A wide-band oxygen sensor chip and preparation method thereof

Abstract

The present invention discloses a wide-band oxygen sensor chip and a preparation method thereof, wherein the chip substrate layer is composed of a first dielectric layer, a second dielectric layer, a third dielectric layer and a fourth dielectric layer; an oxygen pumping outer electrode is provided on the first dielectric layer; an oxygen pumping 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 the electrode portion of the reference electrode at least partially overlaps with the oxygen pumping inner electrode in the projection direction of the third dielectric layer and the electrode portion of the reference electrode is provided with an ion barrier layer. The present invention reduces the difference in ion diffusion paths from the upper and lower electrodes of the oxygen pumping inner electrode to the reference electrode by setting the position of the reference electrode and setting an ion barrier layer on the reference electrode, so that the chip can not only achieve the target internal resistance and have high test accuracy, but also test data is accurate 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 in particular to a wide-band oxygen sensor chip and a preparation method thereof. Background Art

[0002] Wide-range oxygen sensor chips are mainly used in automotive electronic fuel injection engine control systems. They can accurately detect exhaust gas with an air excess coefficient λ>0.65, meet the clean emission and fuel injection closed-loop control of the vehicle under different driving conditions, greatly improve the pollution of automobile exhaust to the environment, and significantly improve the economy of engine combustion.

[0003] Generally, the wide-band 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 on-board controller adjusts the heating supply voltage to maintain the internal resistance of the Nernst unit at the target value (such as 300Ω). At this time, the chip is kept near the operating temperature (such as 820℃), 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 it and the reference electrode. The controller adjusts the oxygen content in the sensing chamber to be constant by pumping oxygen inward or outward, so that the Nernst potential is stabilized at the target value (such as 450mV). The size and direction of the oxygen pump current IP correspond to the λ value of the gas entering the sensing chamber. Finally, the pump current conversion signal is fed back to the ECU by the control unit, thereby realizing the control of the injection amount and achieving the purpose of clean emissions.

[0004] Based on the control requirements of the target internal resistance, the existing oxygen sensor chip often sets the relative position of the pump oxygen inner electrode and the reference electrode far apart, resulting in a large temperature difference between the operating temperatures, generating a thermoelectric potential, causing the corresponding relationship between the chip Nernst unit generated potential and the gas concentration to deviate from the reference, and the chip's detection accuracy for over-rich or over-lean atmospheres is reduced. The existing patent CN210690468U discloses adjusting the relative position of the reference electrode and the heater to control the internal resistance. Although this method can place the reference electrode in a temperature zone with good catalytic activity, due to the large difference in the ion transmission path between the equipotential upper and lower pump oxygen inner electrodes and the reference electrode, electrode polarization is easily generated. When the test atmosphere switches between lean and rich combustion (near λ=1.0, the optimal air-fuel ratio), the Nernst unit feeds back an inaccurate signal to the controller, and the controller then incorrectly regulates the pump unit voltage, ultimately causing noise in the output waveform. Another patent CN209764784U discloses improving the stability of signal output from the perspective of improving chip insulation, but the setting method of its reference electrode will also cause ripple problems near λ=1.0. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the static detection accuracy of wide-band oxygen sensor chip is low and the output waveform has noise in the dynamic atmosphere near λ=1.0. In view of the above shortcomings of the prior art, a high-precision wide-band oxygen sensor chip and its preparation method are proposed.

[0006] A wide-band oxygen sensor chip 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, a second dielectric layer, a third dielectric layer and a fourth dielectric layer; An oxygen pumping outer electrode is provided on the first dielectric layer; an oxygen pumping inner electrode is provided between the first dielectric layer and the second dielectric layer, and the oxygen pumping inner electrode comprises an upper oxygen pumping inner electrode and a lower oxygen pumping inner electrode with a common electrode lead; a reaction chamber is provided in the oxygen pumping inner electrode, so that the gas to be measured can enter the reaction chamber to undergo a catalytic reaction at the oxygen pumping inner electrode; the substrate layer has an air inlet for the gas to be measured to flow in, and the air inlet is connected to the reaction chamber to form the gas diffusion channel; A reference electrode is provided between the second dielectric layer and the third dielectric layer, the reference electrode comprising an electrode portion and a lead portion that are directly connected, the electrode portion at least partially overlaps with the oxygen pumping inner electrode in the projection direction of the third dielectric layer, so that the operating temperature of the reference electrode is close to the operating temperature of the oxygen pumping inner electrode; An ion blocking layer is provided above the electrode portion, the ion blocking layer exceeds the end of the electrode portion in the length direction and completely covers the electrode portion of the reference electrode in the width direction to change the ion diffusion path from the oxygen pumping inner electrode to the reference electrode; A heater is provided between the third medium layer and the fourth medium layer.

