JP4779466B2 - Barium titanate semiconductor porcelain composition - Google Patents

Description

The present invention relates to a semiconductor ceramic composition, and more particularly to a barium titanate (BaTiO ₃ ) -based semiconductor ceramic composition used for a demagnetizing positive temperature coefficient thermistor.

In recent years, barium titanate (BaTiO ₃ ) -based semiconductor ceramic compositions having large positive resistance temperature characteristics have been developed. This barium titanate-based semiconductor porcelain composition has a resistance value that suddenly increases when the Curie temperature is exceeded, reducing the amount of current that passes through it. It is widely used for various applications such as circuits.

  In particular, in the demagnetizing positive temperature coefficient thermistor, there is an increasing demand to attenuate the current gently at a low price. For this reason, it is required to improve both the withstand voltage and the attenuation current characteristics.

  Patent Document 1 discloses a demagnetizing positive temperature coefficient thermistor, and when α which is a parameter representing resistance temperature characteristics is reduced, the maximum value ρmax of the current change ratio ρ representing attenuation current characteristics increases (= current is gradually attenuated). It is shown that the resistance temperature characteristic α of a semiconductor ceramic used as a demagnetizing positive temperature coefficient thermistor is 10% / ° C to 17% / ° C. By setting such a resistance temperature characteristic α, the attenuation current characteristic ρmax is 0.7 or more and the withstand voltage is 100 V / mm or more.

On the other hand, in Patent Document 2, Fe is added to a basic composition such as BaNdTiO ₃ or BaSbTiO ₃ in an amount of 0.001 wt% to 0. 007 wt% is added. It is shown that the resistance temperature characteristic α is increased by increasing the amount of Fe added. It is stated that when the addition amount of Fe does not reach 0.001 wt%, the resistance-temperature characteristic α is the same as when Fe is not added.
JP 2002-175902 A Japanese Patent Publication No.46-22266

  In Patent Document 1, by adjusting the cooling temperature gradient in the manufacturing process of the semiconductor ceramic, the oxidation temperature of the semiconductor ceramic is varied to reduce the resistance temperature characteristic α, thereby increasing the attenuation current characteristic ρmax. The manufacturing process is complicated.

  In Patent Document 2, the amount of Fe added is 0.001 wt% to 0.007 wt%, but when converted to mol based on the composition shown in the examples of the present invention, 0.000038 mol-0 .000267 mol. Increasing the added amount of Fe in this range increases the resistance temperature characteristic α. However, if the resistance temperature characteristic α increases, the attenuation current characteristic ρmax decreases, which is not desirable as a demagnetizing positive characteristic thermistor. Therefore, the attenuation current characteristic ρmax required for the demagnetizing positive characteristic thermistor cannot be satisfied.

  An object of the present invention is to provide a demagnetizing positive temperature coefficient thermistor capable of improving both the withstand voltage and the attenuation current characteristic ρmax without complicating the manufacturing process.

To solve the above problems, barium titanate diameter semiconductor ceramic composition of the present invention, the main component is expressed by the formula of titanium represented by _{(Ba 1-pqrs Sr p Pb} q Ca r Er s) m TiO 3 The barium-based semiconductor ceramic composition, wherein p, q, r, s, and m are 0.150 ≦ p ≦ 0.195, 0.0195 ≦ q ≦ 0.0240, and 0.120 ≦ r ≦, respectively. 0.165, 0.0029 ≦ s ≦ 0.0032, 0.998 ≦ m ≦ 1.002, and Mn as a subcomponent is 0.000300 mol or more and 0.1 or more mol per 1 mol of the main component. 000350 mol or less, Si is contained 0.018 mol or more and 0.021 mol or less with respect to 1 mol of the main component, and Fe is 0.000010 mol or more and 0.000035 mol with respect to 1 mol of the main component. Containing less than mol .

  To sum up the disclosures of Patent Documents 1 and 2, it is better not to add Fe in order to reduce the resistance temperature characteristic α. On the contrary, the present invention can reduce the resistance temperature characteristic α and increase the attenuation current characteristic ρmax by adding a small amount of Fe. In Patent Document 2, the resistance temperature characteristic α increases as the amount of Fe added increases. On the other hand, in the present invention, in the range where the amount of Fe added is smaller than that in Patent Document 2, the resistance temperature characteristic increases as the amount of Fe added increases. It has been found that the characteristic α does not increase but decreases. In the present invention, the resistance temperature characteristic α decreases as the amount of Fe added increases, and as a result, the attenuation current characteristic ρmax can be increased.

