A Wide-Range Oxygen Sensor Chip and Its Preparation Method

Abstract

The present invention discloses a wide-range oxygen sensor chip and a preparation method thereof. The chip substrate layer is composed of a first dielectric layer, a second dielectric layer, a third dielectric layer and a fourth dielectric layer; a pump oxygen outer electrode is provided on the first dielectric layer; a pump oxygen inner electrode is provided between the first dielectric layer and the second dielectric layer; a reference electrode is provided between the second dielectric layer and the third dielectric layer, and a heater is provided between the third dielectric layer and the fourth dielectric layer; wherein at least a part of the electrode part of the reference electrode coincides with the projection direction of the pump oxygen inner electrode on the third dielectric layer, and an ion blocking layer is provided on the electrode part of the reference electrode. By setting the position of the reference electrode and providing an ion blocking layer on the reference electrode, the present invention reduces the difference in the ion diffusion path from the upper and lower electrodes of the pump oxygen inner electrode to the reference electrode, so that the chip can not only achieve the target internal resistance and has high test accuracy, but also has accurate test data near λ = 1.0 in a dynamic atmosphere without the influence of clutter signals.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen sensor chips, and particularly relates to a wide-range oxygen sensor chip and a preparation method thereof. Background Art

[0002] The wide-range oxygen sensor chip is mainly applied to the control system of an automotive electronic fuel injection engine, and can accurately detect the exhaust gas with an air excess coefficient λ>0.65, meet the clean emission and closed-loop control of fuel injection of the vehicle under different driving conditions, greatly improve the environmental pollution caused by automotive exhaust gas, and significantly improve the fuel economy of engine combustion.

[0003] Generally, the wide-range oxygen sensor chip is composed of a pump unit (pump oxygen outer electrode - pump oxygen inner electrode), a Nernst unit (pump oxygen inner electrode - reference electrode), and a heating unit. In the working state, the vehicle-mounted controller adjusts the heating supply voltage to maintain the internal resistance of the Nernst unit at a target value (such as 300Ω). At this time, the chip is maintained near the working temperature (such as 820°C), ensuring the stability of the chip signal output. After the exhaust gas enters the reaction chamber through the gas diffusion channel, a Nernst potential is generated between the exhaust gas and the reference electrode. The controller adjusts the oxygen content in the induction chamber to be constant by pumping oxygen in or out, so that the Nernst potential is stabilized at a target value (such as 450mV). The magnitude and direction of the pump oxygen current IP have a corresponding relationship with the λ value of the gas entering the induction chamber. Finally, the pump current conversion signal is fed back to the ECU by the control unit, thereby realizing the control of the fuel injection amount and achieving the purpose of clean emission.

[0004] Based on the control requirement of the target internal resistance, the relative positions of the pump oxygen inner electrode and the reference electrode in the existing oxygen sensor chips are often set relatively far apart, resulting in a large temperature difference in the working temperature between the two, generating a thermoelectric potential, causing the corresponding relationship between the potential generated by the Nernst unit of the chip and the gas concentration to deviate from the reference, and the detection accuracy of the chip for too rich or too lean atmospheres decreases. The existing patent CN210690468U discloses adjusting the internal resistance by adjusting the relative positions of the reference electrode and the heater. Although this method can make the reference electrode in a temperature zone with better catalytic activity, due to the large difference in the ion transport paths between the upper and lower pump oxygen inner electrodes and the reference electrode with equal potential, electrode polarization is likely to occur. When the test atmosphere switches between lean combustion and rich combustion (near λ = 1.0, the best air-fuel ratio), the Nernst unit feeds back inaccurate signals to the controller, and then the controller makes incorrect regulation of the pump unit voltage, ultimately causing clutter in the output waveform. Another patent CN209764784U discloses improving the stability of signal output from the perspective of improving the insulation of the chip, but the setting method of its reference electrode will also cause problems with ripples near λ = 1.0. Summary of the Invention

[0005] The object of the present invention is to solve the problems of low static detection accuracy of the wide-range oxygen sensor chip and the presence of clutter in the output waveform in the dynamic atmosphere near λ = 1.0. In view of the above deficiencies of the prior art, a high-precision wide-range oxygen sensor chip and its preparation method are proposed.

[0006] A wide-range oxygen sensor chip includes a substrate layer and a gas diffusion channel provided in the substrate layer. The substrate layer includes a first dielectric layer, a second dielectric layer, a third dielectric layer, and a fourth dielectric layer from top to bottom.

