KR101636546B1 - Oxygen Sensor Using Reference Electrode Capable of Fixing Metal Activity and Solid Electrolyte - Google Patents

Abstract

The present invention discloses a solid electrolyte oxygen sensor. The solid electrolyte oxygen sensor includes: a solid electrolyte that functions as a conductor with respect to cations of Na; a sensing electrode and a reference electrode formed on a surface of the solid electrolyte; And a first electrode and a second electrode respectively connected to the sensing electrode and the reference electrode, wherein the sensing electrode is made of a compound whose thermodynamic activity against Na ₂ O is constantly fixed at an isothermal state, And is made of a compound in which the activity of Na is constantly fixed in an isothermal state.
According to the present invention, since the structure for strictly separating the sensing electrode of the oxygen sensor and the reference electrode is not required, the structure of the oxygen sensor is simple and the oxygen sensor using the oxygen ion conductor such as YSZ is used as the solid electrolyte, The driving temperature can be further lowered.

Description

Technical Field [0001] The present invention relates to an oxygen sensor using a reference electrode and a solid electrolyte,

The present invention relates to a gas sensor capable of measuring the concentration of oxygen gas in an electrochemical manner according to the Nernst principle.

Oxygen sensors are used extensively for the purpose of measuring air pollution, improving fuel efficiency and thermal efficiency in combustion devices such as automobiles and boilers, reducing hazardous components in exhaust gases, and controlling the oxygen concentration in production facilities requiring oxygen.

There are various kinds of oxygen sensors, among which oxygen sensors using a solid electrolyte have a simple structure and can be used not only in manufacturing a sensor of a small element type, but also in a mass production, because they are cheap and reproducible and widely used .

As shown in FIG. 1, the solid electrolyte oxygen sensor A has a structure in which the sensing electrode 10, the solid electrolyte 20, and the reference electrode 30 are sequentially stacked.

When the solid electrolyte oxygen sensor A is operated, an electromotive force is induced between the sensing electrode 10 and the reference electrode 30, and the oxygen of the atmosphere in which the reference electrode 30 is exposed by thermodynamic theory The oxygen partial pressure of the atmosphere in which the sensing electrode 10 is exposed can be quantitatively calculated from the concentration and electromotive force measurement results.

The sensing electrode 10 is made of a metal material which is not reactive with the solid electrolyte 20 such as platinum (Pt), silver (Ag), gold (Au) or the like and promotes the reaction between the solid electrolyte 20 and oxygen gas .

The solid electrolyte 20 is made of an oxygen ion conductor such as YSZ (Yttria Stabilized Zirconia). The solid electrolyte 20 functions to generate electromotive force by moving the oxygen ions from the higher part of the oxygen gas to the lower part when the partial pressure difference of the oxygen gas occurs in the upper part and the lower part.

The reference electrode 30 may be made of the same material as the sensing electrode 10 or may be a mixture of metal and metal oxide such as Ni / NiO, Ti / TiO ₂ , Cu / Cu ₂ O, The reference electrode 30 needs to be in contact with a reference gas in which the oxygen concentration is maintained constant by separating the oxygen concentration from the measurement atmosphere to be measured.

During the operation of the solid electrolyte oxygen sensor A, the following half-cell reaction prevails in the sensing electrode 10 and the reference electrode 30.

For reference, oxygen ions generated in the half-cell reaction of the sensing electrode 10 are transported toward the reference electrode 30 through the solid electrolyte 20.

Sensing electrode: 1 / 2O _{2 , sensing} + 2e ^{-1 -} O ^{2 -}

Reference electrode: O ^{2 -} ↔ 1 / 2O _{2 , reference} + 2e ^-

Here, O _{2, reference,} and O _{2, sensing} denote the oxygen gas present in the measurement atmosphere and the reference atmosphere, respectively.

The electromotive force generated between the sensing electrode 10 and the reference electrode 30 can be derived from the thermodynamic theory from the two half-cell reactions and can be expressed by the following equation (1).

≪ Formula 1 >

Electromotive force (V):

In the above equation (1), R is an ideal gas constant and F is a Faraday constant.