[0007] Furthermore, the operating temperature of the oxygen pump inner electrode is 780-820°C.

[0008] Furthermore, the ion blocking layer exceeds the end of the electrode portion by 0.1 to 4.3 mm in the length direction.

[0009] Furthermore, the ion barrier layer is at least one of a porous zirconium oxide layer, a porous aluminum oxide layer, a dense aluminum oxide layer and a cavity layer, and the thickness of the ion barrier layer is 2-30 μm.

[0010] Furthermore, the electrode area is 0.3-15 mm 2 , thickness is 2~36μm.

[0011] Furthermore, the upper and lower surfaces of the lead portion of the reference electrode are provided with a first insulating layer and a second insulating layer respectively.

[0012] Furthermore, the first insulating layer and the second insulating layer are both made of porous alumina, and have a thickness of 2-20 μm.

[0013] Furthermore, a porous protective layer is provided on the oxygen pumping outer electrode to block pollutants in the gas to be measured.

[0014] Furthermore, a gas inlet penetrating through the first dielectric layer is provided on the first dielectric layer, and the gas inlet is connected to the reaction chamber of the oxygen pumping inner electrode to form the gas diffusion channel.

[0015] Furthermore, an air inlet is provided at the end between the first dielectric layer and the second dielectric layer, and the air inlet is connected to the reaction chamber in the oxygen pumping inner electrode to form the gas diffusion channel.

[0016] By adopting the above technical solution: the dynamic response stability near λ=1.0 and the full-range detection accuracy are significantly improved and enhanced.

[0017] The present invention also proposes a method for preparing the wide-band oxygen sensor chip, comprising the following steps: S1, making green sheets of dielectric layers, using solid electrolyte 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, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer; S2, blank processing, firstly processing the conductive hole on the dielectric layer blank, then printing the oxygen pumping outer electrode on the upper surface of the first dielectric layer, printing the protective layer above the oxygen pumping outer electrode, printing the oxygen pumping inner electrode between the first dielectric layer and the second dielectric layer, the oxygen pumping inner electrode comprising the upper oxygen pumping inner electrode and the lower oxygen pumping inner electrode of the common electrode lead; printing the reference electrode between the second dielectric layer and the third dielectric layer; the reference electrode comprising a directly connected electrode portion and a lead portion, the electrode portion and the oxygen pumping inner electrode at least partially overlap in the projection direction of the third dielectric layer, so that the operating temperature of the reference electrode is equivalent to that of the oxygen pumping inner electrode; printing the ion blocking layer and the first and second insulating layers covering the lead portion on the electrode portion and the lead portion of the reference electrode respectively; printing the heater upper insulating layer, the heater and the heater lower insulating layer in sequence on the upper surface of the fourth dielectric layer, and printing the heater pin on the lower surface of the fourth dielectric layer; S3, block pressing, the first medium layer, the second medium layer, the third medium layer and the fourth medium layer 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 process to form a block, 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.

[0018] Preferably, the solid electrolyte powder is yttria-stabilized zirconium oxide powder.

