JPS60170758A - Semiconductor gas detecting element - Google Patents

Abstract

PURPOSE:To obtain a gas detecting element having the low temp. coefft., of resistance by containing a prescribed quantity of SiO2, Al2O3, MgO, PtCl in SnO2, calcining them by hot pressing method and providing a RuO2 system electrode thereto. CONSTITUTION:0.1-20wt% silicon oxide, 0.1-30wt% aluminum oxide, 0.1- 5wt% magnesium oxide and 0.1-10wt% platinum chloride are added to a stannic oxide powder and mixed therewith, then calcined to 600-1,000 deg.C temp. under 100-1,000kg/cm<2> impressing pressure by hot pressing method to form a gas sensitive body 1. Ruthenium oxide system thick film resistance paste having 10OMEGA/square-10OMEGA/square sheet resistance is painted to the body 1, said body is baked at 600 deg.C to form an electrode 2, and the gas detecting element is obtained. The temp. coefft. (1/R.DELTAR/DELTAT) of said element is 5.1X10<-3>/ deg.C in 1,000ppm gaseous isobutane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor gas sensing element using a metal oxide semiconductor whose resistance value changes due to gas adsorption.

[Prior art]

Conventionally, this type of semiconductor gas horizontal thin device has been manufactured using raw material powders of toethylcellulose and terpineol with stannic oxide (Sn02)'fc as the main component on an alumina substrate printed with a thick film as a conductor tl-electrode of gold, platinum, etc. It is made by kneading an organic vehicle consisting of the following ingredients into a paste and printing a thick film on the gas-sensitive paste. Usually, this type of semiconductor gas detection element uses isobutane (iC4H1G) as the gas to be detected.
In order to promote adsorption and desorption of gas and methane (CH4) gas, it is heated to about 400°C. However, since the temperature coefficient of resistance of the element in the gas to be detected is high in this temperature atmosphere, it is easily affected by the ambient temperature. Therefore, when applied to a gas leak alarm, a highly accurate element temperature control circuit is required. It cannot be avoided from being priced out.

[Summary of the invention]

The purpose of the present invention is to solve these problems by adding 0.1 to 2 Qwt% of silicon oxide ('5ins) to stannic oxide (SnO2) and aluminum oxide (Al*Os).
0.1~30wt9J, magnesium oxide (MgO
) and 0.1 to 10 wt% of platinum chloride (PtC4) were heated using a hot press method at a firing temperature of 600 to 1000°C and a pressure of 7Jl marked 100.
A gas sensitive body was formed by firing at ~1000 kg/cIIL'', and a ruthenium oxide (RuO□)-based thick film resistance paste with a sheet resistance of 10Q/mm ~ IOKΩ/mm was baked on the gas sensitive body as an electrode. be a sign.

[Explanation of Examples]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing one embodiment of a gas detection element according to the present invention. 2wt'% silicon oxide in stannic oxide powder
, aluminum oxide k1wt, magnesium oxide 1
wt% and 0.9 wtfr of platinum chloride, mixed in a ball mill for 46 hours, calcined at 700° C. for 2 hours, and re-pulverized to obtain a mixed powder. The mixed powder thus obtained was molded using a press, etc., and then hot pressed to give a weight of 550 kg/cIIL.
2 hours at a pressure of A ruthenium oxide thick film resistor paste having a notebook resistance of 100 Ω is applied to both ends of the electrode 2 and baked at 600° C. to form electrodes 2, thereby obtaining a gas sensing element.

Here, the temperature coefficient (TCR) of the gas sensing element is isobutane gas at °C 110001) p 'l' CB
.

is 5. The TCR of the conventional original model gas sensing element is 2.OX 10''/'0.

2 and 3 show 2 wt% silicon oxide, 1 wt% aluminum oxide, and 1 wt% magnesium oxide.

The main (basic) composition is 0.9 wt% platinum chloride, 01 to 20 wt% silicon oxide, and 0 total aluminum oxide.
．． 1-30wt%, magnesium oxide 0.1-swt
Isobutane gas 1 at 400°C for an element developed with H and platinum chloride in the range of 0.1 to 1Qwt%, respectively.
T CIL and sensitivity (R, A/I (
, , :R, A=device resistance in air s RG "device resistance in isobutane gas 11000pp" is shown. Also, in FIGS. 4 and 5, silicon oxide, aluminum oxide, magnesium oxide, Isobutane 11000 at 400°C was obtained by developing each component in the same manner as above, with central composition Q and platinum chloride at 1wt%.
TCR and sensitivity in pp are shown.

