JPS5878413A - Composite function element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention provides a sintered body obtained by incorporating a trace amount of lithium carbonate (L 12 Co a ) into strontium titanate-based semiconducting porcelain, which itself has voltage nonlinearity and is extremely The present invention relates to a multifunctional device having a large dielectric constant.

Conventionally, Si has been used as a ceramic material with voltage nonlinear resistance.
There are C varistors and varistors whose main ingredient is zinc oxide. Such a varistor has a current-voltage characteristic approximately represented by I=(V/C)''. Here, C is a constant specific to the varistor, and a is a voltage nonlinear index.

The SiC varistor utilizes a contact barrier between SiC particles, and a is about 2 to 7. In addition, zinc oxide varistors contain Bi2O3゜C0O2M in zinc oxide (ZnO).
This is an element obtained by adding a small amount of nO2, 5b203, etc. and firing it, and its voltage nonlinearity index α is as high as 60. Since such elements have excellent performance in absorbing high voltages, they are used for voltage stabilization of electronic devices and protection from abnormal high voltages (surges).

However, such conventional varistors have a small dielectric constant and a large dielectric loss angle (tan δ) of 6 to 10%, so they can only be used for varistor applications.

On the other hand, conventional grain boundary layer type semiconductor ceramic capacitor elements with a large dielectric constant (more precisely, apparent dielectric constant) have been developed by reoxidizing or valence-compensating the grain boundaries of semiconductor ceramics such as barium titanate and strontium titanate. This is an element obtained by insulating it.

The apparent dielectric constant of this element reaches 60,000 to 60,000. In addition, if the composition and conditions are selected appropriately, tan δ can be reduced to 1%.
They are used both domestically and internationally as small, large-capacity capacitors. However, when a current of 1 mA or more passes through the element, it is destroyed and loses its function as a capacitor.

The device of the present invention is an epoch-making multifunctional device that simultaneously has the functions of the two devices described above. In other words, at high voltage, it acts as a varistor and passes high voltage current.

At low voltages, it is an element with a complex function of passing abnormal frequency band current as a capacitor.

Nowadays, electrical and electronic equipment has come to require extremely sophisticated control, and not only industrial equipment, but also consumer equipment has come to require extremely high precision due to the application of microcomputers. Furthermore, since the logic 1' circuits constituting microcomputers and the like operate using pulse signals, they inevitably have the disadvantage of being susceptible to noise. For this reason, electronic computers, banking machines,
Once traffic control equipment malfunctions or is damaged due to noise or surges, it becomes a social problem. Noise filters have conventionally been used as a measure against such problems. Noise is an interfering voltage other than the intended signal voltage when operating electronic equipment, and can be divided into those generated artificially and those generated by natural phenomena.

Such noise was removed using a circuit that combined a coil and a capacitor. However, artificially generated noise, especially from 3JALFR equipment on power transmission lines, and noise caused by natural phenomena, especially from lightning surges, have a low fundamental frequency of about 6 to 20 KHz, and conventional coils and capacitors cannot be used. It was not possible to remove these noises only by the combination of In view of these problems, noise filters that use a voltage nonlinear resistor (varistor) between the lines or between the lines and the ground have recently been frequently used. Since such a noise filter can remove a very wide range of noise, it is effective in preventing malfunctions of microcomputer-controlled equipment.

However, such a noise filter has the drawbacks of requiring a large number of parts within the set, increasing costs, and going against the trend of miniaturization.

The device of the present invention has made it possible to solve these problems. That is, since the element of the present invention has a combined function of a varistor and a capacitor, a single element can serve the purpose in a conventional circuit in which a varistor and a capacitor are connected in parallel.

The device of the present invention is obtained by incorporating a very small amount of lithium carbonate into a strontium titanate-based semiconductor ceramic.The contents of the present invention will be explained in detail below with reference to the accompanying drawings, which are examples.

FIG. 1 shows a cross-sectional view of the multifunctional device of the present invention, in which 1 is a sintered body of strontium titanate-based semiconducting porcelain, 2 and 3
is an electrode.

