CN1160565C - Preparation method of thick film air/fuel ratio sensor with wide temperature and narrow resistance band - Google Patents

Abstract

The preparation method of wide temperature and narrow resistance band thick film air/fuel ratio sensor, according to the increase of grain boundary barrier height of N-type transition metal oxide semiconductor in oxidizing atmosphere and the reduction of grain boundary barrier height in reducing atmosphere, adopts rutile type TiO ₂ structure N-type doping is carried out in the body, and P-type compound diffusion is carried out at the grain boundary. The conductivity of the sample decreases sharply in an oxidizing atmosphere, and increases sharply in a reducing atmosphere. The thick film process is used to make the sample in the range of 250 ° C to 800 ° C, so that the lowest resistance value in the oxidation state at the high temperature end and the highest resistance value in the reduction state at the low temperature end have a difference of 1 to 3 orders of magnitude. The performance of the sensor is greatly improved by adopting the preparation method, and the cost is low.

Description

Preparation method of thick film air/fuel ratio sensor with wide temperature and narrow resistance band

1. Technical field

The invention relates to an air/fuel ratio control sensor, and further relates to a preparation method of the sensor for air/fuel ratio control of various engines, combustion equipment and appliances.

2. Background technology

Air/fuel ratio control sensors have appeared on the market with ZrO ₂ concentration cell type, TiO ₂ and other oxide single-phase mixed resistance type. The ZrO ₂ concentration battery type has the problems of lead poisoning, structural phase change and high price in the range of room temperature to 800 ℃, and has the disadvantages of early failure and high cost in use. For this reason, people have done a lot of research on TiO ₂ and other oxide single-phase mixed resistance sensors, because in the wide temperature range from room temperature to 800 ° C, there are: (1) wide resistance band, high resistance state in the reduced state ; (2) Short life; (3) Shortcomings such as complex signal circuit. So it has not been put into use in large quantities so far. The research of IBMD method has been carried out again recently, but due to problems such as high preparation cost, difficulty in guaranteeing performance, and high heating temperature, it has not been popularized. However, with the increase in the number of automobiles, urban air pollution mainly comes from the emission of automobile exhaust. When the air/fuel ratio of various combustion equipment, appliances and automobile engines is improper, on the one hand, a large amount of harmful gases will be emitted, polluting the environment; on the other hand The energy cannot be fully utilized, resulting in waste.

3. Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a long-life, low-price, high-performance preparation method of a thick-film air/fuel ratio sensor with wide temperature and narrow resistance band. The technical scheme adopted in the present invention is: according to the improvement of the grain boundary barrier height of the N-type transition metal oxide semiconductor in the oxidizing atmosphere, and the reduction of the grain boundary barrier height in the reducing atmosphere, the N-type N-type transition metal oxide semiconductor is carried out in the body by using the rutile ^TiO2 structure. Doping, the grain boundary undergoes P-type recombination diffusion. The conductivity of the sample decreases sharply in an oxidizing atmosphere, and increases sharply in a reducing atmosphere. The thick film process is used to make the sample in the range of 250 ° C to 800 ° C, so that the lowest resistance value in the oxidation state at the high temperature end and the highest resistance value in the reduction state at the low temperature end have a difference of 1 to 3 orders of magnitude.

The preparation process of the present invention is:

1) Grinding the semiconductor ceramic powder reagent capable of synthesizing (TiSnNb)O2 _- based rutile structure into a billet, and burning at 1000°C to 1350°C for 30 minutes to 4 hours;

2) Finely pulverize the calcined green body and mix it with (0-20)%wt medium-temperature glass powder to make a sensitive paste for printing;

3) After screen-printing the interdigitated electrodes on the alumina substrate, place them at 800°C to 1000°C for 20 minutes to 1 hour;

4) After screen-printing the sensitive paste, place it at 1000°C-1350°C for 1-2 hours and control the cooling rate at 120°C-180°C per minute to cool the sample and make a sensitive element;

5) Use platinum slurry to weld the platinum wire and the interdigitated electrode lead-out end of the sensitive element, and burn at 800°C to 1000°C for 10 to 20 minutes to cool the sample naturally;

6) Screen-print the heater paste on the back of the sensitive element, and burn it at 650°C-850°C for 10-45 minutes;

7) After impregnating or coating 10%-50% catalyst salt solution, burn at 700°C-1000°C for 30 minutes-2 hours.

