CN102818832A - Porous diffusion barrier limiting current type oxygen sensor and manufacturing method thereof - Google Patents

Abstract

The invention discloses a porous diffusion barrier limiting current type oxygen sensor, which comprises an oxygen pump layer and a porous diffusion barrier layer. The oxygen pump layer is made of La _1-x Sr _x Ga _1-y Mg _y O _{3- δ} material Ceramic sheets, the upper and lower surfaces of the oxygen pump layer are respectively made with a positive electrode layer and a negative electrode layer, and the positive and negative electrode layers are respectively led to a positive electrode lead and a negative electrode lead. The porous diffusion barrier layer is sintered with Al ₂ O ₃ material A circular ceramic sheet is formed, the porous diffusion barrier layer is integrally connected to the lower surface of the negative electrode layer with the axis, and a bare annular upper plane is formed between the upper surface of the porous diffusion barrier layer and the connection of the negative electrode layer. An encapsulation layer is sealed on the upper plane and the outer peripheral surfaces of the oxygen pump layer, the positive electrode layer and the negative electrode layer. The manufacturing method includes the steps of green sheet preparation, primary high-temperature sintering, electrode layer printing, secondary high-temperature sintering, and re-sintering of finished products. The invention has the advantages of simple manufacturing process, stable performance, wide measurement range, high detection precision, short response time and long service life.

Description

A Porous Diffusion Barrier Limiting Current Oxygen Sensor and Its Manufacturing Method

technical field

The invention relates to an oxygen sensor, in particular to a limiting current type oxygen sensor made of medium temperature solid oxygen ion conductor material, in particular to a porous diffusion barrier limiting current type oxygen sensor and its manufacturing method.

Background technique

Oxygen sensors can be divided into concentration potential type and limiting current type according to the principle, and limiting current type oxygen sensors can be divided into pore diffusion barrier type and dense diffusion type. Limiting current oxygen sensors are more and more widely used in the fields of metallurgy, food and oxygen production technology due to their advantages of high measurement accuracy, wide range, fast response time and no need for reference gas. At present, most of the solid electrolytes of limiting current oxygen sensors are YSZ materials. Since this material has high oxygen ion conductivity only when the temperature is higher than 800°C, the working temperature of the sensor must be higher than 800°C. The work has brought about a series of problems, such as the generation of harmful substances at the three-phase interface, difficulty in matching electrode materials, and high energy consumption. In order to solve these problems, it is urgent to reduce the operating temperature of the sensor, and one of the ways is to find a material with higher oxygen ion conductivity in the medium temperature range to replace YSZ as the solid electrolyte of the oxygen sensor.

At present, the intermediate temperature solid oxygen ion conductor materials found in the prior art mainly include δ-Bi ₂ O ₃ , CeO ₂ and La _1-x Sr _x Ga _{1-y Mgy} O _3-δ three materials. However, due to the unstable structure of the δ-Bi ₂ O ₃ material, it will change with the change of temperature; CeO ₂ is easily reduced to Ce ³⁺ in a reducing atmosphere to produce electronic conductivity, ^so that the two Materials are very limited in their application. The conductivity of La _1-x Sr _x Ga _1-y Mg _y O _3-δ is much superior to that of YSZ material under the same conditions, and it has good performance in a wide range of oxygen partial pressure and reducing atmosphere Stability, so this material is considered to be the most likely to replace YSZ as a medium temperature solid oxygen ion conductor material.

Contents of the invention

The technical problem to be solved by the present invention is to provide a limiting current platform of a porous diffusion barrier with stable performance and good mechanical strength in the temperature range of 600°C to 700°C in view of the above-mentioned current state of the art. Type oxygen sensor and its manufacturing method. The sensor has simple manufacturing process and convenient use, and has the characteristics of wide oxygen concentration measurement range, high precision, short response time and long service life.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: a porous diffusion barrier limiting current type oxygen sensor, including an oxygen pump layer and a porous diffusion barrier layer, and the oxygen pump layer is made of La _1-x Sr _x Ga _1-y Mg _{yO 3- δ} material is sintered into a circular ceramic body, and the upper surface and the lower surface of the oxygen pump layer are respectively made of a positive electrode layer and a negative electrode layer by screen printing technology, and the positive electrode layer leads to a positive electrode lead , the negative electrode layer leads to a negative electrode lead, and the porous diffusion barrier layer is a circular ceramic sheet with a larger diameter than the oxygen pump layer and a porous structure sintered with Al ₂ O ₃ material, and the porous diffusion barrier layer is integrally connected with the axis On the lower surface of the negative electrode layer, an exposed annular upper plane is formed between the upper surface of the porous diffusion barrier layer and the connection of the negative electrode layer, on the annular upper plane and the outer circumference of the oxygen pump layer, the positive electrode layer and the negative electrode layer The surface is sealed with an encapsulation layer.

