CN102235992A - Gas sensor and preparation method thereof - Google Patents

Abstract

The invention provides a gas sensor, which comprises an insulating layer, a reference gas layer and a sensing layer from bottom to top, and is characterized in that the insulating layer contains aluminum oxide and glass frit, and the reference gas layer contains yttrium stabilized Zirconia, alumina and glass powder, the sensing layer contains yttrium stabilized zirconia, alumina and glass powder. The present invention also provides a preparation method of the modified gas sensor, which includes sequentially stacking and pressing an insulating layer, a reference gas layer and a sensing layer from bottom to top, and sintering to obtain the gas sensor. In the gas sensor of the present invention, the binding force of each layer is very high, so that the gas sensor has better sealing performance.

Description

A kind of gas sensor and preparation method thereof

technical field

The invention relates to a gas sensor and a preparation method thereof.

Background technique

With the development of social economy, the pollution of the atmospheric environment is becoming more and more serious, and the control of various harmful gas emissions has gradually become a social issue. Among them, industrial waste gas and automobile exhaust are the focus of people's attention, and the monitoring of N _x O in the exhaust gas The content of /C _x H and O ₂ is one of the most studied subjects. At present, the common components used to monitor exhaust gases are mainly automotive oxygen sensors. The automobile oxygen sensor is used to feed back the combustion gas condition to the engine control unit in real time, while the electronic control injection system of the engine precisely controls the air-fuel ratio according to the signal provided by the oxygen sensor, thereby adjusting the air-fuel ratio of the mixture (A/F, air and The mass ratio of gasoline) is near the theoretical value.

For example, CN101042366A discloses a method for preparing a flat-plate oxygen sensor chip. First, a sensor sheet, an intermediate sheet (ie, a reference gas layer) and a heating sheet are prepared by a tape casting method, wherein the base of the sensor sheet, the intermediate sheet, and the heating sheet The material is YSZ, and the insulating layer is aluminum oxide; before lamination and hot pressing, YSZ or ceramic powder containing 80-99% aluminum oxide is printed and coated on both sides of the intermediate sheet. In this method, ceramic powder is coated on both sides of the intermediate sheet, which can improve the bonding force between the sensor sheet, the intermediate sheet, and the heating sheet to a certain extent, but the bonding force of each laminated layer still cannot meet the requirements, which makes the airtightness of the chip oxygen sensor poor.

Contents of the invention

The invention solves the technical problem in the prior art that the heterogeneous combination is difficult in the preparation process, which makes the bonding force of each laminated layer of the gas sensor weak and the sealing performance poor.

The invention provides a gas sensor, which comprises an insulating layer, a reference gas layer and a sensing layer from bottom to top, wherein the insulating layer contains alumina and glass frit, and the reference gas layer contains YSZ, alumina and Glass powder, the sensing layer contains yttrium stabilized zirconia, aluminum oxide and glass powder.

The invention also provides a method for preparing a gas sensor, which comprises sequentially stacking and pressing an insulating layer, a reference gas layer and a sensing layer from bottom to top, and sintering to obtain the gas sensor.

In the gas sensor provided by the present invention, by properly adjusting the composition of the insulating layer, the reference gas layer and the sensing layer, adding aluminum oxide to the reference gas layer and the sensing layer, and adding glass powder to all three stacks, Therefore, the degree of heterogeneous combination of the reference gas substrate, the insulating layer and the sensing layer is improved, and the bonding force between the insulating layer, the reference gas layer and the sensing layer is improved, thereby ensuring that the gas sensor has better sealing performance. It can be seen from the test results in Table 1 that the change in air pressure before and after the test of the gas sensor provided by the present invention is less than 0.05 MPa, and the tensile strength reaches 1.7 MPa or above.

Detailed ways

The invention provides a gas sensor, which comprises an insulating layer, a reference gas layer and a sensing layer from bottom to top, and is characterized in that the insulating layer contains aluminum oxide and glass frit, and the reference gas layer contains yttrium stabilized Zirconia, alumina and glass powder, the sensing layer contains yttrium stabilized zirconia, alumina and glass powder.