By adopting the preparation method of the invention, the performance of the air/fuel ratio sensor is improved, the manufacturing cost is reduced, and the control effect of the air/fuel ratio sensor is further improved.

4. Specific implementation

Example 1: After finely grinding the ceramic powder sample reagent with the composition of 0.63TiO ₂ +0.2SnO ₂ +0.05 Nb ₂ O ₅ +0.12Bi ₂ O ₃ into a blank, it was fired at 1000°C for 30 minutes to make it for printing Sensitive paste; after screen-printing interdigitated electrodes on an alumina substrate, burn at 800°C for 20 minutes; then print sensitive paste with screen, burn at 1000°C for 1 hour, and control the cooling rate Cool the sample at 120°C per minute to make a sensitive element; then use platinum slurry to weld the platinum wire and the interdigital electrode lead-out end of the sensitive element, and burn at 800°C for 10 minutes to cool the sample naturally; The heater paste is screen-printed on the back of the element and fired at 650°C for half an hour; after being immersed in a 10% catalyst PdCl ₂ solution, it is fired at 700°C for 30 minutes.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

Under reducing atmosphere: within 250℃～800℃, the resistance value is 95Ω～250Ω.

Example 2: After grinding the ceramic powder sample reagent with the composition of 0.63TiO ₂ +0.2SnO ₂ +0.05Nb ₂ O ₅ +0.12Bi ₂ O ₃ into a compact, it was burned at 1350°C for 4 hours, and the burned The green body is finely powdered and mixed with 20%wt medium-temperature glass powder to make a sensitive paste for printing; after screen-printing interdigitated electrodes on an alumina substrate, it is burned at 1000°C for 1 hour; After screen-printing the sensitive paste, place it at 1350°C for 2 hours and control the cooling rate at 180°C per minute to cool the sample to make a sensitive element; then use platinum paste to seal the platinum wire and the interdigitated electrode of the sensitive element The leading end is welded, placed at 1000°C for 20 minutes, and the sample is cooled naturally; the heater paste is screen-printed on the back of the sensitive element, and placed at 850°C for 10 minutes; coated with 30% catalyst H ₄ PtCl ₂ After the solution, burn at 1000°C for 2 hours.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

Under reducing atmosphere: within 250℃～800℃, the resistance value is 95Ω～250Ω.

Example 3: After the porcelain powder sample reagent with the composition of 0.63TiO ₂ +0.2SnO ₂ +0.05Nb ₂ O ₅ +0.12Bi ₂ O ₃ was ground and crushed, it was burned at 1150°C for 2 hours. The final green body is finely powdered and mixed with 10%wt medium-temperature glass powder to make a sensitive paste for printing; after screen printing on an alumina substrate to form an interdigitated electrode, place it at 900°C for 40 minutes; then use After screen-printing the sensitive paste, burn it at 1150°C for 1.5 hours, and control the cooling rate at 150°C per minute to cool the sample to make a sensitive element; The lead-out end of the electrode is welded, placed at 900°C for 15 minutes, and the sample is cooled naturally; the heater paste is screen-printed on the back of the sensitive element, and placed at 700°C for 45 minutes; coated with 50% catalyst salt PdCl ₂ After the solution, it was burned at 900°C for 1 hour.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

Under reducing atmosphere: within 250℃～800℃, the resistance value is 95Ω～250Ω.

Example 4: After finely grinding the ceramic powder sample reagent of the component 0.64TiO ₂ +0.3SnO ₂ +0.06Nb ₂ O ₅ into a compact, it was fired at 1000°C for 30 minutes to make a sensitive paste for printing; After screen-printing the interdigitated electrodes on the substrate, burn them at 800°C for 20 minutes; then print the sensitive paste on the screen, burn them at 1000°C for 1 hour, and control the cooling rate at 120°C per minute. The sample is cooled to make a sensitive element; then the platinum wire and the interdigitated electrode terminal of the sensitive element are welded with platinum paste, and burned at 800°C for 10 minutes to cool the sample naturally; a heater is screen-printed on the back of the sensitive element slurry, and burn at 650°C for 10 minutes; after soaking in 10% catalyst H ₄ PtCl ₂ solution, burn at 700°C for 30 minutes.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 85Ω-150Ω.