[0019] The beneficial effects of the present invention are: By arranging the reference electrode and the oxygen pumping inner electrode close to each other, the electrode portion of the reference electrode and the oxygen pumping inner electrode are at least partially overlapped in the projection direction of the third dielectric layer, so that the working temperatures of the reference electrode and the oxygen pumping inner electrode are similar, and the influence of the temperature difference between the oxygen pumping inner electrode and the reference electrode on the Nernst potential is reduced. On this basis, by arranging an ion barrier layer on the electrode portion of the reference electrode, the ion barrier layer exceeds the end of the electrode portion of the reference electrode in the length direction and completely covers the electrode portion of the reference electrode in the width direction, so that the ion transmission of the reference electrode facing the oxygen pumping inner electrode is regulated, and all oxygen ions from the upper and lower oxygen pumping inner electrodes to the reference electrode must bypass the ion barrier layer, reducing the difference in ion diffusion paths from the upper and lower oxygen pumping inner electrodes to the reference electrode, and solving the problem of unstable Nernst electromotive force caused by the large difference in potential between the upper and lower oxygen pumping electrodes when the external atmosphere is quickly switched, 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, so that the oxygen sensor chip can be at the optimal operating 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 dynamic response stability of the chip near λ=1.0 is good, and there is no signal noise interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Longitudinal cross-sectional view of the oxygen sensor chip of Example 1.

[0021] Figure 2 Longitudinal cross-sectional view of the oxygen sensor chip of Example 2.

[0022] Figure 3 Longitudinal cross-sectional view of the oxygen sensor chip of Comparative Example 1.

[0023] Figure 4 Longitudinal cross-sectional view of the oxygen sensor chip of Comparative Example 2.

[0024] Figure 5 Static detection accuracy diagram of Examples 1-2 and Comparative Examples 1-2.

[0025] Figure 6 Dynamic response waveform of Example 1.

[0026] Figure 7Dynamic response waveform of comparative example 1.

[0027] Figure 8 Dynamic response waveform of comparative example 2.

[0028] In the figure, 1, the first dielectric layer; 101, the oxygen pumping outer electrode; 102, the protective layer; 2, the second dielectric layer; 201, the oxygen pumping inner electrode; 201a, the upper oxygen pumping inner electrode; 201b, the lower oxygen pumping inner electrode; 202, the reaction chamber; 3, the third dielectric layer; 301, the reference electrode; 301a, the electrode part; 301b, the lead part; 302, the ion blocking layer; 303, the first insulating layer; 304, the second insulating layer; 4, the fourth dielectric layer; 401, the heater; 5, the air inlet; 6, the reference reaction chamber. DETAILED DESCRIPTION

[0029] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0030] Example 1 A wide-band oxygen sensor chip, such as Figure 1 As shown, it includes a substrate layer and a gas diffusion channel arranged in 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.

[0031] An oxygen pumping outer electrode 101 is disposed on the first dielectric layer 1 , and a protective layer 102 is disposed on the oxygen pumping outer electrode 101 . The protective layer is a porous ceramic material protective layer used to block pollutants in the gas to be measured and maintain the long-term stability of the electrode.

[0032] 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 201 includes an upper oxygen pumping inner electrode 201a and a lower oxygen pumping inner electrode 201b, wherein the upper oxygen pumping inner electrode 201a and the oxygen pumping outer electrode 101 constitute a pump unit of the chip, which is used to pump oxygen from the inside to the outside or from the outside to the inside, and oxygen ions are directed to move by applying pressure to the inner and outer electrodes.

[0033] A reaction chamber 202 is provided between the upper oxygen pumping inner electrode 201a and the lower oxygen pumping inner electrode 201b. After the gas to be measured enters the reaction chamber 202, a catalytic reaction occurs at the oxygen pumping inner electrode 201. The first dielectric layer 1 is also provided with an air inlet 5 penetrating the first dielectric layer 1. The air inlet 5 is connected to the reaction chamber 202 of the oxygen pumping inner electrode to form the gas diffusion channel.

[0034] 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 pump oxygen inner electrode 201b constitute the Nernst unit of the chip to monitor the oxygen concentration in the chamber. The reference electrode 301 includes an electrode portion 301a and a lead portion 301b that are directly connected. The area of ​​the electrode portion is 5 mm 2 The thickness is 10 μm. A heater 401 is provided between the third dielectric layer 3 and the fourth dielectric layer 4, and the electrode portion 301a of the reference electrode 301 completely overlaps with the oxygen pumping inner electrode 201 in the projection direction of the third dielectric layer 3, so that the working temperature of the reference electrode 301 is close to the working temperature of the oxygen pumping inner electrode 201, and the temperature difference potential between the electrodes is reduced as much as possible.

