JPH02100301A - Moisture-sensitive element - Google Patents

Abstract

PURPOSE:To reduce aging and temperature dependency of a resistor by using a porous sintered body ceramic obtained by including a 0.1 to 10mol part of BaCO3 and a 0.01 to 2mol part of Ta2O5 for a main constituent 100 mold part consisting of a 35 to 90mol part of TiO2 and a 10 to 65mol part of SiO2 and then sintering it. CONSTITUTION:A particle weighed with a ratio of a 0.1 to 10mol part of BaCO3 and a 0.01 to 2mol part of Ta2O5 for a main constituent 100mol part consisting of a 35 to 90mol% of TiO2 and a 10 to 65mol% of SiO2 is mixed. Then, after forming it to a specified shape, a porous sintered body ceramic is obtained by sintering it at a temperature of 1250 to 1400 deg.C. A desired humidity sensor can be assembled using this moisure-sensitive element. Thus, it can function within a wide range of detection measurement range (moisture: 5-95% R.H.), thus reducing aging and temperature dependency of a resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a humidity sensing element suitable for a humidity sensor of an aerial FiI device or a humidity control system.

(Prior art) Conventionally, most of the humidity sensing elements used in this type of humidity sensor utilize changes in electrical resistance, and among them, those made of ceramics made of sintered metal oxides are Compared to organic materials, it is superior in terms of deterioration of the material itself, heat resistance, etc.

However, even if the conventional moisture sensing elements made of ceramics have good characteristics in the initial stage, they have the disadvantage that they tend to deteriorate over time when used for a long time. Ta.

For this reason, humidity sensors have been put into practical use that are equipped with heating cleaning heaters for regeneration near the sintered ceramics.

In addition, metal oxides in the composition generally have a negative temperature coefficient of resistance, and the resistance value increases or decreases even with slight temperature changes, so it is difficult to measure humidity under conditions where temperature changes cannot be ignored. However, there was a drawback that the error was large.

(Problems to be Solved by the Invention) As described above, in order to reduce the disadvantages of the conventional moisture sensing element made of metal oxide ceramics, such as carbonization over time and temperature dependence of resistance, heating cleaning heaters, heating cleaning heaters,
This requires a temperature compensation circuit, increases the size of a humidity sensor using these humidity sensing elements, and has the problem of increasing power consumption.

The present invention eliminates such conventional drawbacks and provides a moisture-sensitive element,
Furthermore, as a humidity sensor using this, it has a wide detection and measurement range for humidity, and furthermore, a humidity sensing element that itself reduces the above-mentioned changes over time and temperature dependence of resistance, and a humidity sensing element using this. The aim is to provide a humidity sensor that is

This makes it possible to realize a humidity sensor that does not require a conventional cleaning heater or special temperature compensation circuit.

(Means for Solving the Problems) The moisture sensitive element of the present invention contains 35 to 90 mole parts of TiOz and 5
0.1 to 10 mole parts of BaC0* and Tazo
It is characterized by being made of a porous sintered ceramic body containing 1 to 2 mole parts of Bo and sintered therein.

Furthermore, in order to specifically obtain this, Ti0z35~90
Main component 1 consisting of mol% and 510g1O to 65 mol%
Powders weighed at a ratio of 1 to 10 mol parts of B a CO3 and 01 to 2 mol parts of T az Os 0 to 00 mol parts are mixed, molded into a predetermined shape, and heated to a temperature of 1250 mol. By firing at -1400'C, a porous sintered ceramic is obtained, and a desired humidity sensor is assembled using this humidity sensing element.

(Function) As the moisture sensitive element of the present invention, the main component of its composition is Ti02
35 to 90 mol% and 5iOzlO to 65 mol%, where TiO2 acts as a base material for the moisture-sensitive element, and Sing acts to promote porosity in the case of sintered ceramics. do.

Thus, T i Oz is less than 35 mol %, i.e. 5
If iO- is more than 65 mol%, the resistance value of the resulting sintered ceramic becomes large, the rate of change over time increases, and the strength of the sintered ceramic decreases, which is not preferable. Also, conversely, T i Ot is 90 mol%
If the SiOz exceeds 10% by mole, the temperature dependence of resistance increases and the resulting sintered ceramic becomes insufficiently porous, resulting in a decrease in porosity. Therefore, the tendency of resistance change with respect to humidity change becomes slower, which is undesirable.

Next, regarding the additive components, BaCO3 has the effect of suppressing grain growth and increasing the porosity of the sintered ceramic. Therefore, B a COs, T i O and Sto
When it is less than 0.1 mole part per 100 mole parts of the main component consisting of w, the particle size becomes large and the porosity decreases, so the tendency of resistance change with respect to humidity changes becomes slower, and the temperature dependence of resistance decreases. Sexuality becomes larger. On the other hand, B a C
If Os exceeds 10 mole parts, the resistance value of the sintered ceramic becomes large, which is not preferable.

Next, Taxes acts as a valence control agent for TiO□, and 0.01 parts by mole of the above main component
If it is less than the molar part, the resistance value of the sintered ceramic becomes large, which is not preferable. Moreover, if it exceeds 2 molar parts, the resistance value of the sintered body becomes large, which is not preferable.

As described above, TtO constitutes the base material of the moisture-sensitive element of the present invention, and the above-mentioned predetermined amount of S i Ot
By simultaneously adding 1B a CO3 and TatOs, it was possible to develop excellent moisture sensitivity properties.

The present invention will be further described below with reference to Examples.

(Example) For samples 1 to 20 shown in Table 1, each component raw material was weighed so as to have each composition, and 12
Mixed for an hour. After drying this mixture, a small amount of a binder consisting of polyvinyl alcohol was added and stirred.

Next, the powder was passed through an 80 mesh sieve to obtain granulated powder. This granulated powder was heated to a diameter of 10 mm at a pressure of 1 ton 7 cm.
III11, and was molded into a disk shape with a thickness of 0.8 mm. Next, this was fired in air at a temperature of 1350° C. for 1 hour to obtain a porous sintered ceramic.

Next, RuO□ paste was baked on both sides of this sintered ceramic body, and lead wires were attached and a pair of electrodes were provided.

The moisture sensitivity characteristics of each sample thus obtained were determined by measuring electrical resistance. The results are also summarized in Table 1.

(Effects of the Invention) The humidity sensing element made of the porous sintered ceramic of the present invention functions in a wide detection and measurement range of humidity 5 to 95% (R, t(,), and exhibits resistance change over time and temperature dependence. A humidity sensor equipped with this is small and highly accurate, and has extremely high utility value.

Claims (1)

[Claims] 1. 35 to 90 mole parts of TiO_2 and 1 part of SiO_2
For 100 mole parts of the main component consisting of 0 to 65 mole parts,
0.1 to 10 mole parts of BaCO_3 and Ta_2O_5
1. A moisture-sensitive element comprising a porous sintered ceramic containing 0.01 to 2 mole parts of the porous sintered ceramic.