KR100980821B1 - Multi-layer solid electrolyte for gas sensor, Method of preparing the same and Gas sensor device comprising the same - Google Patents

Abstract

The present invention relates to a multi-layered solid electrolyte for a gas sensor, a method for manufacturing the same, and a gas sensor device including the same. The multi-layered solid electrolyte for a gas sensor of the present invention includes a solid electrolyte for a gas sensor interposed between a sensing electrode and a reference electrode, the solid electrolyte comprising: a first layer formed of an ion conductive solid electrolyte; A barrier layer formed of a metal thin film; And a multilayer structure formed by sequentially stacking a second layer formed of an ion conductive solid electrolyte. In the multi-layered solid electrolyte for a gas sensor of the present invention, the barrier layer interposed between the solid electrolyte layers can prevent deterioration of the electrolyte by inhibiting material movement such as cations and rearrangement of the material.

Barrier Layer, Solid Electrolyte, Gas Sensor

Description

Multi-layer solid electrolyte for gas sensor, method for manufacturing same and gas sensor device comprising same {Multi-layer solid electrolyte for gas sensor, Method of preparing the same and Gas sensor device comprising the same}

The present invention relates to a multi-layered solid electrolyte for a gas sensor, a method for manufacturing the same, and a gas sensor element including the same. More specifically, the multilayered structure for a gas sensor can be excellently maintained for a long time due to suppression of degradation. The present invention relates to a solid electrolyte, a method of manufacturing the same, and a gas sensor device including the same.

Recently, as the interest in environment increases, social demands for a pleasant living environment are increasing, and accordingly, various environmental regulations are gradually strengthened. Accordingly, interest in gas sensors that can detect various harmful gases is also increasing.

Currently, sensors used to detect gases such as carbon dioxide include sensors using gas chromatography and gas sensors using semiconductor compounds such as SnO ₂ or TiO ₂ . However, the gas sensor using gas chromatography has a disadvantage in that the volume and weight are large and expensive, so it is only used for extremely limited purposes. In addition, the gas sensor using the semiconductor compound has the advantage that it is possible to manufacture a sensor in the form of an element, but it is difficult to distinguish the type of gas adsorbed on the surface of the semiconductor compound has a disadvantage inferior gas selectivity.

On the other hand, recently, due to its simple structure, it is possible to manufacture a small element-type sensor and has excellent gas selectivity, and thus, a solid electrolyte type gas sensor capable of quantitatively measuring a specific gas concentration has been developed and attracts attention.

The solid electrolyte type gas sensor element has a basic structure in which a solid electrolyte is interposed between the sensing electrode and the reference electrode. However, a phenomenon in which the output (electromotive force) of the sensor gradually decreases with time has been observed in the conventional sensor using a solid electrolyte, and this phenomenon is one of the important factors of the degradation of the sensor.

However, no effective solution has been reported so far, and therefore, there is an urgent need to develop a sensor that does not deteriorate even after long-term use.

Accordingly, an object of the present invention is to provide a gas sensor electrolyte and a gas sensor device having the same, which can maintain excellent performance so that sensitivity to a target gas does not decrease even when used for a long time.

In order to solve the above problems, the multi-layered solid electrolyte for a gas sensor of the present invention, in the gas sensor solid electrolyte interposed between the sensing electrode and the reference electrode, the solid electrolyte, the first layer formed of an ion conductive solid electrolyte ; A barrier layer formed of a metal thin film; And a multilayer structure formed by sequentially stacking a second layer formed of an ion conductive solid electrolyte.

The inventors of the present invention, in the sensor element consisting of a conventional sensing electrode, a solid electrolyte and a reference electrode is formed a constant electromotive force according to the gas concentration, which is a cause that a minute current flows when the sensor element is connected to a circuit It has been found that internally, it acts as a power of mass transfer. When such mass transfer or current flow is present, the electrolyte material itself deteriorates or the electrode reaction is not smooth. I found out that I could get away.

Accordingly, in the solid electrolyte of the present invention, the barrier layer interposed between the first layer and the second layer formed of the ion conductive solid electrolyte suppresses the transfer of substances such as cations, thereby preventing deterioration of the solid electrolyte quality and improving the performance of the sensor element. I can keep it.

In addition, in order to solve the above problems, the method for producing a multi-layered solid electrolyte for a gas sensor of the present invention, (S1) to prepare an ion conductive solid electrolyte slurry containing a solid electrolyte powder, a plasticizer, a binder, a dispersant and an organic solvent. step; (S2) casting the slurry on a substrate or a base film and drying to obtain an ion conductive solid electrolyte sheet; (S3) sintering the sheet; (S4) forming a barrier layer by applying a metal paste on one surface of the sintered body, and stacking the second sintered body on the barrier layer; And (S5) sintering the resultant.