[0007] An external oxygen pumping electrode is provided on the first dielectric layer; an internal oxygen pumping electrode is provided between the first dielectric layer and the second dielectric layer. The internal oxygen pumping electrode includes an upper internal oxygen pumping electrode and a lower internal oxygen pumping electrode with a common electrode lead. A reaction chamber is provided inside the internal oxygen pumping electrode for the test gas to enter the reaction chamber and undergo a catalytic reaction at the internal oxygen pumping electrode. An air inlet for the test gas to flow in is provided in the substrate layer, and the air inlet communicates with the reaction chamber to form the gas diffusion channel.

[0008] A reference electrode is provided between the second dielectric layer and the third dielectric layer. The reference electrode includes an electrode part and a lead part directly connected. The electrode part at least partially coincides with the projection direction of the internal oxygen pumping electrode on the third dielectric layer, so that the operating temperature of the reference electrode is close to the operating temperature of the internal oxygen pumping electrode.

[0009] An ion blocking layer is provided above the electrode part. The ion blocking layer extends beyond the end of the electrode part in the length direction and completely covers the electrode part of the reference electrode in the width direction to change the ion diffusion path from the internal oxygen pumping electrode to the reference electrode.

[0010] A heater is provided between the third dielectric layer and the fourth dielectric layer.

[0011] Further, the operating temperature of the internal oxygen pumping electrode is 780 - 820 °C.

[0012] Further, the ion blocking layer extends beyond the end of the electrode part by 0.1 - 4.3 mm in the length direction.

[0013] Further, the ion blocking layer is at least one of a porous zirconia layer, a porous alumina layer, a dense alumina layer, and a cavity layer, and the thickness of the ion blocking layer is 2 - 30 μm.

[0014] Further, the area of the electrode part is 0.3 - 15 mm 2 , and the thickness is 2 - 36 μm.

[0015] Further, first insulating layers and second insulating layers are respectively provided on the upper and lower surfaces of the lead part of the reference electrode.

[0016] Further, the first insulating layer and the second insulating layer are both made of porous alumina and have a thickness of 2 to 20 μm.

[0017] Further, a porous protective layer is provided on the external pump oxygen electrode to block pollutants in the gas to be measured.

[0018] Further, an air inlet penetrating the first dielectric layer is provided on the first dielectric layer, and the air inlet communicates with the reaction chamber of the internal pump oxygen electrode to form the gas diffusion channel.

[0019] Further, an air inlet is provided at the end between the first dielectric layer and the second dielectric layer, and the air inlet communicates with the reaction chamber in the internal pump oxygen electrode to form the gas diffusion channel.

[0020] By adopting the above technical solutions, the dynamic response stability near λ = 1.0 and the full-range detection accuracy are significantly improved.

[0021] The present invention also provides a method for manufacturing the wide-range oxygen sensor chip, including the following steps:

[0022] S1. Fabricating the green sheet of the dielectric layer: preparing a slurry by ball-milling a solid electrolyte powder with a solvent, a dispersant, a binder, a plasticizer, etc., forming a film tape from the slurry by a casting process, and finally cutting, laminating, and pressing the film tape to form the green sheets of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer;

[0023] S2. Processing the green sheet: first, processing via holes in the dielectric layer green sheet, then printing the external pump oxygen electrode on the upper surface of the first dielectric layer, printing the protective layer above the external pump oxygen electrode, printing the internal pump oxygen electrode between the first dielectric layer and the second dielectric layer, where the internal pump oxygen electrode includes an upper internal pump oxygen electrode and a lower internal pump oxygen electrode with a common electrode lead; printing the reference electrode between the second dielectric layer and the third dielectric layer; the reference electrode includes an electrode part and a lead part directly connected, and the electrode part at least partially coincides with the projection direction of the internal pump oxygen electrode on the third dielectric layer so that the working temperature of the reference electrode is equivalent to that of the internal pump oxygen electrode; printing an ion blocking layer on the electrode part and the lead part of the reference electrode and the first and second insulating layers covering the lead part; printing the upper insulating layer of the heater, the heater, and the lower insulating layer of the heater on the upper surface of the fourth dielectric layer in sequence, and printing the heater pins on the lower surface of the fourth dielectric layer;

[0024] S3. Press and laminate the wafers. Stack the first, second, third, and fourth dielectric layers that have completed printing in sequence from bottom to top in the order of four, three, two, and one, and then perform warm isostatic pressing to form wafers. The working pressure of the warm isostatic pressing process is 10 - 25 MPa, and the water temperature is 65 - 90 °C;

[0025] S4. Cut. Cut the above wafers into individual chip green bodies according to the designed length and width dimensions;

[0026] S5. Co - fire. Debind and sinter the chip green bodies. The sintering temperature is 1400 - 1500 °C, and the holding time is 1 - 6 h.