[0035] The on-board controller of a general car manufacturer (BOSCH of Germany) heats the chip by applying different voltages to the chip heater 401 to maintain the Nernst unit internal resistance of the chip at a target value. The Nernst unit internal resistance value of the chip corresponds to the optimal operating temperature of the chip. In this way, the chip is stabilized at the optimal operating temperature by regulating the internal resistance, thereby ensuring the stability of the chip signal output.

[0036] An ion blocking layer 302 is provided on the upper surface of the electrode portion 301a. 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. In the present embodiment, the ion blocking layer 302 is a porous aluminum oxide layer. In the present embodiment, the ion blocking layer 302 exceeds the end of the electrode portion 301a of the reference electrode 301 by 2 mm 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 bypass the ion blocking layer 302 to reach the electrode portion 301a of the reference electrode 301, thereby reducing the difference in ion diffusion paths from the upper and lower oxygen pumping electrodes to the electrode portion 301a of the reference electrode 301, and 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 is switched quickly, thereby weakening the influence of electrode polarization and improving the stability and accuracy of the Nernst electromotive force. In this way, on the one hand, the Nernst resistance of the oxygen sensor chip can reach the target internal resistance of 300Ω, so that the oxygen sensor chip can be at the optimal operating temperature of 820℃. At this time, the catalytic reaction activity of the Nernst unit is good and the detection accuracy is high; on the other hand, the dynamic response stability of the chip near λ=1.0 (optimal air-fuel ratio) is good, and there is no interference from clutter signals.

[0037] The upper surface of the reference electrode lead portion 301b is provided with a first insulating layer 303, and the lower surface of the lead portion is provided with a second insulating layer 304. The first insulating layer 303 and the second insulating layer 304 are both made of porous alumina, and the thickness is 20 μm, which greatly improves the insulation performance of the reference electrode 301 and also reduces the signal interference between the reference electrode 301 and the oxygen pumping inner electrode 201.

[0038] A method for preparing a wide-band oxygen sensor chip according to an embodiment of the present application comprises the following steps: 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, the second dielectric layer, the third dielectric layer, and the fourth dielectric layer; S2, blank processing, firstly processing the conductive hole on the dielectric layer blank, then printing the oxygen pumping outer electrode on the upper surface of the first dielectric layer, printing the protective layer above the oxygen pumping outer electrode, printing the oxygen pumping inner electrode between the first dielectric layer and the second dielectric layer, printing the ion barrier layer, the reference electrode, and the reference electrode lead insulating layer between the second dielectric layer and the third dielectric layer, printing the heater upper insulating layer, the heater, and the heater lower insulating layer on the upper surface of the fourth dielectric layer in sequence, and printing the heater pin on the lower surface of the fourth dielectric layer; blank processing, firstly processing the conductive hole on the dielectric layer blank, then printing the oxygen pumping outer electrode 101 on the upper surface of the first dielectric layer 1, printing the protective layer 102 above the oxygen pumping outer electrode 101, and printing the inner electrode 102 on the first dielectric layer 1 and printing an oxygen pumping inner electrode 201 between the second dielectric layer 2, the oxygen pumping inner electrode 201 comprising an upper oxygen pumping inner electrode 201a and a lower oxygen pumping inner electrode 201b with a common electrode lead; printing a reference electrode 301 between the second dielectric layer 2 and the third dielectric layer 3; the reference electrode 301 comprising an electrode portion 301a and a lead portion 301b directly connected, the electrode portion 301a partially overlaps with the oxygen pumping inner electrode 201 in the projection direction of the third dielectric layer 3, so that the operating temperature of the reference electrode 301 is equivalent to that of the oxygen pumping inner electrode 201; printing an ion blocking layer 302 and a first and a second insulating layer covering the lead portion on the electrode portion 301a and the lead portion 301b of the reference electrode 301 respectively; S3, block pressing, the first dielectric layer 1, the second dielectric layer 2, the third dielectric layer 3 and the fourth dielectric 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 process to form a block, wherein the working pressure of the warm isostatic pressing process is 20 MPa and the water temperature is 80°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 1420°C for 3 hours.