)을 알면, 감지 전극(10)이 위치하는 측정 대기의 산소 분압(

)을 쉽게 계산할 수 있다. 하지만 감지 전극(10)과 기준 전극(30)이 각각 측정 대기 및 기준 대기로부터 완벽하게 분리되지 않으면 상기 수식1에 의해 계산되는 산소 분압(

)을 신뢰할 수 없다. 따라서, 기존의 고체 전해질 산소 센서(A)는 구동 메커니즘이 간단하더라도 구조적 형태와 응용 분야에 있어서 많은 제약이 따르는 문제가 있었다.According to Equation 1, the electromotive force V measured through the sensing electrode 10 and the reference electrode 30 and the oxygen partial pressure of the reference atmosphere 30 in which the reference electrode 30 is located

, The oxygen partial pressure of the measurement atmosphere in which the sensing electrode 10 is located

) Can easily be calculated. However, if the sensing electrode 10 and the reference electrode 30 are not completely separated from the measurement atmosphere and the reference atmosphere, respectively, the oxygen partial pressure

) Can not be trusted. Therefore, although the conventional solid electrolyte oxygen sensor (A) has a simple driving mechanism, there is a problem that there are many restrictions in the structural form and application field.

In addition, an oxygen ion conductor such as YSZ can generate an electromotive force of sufficient magnitude that can be measured only at a high temperature state of 700 degrees or more. However, if the operating temperature of the oxygen sensor is too high, the power consumption is increased and the durability of the sensor is lowered. Therefore, there is a limitation in the application field.

The present invention has been made in recognition of the above-described problems of the prior art, and it is an object of the present invention to provide an oxygen sensor that can be driven at a lower temperature than an oxygen sensor using oxygen ion conductors and does not require strict separation of the atmosphere in which the sensing electrode and the reference electrode are exposed. There is a need to provide a solid electrolyte oxygen sensor that does not incur constraints.

According to an aspect of the present invention, there is provided a solid electrolyte oxygen sensor comprising: a solid electrolyte that functions as a conductor against positive ions of a metal; a sensing electrode and a reference electrode formed on a surface of the solid electrolyte; And first and second terminals connected to the sensing electrode and the reference electrode, respectively,

Wherein the sensing electrode is made of a compound in which the thermodynamic activity of Na ₂ O is constantly fixed in an isothermal state and the reference electrode is made of a compound in which the thermodynamic activity of Na is constantly fixed at an isothermal state.

According to an aspect of the present invention, the solid electrolyte is not particularly limited as long as it is a material capable of transporting cations of Na participating in the half cell reaction of the oxygen sensor. Preferably, NASICON (Na _{1 + x} Zr ₂ Si _x P _{3- x} O ₁₂ ), NBA (Na ₂ O · 11Al ₂ O ₃ ), or Na β-alumina (Na ₂ O · χAl ₂ O ₃ ).

According to another aspect, the reference electrode is not particularly limited as long as it is a compound having a number of phases and a number of components that allow the thermodynamic activity of Na to be fixed at an isothermal state, preferably Na Na alloy such as -Si, Na-Mg or Na-Sr, or an Na oxide such as Na _x CoO ₂ .

According to another aspect of the present invention, the sensing electrode is not particularly limited as long as it is a compound having a number of phases and a number of components that allow the thermodynamic activity of Na ₂ O to be constantly maintained in an isothermal state. Advantageously _{Na 2 Ti 3 O 7 -Na 2} Ti 6 O 13, Na 2 Ti 6 O 13 -TiO 2, Na 2 TiO 3 -Na 2 Ti 3 O 7, Na-MO such as NaFeO ₂ -Na ₂ FeO ₂ (M is at least one element selected from transition metals including Ti and Fe).