[0027] Preferably, the solid - state electrolyte powder is yttria - stabilized zirconia powder.

[0028] The beneficial effects of the present invention are as follows:

[0029] By arranging the reference electrode close to the oxygen - pumping inner electrode and making at least part of the electrode part of the reference electrode coincide with the projection direction of the oxygen - pumping inner electrode on the third dielectric layer, the working temperatures of the reference electrode and the oxygen - pumping inner electrode are close, reducing the influence of the temperature difference between the oxygen - pumping inner electrode and the reference electrode on the Nernst potential. On this basis, by setting an ion - blocking layer on the electrode part of the reference electrode, the length direction of the ion - blocking layer exceeds the end of the electrode part of the reference electrode, and the width direction completely covers the electrode part of the reference electrode. In this way, the ion transport on the side of the reference electrode facing the oxygen - pumping inner electrode is regulated. All oxygen ions from the upper and lower oxygen - pumping inner electrodes to the reference electrode have to bypass the ion - blocking layer, reducing the difference in the ion diffusion paths from the upper and lower oxygen - pumping inner electrodes to the reference electrode, solving the problem of unstable Nernst electromotive force caused by large potential differences between the upper and lower oxygen - pumping electrodes when the external atmosphere switches rapidly, thereby weakening the influence of electrode polarization and improving the stability and accuracy of the Nernst electromotive force. Finally, the Nernst resistance of the chip can reach the target internal resistance, enabling the oxygen sensor chip to be at the optimal working temperature. At this time, the catalytic reaction activity of the Nernst unit is good, and the detection accuracy is high; at the same time, the chip has good dynamic response stability near λ = 1.0, without signal clutter interference. Description of the Drawings

[0030] Figure 1 Longitudinal sectional view of the oxygen sensor chip in Embodiment 1.

[0031] Figure 2 Longitudinal sectional view of the oxygen sensor chip in Embodiment 2.

[0032] Figure 3 Longitudinal sectional view of the oxygen sensor chip in Comparative Example 1.

[0033] Figure 4Longitudinal sectional view of the oxygen sensor chip of Comparative Example 2.

[0034] Figure 5 Static detection accuracy diagrams of Examples 1-2 and Comparative Examples 1-2.

[0035] Figure 6 Dynamic response waveform diagram of Example 1.

[0036] Figure 7 Dynamic response waveform diagram of Comparative Example 1.

[0037] Figure 8 Dynamic response waveform diagram of Comparative Example 2.

[0038] In the figure, 1 is the first dielectric layer; 101 is the external pump oxygen electrode; 102 is the protective layer; 2 is the second dielectric layer; 201 is the internal pump oxygen electrode; 201a is the upper internal pump oxygen electrode; 201b is the lower internal pump oxygen electrode; 202 is the reaction chamber; 3 is the third dielectric layer; 301 is the reference electrode; 301a is the electrode part; 301b is the lead part; 302 is the ion blocking layer; 303 is the first insulating layer; 304 is the second insulating layer; 4 is the fourth dielectric layer; 401 is the heater; 5 is the air inlet; 6 is the reference reaction chamber. Detailed implementation manners

[0039] The following are specific embodiments of the present invention and, in conjunction with the accompanying drawings, further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0040] Example 1

[0041] A wide-range oxygen sensor chip, as Figure 1 shown, includes a substrate layer and a gas diffusion channel provided on the substrate layer. The substrate layer includes a first dielectric layer 1, a second dielectric layer 2, a third dielectric layer 3, and a fourth dielectric layer 4 from top to bottom.

[0042] An external pump oxygen electrode 101 is provided on the first dielectric layer 1, and a protective layer 102 is provided on the external pump oxygen electrode 101. The protective layer is a porous ceramic material protective layer for blocking pollutants in the gas to be measured and maintaining the long-term stability of the electrode.

[0043] An internal pump oxygen electrode 201 is provided between the first dielectric layer 1 and the second dielectric layer 2. The internal pump oxygen electrode 201 includes an upper internal pump oxygen electrode 201a and a lower internal pump oxygen electrode 201b. The upper internal pump oxygen electrode 201a and the external pump oxygen electrode 101 form a pump unit of the chip for pumping oxygen from the inside to the outside or from the outside to the inside, and by applying pressure to the internal and external electrodes, oxygen ions are made to move directionally.

