoxide method.

[Problem to be solved by the invention] PTC thermistor for overcurrent protection of motors, transformers, etc.21
! When applied to devices, air conditioner blower resistors, or motor start-up elements, low-resistance P is used to prevent malfunctions due to self-heating or to reduce voltage drop.
A TC thermistor is required.

However, no matter which method is used, the room temperature specific resistance of this semiconductor ceramic is limited to 5 Ω·cm. For this reason, conventional methods have been to increase the element shape and reduce the element thickness.
Alternatively, this has been dealt with by methods such as using multiple thermistors connected in parallel, but as the size of the thermistor increases, the space required during design is large, and the cost also increases significantly.

The present invention overcomes the above-mentioned problems, and aims to provide a method for manufacturing positive characteristic semiconductor porcelain that can easily achieve a low resistivity of 5Ω/C1 or less without increasing the size of the PTC thermistor. purpose.

[Means for Solving the Problem 3] The method for producing positive characteristic semiconductor porcelain of the present invention uses powder having a chemical composition of TiO2-X with X of 0.02 or more or T by calcining as a titanium oxide raw material. r o
2-X A mixing step of mixing raw material powders containing powder having a chemical composition as shown in FIG. A molding step of molding a molded body of a predetermined shape from the calcined barium titanate powder, and a firing step of firing the molded body in the atmosphere.

By the way, regarding the *'am structure of the P 1'C element, 3
There are various theories such as hopping conduction of dN atoms, but the general theory is that free electrons are generated due to the generation of WJ elemental defects.

The resistance of a PTC element is expressed by the sum of the resistance of the bulk (particles that make up the element) and the grain boundaries. Generally, the resistance of the bulk at temperatures below the Curie temperature (Tc) is the resistance at temperatures above TC It is known that grain boundary resistance is dominant. Therefore, when it comes to lowering the resistance of PTC elements, the bulk ! I
i n is important.

The room temperature resistivity of this PTC* element is generally expressed as follows.

ρ(P'rC)-D (bu l k)-1/ (n
(D)・e・μ) (n(D)-donor density, e-electron charge, μ-mobility) Therefore, the resistance of the PTC cord is the donor density,
It depends on the concentration of oxygen vacancies in the bulk, and P with low resistance
In order to obtain a TC element, it is necessary to increase the concentration of oxygen vacancies.

In addition, for this /=, the P 1' C element is Nz, Ar,
The concentration of oxygen defects in the bulk is increased by heat treatment (baking) in a neutral/reducing atmosphere such as 82! Although it is possible to make it resistive, there is a problem in that the grain boundaries that generate the PTC characteristic are reduced and the two-dimensional C characteristic disappears or deteriorates.

In the present invention, titanium oxide raw material powder containing a reduced titanium oxide that has been reduced in advance is produced in a conventional manner, so that the grain boundaries that govern PTC characteristics are not reduced (and only the bulk is selected). 1 in the bulk
A low resistance PTC element with 1311 defect III is manufactured.

As the titanium oxide raw material for the raw material powder of the present invention, X is 0
．． The powder can be made into a powder having a chemical composition of T i O2-x of 02 or more, or a powder having a chemical composition of T f Oz-x by calcination.

For this reason, TtO1-1203 is used as a titanium oxide raw material.
, Ti30a, and other reduced oxides of titanium can be used alone or in combination. Further, it is also possible to use a mixture of TiO2 in the reduced oxide of f-tan. However, it is necessary that the titanium oxide raw material powder as a whole has a chemical composition represented by TiO2-x, where x is 0.02 or more. If this X is less than 0.02, reduce the specific resistance to 5
It is not possible to reduce the resistivity to Ω·cm or less, resulting in insufficient reduction in specific resistance. Furthermore, a 1!1 ratio in which X exceeds 1 is not preferable because the powder develops metallic properties.

Note that the raw material powder used in the present invention can contain a semiconductor additive or a positive characteristic additive (P-type additive). This semiconductor additive includes YtO3, La
x03, NbzOs, Cez03LJ″3 and Dingato
At least one of s, etc. can be used, and usually,
Y2O3 is used. As a P-type additive, Mn0
At least one of z, FezO3, Cr2O2, CuO, NiO, etc. can be used, and usually MnO
2 is used.

The above-mentioned hot substances are not limited to the above-mentioned oxides, but nitrates, carbonic acid 43, etc., which become oxides upon firing, can also be used.

Even if the added oil of this semiconductor low-temperature substance becomes excessive or decreases, the room temperature resistivity increases.
In order to make the specific resistance at room temperature 5Ω・cm or more, this semiconductor additive is added at a concentration of 0.0 mol per 100 mol of barium titanate.
A good addition range is 5'El to 0.5 mol.

When containing both a semiconductor additive and a P-type additive,
Mixing ratio of semiconducting additive: 1, barium titanate: 10
0.05-E to 0.5,
The content of the P-type additive is preferably 0.15 mol or less. When a P-type additive is added, the RT characteristic (ΔR) becomes good, but if it is added in excess, the specific resistance at room temperature decreases, so it is preferably 0°15 mol or less. Furthermore, P
It is presumed that the reason why △1(f) becomes better due to the addition of molding additives is that the P-type compound, which is thought to precipitate at the grain boundaries, becomes an oxygen supplier and prevents reduction at the grain boundaries. Ru.

Also, the heating temperature number in the firing process is 1280 to 17
100°C is preferred. At temperatures lower than 1280℃,
Sintering is insufficient, and 4 degrees above 1400° C. is not preferable because it results in oversintering and causes problems in lowering the resistance.