Correspondingly, in FIGS. 6 and 7, silicon oxide is 20 wt%.

Aluminum oxide 30wt%, magnesium oxide 5wt
%.

The TCR and sensitivity in isobutane gas of 11,000 ppm at 400° C. are shown for a device developed in the same manner with each component having a central composition of 0.9 wt % e of platinum chloride.

Note that the conditions for forming these elements are the same as those described above. On the other hand, thick film gas sensing elements were fabricated using the conventional method for each of the compositions shown in FIGS. 2 to 7, but there was no significant relationship between the composition and TCR, and the TCR was 1. 8
X 10 = ~2.2 X 10-''7°C.

As is clear from FIGS. 2 to 7, silicon oxide.

If each of aluminum oxide, magnesium oxide, and platinum chloride is less than 0.1 wt%, the effect of lowering TCR'ji is not sufficient. Also, silicon oxide is 20wt%.

Aluminum oxide is 30wt%, magnesium oxide is 5%
If wt% and platinum chloride exceed 10 wt%, the sensitivity to inbutane gas will be 10 or less, resulting in insufficient performance of the gas detection element.

Next, the effects of electrode materials will be described.

The collector electrode material having the composition of the above example has a resistance of 7 points and 10 points.
The '1' CR and sensitivity of the device are shown in FIGS. 8 and 9, respectively, in the case of a ruthenium oxide thick film resistor paste of Ω/Ω to 10 4 Ω/Ω.

On the other hand, when Au and Ag conductor pastes are used as electrode materials, the TCR is 1.9X 10 ''10
゜1,7 x 10'-''/'O.As is clear from these results, the ruthenium oxide-based thick film resistance paste t having a sheet resistance of 10Ω/hole to 10'Ω/hole.
By using it as an electrode material, j) a gas sensing element with low TCR can be obtained. Note that if the sheet resistance is less than 10 Ω/mouth, the effect of lowering TC)tf is not sufficient, and if the note resistance is greater than 10 4 Ω/mouth, the sensitivity is insufficient and unsuitable.

When forming the reaction body, the applied pressure of hot press 'e100kg/
The 'l' Cl values and sensitivities for the device when loaded in the range of cIrL2 to 1σookgm2 are also shown.

It can be seen from both figures that the TC)t and sensitivity of the gas sensing element are good in the applied pressure range of 100 to 1000 kg/cm2. In addition, the applied pressure is 100k
If the gZ thickness is less than 2, the sinterability will not be sufficient and it will break easily.

Moreover, the effect of lowering TCR is not sufficient. Furthermore, if the applied pressure exceeds 1000 kg/cmz, the element becomes too dense, resulting in poor gas permeability and a decrease in sensitivity.
The figure shows the TCR and sensitivity of the gas detection element when the temperature is varied in the range of 0°C to 1000°0. 600
A highly sensitive gas sensing element with a low TCR can be obtained in the firing temperature range of 600°C to 1000°C.
It has been found that a firing temperature lower than 0.degree. C. does not have a sufficient effect of lowering TCR, and a firing temperature higher than 100"C does not provide sufficient sensitivity.

In the above embodiment, a case was described in which the scum detection element was tested in an inbutane gas atmosphere, but it works similarly even in methane scum.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a gas detection element with a low temperature coefficient of resistance in a gas to be detected, thereby facilitating the realization of a low-cost and highly reliable gas leak alarm.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a gas detection element according to the present invention, and FIGS. 2 to 13 are diagrams showing evaluation results of the gas detection element of the same embodiment. 1... Gas sensitive body, 2... Electrode. l ---m-, Quantity of No. 5 eggplant (V grated 7 pigeons 5 are spicy ((st-/-) , h ) 85 Fig. 4-ante fwt〆fu 86 section k Force 0'% (tutl) $7 Fig. erJ 77n Fx ly' (Kl/1m2) ρθ
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Claims (1)

[Claims] Add 0.1 to 20 Wt of silicon oxide to stannic oxide, 1 to 3 Qwt% of aluminum oxide, 0.1 to 5 wt of magnesium oxide, and 0.1 to 10 wt of platinum chloride.
A gas sensitive body formed by firing a powder containing H at a temperature of 600 to 1,000°C and an applied pressure of 100 to 1,000 kg/'c+n'', and a sheet resistance formed on this gas sensitive body of lOΩ/mouth to IOKΩ/ 1. A semiconductor gas sensing element comprising an electrode made of a ruthenium oxide thick film resistor paste.