Example 5: after finely grinding the ceramic powder sample reagent of the component 0.64TiO ₂ +0.3SnO ₂ +0.06Nb ₂ O ₅ to make a green body, place it at 1200°C for 2 hours, and finely powder the fired green body Then mix it with 8%wt medium-temperature glass powder to make a sensitive paste for printing; after screen-printing the interdigitated electrodes on the alumina substrate, burn at 900°C for 40 minutes; then use the screen-printed sensitive paste , placed at 1100°C for 1.5 hours, and the cooling rate was controlled at 150°C per minute to cool the sample to make a sensitive element; then use platinum slurry to weld the platinum wire and the interdigitated electrode lead-out end of the sensitive element, and place Burn at 900°C for 16 minutes, let the sample cool naturally; screen print heater paste on the back of the sensitive element, and burn at 700°C for 25 minutes; soak in 25% catalyst PdCl ₂ solution, burn at 900°C 1 hour.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 85Ω-150Ω.

Example 6: after finely grinding the porcelain powder sample reagent of the component 0.64TiO ₂ +0.3SnO ₂ +0.06Nb ₂ O ₅ to make a compact, place it at 1350°C for 4 hours, and finely powder the fired body After mixing with 20%wt medium-temperature glass powder to make a sensitive paste for printing; after screen-printing an interdigitated electrode on an alumina substrate, burn it at 1000°C for 1 hour; then use a screen-printed sensitive paste , placed at 1350°C for 2 hours, and the cooling rate was controlled at 180°C per minute to cool the sample to make a sensitive element; then use platinum slurry to weld the platinum wire and the interdigitated electrode lead-out end of the sensitive element, and place Burn at 1000°C for 20 minutes, let the sample cool naturally; screen print the heater paste on the back of the sensitive element, and burn at 850°C for 45 minutes; after coating 50% catalyst H ₄ PtCl ₂ solution, Sear for 2 hours.

The prepared sample is in an oxidizing atmosphere: within 250°C-800°C, the resistance value is 50kΩ-1000kΩ.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 85Ω-150Ω.

Example 7: after finely grinding the ceramic powder sample reagent with the composition of 0.63TiO ₂ +0.30SnO ₂ +0.07Nb ₂ O ₅ to make a green body, place it at 1000°C for 4 hours, and then finely powder the fired green body After mixing with 20%wt medium-temperature glass powder to make a sensitive paste for printing; after screen-printing interdigitated electrodes on an alumina substrate, burn at 800°C for 1 hour; and then screen-print the sensitive paste, Burn at 1000°C for 2 hours, control the cooling rate at 120°C per minute, cool the sample, and make a sensitive element; then use platinum slurry to weld the platinum wire and the interdigitated electrode lead-out end of the sensitive element, place at 1000 Burn for 10 minutes at ℃, let the sample cool naturally; screen print the heater paste on the back of the sensitive element, and burn at 850°C for 10 minutes; after coating 50% catalyst PdCl ₂ solution, burn at 700°C for 2 Hour.

The prepared sample is in an oxidizing atmosphere: within 250°C to 800°C, the resistance value is 200kΩ to 5×10 ⁶ Ω.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 150Ω-220Ω.

Example 8: after finely grinding the ceramic powder sample reagent of the component 0.63TiO ₂ +0.30SnO ₂ +0.07Nb ₂ O ₅ into a compact, place it at 1350°C for 30 minutes to make a sensitive paste for printing; After screen-printing the interdigitated electrodes on the aluminum substrate, burn them at 1000°C for 20 minutes; then print the sensitive paste on the screen, burn them at 1350°C for 1 hour, and control the cooling rate at 180°C per minute. The sample is cooled to make a sensitive element; then the platinum wire and the interdigitated electrode terminal of the sensitive element are welded with platinum paste, and burned at 800°C for 20 minutes to cool the sample naturally; a heater is screen-printed on the back of the sensitive element slurry, and burn at 650°C for 45 minutes; soak in 10% catalyst H ₄ PtCl ₂ solution, and burn at 1000°C for 30 minutes.

The prepared sample is in an oxidizing atmosphere: within 250°C to 800°C, the resistance value is 200kΩ to 5×10 ⁶ Ω.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 150Ω-220Ω.