According to another aspect of the present invention, there is provided a solid electrolyte oxygen sensor comprising: a solid electrolyte made of a compound that functions as a conductor against cations of Na and has a constant thermodynamic activity of Na ₂ O at an isothermal state; As a solid electrolyte oxygen sensor used,
A reference electrode formed on one surface of the solid electrolyte and made of a compound whose thermodynamic activity of Na is constantly fixed in an isothermal state; A first terminal directly connected to a surface of the opposite surface of the solid electrolyte opposite to the surface on which the reference electrode is formed; And a second terminal connected to the reference electrode, wherein a surface portion of the solid electrolyte to which the first terminal is connected functions as a sensing electrode for sensing the oxygen concentration.

delete

In another aspect of the present invention, the solid electrolyte is not particularly limited as long as it is a material capable of transporting cations of Na participating in the half-cell reaction of the oxygen sensor, preferably NASICON (Na _{1 + x} Zr ₂ Si _x P _3-x O ₁₂ ), NBA (Na ₂ O 11Al ₂ O ₃ ), or Na β-alumina (Na ₂ O x Al ₂ O ₃ ).

Preferably, the reference electrode is not particularly limited as long as it is a compound having the number of phases and the number of components that allow the thermodynamic activity of Na to be fixed at an isothermal state. Preferably, the Na Alloy or Na oxide.

According to the present invention, since the structure for strictly separating the sensing electrode of the oxygen sensor and the reference electrode is not required, the structure of the oxygen sensor is simple and the oxygen sensor using the oxygen ion conductor such as YSZ is used as the solid electrolyte, The driving temperature can be lowered. Therefore, the application field of the oxygen sensor is wide and the power consumption can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, And should not be construed as interpretation.
1 is a cross-sectional view illustrating the structure of a solid electrolyte oxygen sensor according to the prior art.
2 is a cross-sectional view illustrating the structure of a solid electrolyte oxygen sensor according to an embodiment of the present invention.
3 is a cross-sectional view showing the structure of a solid electrolyte oxygen sensor according to another embodiment of the present invention.
FIG. 4 is a graph showing a result of measuring electromotive force according to an oxygen partial pressure at an isothermal condition of 600 ° C. using a solid electrolyte oxygen sensor fabricated according to an embodiment of the present invention, and comparing measured electromotive force and theoretical electromotive force.
FIG. 5 is a graph showing the results of measurement of electromotive force according to oxygen partial pressure and comparison of measured electromotive force and theoretical electromotive force at an isothermal condition of 700 ° C. using a solid electrolyte oxygen sensor manufactured according to an embodiment of the present invention.

Hereinafter, a solid electrolyte oxygen sensor according to the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that the idea of the present invention can be sufficiently transmitted. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms. Also, like reference numerals designate like elements throughout the specification.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the following description and the accompanying drawings, descriptions of well-known functions and constructions that may unnecessarily obscure the gist of the present invention will be omitted.

2 is a cross-sectional view illustrating the structure of a solid electrolyte oxygen sensor according to an embodiment of the present invention.

As shown in the figure, a solid electrolyte oxygen sensor (B) according to an example of the present invention includes, as similar to a conventional solid electrolyte oxygen sensor (A), a sensing electrode 40, a solid electrolyte 50 having conductivity with respect to metal cations participating in the half cell reaction, and a reference electrode 60, and the electromotive force V (V) between the sensing electrode 40 and the reference electrode 60 (70) and a second terminal (80) formed on the sensing electrode (40) and the reference electrode (60), respectively.

The solid electrolyte oxygen sensor B is a type of electromotive force gas sensor which includes a sensing electrode 40 and a reference electrode 60 formed on a solid electrolyte 50 and has two electrodes that vary depending on the concentration of a gas to be measured It is a gas sensor based on the so-called Nernst principle that measures the concentration of gas in accordance with the potential difference between solid electrolytes.

In order to smoothly operate the solid electrolyte oxygen sensor B, the ion conductivity of the solid electrolyte 50 with respect to the metal cations must be high and the equilibrium reaction between the oxygen gas and the sensing electrode 40 must be induced and maintained in a short time . Accordingly, the solid electrolyte oxygen sensor B can be mounted and mounted on a heater pad (not shown), which can be heated to a temperature of several hundreds or more.

Preferably, the heater pad has a structure in which a high temperature heating line such as platinum (Pt) or tungsten (W) is formed in a predetermined pattern on the surface of an insulating material such as an alumina pad.

Since the heater pads are widely known in the technical field to which the gas sensor belongs, a detailed description thereof will be omitted, and the presence or absence of the heater pads does not limit the scope of the present invention.