In order to optimize the above technical solutions, the measures taken also include:

The above-mentioned encapsulation layer is a high-temperature sealing glass glaze; the oxygen pump layer is a dense La _1-x Sr _x Ga _1-y Mg _y O _3-δ ceramic disc with a diameter of about 7.5mm and a thickness of about 0.6mm; a porous diffusion barrier The layer is an Al ₂ O ₃ ceramic disc with a porous structure, about 10.5 mm in diameter and about 0.7 mm in thickness.

The above-mentioned positive electrode lead and negative electrode lead are respectively used to connect the positive and negative electrodes of the power supply.

In the aforementioned La _1-x Sr _x Ga _1-y Mg _y O _3-δ material, the value ranges of x and y are 0.1≤x≤0.2 and 0.1≤y≤0.2, respectively.

The materials of the above-mentioned positive electrode layer and negative electrode layer as well as the positive electrode lead and the negative electrode lead are all platinum.

The thicknesses of the positive electrode layer and the negative electrode layer are both 20um.

The present invention also provides a manufacturing method of a porous diffusion barrier limiting current type oxygen sensor, the method comprising the following steps:

Blank preparation: first use a mold and a hydraulic press to press La _1-x Sr _x Ga _1-y Mg _y O _3-δ powder and Al ₂ O ₃ powder respectively into an oxygen pump layer green sheet with a diameter of 10mm and a diameter of 13mm porous diffusion barrier blank;

One-time high-temperature sintering: sending the above-mentioned oxygen pump layer green sheet and porous diffusion barrier layer green sheet into a high-temperature sintering furnace for sintering to obtain a dense oxygen pump layer ceramic sheet and a porous structure porous diffusion barrier layer ceramic sheet;

Electrode layer printing: Use a high-precision screen printing machine to print a positive electrode layer and a negative electrode layer on the upper and lower sides of the above-mentioned oxygen pump layer ceramic sheet, and at the same time lead the positive electrode lead and the negative electrode layer respectively from the positive electrode layer and the negative electrode layer. Electrode leads;

Secondary high-temperature sintering: The side of the oxygen pump layer ceramic sheet with the negative electrode layer is connected with the above-mentioned porous diffusion barrier layer ceramic sheet by means of platinum slurry adhesion, and they are sent together into a high-temperature sintering furnace for sintering to obtain an oxygen sensor with an integrated structure Blank;

Re-sintering of the finished product: after natural cooling, the above-mentioned oxygen sensor blank is coated with glass glaze on the exposed upper plane of the porous diffusion barrier layer and the outer peripheral surface of the negative electrode layer, oxygen pump layer, and positive electrode layer, and then sent to the high-temperature sintering furnace The product is obtained by medium sintering.

The time for the oxygen pump layer green sheet to be sintered in the high-temperature sintering furnace in the above-mentioned primary high-temperature sintering is 2h to 6h, and the furnace temperature is 1350°C to 1500°C; the time for the porous diffusion barrier layer green sheet to be sintered in the high-temperature sintering furnace is 3h to 6h, furnace temperature is 1500℃～1550℃.

In the above-mentioned secondary high-temperature sintering, the sintering temperature in the high-temperature sintering furnace is 900° C. to 1000° C., and the time is 1 hour.

In the re-sintering of the above-mentioned finished product, the sintering temperature of the high-temperature sintering furnace is 900° C., and the time is 1 h to 3 h.

Compared with the prior art, the oxygen pump layer of the oxygen sensor of the present invention is made of La _1-x Sr _x Ga _1-y Mg _y O _3-δ material whose conductivity is 2 to 4 times larger than that of YSZ material under the same conditions , the porous diffusion barrier layer is Al ₂ O ₃ ceramic sheet with a porous structure, so the product can exhibit good performance in the medium temperature range, and a good limiting current platform appears, and the oxygen concentration can be measured in the range of 0 to 80%. The response time is in the range of 10s ~ 15s. It greatly reduces the situation that the traditional oxygen sensor needs to work in a high temperature environment of 800 ° C, and improves the service life of the oxygen sensor. The invention has the advantages of simple manufacturing process, stable performance, wide measurement range, high detection precision and short response time. It can be widely used in fields such as metallurgy, food and oxygen production.

