JPS6144404A - Porcelain composition for voltage nonlinear resistor - 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 (Industrial Field of Application) The present invention relates to a ceramic composition for a voltage nonlinear resistor,
The present invention relates to a strontium nathanate-based ceramic composition for a voltage nonlinear resistor having a high bending strength.

(Prior Art) It is known that a voltage nonlinear resistor (hereinafter referred to as "varistor") can be obtained by increasing the resistance of the grain boundaries of strontium titanate-based semiconductor ceramics. An application of this type of varistor is a ring varistor for absorbing sparks in micro motors. This ring barista is
Usually, it is mounted as is without being covered with a resin dip or the like, so a material with high bending strength is required. In particular, varistors used in micro motors and the like are small, so high bending strength is required as an important characteristic.

(Problems to be solved by the invention) Conventional varistors made of strontium titanate-based semiconductor porcelain have low bending strength, and therefore the wall thickness must be around 1n, which makes them suitable for use in micro motors where miniaturization is desired. It was not suitable for a barista.

Therefore, the main object of the present invention is to provide a porcelain composition for varistor use that develops good varistor properties and has a high bending strength.

(Means for Solving the Problems) The present invention provides strontium titanate or strontium titanate as a main component containing other titanates, zirconates, and stannates.
99.88 mol%, the total of at least one of Er2O3 and Ho2O3 and at least one of Ta2O5 and Nb2O5 is 0.1 to 1.0 mol%, MnO
This is a ceramic composition for a voltage nonlinear resistor, in which □ is 0.02 to 0.2 mol%, the crystal grains of the ceramic are semiconductor, and the crystal grain boundaries are made highly resistive.

(Effects of the Invention) According to the present invention, an excellent porcelain composition for a varistor having a nonlinear coefficient (α) of 7.5 or more and a bending strength of 2.5 kg or more can be obtained.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Example) Main components 5rTi03, CaTiO3, BaZr
Each powder of O3 and BaSnO3, and a semiconducting agent, Er2O3 +'Ho2 o3. Ta2O, and Nb
2O, were weighed, 3 to 10% by weight of binder was added, and the powders were wet-pulverized in a polypot for about 10 hours so as to obtain porcelain having the composition ratio shown in Table 1. After dehydration, the particles were sized using a Saran G5O mesh, with an outer diameter of 13.5 m and an inner diameter of 8.
A crane and a ring-shaped piece with a wall thickness of 1.2 mm,
Preliminary firing was performed at 1100°C for 1 hour, followed by nitrogen 9
7% hydrogen and 3% hydrogen at 1380° C. for 2 hours. The fired porcelain had an outer diameter of 11 mm, an inner diameter of 6.6 mm, and a wall thickness of 1 fi.

Furthermore, three silver electrodes were formed on one side of the ring-shaped porcelain with a gap of 1.5 mm, and a silver electrode was formed on the entire surface of the other side to prepare a sample. In the thus obtained varistor, the porcelain crystal grains are semiconductor, and the porcelain grain boundaries are made high and low.

Connect the obtained sample to a constant current power supply and apply 1 mA and lo
The voltage value at mA was measured for each.

The voltage values at that time were determined as El and EIO, respectively. And the threshold voltage (V th ) is EIO
The nonlinear coefficient (α) was determined using the following formula.

α-1/' (JogEl O/E1) In addition, the bending height is measured using a push-pull gauge.As shown in the drawing, the lower surface of sample A is supported by supports B and C.
A static load (W) is applied in the direction of the arrow in the drawing using a cutting edge from the top surface of sample A to approximately midway between supports B and C.
It is expressed by the static load when sample A breaks.

The measurement results are shown in Table 1. Note that the bending strength indicates a value on the verge of destruction of the sample. In Table 1, the samples marked with * are outside the scope of this invention, and all other samples are within the scope of this invention.

(Left below) Comparative example 5rTi03 is the main component, Y2Os is the semiconducting agent
, Nbz O5, WO3, l, a2 o, etc.
It was weighed so as to obtain porcelain having the composition shown in the table, and then treated in the same manner as in the example to obtain a sample.

The threshold voltage (
vth), nonlinear coefficient (α), and bending strength (kg), and the results are shown in Table 2.

(The following is a blank space) As is clear from a comparison of Tables 1 and 2 of the Sanskrit 2, at least one of Er2O3°H,03 and Ta2O5, Nb2O5 are used as semiconductor forming agents, as in the present invention. By including at least one of these, the threshold voltage and nonlinear coefficient were comparable to conventional ones in terms of characteristics, and the bending strength was improved by about 20 to 80%.

[Brief explanation of drawings]

The drawing is a schematic diagram illustrating a method for measuring bending strength. Patent applicant Murata Manufacturing Co., Ltd. Representative Patent attorney Oka 1) Zen Kei (1 idiot)

Claims (1)

[Scope of Claims] Strontium titanate, or strontium titanate as a main component and containing other titanates, zirconates, and stannates, the main component of which is 98.80 to 99.88 mol%, Er_2O_3 and Ho_2O_3. The total of at least one of them and at least one of Ta_2O_5 and Nb_2O_5 is 0.1 to 1.0 mol%, MnO_
A ceramic composition for a voltage nonlinear resistor, comprising 0.02 to 0.2 mol% of 2.