The inventors of the present invention have found through a large number of experiments: the reference gas layer contains alumina, which can improve the bonding force between the reference gas layer and the insulating layer; similarly, the sensing layer also contains alumina to ensure that the sensing layer and the reference layer Part of the specific gas layer is combined homogeneously, thereby improving the binding force; in addition, the insulating layer, the reference gas layer and the sensing layer of the present invention all contain glass powder, which makes the insulating layer, the reference gas layer and the sensing layer Part of the material is homogeneous; on the other hand, glass powder can be used to enhance the bonding degree of alumina and YSZ, specifically including (1) alumina in the insulating layer and YSZ in the reference gas layer, (2) YSZ in the reference gas layer and alumina, (3) YSZ in the reference gas layer and alumina in the sensing layer, (4) alumina in the reference gas layer and YSZ in the sensing layer, and (5) alumina and YSZ in the sensing layer combination between. Therefore, the insulating layer, the reference gas layer and the sensing layer of the gas sensor of the present invention have higher bonding force, so that the gas sensor has better sealing performance and prolong the service life of the gas sensor of the present invention.

In addition, the inventors of the present invention also found that the glass powder contained in the sensing layer also has the following advantages: (a) the glass powder can inhibit the excessive growth of zirconia grains in the sensing layer, making the electrical properties of YSZ more stable; (b) Glass powder can reduce the grain boundary resistance between zirconia grains, especially reduce the boundary resistance value between zirconia and electrodes, thereby reducing voltage loss and enhancing voltage signal.

The content of aluminum oxide in the insulating layer is 92-98wt%, the content of glass powder is 2-8wt%; the content of yttrium-stabilized zirconia in the reference gas layer is 85-95wt%, and the content of aluminum oxide is 2 -8wt%, the content of glass powder is 2-8wt%; the content of yttrium-stabilized zirconia in the sensing layer is 80-95wt%, the content of aluminum oxide is 2-15wt%, and the content of glass powder is 2-8wt% %.

The insulating layer, the reference gas layer and the sensing layer of the present invention all contain glass powder, and the glass powder is a kind of material with a glass phase formed by pre-calcination of various inorganic oxides known to those skilled in the art. Preferably, the glass powder used in the present invention contains 5-40wt% silicon oxide, 30-60wt% boron oxide, 10-35wt% bismuth oxide, 2-10wt% lithium oxide, 5-20wt% strontium oxide, 2-20wt% % lead oxide, 5-25 wt% alumina and 2-8 wt% zirconia.

In the glass powder, silicon oxide, boron oxide and bismuth oxide are the main phases of the glass, which is beneficial to the interpenetration of the zirconia and aluminum oxide layers, thereby enhancing the bonding degree of aluminum oxide and YSZ; lithium oxide and strontium oxide can improve the high temperature of the glass. Electrical conductivity; lead oxide is used to extend the glass transition temperature and enhance the chemical stability of the glass body; aluminum oxide is used to improve the strength of the glass powder during sintering, and also helps crystallization; zirconia helps crystallization and strengthens the glass phase Excellent strength and thermal shock resistance, and effectively reduce the thermal expansion coefficient of the glass phase.

As a preferred embodiment of the present invention, the glass frit may also contain 2-10 wt% regulator, and the regulator is selected from nickel oxide, scandium oxide or europium oxide. The glass frit regulator can form a mixed transition phase at the boundary between YSZ and the electrode in the sensing layer, reducing the boundary resistance and the internal resistance of the sensor.

In the present invention, the insulating layer of the gas sensor is provided with a heater for heating the sensing layer to make the sensing layer reach the working temperature. A heater substrate is arranged under the insulating layer. The upper and lower surfaces of the sensing layer are respectively provided with sensing electrodes, which are respectively used as test electrodes and reference electrodes for testing the gas concentration difference on both sides of the sensing layer.

