CN85107480B - Porous ceramics sensitive to humidity - Google Patents

Abstract

The present invention relates to a resistor type humidity sensitive of which the resistance is changed via the change of relative humidity. A humidity sensitive body takes ZnCr2O4, LiZnVO4 as principal components which are respectively has 40 to 98.8 mol% and 10 to 0.1 mol%, and Y2O3 and SnO2 are added so as to form a joint sintered body. The element has the characteristics of small size, good ageing resistance, no heat cleaning, long-term use, rapid response, small temperature coefficient, moderate resistance value, high measuring precision, etc., and the element can be used as a humidity measurement and control element of textiles, meteorology, warehouses and air conditioning systems.

Description

A kind of humidity sensitive porous ceramic film material

The present invention is the resistive moisture sensor that a kind of resistance changes with relative humidity variations.This element can be used for measuring the relative humidity of physical system, its a kind of electronic sensor.

The wet body of the sense of resistive moisture sensor use at present mainly is: (1) lithium chloride; (2) Fe ₃O ₄Thick-film type; (3) MgCr ₂O ₄-TiO ₂, TiO ₂-V ₂O ₃, Ca ₁₀(PO ₄) _{5 〉}(OH) ₂Deng sintered compact.The wet resistance characteristic of lithium chloride humidity-sensitive element linearly changes, and sensitivity is also higher, but its contamination resistance is poor, and the time of response is long, and volume is big, and the life-span is short, can not at high temperature work.MgCr ₂O ₄-TiO ₂Ceramic moisture-sensitive element, it is wide to have useful range, and the time of response is short, and the advantage that can at high temperature work, but aging easily needs regularly warm wash, therefore can not in closed loop control system, use for a long time, and the resistance value very high (10 during low humidity ⁷～10 ⁸This uses Ω to secondary instrument and brings difficulty.In order to solve the problem that above-mentioned humidity-sensitive element exists, Toshiba Corp has developed H104 type and H104C type humidity-sensitive element, and the wet body of its sense is respectively: ZnCr ₂O ₄-LiZnVO ₄, ZnCr ₂O ₄-V-Zn-Li-Cu-O, this ceramic moisture-sensitive element functional, and commercialization occupy advanced international standard.But several important indicators still exist tangible deficiency.

As: the time of response is long: 10 → 90%RH, 90 → 10%RH

Be 2 minutes

Measuring accuracy is poor: ± 5%RH-± 10%RH

Temperature factor is bigger: 1%RH/ ℃

(annotate: documents, the lt of Toshiba " No. 1, I-(37 volume) is clear and reached in 57 years

The lt of Toshiba " No. 8, I-(39 volume) clear and 59 years)

And contrasting H104 type ceramic moisture-sensitive element, the present invention is significantly improved at aspect of performance.Element ageing resistance of the present invention is good, without warm wash, and the energy life-time service, the time of response is short, and temperature factor is little, the measuring accuracy height.

Its main performance index is:

Time of response: 50～90%RH 20 seconds

90～50%RH 40 seconds

Measuring accuracy :≤4%RH

Temperature factor: 0.3%RH/C °

Wet-resistance characteristic (negative exponent characteristic):

10%RH-98%RH

3×10 ⁶Ω-3×10 ³Ω

The ratio range of humidity-sensitive element of the present invention is:

ZnCr ₂O ₄40-98.8 mol%

LiZnVO ₄10-0.1 mol%

Y ₂O ₃10-0.1 mol%

SnO ₂40-1 mol%

Its process for making is:

1. at first prepare ZnCr respectively by stoicheiometry ₂O ₄, LiZnVO ₄, then according to a certain percentage with LiZnVO ₄, Y ₂O ₃, SnO ₂Mix ZnCr ₂O ₄In.

2. the raw material of getting ready is carried out 24 hours wet ball-millings.

3. the raw material that ball milling is good was 800～900 ℃ of following pre-burnings 1～2 hour.

4. pre-burned raw material is sieved, add suitable amount of adhesive, adopt rolling formation, make 4 * 4 * 0.25mm ³Or 12 * 15 * 0.25mm ³Thin slice, this technology is convenient to produce by batch.

With the slice, thin piece of forming 900～1400 ℃ of following sintering 1～5 hour.

6. be coated with RuO ₂Electrode or steam interdigital gold electrode.

7. last top electrode lead-in wire.

So just made humidity-sensitive element.

From the wet body of above-mentioned sense as can be known is to adopt conventional stupalith manufacturing process.Because the wet body of sense is the sintered compact that forms by high temperature sintering, so thermal characteristics is stable, ageing resistance is good, and fabrication yield is also very high.

Below be several formulation examples:

Test portion: component (mol%)

NO. ZnCr ₂O ₄LiZnVO ₄Y ₂O ₃SnO ₂

1 95 3 1 1

2 93 2 1 4

3 87 2 1 10

4 82 2 1 15

5 76 3 1 20

6 68 5 2 25

7 63 5 2 30

8 61 7 2 30

9 51 7 2 40

10 47 10 3 40

Claims (9)

1, a kind of resistance is characterized in that with the resistive moisture sensor that the variation of relative humidity changes element is to be mixed with Y ₂O ₃, SnO ₂ZnCr ₂O ₄-LiZnVO ₄Sintered compact.

2, according to the described resistive moisture sensor of claim 1, wherein ZnCr ₂O ₄-LiZnVO ₄Ratio range be:

ZnCr ₂O ₄40-98.8 mol%

LiZnVO ₄10-0.1 mol%

3, according to claim 1 or 2 described resistive moisture sensors, the metal oxide of being mixed is Y ₂O ₃, SnO ₂, its ratio range is respectively:

Y ₂O ₃10-0.1 mol%

SnO ₂40-1 mol%

4, according to the substrate of claim 1 or 2 described resistive moisture sensors, adopt film rolling forming process.

5, according to the substrate of the described resistive moisture sensor of claim 3, adopt film rolling forming process.