In addition, in order to solve the above problems, the method for producing a multi-layered solid electrolyte for a gas sensor of the present invention, (S1) to prepare an ion conductive solid electrolyte slurry containing a solid electrolyte powder, a plasticizer, a binder, a dispersant and an organic solvent. step; (S2) casting the slurry on a substrate or a base film and drying to obtain an ion conductive solid electrolyte sheet; (S3) forming a barrier layer by applying a metal paste on one surface of the sheet, and stacking a second sheet on the barrier layer; And (S4) sintering the resultant.

In addition, in order to solve the above problems, the present invention can provide a gas sensor device having a multi-layered solid electrolyte according to the present invention.

In the multilayered solid electrolyte of the present invention, deterioration is prevented by suppressing material movement such as cations and rearrangement of the material in the electrolyte. Accordingly, the gas sensor having the multilayered structure electrolyte of the present invention is capable of long-term use. This may not be degraded.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

1 schematically shows an embodiment of a solid electrolyte 10 of a multilayer structure according to the present invention. However, the configuration described in the embodiments and drawings described below are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, which can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

The multi-layered solid electrolyte 10 according to the present invention includes a first layer 11 formed of an ion conductive solid electrolyte, a barrier layer 12 formed of a metal thin film, and a second layer 13 formed of an ion conductive solid electrolyte. Is done.

The ion conductive solid electrolyte first layer 11 and the second layer 13 are prepared by preparing an ion conductive solid electrolyte slurry, and applying the same to a substrate or a base film in a predetermined form and drying the sheet to form a sheet. It can be obtained by sintering. The slurry may be used without limitation, the slurry commonly used in the art for producing an ion conductive solid electrolyte layer, and may be prepared, for example, including a solid electrolyte powder, a plasticizer, a binder, a dispersant, and an organic solvent.

The solid electrolyte powder may use a conventional cationic conductive solid electrolyte material known in the art, for example, sodium ion conductor Nasicon (NASICON), sodium beta alumina (Na-β-Alumina) or lithium ion conductor lithium lanthanum Titanate (lithium lanthanum titanate, LLT) and the like, but is not limited thereto.

As the plasticizer, polyethylene glycol, polyalkylene glycol, dibutyl phthalate or dioctyl phthalate, or a mixture thereof, which are commonly used in the art, may be used. However, it is not limited thereto. The amount of the plasticizer may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the solid electrolyte powder, and the sheet formed by drying the slurry in the above range may have the ductility that is easiest to handle.

As the binder, polyvinyl butyral, polyvinyl alcohol or polyacrylate esters, or mixtures thereof, which are commonly used in the art, may be used. no. The binder may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the solid electrolyte powder, and the sheet formed by drying the slurry in the above range may have the easiest strength to handle.

As a dispersant, glycerol trioleate, fish oil or phosphate ester, or a mixture thereof, which are commonly used in the art, may be used, but are not limited thereto. The content of the dispersant may include 0.1 to 10 parts by weight based on 100 parts by weight of the solid electrolyte powder, and may have a viscosity most suitable for handling the slurry in the above range.

As the organic solvent, trichloroethylene (TCE), ethyl alcohol (EtOH), toluene or methyl ethyl ketone (MEK), or mixtures thereof commonly used in the art May be used, but is not limited thereto. The content of the organic solvent may include 50 to 200 parts by weight based on 100 parts by weight of the solid electrolyte powder, the slurry may have the most suitable viscosity for handling in the above range.

The thickness of the ion conductive solid electrolyte first layer 11 and the second layer 13 may be appropriately adopted as necessary, and may be, for example, 200 to 1000 μm, but is not limited thereto. In the above thickness range, the performance of the sensor element can be sufficiently expressed and economical.

The barrier layer 12 formed of the metal thin film may be obtained using a metal paste for barrier layer formation. The metal paste for forming the barrier layer may include a metal, a binder, a dispersant, and a solvent, and a metal paste commercially available in the art (8880 Gold conductor of Electro Science Lab. Inc. (USA), Tanaka Kikinzoku Group, Japan) A-5-50, C-5729 from Heraeus (Germany), etc.) may also be used.

As a metal that can be used for the barrier layer forming metal paste according to the present invention, any metal can be used without limitation as long as it has excellent chemical safety and conductivity, and can inhibit material movement such as cations present in the electrolyte when forming the barrier layer. For example, gold (Au), silver (Ag), copper (Cu), platinum (Pt), aluminum (Al), or the like can be used, and preferably gold or platinum can be used.