The composition of the raw material powder used in the present invention is BaT +
It is not limited to those having a sintered body composition containing 03, Pb, and Sr, but for Tc and 1<-1 characteristics (△R),
A similar effect can be obtained by adding raw material powder that has a sintered body composition containing other elements such as 3n, Fe, and Or.

[Example] The present invention will be explained below with reference to Examples.

In this example, as shown in FIG. 1, heating, drying, calcination, pulverization, granulation, molding, and firing were carried out to produce each predetermined semiconductor porcelain with the raw material composition shown in the table. In addition, test example N
o, 5 to 11 and Nos. 13 to 21 are test examples according to the present invention, in which the titanium oxide raw material #1 contains a reduced oxide of titanium, and the titanium oxide raw material as a whole has Xh<0.
．． It has a chemical composition represented by 102-X of 02 or more.

In addition, test examples No. 4 and No. 12 are comparative examples,
Although a reduced oxide of titanium is included as a titanium oxide raw material, the titanium oxide raw material as a whole has a chemical composition represented by r i 02-X where X is smaller than 0.02. Also, test example no.

1 to 3 show conventional examples in which TiO2 was used alone as a titanium oxide raw material. Furthermore, in Table 1, x1 indicates a value of 1 in the chemical composition formula (102-x) of the entire titanium oxide raw material 11.

The manufacturing method of Test Example No. 11 (the present invention) is described above, and the other test examples are similar to this method except that the composition of the starting materials is different.

1. BaCOx. OOE le, T'i0 1゜02
t-ru, Y! 03 is 0.0025 mole and 3+Q+ is 0511^1 part, △1 for a total of 100 black market items.
103 to 0.3 @ between, and M n Ot to 0.0
After blending 0027, add pure water to a ball mill using 1 convex agate and press at 20 o'clock! j JC mixed.

Its IQ is 150'C124 hours! , 1 drying, and further calcining at 1100℃ for 4 hours to obtain a titanium liquor barium calcined powder with a temperature of 1.7. Then, this calcined powder was wet-pulverized using a ball mill.
t% was added and granulated in a spray dryer. Then, the grain powder was molded with a mold at a molding pressure of 500 kg/as2, and 135
I'l is a fired product that is fired at 0°C for 1 hour.

Next, the end face of each fired body was polished, and the N1 electroless method was polished.
and an Ag-based electrode, its specific resistance (ρ+o
) and RT characteristics (△R= l o g(Rwax
, -'Rsin > ) was evaluated, and the results are also shown below. In addition, test example No. 1 <Conventional example)
FIG. 2 shows the RT characteristics for No. 1 and No. 11 (invention). In addition, the specific resistance (ρxo) is 5Ω
-Cals below, 1-1 characteristics (△R) 2 digits or more are O, otherwise 1. It was set as L△.

According to this result, TO! The specific resistances of the conventional examples (Nos. 1 to 3) in which only 1 was used were as high as 6.2 Ω·cmL×10. In addition, as the titanium oxide source n, T101 and TiO or Ti1z and li+0
Comparative VAs (No. 4 and 12
) has a specific resistance of 5.5Ω・caP? It was like an epidemic.

In the other test examples (invention), although the RT characteristics (ΔR) were slightly deteriorated, the specific resistances were all as small as 50·C or less compared to the conventional examples and comparative examples. That is, the titanium oxide raw material contains a reduced oxide of f-tanium (Tiz10, Tiz03), and titanium oxide?
5 If the chemical composition formula Ti0z-X of the raw material as a whole has a value of X greater than OO2, P1 with low resistance
I can get C# completion, @For example, test example N015
It can be seen that due to the unity of ~11 (water R light), the specific resistance becomes lower as the value of j30 becomes smaller in the chemical composition formula T i O2-X of the titanium oxide raw material as a whole. In particular, the specific resistance of test example No. 11 is 1°10・CI
Therefore, it was possible to obtain an extremely good bond.
03 (No, 5-11.13-17.19.21
) only, l) b or (N) containing Sr.
o, 18.20), it was possible to obtain a similar effect.

[R Ming's 211 Song j Water f Ming's special method uses as a starting material a chemical composition of r' i 02-X where X is 0°021s1-.
Tan II! ! Ordinary li? The grain boundaries that govern PTC properties are formed by sintering in the atmosphere (firing in the atmosphere). This method selectively removes only the bulk without causing damage to the bulk, thereby reducing the number of M-type defects in the C bulk. According to this manufacturing method, it is possible to manufacture a semiconductor 48 with 0 (resistance) and small diameter i' [characteristics. S
It becomes possible to apply it to adventure equipment, etc., and the range of application and the degree of freedom of installation 31 are expanded. Furthermore, since the desired element resistance can be reduced by 17% with a smaller shape than conventional products, it is possible to reduce the size of applied products by 5%.
1-down 1. It is also possible to earn money.

[Brief explanation of the drawing]

Figure 1 shows the 51 people who made the Mokubimei.
No. 21q, there is a graph e showing an example of the resistance-temperature characteristics of the L actual pressure example. Patent Applicant Nippon City Rental Co., Ltd. Agent Benl1lIF Required Hiroshi Figure 1 Figure 2 Temperature (°C)

Claims (1)

[Claims] (1) As a titanium oxide raw material, T with x of 0.02 or more
A mixing step of mixing raw material powder including a powder having a chemical composition represented by iO_2_-_x or a powder having a chemical composition that becomes TiO_2_-_x by calcination, and calcination of the mixed powder mixed in the mixing step. a calcination step in which a barium titanate calcined powder is mainly synthesized, a molding step in which a molded body of a predetermined shape is formed from the barium titanate calcined powder, and then a firing step in which the molded body is fired in the atmosphere. A method for producing positive characteristic semiconductor porcelain, comprising the steps of: