JPH01143201A - Variable positive temperature coefficient resistance(ptcr) element - Google Patents

Abstract

PURPOSE:To control freely the exothermic temperature variation range of an element, by causing its exothermic temperature to be adjustable by changing a working voltage of the element itself and determining even such temperature variation range at the manufacturing stage of its element. CONSTITUTION:Being basic materials having specific particle sizes of less than a submicron, barium titanate oxalate and strontium titanate oxalate comprise titanium oxide and antimony oxide as basic compositions and they are composed of an expression: (Ba1-x-ySbySrx)TiO3, provided that x<=0.35, y=0.001-0.1. When x is 0.35 or more, it is impossible to control temperature widths in a state that is more than a room temperature and when y is less than 0.001, it is unable to make its element semiconductive and further, when it is more than 0.1%, its element turns into insulated one and then, it is not preferable for the element to have such a state. Further, as to a burning temperature after the foregoing materials are mixed and reduced to powder, it is enough to have a temperature 1100 deg.C-1250 deg.C that is lower than by 50 deg.-100 deg.C than temperature which are prevailing in conventional process such as a dry or wet burning system. And then, as occasion demands, auxiliaries for sintering of SiO2 0.01-2.0 atomic %, BN 0.01-4.0 atomic %, TiO2 0.01-0.6 atomic % are added to the foregoing compositions. The resultant addition not only promotes sintering treatment but also contributes to the improvement of practical characteristics of PTCR obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable PTCR element that can control the Curie point over a wide range from room temperature to 120°C.

Barium titanate-based semiconductor porcelain (PTC thermistor) has a positive temperature coefficient, that is, the property that the resistance value increases as the temperature rises (PTCR property), and this property can be used to create current-limiting elements, constant temperature heating elements, and motors. It is used in a variety of applications, including as a starter device for televisions, and as an automatic degaussing device for color televisions.

(Prior art) Conventionally, the basic composition of barium titanate contains La-, Ce1Y.
By adding one or more rare earth elements such as SNb, Sb, Nb, etc., improved semiconductor ceramics with positive resistance-temperature characteristics are obtained and are used in heat-sensitive elements, current control elements, etc. Furthermore, by replacing a part of Ba in BaTi0a with PB or the like, it is used for various applications as barium titanate semiconductor ceramics in a high temperature range.

(Problem to be solved by the invention) However, since the resistance change of these ceramics occurs suddenly only at a certain temperature (Curie point) determined by the composition, it is difficult to use sensitive switching elements or constant temperature. Its main use was as a heating element.

In addition, since the PTCR element itself was used as a constant temperature heating element as mentioned above, it was necessary to increase the number of elements for devices that could change the temperature freely, and it was necessary to cope with various temperatures. If they were to do so, they would need an element that could handle that temperature.

Also, with nichrome wire, etc., it is possible to have a certain range of heat generation temperature by controlling the voltage from the power supply, but with a PTCR heating element, the heat generation temperature does not change no matter how the voltage changes. Because of this, its uses were extremely limited.

(Means for Solving the Invention) Therefore, the present invention allows the element itself to change the heat generation temperature by changing the voltage, and also determines the temperature range (additives, firing temperature, etc.) at the stage of creating the element. if you can,
The idea was to create a variable heating element that is effective at low temperatures.

In other words, the temperature coefficient of resistance (the slope of the rising curve) above the Curie point is lower than the conventional PTCR pattern (a pattern that shows a rapid resistance change of 10 to 107 above the Curie point without much change in resistance up to the Curie point). By making it small, a device is created in which the resistance increases gradually over a certain temperature range. For example, in the Sr system, the end point of the resistance increase phenomenon is observed at about 2 to 300°C below the Curie point.

Furthermore, by reducing the temperature coefficient of resistance, the temperature range of heat generation can be increased.

From this point of view, as a specific means to reduce the temperature coefficient of resistance of this PTCR, the primary particles have a particle size of submicron or less, for example, 0.2~
Oxalate powder with a particle size of 0.5 μm is used as the raw material powder.

2. Firing conditions (temperature,
) and sinter it.

3. Add sintering aids such as 5iOz and BNSTiOz.

4. The main firing temperature is 1100 to 1250°C.

It is something.

Therefore, an element (Ba 6., IHSb 0.6HSr6.3) created by the oxalate decomposition method in the present invention
Elements made using 03 and conventional oxide mixed system (same composition)
The relationship between the PTCR characteristics and heat generation characteristics is shown in the reference diagram ta+, (
The explanation will be based on bl.

As you can see from the reference diagram, the pattern (a) (bl) of the conventional product
-1, the resistivity increases rapidly above the Curie point (Tc), so no current flows. In addition, (as shown in bl-1, no matter how much the voltage is changed, heat is generated only at a constant temperature. However, as shown in fat-2 and fat-3, the temperature of the device of the present invention is gentle with a certain temperature range from the rise. It has the property of increasing resistance as (bl-
As shown in 2 and 3, it can be seen that by changing the voltage, the heat generation temperature also changes.

In addition, 2 (firing temperature 1200℃) and 3 (same temperature 1250℃)
Comparing ``C)'', the temperature range of heat generation is small, such as those with a large resistance temperature coefficient like 2 (see (b)-2).
This type generates heat in the range of 50-120'C. However, the voltage was varied from 20 to 100 V. )Become. In addition, the smaller the temperature coefficient of resistance is, the wider the temperature range of heat generation (see (b)-3).
Generates heat in the range. ).

The present invention will be explained in detail below.