Description of drawings

Fig. 1 is the structural representation of the embodiment of the present invention;

Fig. 2 is the I-V curve figure of the present invention at 650 ℃;

Fig. 3 is the relationship figure of limiting current value and oxygen concentration of the present invention;

Figure 4 is a response time graph of the present invention.

Detailed ways

Embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Reference signs therein are: oxygen pump layer 1; porous diffusion barrier layer 2; positive electrode layer 3; negative electrode layer 4; packaging layer 5; positive electrode lead 6; negative electrode lead 7; power supply 8; ammeter 9.

As shown in Fig. 1, a kind of porous diffusion barrier limiting current type oxygen sensor of the present invention comprises oxygen pump layer 1 and porous diffusion barrier layer 2, and oxygen pump layer 1 adopts La _1-x Sr _x Ga _1-y Mg _y O A circular ceramic sheet made of _3-δ material sintered, and the upper surface and lower surface of the oxygen pump layer 1 are respectively made of a positive electrode layer 3 and a negative electrode layer 4 by screen printing technology, and the positive electrode layer 3 leads to a positive electrode layer. The electrode lead 6, the negative electrode layer 4 leads to the negative electrode lead 7, the porous diffusion barrier layer 2 is a circular ceramic sheet with a diameter larger than the _oxygen pump layer 1 and a porous structure sintered with _Al2O3 material, the porous diffusion barrier layer The barrier layer 2 is integrally connected to the lower surface of the negative electrode layer 4 with the axis, and a bare annular upper plane is formed between the upper surface of the porous diffusion barrier layer 2 and the connection of the negative electrode layer 4, and the oxygen pump layer and the 1. The encapsulation layer 5 is sealed on the outer peripheral surfaces of the positive electrode layer 3 and the negative electrode layer 41 . The oxygen pump layer 1 of the present invention is made of La _1-x Sr _x Ga _1-y Mgy _{O 3-δ} material, replacing the traditional YSZ material, La _1-x Sr _x Ga _{1-y Mgy} O _3-δ The electrical conductivity of the material is 2 to 4 times that of the YSZ material under the same conditions, and it has good performance stability in a wide range of oxygen partial pressure and in a reducing atmosphere, so it is used as a medium temperature solid oxygen ion conductor material The most ideal material. The porous diffusion barrier layer 2 is a ceramic sheet with a porous structure made of sintered Al ₂ O ₃ material, so oxygen molecules in the environment can freely diffuse through it. The product of the present invention has stable working performance at 600°C-700°C, has a good limiting current platform, can measure oxygen concentration in the range of 0-80%, and has a response time in the range of 10s-15s, with stable performance and a wide measurement range , high detection accuracy, short response time and long service life. As can be seen from Fig. 1, the present invention can set up ammeter 9 in circuit when working.

The encapsulation layer 5 of the present invention is a high-temperature sealing glass glaze.

In the embodiment, the positive electrode lead 6 and the negative electrode lead 7 are respectively used to connect the positive and negative electrodes of the power supply 8 .

In the La _1-x Sr _x Ga _1-y Mg _y O _3-δ material of the present invention, the value ranges of x and y are 0.1≤x≤0.2 and 0.1≤y≤0.2, respectively.

The materials of the positive electrode layer 3 and the negative electrode layer 4 and the positive electrode lead 6 and the negative electrode lead 7 of the present invention are all platinum.

Both the positive electrode layer 3 and the negative electrode layer 4 of the present invention have a thickness of 20um.

The oxygen pump layer 1 and the porous diffusion barrier layer 2 of the present invention are made into ceramic discs through sintering. After sintering, the diameter of the oxygen pump layer 1 is about 7.5 mm, the thickness is about 0.6 mm, and the diameter of the porous diffusion barrier layer 2 is about 10.5 mm. , the thickness is about 0.7mm.

The present invention also provides a manufacturing method of a porous diffusion barrier limiting current type oxygen sensor, the method comprising the following steps:

Blank preparation: first use a mold and a hydraulic press to press La _1-x Sr _x Ga _1-y Mg _y O _3-δ powder and Al ₂ O ₃ powder respectively into an oxygen pump layer green sheet with a diameter of 10mm and a diameter of 13mm porous diffusion barrier blank;

One-time high-temperature sintering: sending the above-mentioned oxygen pump layer green sheet and porous diffusion barrier layer green sheet into a high-temperature sintering furnace for sintering to obtain a dense oxygen pump layer ceramic sheet and a porous structure porous diffusion barrier layer ceramic sheet;