According to one aspect, the solid electrolyte (50) is not particularly limited as long as it is a material capable of transporting positive ions of a metal participating in a half-cell reaction.

Preferably, the metal may be Na and the solid electrolyte 50 may be selected from the group consisting of NASICON (Na _{1 + x} Zr ₂ Si _x P _{3 - x} O ₁₂ ) having good conductivity for Na cation (Na ⁺ ), NBA (Na ₂ O. 11Al ₂ O ₃ ) or Na β-alumina (Na ₂ O χAl ₂ O ₃ ).

The sensing electrode 40 is an electrochemical reactant participating in the half-cell reaction of the oxygen sensor, and includes a metal or an oxide of the metal transported in a cationic state by the solid electrolyte 50, May be composed of a compound having a number of phases and a number of components that allow the thermodynamic activity of the metal or its oxide to be fixed at a constant level.

Preferably, when the solid electrolyte 50 has conductivity with respect to the Na cation (Na ⁺ ), the sensing electrode 40 may be formed of a mixture of Na-MO and more (M is a transition metal group containing Ti and Fe) At least one selected element).

For example, the sensing electrode 40 may be formed of a metal such as Na ₂ Ti ₃ O ₇ -Na ₂ Ti ₆ O ₁₃ , Na ₂ Ti ₆ O ₁₃ -TiO ₂ , Na ₂ TiO ₃ -Na ₂ Ti ₃ O ₇ , -Ti-O biphasic mixture or NaFeO ₂ -Na ₂ FeO can be made of a mixture-over Na FeO _2, and so on.

When the sensing electrode 40 is made of a mixture of Na-MO and more, the thermodynamic activity of the Na ₂ O in the ideal mixture is constantly fixed in the isothermal state because of the Gibbs phase rule This is possible.

Specifically, the Gibbs phase rule for a condensed system, such as a solid matter, can be expressed as: " (2) "

&Quot; (2) "

In the condensation system  Gibbs phase rule: F = C - P + 1

Here, the parameter F represents the degree of freedom of the condensation system as a minimum number of intensive variables that must be fixed to fully describe the condensation system. The parameter C represents the number of components constituting the condensation system in the equilibrium state, the parameter P represents the number of phases constituting the condensation system in the equilibrium state, and the last numeral 1 represents the degree of freedom with respect to the temperature in the condensation system.

In the case of a mixture of Na-Ti-O and more, the parameter C is 2 (two oxides constitute Na ₂ O / TiO ₂ ), the parameter P is also 2 (two phases, for example Na ₂ Ti ₆ O ₁₃ / Na ₂ Ti ₃ O ₇ or Na ₂ Ti ₆ O ₁₃ / TiO ₂ ), the degree of freedom F according to the Gibbs phase rule becomes 1. [

If the temperature is determined, the thermodynamic properties of Na ₂ O, which is one of the constituent components of the ideal mixture, are not related to the other parameters It can be fixed constantly.

The application of the above-mentioned Gibbs phase rule can be similarly applied to a mixture of Na-Fe-O and more.

Separately from the above theoretical verification, the experimental results on the fact that the thermodynamic activity of Na ₂ O in the ideal mixture is constantly fixed in the isothermal state when the sensing electrode 40 is made of a mixture of Na-MO and more The verification result will be described later.

Examples of the material that can be used as the reference electrode 60 include a metal or an oxide thereof transported in a cationic state through the solid electrolyte 50 similarly to the sensing electrode 40, And is not particularly limited as long as it is a compound having the number of the components and the number of the phases such that the thermodynamic activity of the oxide is fixed to a constant value.

Preferably, the reference electrode 60 may be made of Na oxide whose thermodynamic activity of Na is constantly fixed at an isothermal state such as Na _x CO ₂ (x is 0.70 to 0.76).

Here, Na _x CoO ₂ has a crystal structure in which a CoO ₆ octahedral is bonded along an edge, and Na ⁺ ions can be inserted along an interlayer boundary of an (CoO ₂ ) _n- layer structure existing in the crystal structure .

The fact that the Na activity in the Na _x CoO ₂ system is fixed in the isothermal state will be confirmed by the experimental results described later.