As mentioned above, the present invention uses barium oxalate titanate, strontium oxalate titanate, titanium oxide, and antimony oxide as a base material having a specific particle size of submicron or less as a basic composition (Ba1-x-y 5bySrx) Tto 3
It is composed of X≦0.35 and y = 0.001 to 0.1. If X is 0.35 or more, it becomes impossible to control the temperature above room temperature, and if y is less than 0.001, it cannot be made into a semiconductor and 0. If it exceeds 1%, it becomes an insulator, which is not preferable.

In addition, the firing temperature after mixing and pulverization is 1100-1250°C, which is 50-100°C lower than the conventional dry method or other wet method.
°C is sufficient. In addition, as a sintering aid if necessary, 5iOz 0.01 to 2.0% or less, BN
The addition of 0.01% to 4.0% or less of O and 0.01% to 0.6% of Ti contributes to promoting sintering and improving the practical characteristics of the resulting PTCR.

The particle size of the sintering aids to be added is approximately 0.01 μm to several μm, and together with the effects of these aids, the PT
The relative density of the CR element is preferably 80 to 90%, which is a certain degree of porosity.

As described above, since the present invention uses submicron or smaller main raw material powder and sintering aid, the main firing temperature is 1100 to 12
The temperature is about 50°C. Either it is possible to sinter at a temperature higher than this temperature, or the sintering progresses too much and the relative density increases too much due to densification, so that although the room temperature resistance of the element is low, the resistance change with respect to temperature rise is almost negligible. Furthermore, if the material is fired at a temperature below this temperature, sintering will be insufficient and the relative density will be low, and even if sintering is achieved due to the effect of the sintering aid, the room temperature resistance will be quite high, making it impractical.

Note that SiO, BN, TiO2, etc. are used as sintering aids to improve practical properties.
iOz has improved practical characteristics such as current testing, and Ti0z
Although it tends to lower the Curie point a little, it makes the rise characteristics around the Curie point broader.

Furthermore, by adding BN, the temperature coefficient of resistance becomes smaller, and the heat generation temperature range of the PTCR element itself becomes wider.

The synergistic effect of these additives results in a broader rise and a smaller temperature coefficient of resistance (slope), which is benign for the variable PTCR element.

The present invention will be explained below with reference to Examples, but is not limited thereto.

Example 1 Produced by oxalate method, purity 99.9%, average particle size 0.
The main raw material BaTi0 (C20
< ) z ・4)+20.5rTiO(C204)
2 ・4H20, using Sbz 03 as a semiconductor material, the basic composition (Ba o, ses Sb O, OQ2
Sr Q, 3) It was blended to become TiO3, 0.02 atomic% of TiOz was added, and it was completely mixed and ground using a ball mill, and then molded into a disk shape of 8 pieces φ x 2fi at a molding pressure of about 700 kg/-. .

Firing is pre-firing at 800℃ for 3 hours, then main firing for 1 time.
PT was carried out at 200°C to 1350°C according to the conventional method (applying ohmic electrode paste to the molded body and baking at 500°C).
A CR element was created.

The relationship between the firing temperature and the PTCR characteristics of the obtained device was determined as follows.
It is shown in the table and ff11 figure.

It is. Formally, it is expressed by the following formula.

T2 -Tt As can be seen from Figure 1, sintering at temperatures above 1300°C results in low room temperature resistance but no PTCR characteristics;
For those fired at 00°C and 1250°C, the specific resistance value shows a large change of 4 to 6 orders of magnitude depending on the temperature.
The temperature coefficient of resistance is 5.5 to 6.7 (%/°C), which allows temperature control by changing the voltage to 3 to 8 (%/'C).
), and if this is 3 or less, control becomes poor.

Table 2 shows various physical properties when a constant voltage is applied to this element itself.

Table 2 Also, FIG. 2 shows the relationship between voltage and heat generation temperature for sintered elements at 1200°C and 1250'C.

From the above, it is possible to create a variable PTCR element whose heat generation temperature can be freely changed by smoothing the rise characteristics of the PTCR characteristics and reducing the temperature coefficient of resistance.

Example 2 The same basic composition as Example 1, but with TiOz as a sintering aid.
(0.4 atomic%), 5iOz (0.6 atomic%
) and BN (0.6 atomic %) were respectively added and fired in the same manner at a firing temperature of 1200°C, and the PTCR characteristics of the resulting elements were investigated. The results are shown in FIG.

As can be seen from FIG. 3, broad changes in the characteristic values are observed with the addition of each auxiliary agent.

(Effects of the Invention) As described above, the PTCR element manufactured by using oxalate of the present invention can freely change its temperature coefficient of resistance (fiJ), so the heat generation temperature range can be freely controlled, and by changing the voltage. This makes it possible to manufacture an accident-controlled heating element whose heat generation temperature also changes.

[Brief explanation of the drawing]

1 and 3 are graphs showing the PTCR characteristics in Example 1 and Example 2, and FIG. 2 is a graph showing the voltage and heat generation temperature characteristics in Example 1. Reference figures are graphs showing the PTCR characteristics, voltage, and heat generation temperature characteristics of the conventional oxide mixed system and the present invention using oxalate. Figure 1 Temp (℃) Voltage (V) Figure 3 Procedural amendment document February 70, 1988

Claims (2)

[Claims] (1) The basic composition is barium oxalate titanate, whose primary particles are submicron or smaller as the main raw material, strontium oxalate titanate, titanium oxide, and antimony oxide (Ba_1
＿−＿x＿−＿ySb_ySr_x)TiO_3(x≦
0.35y = 0.001 to 0.1) after being mixed, crushed and pre-fired, and then main fired.
TCR element. (2) The variable PTCR element according to claim 1, wherein at least one of SiO_2, BN, and TiO_2 is added as an auxiliary agent.