Electrode layer printing: Use a high-precision screen printing machine to print a positive electrode layer and a negative electrode layer on the upper and lower sides of the above-mentioned oxygen pump layer ceramic sheet, and at the same time lead the positive electrode lead and the negative electrode layer respectively from the positive electrode layer and the negative electrode layer. Electrode leads;

Secondary high-temperature sintering: The side of the oxygen pump layer ceramic sheet with the negative electrode layer is connected with the above-mentioned porous diffusion barrier layer ceramic sheet by means of platinum slurry adhesion, and they are sent together into a high-temperature sintering furnace for sintering to obtain an oxygen sensor with an integrated structure Blank;

Re-sintering of the finished product: after natural cooling, the above-mentioned oxygen sensor blank is coated with glass glaze on the exposed upper plane of the porous diffusion barrier layer and the outer peripheral surface of the negative electrode layer, oxygen pump layer, and positive electrode layer, and then sent to the high-temperature sintering furnace The product is obtained by medium sintering.

The time for the oxygen pump layer green sheet to be sintered in the high-temperature sintering furnace in the above-mentioned primary high-temperature sintering is 2h to 6h, and the furnace temperature is 1350°C to 1500°C; the time for the porous diffusion barrier layer green sheet to be sintered in the high-temperature sintering furnace is 3h to 6h, the furnace temperature is 1500℃～1550℃.

In the above-mentioned secondary high-temperature sintering, the sintering temperature in the high-temperature sintering furnace is 900° C. to 1000° C., and the time is 1 hour.

In the re-sintering of the above-mentioned finished product, the sintering temperature of the high-temperature sintering furnace is 900° C., and the time is 1 h to 3 h.

The working principle of the oxygen sensor of the present invention is: when the sensor works, the power supply 8 applies a working voltage to the sensor, and the electrons flow out from its negative electrode, and flow into the negative electrode layer 4 through the ammeter 9 and the negative electrode lead wire 7, and are combined with the oxygen sensor under the catalysis of platinum. The nearby oxygen molecules react to convert oxygen molecules into oxygen ions; the oxygen ions are quickly pumped to the positive electrode layer 3 under the action of the potential difference on both sides of the oxygen pump layer 1, and then detach electrons under the catalysis of platinum to become Oxygen molecules return to the environment; since the porous diffusion barrier layer 2 has a porous structure, the oxygen molecules in the environment can freely diffuse to the negative electrode layer 4 through it, and the diffusion capacity is determined by its porosity and external oxygen concentration; and The oxygen pumping ability of the oxygen pump layer 1 increases with the increase of the voltage. When it is greater than the oxygen molecular diffusion ability of the porous diffusion barrier layer 2, a limiting current platform will appear, that is, the current does not increase with the increase of the voltage; therefore The diffusion capacity of oxygen molecules in the porous diffusion barrier layer 2 determines the size of the limiting current, and because the prepared porous diffusion barrier layer 2 has a constant porosity, the external oxygen concentration determines its diffusion capacity; therefore, the external oxygen concentration Determines the size of the limiting current, that is, different oxygen concentrations correspond to different limiting currents. Figure 2 shows the I-V curves measured by the present invention at a temperature of 650°C. From the figure, it can be seen that under different oxygen concentration environments, different limiting current platforms appear when the voltage is 0.6V-1.2V. The limiting current value of each limiting current platform was read, and it was found that it showed a good linear relationship with the oxygen concentration, as shown in Figure 3. Therefore, apply a certain voltage to the sensor, and according to the current value displayed by the ammeter 9, combined with its linear function relationship, the oxygen concentration in the environment can be obtained, so as to achieve the purpose of measuring the oxygen concentration. At the same time, at 650°C, the oxygen concentration changes back and forth between 1% and 40%. The measured response time curve is shown in Figure 4. From the figure, it can be concluded that the response time for rising is 10s-15s, and the response time for falling is 10s-15s. It is 15s-20s, and the repeatability of the sensor is good.

Claims (10)