[0044] There is a reaction chamber 202 between the upper oxygen pumping internal electrode 201a and the lower oxygen pumping internal electrode 201b. After the gas to be measured enters the reaction chamber 202, a catalytic reaction occurs at the oxygen pumping internal electrode 201. There is also an air inlet 5 penetrating through the first dielectric layer 1 on the first dielectric layer 1. The air inlet 5 is communicated with the reaction chamber 202 of the oxygen pumping internal electrode to form the gas diffusion channel.

[0045] A reference electrode 301 is provided between the first dielectric layer 2 and the second dielectric layer 3. The reference electrode 301 and the lower oxygen pumping internal electrode 201b form the Nernst unit of the chip to monitor the oxygen concentration in the chamber; the reference electrode 301 includes an electrode part 301a and a lead part 301b directly connected. The area of the electrode part is 5 mm 2 , and the thickness is 10 μm. A heater 401 is provided between the third dielectric layer 3 and the fourth dielectric layer 4. The electrode part 301a of the reference electrode 301 completely coincides with the projection direction of the oxygen pumping internal electrode 201 on the third dielectric layer 3, so that the operating temperature of the reference electrode 301 is close to the operating temperature of the oxygen pumping internal electrode 201, and the thermal electromotive force difference between the electrodes is reduced as much as possible.

[0046] Generally, the in-vehicle controller of a car company (BOSCH in Germany) heats the chip by applying different voltages to the chip heater 401 to maintain the internal resistance of the Nernst unit of the chip at the target value. The internal resistance value of the Nernst unit of the chip corresponds to the optimal operating temperature of the chip. In this way, by regulating the internal resistance, the chip is stabilized at the optimal operating temperature, ensuring the stability of the chip signal output.

[0047] An ion blocking layer 302 is provided on the upper surface of the electrode part 301a. The ion blocking layer 302 is at least one of a porous zirconia layer, a porous alumina layer, a dense alumina layer, and a cavity layer. In this embodiment, the ion blocking layer 302 is a porous alumina layer. In this embodiment, the ion blocking layer 302 extends 2 mm beyond the end of the electrode part 301a of the reference electrode 301 in the length direction and completely covers the electrode part 301a of the reference electrode 301 in the width direction. In this way, oxygen ions can only bypass the ion blocking layer 302 to reach the electrode part 301a of the reference electrode 301, reducing the ion diffusion path difference between the upper and lower oxygen pumping internal electrodes and the electrode part 301a of the reference electrode 301, solving the problem of unstable Nernst electromotive force caused by the large potential difference between the upper oxygen pumping electrode 201a and the lower oxygen pumping electrode 201b when the external atmosphere switches rapidly, thereby weakening the influence of electrode polarization and improving the stability and accuracy of the Nernst electromotive force. On the one hand, the Nernst resistance of the oxygen sensor chip can reach the target internal resistance of 300 Ω, enabling the oxygen sensor chip to be at the optimal operating temperature of 820 °C. At this time, the catalytic reaction activity of the Nernst unit is good and the detection accuracy is high; on the other hand, the chip has good dynamic response stability near λ = 1.0 (optimal air-fuel ratio) and there is no interference from clutter signals.

[0048] A first insulating layer 303 is provided on the upper surface of the reference electrode lead portion 301b, and a second insulating layer 304 is provided on the lower surface of the lead portion. The materials of the first insulating layer 303 and the second insulating layer 304 are both porous alumina, and the thickness of both is 20 μm. This greatly improves the insulation performance of the reference electrode 301 and also reduces the signal interference between the reference electrode 301 and the inner electrode 201 of the oxygen pump.