The thickness of the barrier layer 12 may be appropriately adopted as necessary, and may be, for example, 1 to 10 μm, but is not limited thereto. The function of the electrolyte is sufficiently exhibited in the above thickness range, and at the same time, the movement of substances such as cations in the electrolyte can be most effectively suppressed.

An example of a method of manufacturing a multilayer structure solid electrolyte of the present invention is as follows.

After fully mixing the ion conductive solid electrolyte slurry prepared as described above, it is applied to a substrate or a carrier film (carrier film) and dried to form a sheet, the sheet may be sintered to obtain an ion conductive solid electrolyte sintered body. At this time, in order to obtain a solid electrolyte sintered body having a desired thickness, one or more sheets prepared above may be laminated and sintered. In the case of stacking a plurality of sheets, it is preferable to stack the sheets so that the forming direction of each sheet to be laminated is orthogonal in consideration of the orientation formed in the forming direction at the time of forming the sheet. At this time, the sintering temperature may be preferably performed at 900 ~ 1300 ℃. In the sintering temperature range, an electrolyte having a high sintered density and high electrical conductivity may be prepared.

When the ion conductive solid electrolyte sintered body is prepared, the barrier layer forming metal paste prepared as described above is coated on one surface thereof, and the barrier layer forming metal paste layer is coated on the metal paste coated so as to be interposed between the two ion conductive solid electrolyte sintered bodies. After adhering another second ion conductive solid electrolyte sintered body and sintering again, the multilayer structure solid electrolyte of the present invention can be obtained. At this time, the sintering temperature may be preferably performed at 700 ~ 1200 ℃. The solvent on the metal paste may be sufficiently removed in the sintering temperature range, and the adhesion state between the solid electrolyte layer and the barrier layer may be the best.

In another embodiment of the present invention, the sintering step for producing an ion conductive solid electrolyte sintered body and the sintering step for obtaining a multilayered solid electrolyte may be simultaneously performed. That is, a barrier layer forming metal paste is applied onto the solid electrolyte layer sheet or sheet laminate, and another second solid electrolyte layer sheet or sheet laminate is adhered to the applied metal paste, followed by sintering. The multilayered solid electrolyte of the invention can be obtained. At this time, the sintering temperature may be determined as the temperature at which both the solid electrolyte sheet and the barrier layer can be sintered, for example, may be 900 ~ 1200 ℃.

The multilayered solid electrolyte of the present invention can be used to fabricate a gas sensor element, and FIG. 2 schematically illustrates one embodiment of a gas sensor element using the multilayered solid electrolyte of the present invention.

The gas sensor device according to the present invention may include a sensing electrode 1, a multilayered solid electrolyte 10, a reference electrode 20, a substrate 30, a heating element pattern 40, and a lead wire 50.

The sensing electrode 1 is formed on one surface of the multi-layered solid electrolyte 10, and may be manufactured by heat-treating a paste for forming a sensing electrode, which is a mixture of metal carbonate and metal, which is conventional in the art. As the metal carbonate, sodium carbonate (Na ₂ CO ₃ ), lithium carbonate (Li ₂ CO ₃ ), or the like may be used, and the metal may include gold, silver, platinum, or the like.

The reference electrode 20 is formed on the other side of the multi-layered solid electrolyte 10 so as to face the sensing electrode 1, and a paste for forming a reference electrode common in the art, for example, an oxide including Na (Na-Ti). -O, Na-Mn-O, Na-Si-O) or a two-phase mixture of an oxide (Li-Fe-O) containing Li, and a reference electrode forming paste mixed with a metal paste prepared by heat treatment Can be. As the metal paste, the same metal paste used for the sensing electrode forming paste may be used.

The substrate 30 is disposed between the reference electrode 20 and the heating element pattern 50 to separate the electrolyte and the electrodes from the heating element, and alumina may be used.

The heating element pattern 40 is formed on one surface of the substrate 30, and typically platinum may be used.

The lead wire 50 is connected between the heating element pattern 40, the substrate 30 and the reference electrode 20, and between the electrolyte 10 and the sensing electrode 1, in particular, between the substrate 30 and the reference electrode 20. And a metal paste used in the manufacture of the sensing electrode or the reference electrode may be applied between the electrolyte 10 and the sensing electrode 1 to facilitate adhesion of each component and attachment of lead wires (not shown).