The heater substrate is a zirconia casting substrate, preferably a 5% mole YSZ casting substrate. The YSZ casting substrate can be commercially purchased or self-made, wherein the self-made method is a method for preparing ceramic substrates by casting method known to those skilled in the art.

In the present invention, the thickness of the insulating layer is 30-60 μm, the thickness of the reference gas layer is 300-600 μm, and the thickness of the electrolyte layer is 300-500 μm. Preferably, the insulating layer has a thickness of 40-50 μm, the reference gas layer has a thickness of 400-600 μm, and the electrolyte layer has a thickness of 400-500 μm.

The present invention also provides a preparation method of the gas sensor, which comprises sequentially stacking and pressing an insulating layer, a reference gas layer and a sensing layer from bottom to top, and sintering to obtain the gas sensor.

Wherein, the method for preparing the insulating layer can adopt the screen printing method commonly used by those skilled in the art, which specifically includes the following steps: printing the insulating layer slurry, the electrode slurry, and the insulating layer slurry on the heater substrate in sequence, and then drying The insulating layer attached to the heater substrate was obtained, which was designated as the first layer. In the present invention, the insulating layer slurry is a mixture containing insulating layer powder material and insulating layer organic vehicle, wherein the insulating layer powder material contains alumina and glass powder.

The organic vehicle of the insulating layer contains organic solvent and organic resin. Various components in the organic carrier of the insulating layer all adopt various components commonly used by those skilled in the art, for example, the organic solvent is selected from one or more of dibutyl phthalate and/or cyclohexanone terpineol One, the organic resin adopts ethyl cellulose and/or polyvinyl butyral. Based on 100 parts by weight of insulating layer powder material, the amount of organic solvent used is 10-35 parts by weight, and the amount of organic resin used is 5-15 parts by weight.

The method for preparing the reference gas layer is well known to those skilled in the art, such as directly adopting the method of dry pressing or coating the reference gas layer slurry, and then drying and forming to obtain the reference gas layer of the present invention, denoted as the second lamellae. In the present invention, the reference gas layer slurry is a mixture containing a reference gas layer powder material and a reference gas layer organic carrier, wherein the reference gas layer powder material contains yttrium-stabilized zirconia, alumina and glass powder . The reference air-layer organic carrier is an organic slurry system commonly used by those skilled in the art for preparing YSZ cast sheets, and details are not described here. Based on 100 parts by weight of the reference gas layer powder material, the amount of the reference gas layer organic carrier is 20-60 parts by weight.

The method for preparing the sensing layer generally includes: first casting the sensing layer slurry to obtain the sensing layer substrate, and then coating the electrode slurry on the upper and lower surfaces of the sensing layer substrate through a screen printing process, Finally, the sensing layer can be obtained by drying, which is recorded as the third layer. In the present invention, the sensing layer slurry is a mixture containing sensing layer powder material and sensing layer organic carrier, wherein the sensing layer powder material contains yttrium stabilized zirconia, alumina and glass powder. The organic carrier of the sensing layer is an organic slurry system commonly used by those skilled in the art for preparing YSZ casting sheets, which will not be described in detail here. Based on 100 parts by weight of the powder material of the sensing layer, the amount of the organic vehicle for the sensing layer is 20-60 parts by weight.

In the present invention, the content of alumina in the insulating layer powder material is 92-98wt%, and the content of glass powder is 2-8wt%; the content of yttrium-stabilized zirconia in the reference gas layer powder material is 85% -95wt%, the content of alumina is 2-8wt%, the content of glass powder is 2-8wt%; the content of yttrium-stabilized zirconia in the powder material of the sensing layer is 80-95wt%, and the content of alumina is 2-15wt%, and the content of glass powder is 2-8wt%.

In the preparation method of the present invention, the electrode slurry used is the electrode slurry commonly used by those skilled in the art, such as pure palladium, gold, platinum slurry or palladium, gold, platinum alloy slurry. The electrode slurry may also contain one or more of terpineol, triolein and castor oil.