[0049] A method for preparing a wide-range oxygen sensor chip according to an embodiment of the present application includes the following steps:

[0050] S1. Fabricating a green sheet of the dielectric layer. A slurry is prepared by ball-milling and mixing yttria-stabilized zirconia powder with a solvent, a dispersant, a binder, a plasticizer, etc. The slurry is formed into a film tape by a tape casting process, and finally the film tape is cut, laminated, and pressed to form a green sheet of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer;

[0051] S2. Processing the green sheet. First, via holes are processed on the dielectric layer green sheet. Then, an outer oxygen pump electrode is printed on the upper surface of the first dielectric layer, a protective layer is printed above the outer oxygen pump electrode, an inner oxygen pump electrode is printed between the first dielectric layer and the second dielectric layer, an ion barrier layer, a reference electrode, and a reference electrode lead insulating layer are printed between the second dielectric layer and the third dielectric layer, an upper insulating layer of the heater, a heater, and a lower insulating layer of the heater are printed in sequence on the upper surface of the fourth dielectric layer, and heater pins are printed on the lower surface of the fourth dielectric layer; Processing the green sheet. First, via holes are processed on the dielectric layer green sheet. Then, an outer oxygen pump electrode 101 is printed on the upper surface of the first dielectric layer 1, a protective layer 102 is printed above the outer oxygen pump electrode 101, an inner oxygen pump electrode 201 is printed between the first dielectric layer 1 and the second dielectric layer 2. The inner oxygen pump electrode 201 includes an upper inner oxygen pump electrode 201a and a lower inner oxygen pump electrode 201b with a common electrode lead; A reference electrode 301 is printed between the second dielectric layer 2 and the third dielectric layer 3. The reference electrode 301 includes an electrode portion 301a and a lead portion 301b that are directly connected. The electrode portion 301a partially overlaps with the inner oxygen pump electrode 201 in the projection direction on the third dielectric layer 3 so that the working temperatures of the reference electrode 301 and the inner oxygen pump electrode 201 are equivalent; An ion barrier layer 302 and the first and second insulating layers covering the lead portion are printed on the electrode portion 301a and the lead portion 301b of the reference electrode 301 respectively;

[0052] S3. Pressing the blocks. The first dielectric layer 1, the second dielectric layer 2, the third dielectric layer 3, and the fourth dielectric layer 4 that have completed printing are superposed in alignment from bottom to top in the order of four, three, two, and one, and then hot isostatic pressing is performed to form a block. The working pressure of the hot isostatic pressing process is 20 MPa, and the water temperature is 80 °C;

[0053] S4. Slitting: Slice the above-mentioned bar blocks according to the designed length and width dimensions to form single chip blanks.

[0054] S5. Co-firing: Debind and sinter the chip blanks. The sintering temperature is 1420 °C and the heat preservation time is 3 h.

[0055] Example 2

[0056] The difference between Example 2 and Example 1 is that, as Figure 2 shown, a pump oxygen internal electrode 201 is provided between the first dielectric layer 1 and the second dielectric layer 2. The pump oxygen internal electrode 201 includes an upper pump oxygen internal electrode 201a and a lower pump oxygen internal electrode 201b. Among them, the upper pump oxygen internal electrode 201a and the pump oxygen external electrode 101 constitute the pump unit of the chip, which is used to pump oxygen from the inside to the outside or from the outside to the inside. By applying pressure to the internal and external electrodes, oxygen ions can move directionally.

[0057] A reaction chamber 202 is provided between the upper pump oxygen internal electrode 201a and the lower pump oxygen internal electrode 201b. After the gas to be measured enters the reaction chamber 202, a catalytic reaction occurs at the pump oxygen internal electrode 201. An air inlet 5 is provided at one end between the first dielectric layer 1 and the second dielectric layer 2. The air inlet 5 is communicated with the reaction chamber 202 of the pump oxygen internal electrode 201 to form the gas diffusion channel. The air inlet 5 is arranged on the side surface of the substrate layer, which can optimize the diffusion path of oxygen, improve the response speed and accuracy of the sensor. This design can also enable oxygen to effectively enter the inside of the sensor and react with the pump oxygen internal electrode 201, thereby generating an accurate measurement signal.

[0058] The reference electrode 301 includes an electrode part 301a and a lead part 301b that are directly connected. The area of the electrode part 301a is 5 mm 2 , and the thickness is 10 μm. The electrode part 301a of the reference electrode 301 partially overlaps with the pump oxygen internal electrode 201 in the projection direction of the third dielectric layer 3, so that the operating temperature of the reference electrode 301 is basically the same as that of the pump oxygen internal electrode 201.