<Example> 50.22 to 47.96 moles of strontium carbonate, 49.7 to 48.71 moles of titanium oxide, 0.01 to 1.0 moles of lithium carbonate, and niobium oxide, tantalum oxide, neodymium oxide. 0.0 of at least one of the following
After thoroughly mixing the composition containing 6 to 0.6 mol, calcining in the range of 1100 to 1260''C for 1 to 6 hours, pulverizing, adding an organic inder, and granulating. The molded body was molded at a temperature of 1300 to 1460 in a reducing atmosphere.
After firing for 1 to 6 hours at a temperature of 0.2 to 0.0 °C, the specific resistance is 0.2 to 0.
A sintered body having an average particle diameter of 20 to 60/Jm was prepared at 6Ωam. The shape of this sintered body is 7.6φ x 0.7 amount (w)
It is. After this, 0.
Heat treatment was performed in air for 5 to 6 hours to obtain a sintered body 1 shown in FIG. Further, electrodes 2.3 were formed on both surfaces of this sintered body 1. The electrode diameter was 6.0φ(-).

The characteristics of the device thus obtained are shown in the table below.

In the table below, 'Ti/'Sr' represents the composition ratio of titanium oxide and strontium carbonate converted into the atomic ratio of titanium and strontium.

ε is the dielectric constant at IKHz, and tan δ is the dielectric loss angle. α is a voltage nonlinear index calculated from the nocrystal voltage at 1 mA and 1 omA.

Surge withstand capacity is a value that indicates how much large current such as lightning surge can be absorbed by the element, and the greater the surge withstand capacity, the better the varistor is. In the test, the applied pulse was a current waveform of 8×20 μsec, and the current peak value at which the varistor voltage v1 mA deteriorated by 0.10% with respect to the initial value was defined as the surge withstand capacity. The number of pulse applications is two.

(Hereinafter referred to as gold and white) As is clear from the table above, the 'Ti/NSr ratio is 0.9.
It has the function of a varistor and a capacitor in the range of 0 to 1.26, but the range of 0.97 to 1.036 is particularly good.

In addition, the amount of lithium carbonate added was Flo, 01 to 1.
Since the sintered body 1 has polycrystalline grains with uniform grain growth in the 0 molar range, the surge resistance is large. When the amount of lithium carbonate added was 0.01 mmol or less, a was 6 or less, and the surge resistance was also 6oA or less. Furthermore, if the amount of lithium carbonate added exceeds 1.0 molar ratio, the sintered body will have polycrystalline grains with non-uniform grain growth, and the sintered body will tend to bend, resulting in large variations in properties and surges. The tolerance is still a
Small, below OA.

Niobium oxide, tantalum oxide, and neodymium oxide are compatible with each other, and during firing, in the range of 0.05 to 0.6 mol, they form a solid solution in the lattice of microcrystals mainly composed of strontium titanate, and the atomic side splits. , and was able to reduce the resistance of the sintered body to a range of 0.2 to 0.6 Ω/steel. If the amount is greater or less than this range, the specific resistance will increase, making it impossible to increase the surge resistance. Samples 3.7 to 10.13 to 16 in the above table fall within the range of the present invention, and the others are comparative examples.

Next, we made a circuit as shown in Fig. 2 using such an element, and investigated the output situation with respect to the noise input a shown in Fig. 6. As a result, the output situation curve shown in Fig. 6 was obtained. I was able to suppress the noise. Incidentally, the output condition of the conventional filter circuit shown in FIG. 3 is like the output condition curve C in FIG. 6, and noise is not sufficiently removed. Also, the fourth
Although the conventional filter circuit including the varistor shown in the figure can obtain the same effect as the circuit shown in FIG. 2 using the element of the present invention, the number of components is large due to the varistor included. In FIGS. 2 to 4, 4 is the element of the present invention, 6 is a coil, 6 is a capacitor, and 7 is an element of the present invention.
is a barista.

As described above, the device of the present invention has an unprecedented complex function and can play the roles of a variator and a capacitor at the same time. It contributes to cost reduction, and has great utility such as 0, which can be applied to prevent malfunction and destruction of microcontroller control equipment in the future, and its industrial value is enormous. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multifunctional device of the present invention, FIG. 2 is a circuit diagram of a noise filter circuit using the device of the present invention, FIGS. 3 and 4 are circuit diagrams of a conventional noise filter circuit, and FIG. 6
The figure is a diagram showing the situations of input noise and output noise corresponding to the circuits shown in FIGS. 2 to 4. 1... Sintered body of strontium titanate semiconducting porcelain, 2, 3... Electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure, Figure 2 - Figure 5 - Kariura table (1'lN1)

Claims (1)

[Claims] The ratio of the number of atoms of titanium and strontium is 0.97 to 1.
036 and lithium carbonate from 0.01 to 1.0
It contains at least one element among niobium, tantalum, and neodymium as a valence control element system, and its content is 0.06 to 0.6 as an oxide.
A multifunctional device formed by forming one or more pairs of electrodes on the surface of a sintered body of strontium titanate-based semiconductor ceramic having a mole content of 0.