[0039] Example 2 The difference between Example 2 and Example 1 is that Figure 2As shown, an oxygen pumping inner electrode 201 is provided between the first dielectric layer 1 and the second dielectric layer 2, and the oxygen pumping inner electrode 201 includes an upper oxygen pumping inner electrode 201a and a lower oxygen pumping inner electrode 201b, wherein the upper oxygen pumping inner electrode 201a and the oxygen pumping outer electrode 101 constitute a pump unit of the chip, which is used to pump oxygen from the inside to the outside or from the outside to the inside, and oxygen ions are directed to move by applying pressure to the inner and outer electrodes.

[0040] A reaction chamber 202 is provided between the upper oxygen pumping inner electrode 201a and the lower oxygen pumping inner electrode 201b. After the gas to be measured enters the reaction chamber 202, a catalytic reaction occurs at the oxygen pumping inner 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 connected to the reaction chamber 202 of the oxygen pumping inner electrode 201 to form the gas diffusion channel. The air inlet 5 is provided on the side of the substrate layer, which can optimize the diffusion path of oxygen and improve the response speed and accuracy of the sensor. This design can also enable oxygen to effectively enter the sensor and react with the oxygen pumping inner electrode 201, thereby generating an accurate measurement signal.

[0041] The reference electrode 301 includes an electrode portion 301a and a lead portion 301b which are directly connected. The area of ​​the electrode portion 301a is 5 mm 2 The electrode portion 301a of the reference electrode 301 partially overlaps with the oxygen pumping inner electrode 201 in the projection direction of the third dielectric layer 3, so that the operating temperature of the reference electrode 301 is substantially equal to the operating temperature of the oxygen pumping inner electrode 201.

[0042] 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 aluminum oxide layer. In the present embodiment, the ion blocking layer 302 exceeds the end of the electrode portion 301a by 4 mm in the length direction and completely covers the electrode portion 301a of the reference electrode 301 in the width direction, so that oxygen ions can only bypass the ion blocking layer 302 to reach the electrode portion 301a of the reference electrode 301, thereby reducing the difference in ion diffusion paths from the upper and lower oxygen pumping electrodes to the electrode portion 301a of the reference electrode 301, and 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 is switched rapidly, thereby weakening the influence of electrode polarization and improving the stability and accuracy of the Nernst electromotive force. In this way, on the one hand, the Nernst resistance of the oxygen sensor chip can reach the target internal resistance of 300Ω, so that the oxygen sensor chip can be operated at a temperature of 780°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 dynamic response stability of the chip near λ=1.0 (optimal air-fuel ratio) is good, and there is no interference from clutter signals.

[0043] Comparative Example 1 like Figure 3As shown, the difference between Comparative Example 1 and Example 1 is that Figure 3 As shown, the reference electrode 301 and the oxygen pumping inner electrode 201 do not overlap in the projection direction of the third dielectric layer 3, resulting in a large temperature difference between the operating temperatures of the reference electrode 301 and the oxygen pumping inner electrode, poor catalytic reaction activity of the chip Nernst unit, slow response, and slow output signal speed.

[0044] In Comparative Example 1, the area of ​​the electrode portion 301a is 5 mm 2 , with a thickness of 10μm. There is no ion barrier layer 302 on the upper surface of the electrode portion 301a, and a reference reaction chamber 6 is provided on the lower surface of the electrode portion for storing oxygen, which also has the function of alleviating signal attenuation. Since there is no ion barrier layer 302 on the upper surface of the electrode portion 301a in this comparative example, the ion diffusion path difference of oxygen ions from the upper and lower oxygen pumping inner electrodes 201 to the electrode portion 301a of the reference electrode 301 is large, resulting in unstable Nernst electromotive force of the chip, which is greatly affected by electrode polarization, and the dynamic response stability of the chip near λ=1.0 (optimal air-fuel ratio) is poor and interfered by clutter signals.

[0045] Comparative Example 2 like Figure 4 As shown, the difference between Comparative Example 2 and Example 1 is that the reference electrode 301 and the oxygen pumping inner electrode 201 partially overlap in the projection direction of the third dielectric layer 3, so that the temperature difference between the working temperature of the reference electrode 301 and the working temperature of the oxygen pumping inner electrode is small, the catalytic reaction activity of the chip Nernst unit is poor, the response is slow, and the output signal speed is slow.