Hereinafter, the present invention will be described in detail with reference to Examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

<Multilayer Structure Solid Electrolyte Preparation>

As shown in Table 1, a solid electrolyte powder, a plasticizer, a binder, a dispersant, and an organic solvent were prepared.

ingredient designation content Solid electrolyte powder Nashikon 40 g Plasticizer Polyethylene glycol 0.9 g Dioctyl phthalate 1.0 g bookbinder Polyvinyl Butyral 5.0 g Dispersant Glyceryl Trioleate 0.7 ml Organic solvent Trichloroethylene 55 g Ethyl alcohol 20.3 g

The raw materials were uniformly mixed using a Planetary Ball Mill (PM-100) to prepare an ion conductive solid electrolyte slurry. In order to remove the air in the slurry and to obtain a slurry having a suitable viscosity, a degassing treatment was performed using a rotary vacuum pump.

The resulting slurry was cast to a thickness of about 150 μm on a carrier film traveling at a rate of 0.7 cm / s. The cast slurry was dried at room temperature to obtain a sheet. The sheet was cut into 4 cm × 4 cm, and then laminated so that the casting directions of the cut sheets were orthogonal, and compression molding was performed using a hot plate press at 70 ° C. to obtain a sheet laminate having a thickness of 380 μm. The prepared sheet laminate was heated to 100 ° C. at a temperature increase rate of 1.6 ° C./min, heated to 600 ° C. at a temperature increase rate of 1 ° C./min, maintained for 2 hours, and further heated to 1150 ° C. at a temperature increase rate of 3 ° C./min. After sintering for 8 hours. Thereafter, air cooled to room temperature in a furnace to obtain a solid electrolyte.

Gold paste (Gold conductor-8880, Electro Science Lab. Inc.) was applied to one surface of the obtained solid electrolyte to form a barrier layer, and another solid electrolyte was laminated thereon, and then heated to 1000 ° C. A multilayered solid electrolyte was obtained.

<Manufacture of gas sensor element>

On one surface of the obtained multi-layered solid electrolyte, a reference electrode forming paste, in which a two-phase mixture of Na-Ti-O oxides and the gold paste was mixed, was applied and dried. On the other side of the multi-layered solid electrolyte, a gold paste was applied and dried to attach a metal lead wire.

On the other hand, platinum paste (TR-7905, Tanaka Kinkinzoku KK Co., Ltd.) was applied to one surface of an alumina substrate having a thickness of 0.3 mm in a predetermined pattern, and gold paste was applied to one side of the alumina substrate to facilitate the attachment of electrodes and leads and dried. To obtain a substrate on which a heating element pattern was formed.

The multi-layered solid electrolyte having the reference electrode forming paste layer was attached to the substrate such that the gold paste coated layer of the substrate and the reference electrode forming paste layer were in contact with each other. At this time, the gold lead wire is attached together to the gold paste coated layer of the substrate, the gold lead wire is also attached to the heating element pattern and the gold paste layer applied to the multi-layer solid electrolyte, and then the whole is heat-treated at 1000 ° C. for 1 hour. The primary structure was obtained.

In the primary structure, a sensing electrode forming paste in which sodium carbonate and a gold paste is mixed is applied to a surface to which a gold lead wire of the multilayer structure is attached, and heat treated at 750 ° C. for 30 minutes to provide a gas sensor having a multilayer solid electrolyte. The device was obtained.

Comparative example

A gas sensor device having a solid electrolyte was obtained in the same manner as in Example, except that a barrier layer was not formed on the solid electrolyte.

Experimental Example

Two sensors prepared according to Examples and Comparative Examples were placed in the same experimental chamber, and the behavior of each sensor was measured at 500 ° C. while maintaining a constant carbon dioxide concentration of 100 ppm. The results are shown in FIG. 3.

In FIG. 3, the rapid decrease in electromotive force initially occurs because the operating temperature of the finished device is different from the heat treatment process in the device manufacturing process, and is a process in which the equilibrium is performed at the operating temperature of the device. can do.

As shown in FIG. 3, the sensor of the embodiment maintains a constant electromotive force for 200 hours or more, while the sensor of the comparative example shows that the electromotive force decreases continuously. The magnitude of the reduced electromotive force during the measurement is about 10 mV, which translates into a concentration change of about 50% in terms of carbon dioxide concentration. That is, although the concentration of carbon dioxide to be measured by the sensor is kept constant, in the comparative example, the electromotive force of the sensor is changed, and as a result, an error in gas concentration measurement is generated up to 50%.

Therefore, it can be seen that the sensor of the embodiment using the solid electrolyte having the barrier layer effectively suppresses the movement and rearrangement of the material, thereby preventing the degradation of the performance of the sensor.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.

1 is a schematic cross-sectional view of a multilayer structure solid electrolyte according to an embodiment of the present invention.

2 is a schematic cross-sectional view of a gas sensor device according to an embodiment of the present invention.