[0059] An ion blocking layer 302 is provided on the upper surface of the electrode portion 301a, and the ion blocking layer 302 is a porous alumina layer; in this embodiment, the ion blocking layer 302 extends 4 mm beyond the end of the electrode portion 301a in the length direction and completely covers the electrode portion 301a of the reference electrode 301 in the width direction. In this way, oxygen ions can only reach the electrode portion 301a of the reference electrode 301 by bypassing the ion blocking layer 302, reducing the ion diffusion path difference between the upper and lower oxygen pumping inner electrodes and the electrode portion 301a of the reference electrode 301, solving the problem of unstable Nernst electromotive force caused by a large potential difference between the upper oxygen pumping electrode 201a and the lower oxygen pumping electrode 201b when the external atmosphere is rapidly switched, thereby weakening the influence of electrode polarization and improving the stability and accuracy of the Nernst electromotive force. On the one hand, the Nernst resistance of the oxygen sensor chip can reach the target internal resistance of 300 Ω, enabling the oxygen sensor chip to operate at a working temperature of 780 °C. At this time, the catalytic reaction activity of the Nernst unit is good and the detection accuracy is relatively high; on the other hand, the chip has good dynamic response stability near λ = 1.0 (optimal air-fuel ratio) and is not interfered by clutter signals.

[0060] Comparative Example 1

[0061] As Figure 3 shown, the difference between Comparative Example 1 and Example 1 is that, as Figure 3 shown, the projections of the reference electrode 301 and the oxygen pumping inner electrode 201 in the projection direction of the third dielectric layer 3 do not coincide, resulting in a large temperature difference between the working temperatures of the reference electrode 301 and the oxygen pumping inner electrode. The catalytic reaction activity of the Nernst unit of the chip is poor, the response is slow, and the output signal speed is slow.

[0062] In Comparative Example 1, the area of the electrode portion 301a is 5 mm 2 , and the thickness is 10 μm. An ion blocking layer 302 is not provided on the upper surface of the electrode portion 301a, and a reference reaction cavity 6 is provided on the lower surface of the electrode portion for storing oxygen and simultaneously having the effect of alleviating signal attenuation. Since the ion blocking layer 302 is not provided on the upper surface of the electrode portion 301a in this comparative example, the ion diffusion path difference from the upper and lower oxygen pumping inner electrodes of the oxygen pumping inner electrode 201 to the electrode portion 301a of the reference electrode 301 is large, resulting in unstable Nernst electromotive force of the chip, large influence of electrode polarization, poor dynamic response stability of the chip near λ = 1.0 (optimal air-fuel ratio), and interference from clutter signals.

[0063] Comparative Example 2

[0064] As Figure 4As shown in the figure, the difference between Comparative Example 2 and Example 1 is that the reference electrode 301 and the inner oxygen pumping electrode 201 partially overlap in the projection direction of the third dielectric layer 3, resulting in a smaller temperature difference between the operating temperature of the reference electrode 301 and that of the inner oxygen pumping electrode. The catalytic reaction activity of the chip Nernst unit is poor, the response is slow, and the output signal speed is slow.

[0065] In Comparative Example 2, the area of the electrode part 301a is 2 mm 2 , and the thickness is 10 μm. In this comparative example, the small size of the reference electrode 301 will result in a weak signal generated by the reference electrode 301. In a low-concentration oxygen environment, it is more difficult to accurately detect the weak signal, resulting in an increase in measurement error. Therefore, when testing the static detection accuracy of the comparative example, it deviates from the standard value within the range of λ > 1.7.

[0066] In Comparative Example 2, there is no ion blocking layer 302 on the upper surface of the electrode part 301a. During the diffusion process of oxygen ions, they directly enter the electrode part 301a, resulting in a reduction in the internal resistance of ion transport and failing to reach the target internal resistance of the chip, resulting in poor dynamic detection accuracy of the oxygen sensor chip. Since there is no ion blocking layer 302 on the upper surface of the electrode part 301a in this comparative example, the difference in the ion diffusion path from the upper and lower inner oxygen pumping electrodes of the inner oxygen pumping electrode 201 to the electrode part 301a of the reference electrode 301 is large, resulting in instability of the chip Nernst electromotive force and being greatly affected by electrode polarization. The dynamic response stability of the chip is poor and there is clutter signal interference near λ = 1.0 (the best air-fuel ratio).

[0067] The comprehensive performance, static detection accuracy, and dynamic response of the oxygen sensor chips in Examples 1-2, Comparative Example 1, and Comparative Example 2 were detected, and the detection methods are as follows:

[0068] 1. Signal stability: In an air atmosphere, connect the chip to a signal detector (commonly known as a lambda meter) and record the output oxygen signal value for 10 minutes. If the absolute value of the signal change before and after is less than 0.2%, it is judged as excellent, and 0.2 - 0.5% is judged as good.