1. A porous diffusion barrier limiting current type oxygen sensor, comprising oxygen pump layer (1) and porous diffusion barrier layer (2), is characterized in that: described oxygen pump layer (1) adopts La _1-x Sr _x Ga _1-y Mg _y O _3-δ material is sintered into a circular ceramic sheet, and the upper surface and the lower surface of the oxygen pump layer (1) are respectively made of a positive electrode layer (3) and a negative electrode layer (3) by screen printing technology. An electrode layer (4), the positive electrode layer (3) leads to a positive electrode lead (6), the negative electrode layer (4) leads to a negative electrode lead (7), and the porous diffusion barrier layer (2) It is a circular ceramic sheet with a diameter larger than the oxygen pump layer (1) and a porous structure formed by sintering Al ₂ O ₃ material. The porous diffusion barrier layer (2) is integrally connected to the negative electrode layer (4) with the axis On the lower surface, an exposed annular upper plane is formed between the upper surface of the porous diffusion barrier layer (2) and the connection of the negative electrode layer (4), and the oxygen pump layer (1), the positive electrode layer ( 3) and the outer peripheral surface of the negative electrode layer (4) are sealed with an encapsulation layer (5). 2. A kind of porous diffusion barrier limiting current type oxygen sensor according to claim 1, characterized in that: the packaging layer (5) is a high-temperature sealing glass glaze; the oxygen pump layer (1) is dense La _{1- x} Sr _x Ga _1-y Mg _y O _3-δ ceramic disc with a diameter of about 7.5 mm and a thickness of about 0.6 mm; the porous diffusion barrier layer (2) is an Al ₂ O ₃ ceramic disc with a porous structure and a diameter of about It is 10.5mm and the thickness is about 0.7mm. 3. A porous diffusion barrier limiting current oxygen sensor according to claim 2, characterized in that: said positive electrode lead (6) and negative electrode lead (7) are respectively used to connect to the positive electrode of the power supply (8). negative electrode. 4. A porous diffusion barrier limiting current type oxygen sensor according to claim 3, characterized in that: in the La _1-x Sr _x Ga _1-y Mg _y O _3-δ material, x and y are The value ranges are 0.1≤x≤0.2 and 0.1≤y≤0.2 respectively. 5. A porous diffusion barrier limiting current oxygen sensor according to claim 4, characterized in that: said positive electrode layer (3) and negative electrode layer (4) and positive electrode lead (6) and negative electrode The material of lead wire (7) is platinum. 6. A porous diffusion barrier limiting current oxygen sensor according to claim 5, characterized in that: the thickness of the positive electrode layer (3) and the negative electrode layer (4) are both 20um. 7. A method of manufacturing the porous diffusion barrier limiting current type oxygen sensor according to claim 1, characterized in that: the method comprises the following steps: Blank preparation: first use a mold and a hydraulic press to press La _1-x Sr _x Ga _1-y Mg _y O _3-δ powder and Al ₂ O ₃ powder respectively into an oxygen pump layer green sheet with a diameter of 10mm and a diameter of 13mm porous diffusion barrier blank; One-time high-temperature sintering: sending the above-mentioned oxygen pump layer green sheet and porous diffusion barrier layer green sheet into a high-temperature sintering furnace for sintering to obtain a dense oxygen pump layer ceramic sheet and a porous structure porous diffusion barrier layer ceramic sheet; Electrode layer printing: Use a high-precision screen printing machine to print a positive electrode layer and a negative electrode layer on the upper and lower sides of the above-mentioned oxygen pump layer ceramic sheet, and at the same time lead the positive electrode lead and the negative electrode layer respectively from the positive electrode layer and the negative electrode layer. Electrode leads; Secondary high-temperature sintering: The side of the oxygen pump layer ceramic sheet with the negative electrode layer is connected with the above-mentioned porous diffusion barrier layer ceramic sheet by means of platinum slurry adhesion, and they are sent together into a high-temperature sintering furnace for sintering to obtain an oxygen sensor with an integrated structure Blank; Re-sintering of the finished product: after natural cooling, the above-mentioned oxygen sensor blank is coated with glass glaze on the exposed upper plane of the porous diffusion barrier layer and the outer peripheral surface of the negative electrode layer, oxygen pump layer, and positive electrode layer, and then sent to the high-temperature sintering furnace The product is obtained by medium sintering. 8. The manufacturing method of a porous diffusion barrier limiting current type oxygen sensor according to claim 7, characterized in that: the oxygen pump layer green sheet is sintered in a high temperature sintering furnace for 2 hours to 6h, the furnace temperature is 1350°C-1500°C; the sintering time of the porous diffusion barrier green sheet in the high-temperature sintering furnace is 3h-6h, and the furnace temperature is 1500°C-1550°C. 9. The manufacturing method of a porous diffusion barrier limiting current type oxygen sensor according to claim 8, characterized in that: in the second high-temperature sintering, the sintering temperature of the high-temperature sintering furnace is 900°C to 1000°C, and the time for 1h. 10. The manufacturing method of a porous diffusion barrier limiting current type oxygen sensor according to claim 9, characterized in that: in the re-sintering of the finished product, the sintering temperature of the high-temperature sintering furnace is 900°C, and the time is 1h-3h .

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