Alternatively, the reference electrode 60 may be made of an Na alloy, such as Na-Si, Na-Mg, or Na-Sr such that the thermodynamic activity of Na can be fixed regardless of the atmosphere.

The reference electrode 60 is made of a compound A _x MX _z (A is an element belonging to the same group as Na, M is a transition metal, and X is a group belonging to the same group as oxygen) having the same crystallographic structure as Na _x CoO ₂ Element).

In this case, the solid electrolyte 50 should be selected as a substance capable of citing the cation of the element A, and the sensing electrode 40 should also contain the element A or its oxide as a component showing reactivity with the oxygen gas, And the thermodynamic activity of the element A or its oxide is fixed.

The first terminal 70 and the second terminal 80 are used to measure an electromotive force induced between the sensing electrode 40 and the reference electrode 60.

The material that can constitute the first terminal 70 and the second terminal 80 is not particularly limited as long as it can measure the electromotive force and preferably includes gold (Au), silver (Ag) Platinum (Pt), or the like, or an alloy thereof.

Although the first terminal 70 and the second terminal 80 are illustrated as having a pad shape, they may have a wire shape. Therefore, the scope of the present invention is not limited by the shape of the first terminal 70 and the second terminal 80. [

3 is a cross-sectional view illustrating the structure of a solid electrolyte oxygen sensor (B ') according to another embodiment of the present invention.

The solid electrolyte oxygen sensor B 'shown in FIG. 3 has a structure in which the surface area of the solid electrolyte 50 in which the first terminal 70 is formed does not have a separate sensing electrode and functions as a sensing electrode. .

The reason why the sensing electrode can be omitted is that the solid electrolyte 50 is made of a material such as NASICON (Na _{1 + x} Zr ₂ Si _x P _{3 -x} O ₁₂ ), NBA (Na ₂ O · 11Al ₂ O ₃ ) Na ₂ O · χ Al ₂ O ₃ ), the thermodynamic activity of Na ₂ O, which is one of the components of the solid electrolyte 50, as in the case of the sensing electrode 40 made of Na-MO or more, Because it can be fixed constantly.

For example, when the solid electrolyte 50 is a single phase NASICON, in the Gibbs phase rule, the number of constituent components C is the number of constituent oxides (Na ₂ O, ZrO ₂ , SiO ₂ , P ₂ O ₅ ) The degree of freedom F is 1, since the ratio P is substantially 1 and the parameter P representing the phase is also 1. Therefore, in the case of NASICON, the thermodynamic activity of Na ₂ O can be fixed constantly in the isothermal state as in the case of Na-MO mixture.

<Experimental Example>

Hereinafter, an experimental example according to the present invention will be described. In this experiment, the thermodynamic activity of the electrochemical reactive species participating in the half-cell reaction at the sensing electrode and the reference electrode of the solid electrolyte oxygen sensor is fixed constantly in the isothermal state. Therefore, it is verified that the electro- .

The sensing electrode, the solid electrolyte, and the reference electrode constituting the solid electrolyte oxygen sensor were Na ₂ Ti ₆ O ₁₃ -TiO ₂ mixture, NASICON and Na _x CoO ₂ (x = 0.7-0.76) synthesized by the solid-phase reaction method, Were used.

To fabricate a solid electrolyte oxygen sensor, a NASICON specimen with a cross section of 3 mm × 3 mm and a thickness of 0.2 mm was prepared, and a mixture of Na ₂ Ti ₆ O ₁₃ -TiO ₂ mixture and Na _x CoO ₂ The paste was screen-printed in the form of an electrode, dried and heat-treated to form a sensing electrode and a reference electrode with a thickness of 1 mm or less. Then, a Au paste was screen printed on the sensing electrode and the reference electrode, followed by drying and heat treatment to form a pair of terminals for measurement of electromotive force. Then, the oxygen sensor having a pair of terminals was mounted on a heating pad capable of controlling the temperature. Then, in a state in which an oxygen sensor fabricated in a chamber capable of precisely controlling the oxygen concentration is loaded, a pair of sensing electrodes and a pair of electrodes formed on the reference electrode under two isothermal conditions (600 degrees and 700 degrees) The electromotive force was measured through the terminal of the electrode. At this time, no separate measures were taken to strictly separate the exposed atmosphere from the sensing electrode and the reference electrode.