[0046] In Comparative Example 2, the area of ​​the electrode portion 301a is 2 mm 2 , with a thickness of 10 μm. In this comparative example, the reference electrode 301 is relatively small in size, which results in a weaker signal generated by the reference electrode 301. In a low-concentration oxygen environment, a weaker signal is more difficult to detect accurately, resulting in an increase in the measurement error, so that when the comparative example is tested for static detection accuracy, the deviation from the standard value is within the range of λ>1.7.

[0047] In comparative example 2, the upper surface of the electrode portion 301a is not provided with an ion barrier layer 302. During the diffusion process, oxygen ions directly enter the electrode portion 301a, resulting in a decrease in the internal resistance of ion transmission, which fails to reach the target internal resistance of the chip, resulting in poor dynamic detection accuracy of the oxygen sensor chip. Since the upper surface of the electrode portion 301a is not provided with an ion barrier layer 302 in this comparative example, the ion diffusion path difference of oxygen ions from the upper and lower oxygen pumping inner electrodes 201 to the electrode portion 301a of the reference electrode 301 is large, resulting in unstable Nernst electromotive force of the chip, which is greatly affected by electrode polarization, and the dynamic response stability of the chip near λ=1.0 (optimal air-fuel ratio) is poor and is interfered by clutter signals.

[0048] The comprehensive performance, static detection accuracy, and dynamic response of the oxygen sensor chips in Examples 1 to 2, Comparative Examples 1 and 2 were tested, and the testing method was as follows: 1. Signal stability: In air atmosphere, connect the chip to a signal detector (commonly known as a lambda instrument) for 10 minutes and record the output oxygen signal value. If the absolute value of the signal change before and after is less than 0.2%, it is considered excellent, and 0.2-0.5% is considered good.

[0049] 2. Static detection accuracy: After the chip is packaged, the air inlet is connected to a closed air cavity, and a gas distributor is used to input different atmospheres into the air cavity. The atmospheres include oxygen-rich atmospheres with different concentrations and oxygen-poor atmospheres with different concentrations. The pins are connected to a signal detector (commonly known as a lambda instrument) to record the output λ value in real time.

[0050] 3. Dynamic detection accuracy: After the chip is packaged, it is connected to a combustion test bench (the atmosphere of the combustion test bench changes periodically, and the lambda range is 0.9-1.1), and a lambda instrument is used to collect the sensor's signal waveform in real time.

[0051] 4. Insulation performance: Use an insulation resistance meter to test the insulation resistance between the reference electrode 301 and the oxygen pumping outer electrode 101 in a hot state (about 600°C).

[0052] The comprehensive performance of each embodiment and comparative example is shown in Table 1 below, and the static detection accuracy of each embodiment and comparative example is shown in Figure 7 , the fitting R of the static detection accuracy diagram of each embodiment and comparative example 2 See Table 2.

[0053] Table 1 Comprehensive performance of each embodiment

[0054] It can be seen from Table 1 that 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 are also in a relatively good range, and the dynamic detection accuracy in Comparative Examples 1 and 2 is poor.

[0055] Table 2 Fitting R of static detection accuracy diagram 2

[0056] from Figure 5 It can be seen that in the static detection accuracy test, the test value of Example 1 is almost consistent with the standard value, and the comparative examples 1 and 2 deviate from the standard value when λ<0.8 and λ>2. Figure 5 The measured λ value data shown in the figure, we used linear fitting to fit each embodiment and comparative example, and the corresponding fitting R 2As shown in Table 2, when R 2 >0.9999, the chip’s detection accuracy is very high; when R 2 When it 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.

[0057] Figures 6-8 The dynamic response waveforms of Example 1, Comparative Example 1 and Comparative Example 2 are shown in FIG. Figures 6-8 It can be seen that in the dynamic response test, the signals of Comparative Examples 1 and 2 are extremely unstable and mutate when λ=1±0.02. Embodiment 1 solves the above problem.

[0058] For matters not mentioned above, the prior art applies.

[0059] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached 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 in 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), printing an oxygen pumping inner electrode (201) 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; printing a reference electrode (301) between the second dielectric layer (2) and the third dielectric layer (3); the reference electrode (301) comprising an electrode portion (301a) and a lead portion (301b) directly connected to each other, 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); printing an ion blocking layer and a first and a second insulating layer covering the lead portion 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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