Example 9: after finely grinding the ceramic powder sample reagent of the component 0.63TiO ₂ +0.30SnO ₂ +0.07Nb ₂ O ₅ to make a green body, place it at 1200°C for 3 hours, and finely powder the fired green body Finally, mix it with 15%wt medium-temperature glass powder to make a sensitive paste for printing; after screen-printing the interdigitated electrode on the alumina substrate, burn it at 920°C for 45 minutes; and then use the screen-printed sensitive paste, Burn at 1280°C for 1.5 hours, control the cooling rate at 140°C per minute, cool the sample, and make a sensitive element; then use platinum slurry to weld the platinum wire and the interdigitated electrode terminal of the sensitive element, and place it at 900 Burn at ℃ for 18 minutes, let the sample cool naturally; screen print heater paste on the back of the sensitive element, and burn at 750°C for half an hour, impregnate in 28% catalyst PdCl ₂ solution, burn at 950°C for 1 Hour.

The prepared sample is in an oxidizing atmosphere: within 250°C to 800°C, the resistance value is 200kΩ to 5×10 ⁶ Ω.

The prepared sample is under reducing atmosphere: within 250°C-800°C, the resistance value is 150Ω-220Ω.

Claims (6)

1, the preparation method of wide temp range and narrow resistance band air/fuel ratio thick-film sensor is characterized in that:

1) can synthesize (TiSnNb) O ₂Behind the semiconductor porcelain powder reagent porphyrize base of the rutile structure of base, place 1000 ℃～1350 ℃ calcinations 30 minutes～4 hours;

2) warm glass dust after the base substrate fine-powdered after the calcination and among 0～20%wt is mixed, make the responsive slurry of printing;

3) after serigraphy becomes interdigital electrode on the alumina substrate, 800 ℃～1000 ℃ calcinations 20 minutes～1 hour;

4) use the responsive slurry of serigraphy again after, place 1000 ℃～1350 ℃ calcinations 1～2 hour, cooling velocity is controlled at 120 ℃～180 ℃ of per minutes, make the sample cooling, make sensitive element;

5) weld with the interdigital electrode exit of platinum slurry again, place 800 ℃～1000 ℃ calcinations 10～20 minutes, make the sample natural cooling platinum filament and sensitive element;

6), and place 650 ℃～850 ℃ calcinations 15～45 minutes at sensitive element back side serigraphy well heater slurry;

7) flood or apply 10%～50% catalyzer salt solusion, 700 ℃～1000 ℃ calcinations 30 minutes～2 hours.

2, the preparation method of wide temp range and narrow resistance band air/fuel ratio thick-film sensor according to claim 1 is characterized in that:

1) can synthesize (TiSnNb) O ₂Behind the semiconductor porcelain powder reagent porphyrize base of the rutile structure of base, place 1100 ℃ of calcinations 2 hours;

2) warm glass dust after the base substrate fine-powdered after the calcination and among the 10%wt is mixed, make the responsive slurry of printing;

3) after serigraphy becomes interdigital electrode on the alumina substrate, 900 ℃ of following calcinations 40 minutes;

4) use the responsive slurry of serigraphy again after, place 1100 ℃ of calcinations 1.5 hours, cooling velocity is controlled at 150 ℃ of per minutes, make the sample cooling, make sensitive element;

5) weld with the interdigital electrode exit of platinum slurry again, place 900 ℃ of calcinations 15 minutes, make the sample natural cooling platinum filament and sensitive element;

6), and place 750 ℃ of calcination half an hour at sensitive element back side serigraphy well heater slurry;

7) coating 30% catalyzer salt solusion was 850 ℃ of calcinations 1 hour.

3, the preparation method of wide temp range and narrow resistance band base air/fuel ratio thick-film sensor according to claim 1 is characterized in that: said (TiSnNb) O ₂TiO in the base ₂Content be 0.63mol～0.64mol.

4, the preparation method of wide temp range and narrow resistance band air/fuel ratio thick-film sensor according to claim 1 is characterized in that: said (TiSnNb) O ₂SnO in the base ₂Content be 0.2mol～0.3mol.

5, the preparation method of wide temp range and narrow resistance band air/fuel ratio thick-film sensor according to claim 1 is characterized in that: said (TiSnNb) O ₂Nb in the base ₂O ₅Content be 0.05mol～0.07mol.

6, the preparation method of wide temp range and narrow resistance band air/fuel ratio thick-film sensor according to claim 1 is characterized in that: said salt solusion is PdCl ₂Or H ₄PtCl ₂Solution.