  In the present invention, the resistance temperature characteristic α is moderated by adding Fe to the barium titanate semiconductor ceramic material, and the resistance temperature is adjusted by adjusting the amount of Fe added without complicating the manufacturing process. By controlling the characteristic α, it is possible to satisfy both the withstand voltage and the attenuation current characteristic ρmax of the demagnetizing positive characteristic thermistor. Specifically, the withstand voltage of 100 V / mm or more and the attenuation current characteristic ρmax of 0.690 or more can be sufficiently satisfied.

  Hereinafter, the features of the present invention will be described in detail with reference to examples of the present invention.

Main component expressed by the formula is represented by _{(Ba 1-pqrs Sr p Pb} q Ca r Er s) m TiO 3, manufactured Mn, Si, barium titanate-based semiconductor ceramic composition containing Fe as an auxiliary component Then, room temperature specific resistance, resistance temperature characteristics (α (10-100)), withstand voltage characteristics, and decay current characteristics (ρmax) were examined.

In manufacturing the barium titanate-based semiconductor ceramic composition, first, BaCO ₃ , SrCO ₃ , Pb ₃ O ₄ , CaCO ₃ , TiO ₂ as main components, Er ₂ O ₃ as a semiconducting agent, and addition are added as raw materials. MnCO ₃ , SiO ₂ , Fe ₂ O _3, etc., which are agents, were prepared, and these raw materials were prepared so as to obtain a semiconductor ceramic composition having the ratio shown in Table 1.

  Next, the blended raw materials were wet mixed for 2 hours with a ball mill, dehydrated and dried, and then calcined at about 1200 ° C. for 2 hours. After calcination, the obtained calcination raw material is pulverized, mixed with a binder, dried and granulated. After granulation, a disk-shaped molded body was produced by dry press molding and fired at about 1400 ° C. for 1 hour in the atmosphere. The obtained element size is 2.5 mm in thickness and 10.6 mm in diameter. This element is subjected to Ni electroless plating, and then an Ag paste is applied and baked to form an electrode, and room temperature resistivity, resistance temperature characteristics (α (10-100)), withstand voltage characteristics, attenuation current characteristics (Ρmax) was measured. The results are shown in Table 1.

  Each characteristic shown in Table 1 was measured as follows.

  The room temperature resistivity was determined with a digital multimeter at a measurement temperature of 25 ° C.

  The resistance temperature characteristic α was measured using a digital multimeter at intervals of 5 ° C. in a measurement temperature range of 20 ° C. to 100 ° C. The resistance temperature characteristic α was obtained from the following equation.

R1: specific resistance value 10 times the specific resistance value ρ25 when the element temperature is room temperature (25 ° C) R2: specific resistance value 100 times the specific resistance value ρ25 when the element temperature is room temperature (25 ° C) T1: Element temperature when the specific resistance is R1 T2: Element temperature when the specific resistance is R2,
α (10-100) (% / ° C.) = [ln (R2 / R1) / (T2-T1)] × 100

  With respect to the withstand voltage, a cycle in which a predetermined step voltage was applied for 1 minute and the voltage of the next step was applied unless it was destroyed was repeated until the device was destroyed, and the voltage immediately before destruction was measured as the withstand voltage.

  The attenuation current characteristic ρmax was determined by measuring the current value using an oscilloscope under the conditions of a measurement voltage of 220 V, a frequency of 60 Hz, and a series resistance of 20Ω, to obtain the attenuation current characteristic ρmax. The attenuation current characteristic ρmax was obtained from the following equation. As shown in FIG. 1, the current change ratio ρ is a current change ratio ρ = (I (n + 1) / I) between adjacent current peak values (I (n), I (n + 1)) in the current being attenuated. (N)), and the maximum change ratio ρmax of the current change ratio ρ is defined as the attenuation current characteristic.

  From Table 1, in Comparative Examples 1 and 2 where Fe outside the range of the present invention is less than 0.000010 mol, the withstand voltage is as high as 180 V / mm or more, but the attenuation current characteristic ρmax is 0.683 or less, and the sufficient attenuation current is obtained. The characteristic ρmax cannot be obtained. Particularly, in Comparative Example 1 that does not contain Fe, the attenuation current characteristic ρmax is 0.670, and a highly accurate demagnetization characteristic cannot be obtained.