In the prepared solid electrolyte oxygen sensor, the half-cell reaction predominantly occurring in the sensing electrode and the reference electrode is as follows.

Detection electrode: Na ₂ O ↔ 2Na ⁺ + 2e ^- + 1 / 2O ₂

Reference electrode: Na ⁺ + e ^- ↔ Na

The electromotive force (V) induced by the thermodynamic theory from the two half-cell reactions can be expressed by the following equation (3).

&Quot; (3) &quot;

Electromotive force (V):

는 Na₂O의 포메이션 자유 에너지(formation free energy)로서 온도에 따라 고유하게 결정되는 파라미터이고,

는 감지 전극(40)에서의 Na₂O의 열역학적 활동도를,

는 기준 전극(60)에서의 Na의 활동도를 나타낸다. here,

Is the formation free energy of Na ₂ O and is a parameter that is uniquely determined by temperature,

Shows the thermodynamic activity of Na ₂ O in the sensing electrode 40,

Represents the activity of Na in the reference electrode 60. FIG.

If the activity of Na ₂ O and Na is constantly fixed under isothermal conditions, then the term following the minus sign in equation 3 can be assumed to be a constant that can be determined in advance through experimentation. According to such an assumption, Equation (3) can be expressed as Equation (4).

&Lt; Equation 4 &

4 and 5 are graphs comparing the electromotive force measured through the terminal of the solid electrolyte oxygen sensor with the theoretical electromotive force calculated by the equation 4 according to the oxygen partial pressure contained in the atmosphere in the chamber at 600 ° and 700 °, Graphs showing the results.

In each figure, the symbol &amp; cir &amp; indicates the measured electromotive force, and the solid line indicates the theoretical electromotive force according to the equation (4).

Referring to FIGS. 4 and 5, it can be seen that the measured electromotive force and the theoretical electromotive force are almost the same. That is, the change in the magnitude of the electromotive force due to the partial pressure of oxygen at 600 ° C. and 700 ° C. is almost the same as 2.303 RT / 2F (43 mV / decade at 600 ° C and 48 mV / decade at 700 ° C), which corresponds to the slope of the theoretical EMF . The following facts can be confirmed from these experimental results.

와 기준 전극으로 사용된 Na_xCoO₂에서의 Na에 대한 열역학적 활동도

는 등온 조건에서 일정하다고 볼 수 있다. 이는 깁스의 상 규칙을 이용한 이론적 검증 결과와 일치한다.First, even if the operating temperature of the solid electrolyte oxygen sensor changes by 100 degrees, the measured electromotive force (●) follows the theoretical electromotive force (solid line). Therefore, the parameters included in the equation after the minus sign in Eq. 3, in particular the thermodynamic activity for Na ₂ O in mixtures above the Na-MO used as sensing electrodes

And the thermodynamic activity of Na in Na _x CoO ₂ used as a reference electrode

Can be considered to be constant under isothermal conditions. This is consistent with the theoretical verification results using Gibbs' phase rule.

When the activity of the electrochemical reaction species involved in the half-cell reaction occurring in the sensing electrode and the reference electrode in the process of transporting the cation through the solid electrolyte is fixed at the isothermal condition, the sensing electrode and the reference electrode It can be seen that the oxygen concentration can be accurately measured even if the exposed atmosphere is not strictly separated. If the separation of the atmosphere in which both electrodes are exposed is not required, the structure of the solid electrolyte oxygen sensor can be simplified and there is no restriction in the application field.

In addition, since the measured electromotive force follows the theoretical electromotive force even at 700 degrees as well as at 600 degrees, the driving temperature can be further lowered compared with a solid electrolyte oxygen sensor using a conventional oxygen ion conductor. When the driving temperature of the solid electrolyte oxygen sensor is lowered, not only the power consumption can be lowered but also the life and durability can be improved.