In the present invention, in order to improve the bonding degree of the insulating layer, the reference gas layer and the sensing layer when they are co-fired, thereby improving the airtightness and thermal shock resistance of the gas sensor, preferably, the insulating layer, the reference gas layer are prepared The same organic carrier system is used in the insulating layer organic carrier, the reference gas layer organic carrier and the sensing layer organic carrier respectively used in the insulating layer and the sensing layer.

According to the preparation method provided by the present invention, the first sheet, the second sheet and the third sheet prepared above are stacked in order from bottom to top, keeping the insulating layer of the first sheet upward, and then press, The gas sensor of the present invention can be obtained by sintering. The pressing conditions include: the pressure is 30-250MPa, and the time is 10s-30min; the sintering conditions include: the temperature is 1300-1650°C, and the time is 0.5-4 hours.

The gas sensor and its preparation method of the present invention will be further described below in conjunction with the examples. The raw materials used in Examples and Comparative Examples are all commercially available.

Example 1

(1) Raw material preparation:

Glass powder composition: 20wt% silicon oxide, 40wt% boron oxide, 15wt% bismuth oxide, 5wt% lithium oxide, 5wt% strontium oxide, 2wt% lead oxide, 5wt% aluminum oxide, 2wt% zirconia, 2wt% nickel oxide, 2wt% % scandium oxide, 2 wt% europium oxide.

Insulating layer slurry: 96 parts by weight of alumina, 4 parts by weight of glass powder, and 40 parts by weight of organic vehicle: 30 parts by weight of cyclohexanone terpineol, and 10 parts by weight of ethyl cellulose.

Reference gas layer slurry: 90 parts by weight of yttrium-stabilized zirconia, 5 parts by weight of alumina, 5 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

Sensing layer slurry: 92 parts by weight of yttrium-stabilized zirconia, 5 parts by weight of aluminum oxide, 3 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

(2) Insulating layer slurry, platinum electrode and insulating layer slurry are coated sequentially on one surface of the zirconia casting sheet, and dried to obtain an insulating layer attached to the heater substrate, which is recorded as the first layer.

(3) Dry press the reference air layer slurry, dry and form to obtain the reference air layer, which is recorded as the second sheet.

(4) Casting the sensing layer slurry to prepare a sensing layer substrate; screen printing platinum electrodes on both sides of the sensing layer substrate, and drying to obtain a sensing layer, which is recorded as the third layer.

(5) With the insulating layer of the first sheet facing upwards, the first sheet, the second sheet and the third sheet are stacked in sequence from bottom to top, pressed at 50°C with a force of 110MPa for 20 minutes, and then pressed at 1350°C After sintering for 3 hours, the gas sensor of this embodiment is obtained, denoted as A1.

Example 2

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), insulating layer slurry: 92 parts by weight of alumina, 8 parts by weight of glass powder, and 40 parts by weight of organic vehicle: 25 parts by weight of cyclohexanone terpineol, and 15 parts by weight of ethyl cellulose;

Reference air layer slurry: 90 parts by weight of yttrium-stabilized zirconia, 4 parts by weight of alumina, 6 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

Sensing layer slurry: 92 parts by weight of yttrium-stabilized zirconia, 4 parts by weight of aluminum oxide, 4 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as A2.

Example 3

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), in the insulating layer slurry: the insulating layer slurry: 98 parts by weight of alumina, 2 parts by weight of glass powder, and a total of 40 parts by weight of organic vehicle: wherein 20 parts by weight of cyclohexanone terpineol, ethyl cellulose Plain 20 parts by weight;

Reference air layer slurry: 90 parts by weight of yttrium-stabilized zirconia, 8 parts by weight of alumina, 2 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

Sensing layer slurry: 85 parts by weight of yttrium-stabilized zirconia, 10 parts by weight of alumina, 5 parts by weight of glass powder, and 40 parts by weight of an organic vehicle.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as A3.