[0069] 2. Static detection accuracy: After the chip is packaged, connect the intake end to a closed gas chamber, use a gas mixer to input different atmospheres into the gas chamber, including different concentrations of rich oxygen atmospheres and different concentrations of lean oxygen atmospheres, connect the pins to a signal detector (commonly known as a lambda meter), and record the output λ value in real time.

[0070] 3. Dynamic detection accuracy: After the chip is packaged, connect it to a combustion test bench (the atmosphere of the combustion test bench changes periodically, and the λ range is 0.9 - 1.1), and use a lambda meter to collect the signal waveform of the sensor in real time.

[0071] 4. Insulation performance: Use an insulation resistance meter to measure the insulation resistance between the reference electrode 301 and the outer electrode 101 of the pump oxygen under hot conditions (about 600 °C).

[0072] The comprehensive performance of each example and comparative example is shown in Table 1 below, and the static detection accuracy of each example and comparative example is shown in Figure 7 , and the fitting R of the static detection accuracy diagrams of each example and comparative example 2 See Table 2.

[0073] Table 1 Comprehensive performance of each example

[0074]

[0075] As can be seen from Table 1, the signal stability, static detection accuracy, dynamic detection accuracy, and insulation performance in Example 1 are all excellent. The static detection accuracy and dynamic detection accuracy in Example 2 are lower than those in Example 1, but they are also in a relatively excellent range. The dynamic detection accuracy in Comparative Examples 1 and 2 is poor.

[0076] Table 2 Fitting R of the static detection accuracy diagram 2

[0077]

[0078] From Figure 5 it can be seen that during the static detection accuracy test, the test value of Example 1 is almost the same as the standard value. In Comparative Examples 1 and 2, when λ < 0.8 and λ > 2, they deviate from the standard value. According to Figure 5 the measured λ value data diagram shown, we used linear fitting to fit each example and comparative example, and the corresponding fitting R 2 As shown in Table 2, when R 2 > 0.9999, the detection accuracy of the chip is very high; when R 2 is between 0.999 - 0.9999, the detection accuracy barely meets the standard requirements; when R 2 < 0.999, the detection accuracy is poor. The fitting degree of Examples 1 - 2 is significantly better than that of Comparative Examples 1 and 2, and the fitting degree of Example 1 is the best, reflecting that the detection accuracy of Example 1 is the highest.

[0079] Figures 6 - 8 Figure 42 is the dynamic response waveform diagram of Example 1, Comparative Example 1, and Comparative Example 2. From Figures 6 - 8 it can be seen that during the dynamic response test, in Comparative Examples 1 and 2, the signal is extremely unstable and undergoes mutations when λ = 1 ± 0.02; Example 1 solves the above problems.

[0080] For those not covered above, the prior art applies.

[0081] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications, supplements, or use similar methods for substitution to the described specific embodiments, but will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A wide-band oxygen sensor chip, characterized in that: It comprises a substrate layer and a gas diffusion channel arranged in the substrate layer, wherein the substrate layer comprises, from top to bottom, a first dielectric layer (1), a second dielectric layer (2), a third dielectric layer (3) and a fourth dielectric layer (4); An oxygen pumping outer electrode (101) is provided on the first dielectric layer (1); an oxygen pumping inner electrode (201) is provided between the first dielectric layer (1) and the second dielectric layer (2), the oxygen pumping inner electrode comprising an upper oxygen pumping inner electrode (201a) and a lower oxygen pumping inner electrode (201b) having a common electrode lead; a reaction chamber (202) is provided in the oxygen pumping inner electrode (201) so that the gas to be measured can enter the reaction chamber (202) and undergo a catalytic reaction at the oxygen pumping inner electrode (201); the substrate layer has an air inlet (5) for the gas to be measured to flow in, the air inlet (5) being connected to the reaction chamber (202) to form the gas diffusion channel; A reference electrode (301) is provided between the second dielectric layer (2) and the third dielectric layer (3); the reference electrode (301) comprises an electrode portion (301a) and a lead portion (301b) that are directly connected, and the electrode portion (301a) at least partially overlaps with the oxygen pumping inner electrode (201) in the projection direction of the third dielectric layer (3); An ion blocking layer (302) is also provided above the electrode portion (301a), and the ion blocking layer (302) exceeds the end of the electrode portion (301a) in the length direction and completely covers the electrode portion (301a) of the reference electrode (301) in the width direction, so as to change the ion diffusion path from the oxygen pumping inner electrode (201) to the reference electrode (301); A heater (401) is provided between the third medium layer (3) and the fourth medium layer (4).

