Resistance-type oxygen gas sensor and oxygen sensor device

Abstract

To provide a resistance type oxygen gas sensor that can operate at lower temperature than before and has small temperature dependency.SOLUTION: In a resistance type oxygen gas sensor, an oxygen gas detection part which detects an oxygen gas consists principally of a semiconductor material represented by composition formula RE(Ba2-x,REx)Cu3Oy (where Re is a rare earth element, and 0≤x≤1.2 and 6.0≤y≤7.5 hold for x and y).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resistance-type oxygen gas sensor and an oxygen sensor device. [Background technology]

[0002] In the fields of scientific research, medicine, and industry, there are cases where it is necessary to measure the oxygen gas concentration in the environment. Oxygen sensors that detect oxygen gas include solid electrolyte and galvanic cell types. However, these oxygen sensors have a complex structure, making it difficult to miniaturize them.

[0003] In response to this, a resistance-type oxygen gas sensor has been proposed in which a semiconductor material whose resistivity changes when it comes into contact with oxygen gas under the application of a certain voltage is applied to the oxygen gas detection section (see Patent Document 1). It is believed that such a resistance-type oxygen gas sensor can be more easily miniaturized and reduced in cost than oxygen sensors of the solid electrolyte type and galvanic cell type, and efforts are being made to put it to practical use. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3870261 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned resistance-type oxygen gas sensor, the responsiveness (detection sensitivity) is highly dependent on temperature, so there is still room for improvement.

[0006] Therefore, an object of the present invention is to reduce the temperature dependency of response compared to conventional resistance-type oxygen gas sensors. [Means for solving the problem]

[0007] As a result of extensive research into the operating temperature and responsiveness of resistance-type oxygen gas sensors, the inventors focused on a semiconductor material represented by a specific composition formula, and completed the present invention based on this.

[0008] That is, a gas sensor according to one aspect of the present invention is a resistance-type oxygen gas sensor having an oxygen gas detection portion made of ceramic for detecting oxygen gas, a heater electrode for heating the oxygen gas detection unit; The oxygen gas detection unit has a composition formula of RE(Ba 2-x ,RE x )CuO y (wherein RE is a rare earth element and x is 0.4 ≦x≦1.2, and y is 6.0≦y≦7.5). Effect of the Invention

[0009] According to the resistance-type oxygen gas sensor of the present invention, the temperature dependency of the response can be made smaller than that of the conventional resistance-type oxygen gas sensor. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view illustrating a resistance-type oxygen gas sensor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 3 is a plan view illustrating a resistance-type oxygen gas sensor according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is a circuit diagram illustrating a resistance-type oxygen gas sensor according to the second embodiment. [Figure 6] FIG. 6 is a flowchart showing a method for manufacturing a semiconductor material applied to the oxygen gas detector 13 of the first and second embodiments. [Figure 7] FIG. 7 is a configuration diagram for explaining the oxygen sensor device. [Figure 8]FIG. 8 is a graph showing the relationship between temperature change and resistance change of the specimen 1-4. [Figure 9] FIG. 9 is a graph showing the relationship between the temperature change and the resistivity change of the specimen 1-4. [Figure 10] FIG. 10 is a graph showing the temperature dependence of factor m, which represents the oxygen partial pressure dependence. [Figure 11] FIG. 11 is a diagram showing the oxygen gas response of the specimen 1. As shown in FIG. [Figure 12] FIG. 12 is a diagram showing the oxygen gas response of the specimen 3. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The resistance-type oxygen gas sensor according to an embodiment of the present invention is an oxygen sensor capable of measuring oxygen gas in the environment or a specific atmosphere, and uses a semiconductor material as the oxygen gas detection section, the resistivity of which changes when it comes into contact with oxygen gas while a predetermined voltage is applied.

[0012] In this embodiment, the resistive type means that a semiconductor material whose resistivity changes when it comes into contact with oxygen gas is used.

[0013] [First embodiment] <Configuration of Resistance-Type Oxygen Gas Sensor> Fig. 1 is a plan view illustrating a resistance-type oxygen gas sensor 1 according to a first embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1.

[0014] The resistance-type oxygen gas sensor 1 has a substrate 10, a first electrode 11, a second electrode 12, and an oxygen gas detection unit 13, which are formed on the substrate 10 in the form of a flat plate.