Example 4

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), the glass powder composition: 25wt% silicon oxide, 40wt% boron oxide, 15wt% bismuth oxide, 5wt% lithium oxide, 5wt% strontium oxide, 3wt% lead oxide, 5wt% aluminum oxide, 2wt% zirconium oxide.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as A4.

Example 5

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), the glass powder composition: 25wt% silicon oxide, 25wt% boron oxide, 15wt% bismuth oxide, 5wt% lithium oxide, 10wt% strontium oxide, 5wt% lead oxide, 10wt% aluminum oxide, 5wt% zirconium oxide.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as A5.

Comparative example 1

The gas sensor of this comparative example was prepared by the method disclosed in Example 1 of 101042366A, which is denoted as D1.

Comparative example 2

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), insulating layer slurry: 100 parts by weight of alumina, 40 parts by weight of organic vehicle: 30 parts by weight of cyclohexanone terpineol, 10 parts by weight of ethyl cellulose.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as D2.

Comparative example 3

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), the reference gas layer slurry: 90 parts by weight of yttrium-stabilized zirconia, 10 parts by weight of alumina, and 40 parts by weight of an organic carrier.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as D3.

Comparative example 4

The gas sensor of this embodiment was prepared in the same manner as in Example 1, the difference being that:

In step (1), the sensing layer slurry: 100 parts by weight of yttrium-stabilized zirconia, and 40 parts by weight of an organic vehicle.

Through the above steps, the gas sensor of this embodiment is obtained, denoted as D4.

Performance Testing:

1. Sealing test:

Pour into the gas sensors A1-A5 and D1-D4 with P(0)=1MPa gas, and use the air tightness detector XT070050 (Shenzhen Jinjing Electronic Instrument Co., Ltd.) to test the gas sensors A1-A5 and D1-D4 after 3 minutes The gas pressure P (3min). The test results are shown in Table 1.

2. Binding force test:

Use plug-and-pull tester 16 (Shanghai Gudeng Industrial Co., Ltd.) to apply initial pull-out strength L(0)=1MPa to gas sensors A1-A5 and D1-D4, increase 0.1MPa every 10s, until the gas sensor When the structure of the sample peels off obviously, record the pull-out strength L(t) at this time, and the test results are shown in Table 1.

Table 1

samples P(0)/MPa P(3min)/MPa L(0)/MPa L(t)/MPa A1 1 0.9998 1 2.3 A2 1 0.9995 1 1.9 A3 1 0.9925 1 1.7 A4 1 0.9756 1 1.8 A5 1 0.9520 1 1.7 D1 1 0.6255 1 1.1 D2 1 0.7055 1 1.2 D3 1 0.8174 1 1.3 D4 1 0.4257 1 1.3

As can be seen from the test results of the above table 2, the gas pressure change before and after the gas sensor test of the present invention is less than 0.05MPa, which is obviously lower than the test results of the comparative example, indicating that the gas sensor provided by the present invention has better sealing performance; and the gas sensor of the present invention The tensile strength of the gas sensor reached 1.7 MPa and above, indicating that the layers of the gas sensor of the present invention have better bonding force.

Claims (12)

1. gas sensor, comprise insulation course, reference gas-bearing formation and sensing layer from bottom to up successively, it is characterized in that, described insulation course contains aluminium oxide and glass dust, described reference gas-bearing formation contains yttrium stable zirconium oxide, aluminium oxide and glass dust, and described sensing layer contains yttrium stable zirconium oxide, aluminium oxide and glass dust.

2. gas sensor according to claim 1 is characterized in that, the content of aluminium oxide is 92-98wt% in the described insulation course, and the content of glass dust is 2-8wt%; The content of yttrium stable zirconium oxide is 85-95wt% in the described reference gas-bearing formation, and the content of aluminium oxide is 2-8wt%, and the content of glass dust is 2-8wt%; The content of yttrium stable zirconium oxide is 80-95wt% in the described sensing layer, and the content of aluminium oxide is 2-15wt%, and the content of glass dust is 2-8wt%.