In the present embodiment, the sensing electrode, the solid electrolyte, and the reference electrode constituting the oxygen sensor may have various shapes such as a circle, a rectangle, and an ellipse. Therefore, the present invention is not limited by the shape of the elements constituting the oxygen sensor.

Further, the sensing electrode and the reference electrode may be formed so as to be located on the upper surface or the lower surface, respectively, instead of being formed on the upper surface and the lower surface of the solid electrolyte, respectively. Therefore, the present invention is not limited by the position of the sensing electrode and the reference electrode.

The essential technical idea of the present invention is that a solid electrolyte having conductivity against metal cations at a temperature of 700 ° C or less contains a metal transported in a cationic state by the solid electrolyte on the surface of the solid electrolyte or an oxide of the metal, The thermodynamic activity of a metal or an oxide of the metal can be fixed in an isothermal state to constitute a sensing electrode and a reference electrode.

Therefore, it should be understood that the present invention is not limited by the type of metal transported in a cationic state by the solid electrolyte, or the specific species of the metal or oxide thereof to which the thermodynamic activity is fixed in the sensing electrode and the reference electrode.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Various changes and modifications will be possible.

10, 40: sensing electrode 20, 50: solid electrolyte
30, 60: reference electrode 70, 80: first terminal, second terminal

Claims (11)

A solid electrolyte which functions as a conductor with respect to cations of Na, a sensing electrode and a reference electrode formed on the surface of the solid electrolyte; And a first and a second terminal respectively connected to the sensing electrode and the reference electrode,
Wherein the sensing electrode is made of a compound in which the thermodynamic activity of Na ₂ O is constantly fixed in an isothermal state and the reference electrode is made of a compound in which the thermodynamic activity of Na is fixed at an isothermal state, sensor. The method according to claim 1,
The solid electrolyte may be _one selected from the group consisting of NASICON (Na _{1 + x} Zr ₂ Si _x P _{3 - x} O ₁₂ ), NBA (Na ₂ O 11Al ₂ O ₃ ), or Na β-alumina (Na ₂ O x Al ₂ O ₃ ) Features a solid electrolyte oxygen sensor. The method according to claim 1,
Wherein the reference electrode is an Na alloy in which the activity of Na is fixed in an isothermal state regardless of the atmosphere being exposed. The method of claim 3,
Wherein the Na alloy is Na-Si, Na-Mg, or Na-Sr. The method according to claim 1,
Wherein the reference electrode is an Na oxide whose Na activity is fixed at an isothermal state. 6. The method of claim 5,
Wherein the Na oxide is Na _x CoO ₂ (x = 0.7-0.76). The method according to claim 1,
Wherein the sensing electrode is a mixture of Na-MO _secondary ions whose activity is fixed at an isothermal condition, wherein M is at least one element selected from the group consisting of transition metals including Ti and Fe. sensor. 8. The method of claim 7,
The Na-MO above _{mixture, Na 2 Ti 3 O 7 -Na} 2 Ti 6 O 13, Na 2 Ti 6 O 13 -TiO 2, Na 2 TiO 3 -Na 2 Ti 3 O 7, NaFeO 2 -Na 2 FeO _{2. &} Lt; / RTI &gt; A solid electrolyte oxygen sensor using a solid electrolyte made of a compound which functions as a conductor against cations of Na and whose thermodynamic activity of Na ₂ O is constantly fixed at an isothermal state,
A reference electrode formed on one surface of the solid electrolyte and made of a compound whose thermodynamic activity of Na is constantly fixed in an isothermal state;
A first terminal directly connected to a surface of the opposite surface of the solid electrolyte opposite to the surface on which the reference electrode is formed; And
And a second terminal connected to the reference electrode,
Wherein the surface area of the solid electrolyte to which the first terminal is connected functions as a sensing electrode for sensing oxygen concentration. 10. The method of claim 9,
The solid electrolyte _{is, NASICON (Na 1 + x Zr} 2 Si x P 3 - x O 12), NBA (Na 2 O · 11Al 2 O 3) or β- Na alumina _{(Na 2 O · χAl 2 O} 3) of Wherein the solid electrolyte oxygen sensor is a solid electrolyte. 10. The method of claim 9,
Wherein the reference electrode is a Na alloy or an Na oxide.

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