3 is a graph illustrating a performance measurement result of a sensor according to time of a gas sensor device using a multilayered solid electrolyte and a gas sensor device manufactured according to a comparative example according to an embodiment of the present invention.

Claims (17)

In the solid electrolyte for a gas sensor interposed between the sensing electrode and the reference electrode, The solid electrolyte, A first layer formed of an ion conductive solid electrolyte; A barrier layer formed of a metal thin film; And Second layer formed of ion conductive solid electrolyte Multi-layered solid electrolyte for a gas sensor, characterized in that it comprises a multi-layered structure formed by sequentially stacking. The method of claim 1, The ion conductive solid electrolyte is a multi-layered solid electrolyte for a gas sensor, characterized in that nacicon, sodium beta alumina or lithium lanthanum titanate. The method of claim 1, The first layer and the second layer formed of the ion conductive solid electrolyte is a multi-layered solid electrolyte for a gas sensor, characterized in that the thickness of each 200 ~ 1000 ㎛. The method of claim 1, The barrier layer is a multilayer structure solid electrolyte for a gas sensor, characterized in that it comprises any one or a mixture of two or more selected from the group consisting of gold, silver, platinum, copper and aluminum. The method of claim 1, The thickness of the barrier layer is a multilayer structure solid electrolyte for a gas sensor, characterized in that 1 to 10 ㎛. (S1) preparing an ion conductive solid electrolyte slurry comprising a solid electrolyte powder, a plasticizer, a binder, a dispersant, and an organic solvent; (S2) casting the slurry on a substrate or a base film and drying to obtain an ion conductive solid electrolyte sheet; (S3) sintering the sheet; (S4) forming a barrier layer by applying a metal paste on one surface of the sintered body, and stacking the second sintered body on the barrier layer; And (S5) sintering the resultant Method for producing a multilayer structure solid electrolyte for a gas sensor comprising a. (S1) preparing an ion conductive solid electrolyte slurry comprising a solid electrolyte powder, a plasticizer, a binder, a dispersant, and an organic solvent; (S2) casting the slurry on a substrate or a base film and drying to obtain an ion conductive solid electrolyte sheet; (S3) forming a barrier layer by applying a metal paste on one surface of the sheet, and stacking a second sheet on the barrier layer; And (S4) sintering the resultant Method for producing a multilayer structure solid electrolyte for a gas sensor comprising a. The method according to claim 6 or 7, The solid electrolyte powder is a method of manufacturing a multi-layered solid electrolyte for a gas sensor, characterized in that the powder of nacicon, sodium beta alumina or lithium lanthanum titanate. The method according to claim 6 or 7, The plasticizer is any one or a mixture of two or more selected from the group consisting of polyethylene glycol, polyalkylene glycol, dioctyl phthalate and dibutyl phthalate. The method according to claim 6 or 7, The binder is a polyvinyl butyral, polyvinyl alcohol and polyacrylate ester method for producing a multi-layered solid electrolyte for a gas sensor, characterized in that any one or a mixture of two or more selected from the group consisting of. The method according to claim 6 or 7, The dispersing agent is a method for producing a multilayer structure solid electrolyte for a gas sensor, characterized in that any one or a mixture of two or more selected from the group consisting of glyceryl trioleate, fish oil and phosphate esters. The method according to claim 6 or 7, The organic solvent is any one or a mixture of two or more selected from the group consisting of trichloroethylene, ethyl alcohol, toluene and methyl ethyl ketone. The method according to claim 6 or 7, The barrier layer-forming metal paste includes any one or a mixture of two or more selected from the group consisting of gold, silver, platinum, copper and aluminum. The method of claim 6, The sintering process of the step (S3) is a method of manufacturing a multilayer structure solid electrolyte for a gas sensor, characterized in that carried out at 900 ~ 1300 ℃. The method of claim 6, The sintering process of the step (S5) is a manufacturing method of a multilayer structure solid electrolyte for a gas sensor, characterized in that carried out at 700 ~ 1200 ℃. The method of claim 7, wherein The sintering process of the step (S4) is a method of manufacturing a multilayer structure solid electrolyte for a gas sensor, characterized in that carried out at 900 ~ 1200 ℃. A substrate on which a heating element pattern is printed on one surface, a reference electrode attached to the other surface facing the heating element pattern with respect to the substrate, a solid electrolyte attached to a surface facing the substrate with respect to the reference electrode, and a reference electrode for the solid electrolyte; A gas sensor element having a sensing electrode attached to an opposite surface, The gas sensor element, wherein the solid electrolyte is a multilayer structure solid electrolyte according to any one of claims 1 to 5.

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