  In Comparative Examples 3 and 4 with more than 0.000035 mol of Fe, although the attenuation current characteristic ρmax is obtained, the withstand voltage is 90 V / mm or less, which is insufficient.

  On the other hand, in Examples 1-10 in which Fe is contained in 0.000010 mol to 0.000035 mol, the withstand voltage is 100 V / mm or more, and the attenuation current characteristic ρmax is 0.690 or more. It can be seen that both characteristics are improved by the addition of Fe.

  FIG. 2 shows the relationship between the added amount of Fe and the specific resistance. In Examples 1-10, it turns out that the specific resistance is increasing to 17.3 ohm-cm-21.4 ohm-cm as the addition amount of Fe increases to 0.000010 mol-0.000035 mol.

  FIG. 3 shows the relationship between the added amount of Fe and the resistance temperature characteristic α. In Examples 1 to 10, the resistance temperature characteristic α decreases from 14.1% / ° C. to 10.9% / ° C. as the addition amount of Fe increases from 0.000010 mol to 0.000035 mol. I understand. The resistance temperature characteristic α is moderated by the addition of Fe.

  FIG. 4 shows the relationship between the added amount of Fe and the withstand voltage. In Examples 1 to 10, the withstand voltage decreased to 175 V / mm to 102 V / mm as the Fe addition amount increased from 0.000010 mol to 0.000035 mol. It can be seen that the withstand voltage of 100 V / mm or more is sufficiently satisfied.

  FIG. 5 shows the relationship between the added amount of Fe and the attenuation current characteristic ρmax. In Examples 1 to 10, as the addition amount of Fe increases from 0.000010 mol to 0.000035 mol, the decay current characteristic ρmax increases from 0.690 to 0.744, and the addition amount of Fe increases. It can be seen that the method of current attenuation has become gentler. Further, it can be seen that the attenuation current characteristic ρmax 0.690 or more required for the demagnetization positive characteristic thermistor is sufficiently satisfied.

  As described above, in the present invention, in the barium titanate semiconductor ceramic composition used for the demagnetizing positive temperature coefficient thermistor, the withstand voltage of 100 V / mm is obtained by setting the amount of Fe to 0.000010 mol to 0.000035 mol. As described above, the attenuation current characteristic ρmax 0.690 or more can be satisfied.

In the present invention, the main component a composition _{formula: (Ba 1-pqrs Sr p} Pb q Ca r Er s) expressed in _m TiO _3, Mn as an auxiliary component, Si, barium titanate containing Fe-based semiconductor ceramic composition However, the presence state of the subcomponent does not exclude the case where it is dissolved in the main component.

It is a figure for demonstrating the attenuation | damping current characteristic showing the relationship between an electric current when an alternating voltage is applied to a positive characteristic thermistor element, and time. It is a figure which shows the relationship between the addition amount of Fe of this invention, and a specific resistance. It is a figure which shows the relationship between the addition amount of Fe of this invention, and resistance temperature characteristic (alpha). It is a figure which shows the relationship between the addition amount of Fe of this invention, and a withstand voltage. It is a figure which shows the relationship between the addition amount of Fe of this invention, and the attenuation | damping current characteristic (rho) max.

Claims (1)

Main component expressed by a composition formula: a _{(Ba 1-pqrs Sr p Pb} q Ca r Er s) barium titanate represented by _m TiO ₃ based semiconductor ceramic composition,
p, q, r, s and m are each 0.150 ≦ p ≦ 0.195,
0.0195 ≦ q ≦ 0.0240,
0.120 ≦ r ≦ 0.165,
0.0029 ≦ s ≦ 0.0032,
0.998 ≦ m ≦ 1.002,
In the range of
As a minor component
Mn is contained 0.000300 mol or more and 0.000350 mol or less with respect to 1 mol of the main component,
Si is contained 0.018 mol or more and 0.021 mol or less with respect to 1 mol of the main component, and Fe is contained 0.000010 mol or more and 0.000035 mol or less with respect to 1 mol of the main component. A barium titanate-based semiconductor ceramic composition.

Images