2. The wide-band oxygen sensor chip according to claim 1, characterized in that: The operating temperature of the oxygen pumping inner electrode (201) is 780-820°C.

3. The wide-band oxygen sensor chip according to claim 1, characterized in that: The ion blocking layer (302) exceeds the end of the electrode portion (301a) by 0.1 to 4.3 mm in the length direction.

4. The wide-band oxygen sensor chip according to claim 1, characterized in that: The ion blocking layer (302) is at least one of a porous zirconium oxide layer, a porous aluminum oxide layer, a dense aluminum oxide layer and a cavity layer; the ion blocking layer (302) has a thickness of 2 to 30 μm.

5. The wide-band oxygen sensor chip according to claim 1, characterized in that: The electrode portion (301a) has an area of ​​0.3-15 mm 2 , thickness is 2~36μm.

6. The wide-band oxygen sensor chip according to claim 1, characterized in that: A first insulating layer (303) and a second insulating layer (304) are respectively provided on the upper and lower surfaces of the lead portion (301b) of the reference electrode (301); the first insulating layer (303) and the second insulating layer (304) are both made of porous aluminum oxide and have a thickness of 2 to 20 μm.

7. The wide-band oxygen sensor chip according to claim 1, characterized in that: A porous protective layer (102) is provided on the oxygen pumping outer electrode (101) to block pollutants in the gas to be measured.

8. The wide-band oxygen sensor chip according to claim 1, characterized in that: The first dielectric layer (1) is provided with an air inlet (5) penetrating the first dielectric layer (1), and the air inlet (5) is connected to the reaction chamber (202) of the oxygen pumping inner electrode (201) to form the gas diffusion channel.

9. The wide-band oxygen sensor chip according to claim 1, characterized in that: An air inlet (5) is provided at the end between the first dielectric layer (1) and the second dielectric layer (2), and the air inlet (5) is connected to the reaction chamber (202) in the oxygen pumping inner electrode (201) to form the gas diffusion channel.

10. A method for preparing a wide-band oxygen sensor chip according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, making green sheets of dielectric layers, using yttria-stabilized zirconium oxide powder and solvent, dispersant, adhesive, plasticizer, etc. to mix by ball milling to prepare slurry, forming film strips by tape casting process, and finally cutting, laminating, and pressing the film strips to form green sheets of the first dielectric layer (1), the second dielectric layer (2), the third dielectric layer (3), and the fourth dielectric layer (4); S2, blank processing, firstly processing a via hole on the dielectric layer blank, then printing an oxygen pumping outer electrode (101) on the upper surface of the first dielectric layer (1), printing a protective layer (102) above the oxygen pumping outer electrode (101), and printing an oxygen pumping inner electrode (201) between the first dielectric layer (1) and the second dielectric layer (2), wherein the oxygen pumping inner electrode comprises an upper oxygen pumping inner electrode (201a) and a lower oxygen pumping inner electrode (201b) having a common electrode lead; and printing an oxygen pumping inner electrode (201a) and a lower oxygen pumping inner electrode (201b) between the second dielectric layer (2) and the second dielectric layer (2). A reference electrode (301) is printed between the three dielectric layers (3); the reference electrode (301) comprises an electrode portion (301a) and a lead portion (301b) which are directly connected, the electrode portion (301a) at least partially overlapping with the oxygen pumping inner electrode (201) in the projection direction of the third dielectric layer (3); an ion blocking layer and a first and a second insulating layer covering the lead portion are printed on the electrode portion (301a) and the lead portion (301b) of the reference electrode (301), respectively; The upper insulating layer of the heater (401), the heater (401) and the lower insulating layer of the heater (401) are sequentially printed on the upper surface of the fourth dielectric layer (4), and the pins of the heater (401) are printed on the lower surface of the fourth dielectric layer (4); S3, block pressing, the first medium layer (1), the second medium layer (2), the third medium layer (3) and the fourth medium layer (4) which have been printed are stacked from bottom to top in the order of four, three, two and one, and then pressed by warm isostatic pressing to form a block, wherein the working pressure of the warm isostatic pressing process is 10-25 MPa and the water temperature is 65-90°C; S4, cutting, cutting the above-mentioned block into individual chip green sheets according to the designed length and width dimensions; S5. Co-firing: debinding and sintering the green chip at a sintering temperature of 1400-1500°C and a holding time of 1-6 h.

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