JPS5878412A - 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 small amount of iron oxide (ye203) into strontium titanate-based semiconducting porcelain, which itself has voltage nonlinearity and has an extremely large dielectric constant. The present invention relates to a multifunctional device having the following functions.

Conventionally, 8i was used as a ceramic with voltage non-linear resistance.
There are C varistors and varistors whose main ingredient is zinc oxide.

The risk is approximately expressed as 1 : (v/c)''. Here, C is a constant specific to the risk, and α is the voltage nonlinear index. It is.

The SiC varistor uses contact between SiC particles (rear), and α is about 2 to 7. Also, the zinc oxide varistor uses zinc oxide (ZnO), B12O3, and Coo.

This is an element obtained by adding a small amount of MnO2, 5b203, etc. and firing it, and its voltage nonlinearity index α is 60.
It is an element that spans over 1000 yen. 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. Furthermore, if the composition and conditions are appropriately selected, tan δ can also be used as small-sized, large-capacity capacitors within and outside the 1-inch range. 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. That is, it is an element having a complex function of passing high voltage current as a varistor at high voltage and passing abnormal frequency band current as a capacitor at low voltage.

Nowadays, electrical and electronic equipment has come to require extremely sophisticated control, and not only industrial equipment, but also microcomputer applications and consumer equipment have come to require extremely high precision. Since the logic circuits that make up microcomputers and the like operate on pulse signals, they inevitably have the disadvantage of being susceptible to noise. For this reason, electronic computers, banking machines, traffic control equipment, etc. may malfunction or malfunction due to noise or surges.
If damage occurs, it also 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 circuit breakers 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 disadvantages in that the number of parts in the set increases, the cost is high, and it goes 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 iron oxide (Fe2O3) into a strontium titanate-based semiconductor ceramic.The content 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> Strontium carbonate at 50.22 to 47.95 mol.

49.7 to 48.71 molti titanium oxide, 0 iron oxide
．． 01 to 1.0 molti, and at least one of niobium oxide, tantalum oxide, and neodymium oxide to 0.06 to 1.0
After thoroughly mixing the composition containing 0.5 molt, it was calcined at 1100 to 1260°C for 1 to 6 hours, pulverized, an organic binder was added, granulated, and molded. This molded body was fired in a reducing atmosphere at a temperature of 13oO to 1460'C for 1 to 6 hours to obtain a specific resistance of 0.62 to 0.50.
In step (7), a sintered body having an average particle size of 20 to 60 μm was produced. The shape of this sintered body is 7.6φX O, 7t (m)
It is. After this, 1oo.

-13001: heat treatment in air for 0.5 to 5 hours to obtain the sintered body 1 shown in FIG. Furthermore, electrodes 2 and 3 were formed on both halves of this sintered body 1. The electrode diameter is 6.0φ (m
).

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

In the table below, "rt/NSA" is the composition amount of titanium oxide and strontium carbonate converted into the atomic ratio of titanium and strontium. ε is IKHz
is the dielectric constant at F), and tan δ is the dielectric loss angle. a is a voltage nonlinear index calculated from the varistor 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.

The test applied a pulse with a current waveform of 8 x 20μ8eC.
Then, the varistor voltage v1mA is 010% of the initial value.
The current peak value that deteriorates is defined as the surge withstand capacity. The number of pulse applications is two.

(Left below) As is clear from the table above, it has the function of a varistor and a capacitor when the %NTi/NSr ratio is in the range of 0.90 to 1.26, but especially in the range of 0.97 to 1.036. The range is good. In addition, the amount of iron oxide added is 0.
Since the sintered body has polycrystalline grains with uniform grain growth in the range of 0.01 to 1.0 molar, the surge resistance is large. When the amount of iron oxide added is less than 0.01 molt, α is 6 or less,
The surge resistance was also less than 50A □. In addition, if the amount of iron oxide added exceeds 1.0 molt, 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 surge resistance. Kaya is small with p4sA or less.

Niobium oxide, tantalum oxide, and neodymium oxide are compatible with each other, and during firing, they form a solid solution in the lattice of microcrystals mainly composed of strontium titanate in the range of 0.06 to 0.5 molt, and control the valence. , the resistance of the sintered body is 0
．． It was possible to set the number in the range of 2 to 0.60. If the amount is greater or less than this range, the resistivity will increase,
It was not possible to increase surge resistance. Samples A3°7-10.13-16 in the above table fall within the range of the present invention, and the others are comparative examples.

Next, a circuit as shown in FIG. 2 was made using such an element, and the output situation was investigated for the noise input a shown in FIG. 6. As a result, the output situation curve in FIG. I was able to suppress it. Incidentally, the output situation of the conventional filter circuit shown in FIG. 3 is like the output situation curve C in FIG. 6, and noise is not sufficiently removed. Also, the fourth
A 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, but the number of components is large due to the varistor. 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 composite function and can simultaneously serve as a varistor and a capacitor, such as a noise filter circuit. It contributes to simplification, compactness, high performance, and low cost, and has great utility as it can be applied to other applications in the future, and its industrial value is enormous.

[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 2 Figure 3 Figure 4 Figure 5 Figure 1] 11 J-: Song (MHz)

Claims (1)

[Claims] The ratio of the number of atoms of titanium and strontium is 0. ．． 97-1
．． 036, contains iron oxide in the range of 0.01 to 1.0 molty, and contains niobium as a valence control element,
A pair or more of electrodes are provided on the surface of a sintered body of strontium titanate semiconductor ceramic containing at least one element among tantalum and neodymium, the content of which is in the range of 0.06 to 0.6 molti as an oxide. A multifunctional device formed by forming.