3. gas sensor according to claim 1, it is characterized in that, contain 5-40wt% monox, 30-60wt% boron oxide, 10-35wt% bismuth oxide, 2-10wt% Lithia, 5-20wt% strontium oxide strontia, 2-20wt% massicot, 5-25wt% aluminium oxide and 2-8wt% zirconia in the described glass dust.

4. gas sensor according to claim 3 is characterized in that, the glass dust that also contains 2-10wt% in the described glass dust is adjusted body, and described glass dust is adjusted body and is selected from nickel oxide, scandium oxide or europium oxide.

5. according to each described gas sensor of claim 1-4, it is characterized in that, be provided with well heater in the insulation course, the insulation course below is provided with the well heater substrate, and two surfaces up and down of sensing layer are respectively equipped with test electrode and contrast electrode.

6. gas sensor according to claim 1 is characterized in that, the thickness of insulation course is 30-60 μ m, and the reference thickness of gas is 300-600 μ m, and the thickness of dielectric substrate is 300-500 μ m.

7. the preparation method of the described gas sensor of claim 1 comprises that sintering obtains described gas sensor with the stack compacting successively from bottom to up of insulation course, reference gas-bearing formation and sensing layer.

8. method according to claim 7 is characterized in that, the method for preparing insulation course is included in and is coated with insulating layer coating slurry, electrode slurry, insulation course slurry on the well heater substrate successively, and oven dry can obtain described insulation course at the well heater substrate surface; Described insulation course slurry is the potpourri that contains insulation course powder material and insulation course organic carrier, and described insulation course powder material contains aluminium oxide and glass dust;

The method for preparing the reference gas-bearing formation comprises dry-pressing or the reference gas-bearing formation slurry of filming, and moulding obtains described reference gas-bearing formation; Stating reference gas-bearing formation slurry is the potpourri that contains reference gas-bearing formation powder material and reference gas-bearing formation organic carrier, and described reference gas-bearing formation powder material contains yttrium stable zirconium oxide, aluminium oxide and glass dust;

The method for preparing described sensing layer comprises that first curtain coating sensing layer slurry obtains the sensing layer substrate, and at the upper and lower surface of the sensing layer substrate slurry that prints electrode respectively, oven dry can obtain described sensing layer then; Described sensing layer slurry is the potpourri that contains sensing layer powder material and sensing layer organic carrier, and sensing layer powder material contains yttrium stable zirconium oxide, aluminium oxide and glass dust.

9. method according to claim 8 is characterized in that, the content of aluminium oxide is 92-98wt% in the described insulation course powder material, and the content of glass dust is 2-8wt%; The content of yttrium stable zirconium oxide is 85-95wt% in the described reference gas-bearing formation powder material, and the content of aluminium oxide is 2-8wt%, and the content of glass dust is 2-8wt%; The content of yttrium stable zirconium oxide is 80-95wt% in the described sensing layer powder material, and the content of aluminium oxide is 2-15wt%, and the content of glass dust is 2-8wt%.

10. each described method according to Claim 8, it is characterized in that, contain 5-40wt% monox, 30-60wt% boron oxide, 10-35wt% bismuth oxide, 2-10wt% Lithia, 5-20wt% strontium oxide strontia, 2-20wt% massicot, 5-25wt% aluminium oxide and 2-8wt% zirconia in the described glass dust.

11. method according to claim 10 is characterized in that, the glass dust that also contains 2-10wt% in the described glass dust is adjusted body, and described glass dust is adjusted body and is selected from nickel oxide, scandium oxide or europium oxide.

12. method according to claim 7 is characterized in that, the condition of described compacting comprises: pressure is 30-250MPa, and the time is 10s-30min; The condition of sintering comprises: temperature is 1300-1650 ℃, and the time is 0.5-4 hour.