[0015] An insulating material or a semi-insulating material can be used as the substrate 10. As the insulating material, structural ceramics such as alumina, silicon dioxide, mullite, magnesium oxide, or forsterite, or glass, sapphire, or the like can be used. Furthermore, as the semi-insulating material, silicon carbide, or the like can be used. In addition, any material that is normally used as a substrate for a gas sensor can be used as the substrate 10.

[0016] When a flat-plate-shaped substrate 10 is used, the thickness of the substrate 10 may be 0.05 mm or more and 1.0 mm or less. From the viewpoint of the strength of the substrate 10, the thickness of the substrate 10 is preferably 0.09 mm or more. Moreover, from the viewpoint of heat transfer, the thickness of the substrate 10 is preferably 1.0 mm or less.

[0017] The first electrode 11 and the second electrode 12 can be made of the same material as that usually used for electrodes or lead wires. As the conductive material, copper (Cu), aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), chromium (Cr), tin (Sn), etc. can be suitably used. In addition, a resin electrode made of a conductive resin can also be used.

[0018] The first electrode 11 and the second electrode 12 can be formed on the surface of the substrate 10 by pattern deposition using a sputtering method, an ion plating method, a vacuum deposition method, or a laser ablation method depending on the type of metal used. The first electrode 11 and the second electrode 12 can also be formed on the surface of the substrate 10 by printing an electrode material. Other bonding methods such as wire bonding can also be used.

[0019] 1, the thickness of the first electrode 11 and the second electrode 12 can be set to 0.02 μm or more and 20 μm or less. From the viewpoint of detection performance for oxygen gas to be detected, it is preferable that the thickness is 0.1 μm or more, and from the viewpoint of cost, it is 10 μm or less.

[0020] Although not shown in FIG. 1, the first electrode 11 and the second electrode 12 are structured so as to be electrically connectable to a power supply voltage for applying a voltage to the oxygen gas detection unit 13.

[0021] The oxygen gas detection unit 13 is formed on the substrate 10 so as to be electrically connected by the first electrode 11 and the second electrode 12 .

[0022] In this embodiment, the oxygen gas detection unit 13 has a composition formula of RE(Ba 2-x ,RE x )CuO y (where RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5), i.e., the main component is a semiconductor material represented by the formula (1), i.e., a semiconductor oxide. The semiconductor material constituting the oxygen gas detection unit 13 will be described in detail later.

[0023] In addition, the oxygen gas detection unit 13 has a porous structure and is formed as a film having a predetermined thickness. Since the oxygen gas detection unit 13 has a porous structure, oxygen ions (O 2- ) into the crystal structure, the time required for diffusion is shortened, thereby improving the responsiveness (sensitivity) of the oxygen gas detection unit 13 to oxygen gas.

[0024] 1, the oxygen gas detection unit 13 may be applied to a predetermined region between the first electrode 11 and the second electrode 12, or may be formed so as to connect a part of the first electrode 11 and the second electrode 12. Although not shown in FIG 1, an insulating layer may be formed on the surface of the base material 10, and the first electrode 11 and the second electrode 12 may be disposed on the surface of the insulating layer.

[0025] The resistivity of the oxygen gas detector 13 is preferably 0.035 Ωcm or more, and more preferably 0.21 Ωcm or less.

[0026] If the resistivity is too low, noise components such as contact resistance will become large in the resistance value output from the oxygen gas detection unit 13. On the other hand, if the resistivity is high, the current value applied to the oxygen gas detection unit 13 will be too small, making it difficult to measure the resistance value output from the oxygen gas detection unit 13. From the above perspective, when the resistivity of the oxygen gas detection unit 13 is the above value, the overall size of the resistance-type oxygen gas sensor 1 can be kept within a predetermined size while maintaining oxygen gas detection ability.

[0027] <Semiconductor materials> Next, the oxygen gas detector 13 will be described in detail. The oxygen gas detector 13 is a gas having a composition formula of RE(Ba 2-x ,RE x )CuO y In the above composition formula, x is in the range of 0≦x≦1.2, and y is in the range of 6.0≦y≦7.5.

[0028] In the above composition formula, RE is at least one element selected from rare earth elements (Sc (scandium), Y (yttrium), La (lanthanum), Nd (neodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), Lu (lutetium)).

[0029] The rare earth element RE may be any one of the above elements, or may be a mixture of two or more of them. It is preferable to use the same element for the two REs in the composition formula, since this makes it easier to control the composition of the semiconductor material and to manage it during production.

[0030] In this embodiment, the composition formula: RE(Ba 2-x ,RE x )CuO y A portion of the above is substituted with an element from Group 2 of the periodic table and a rare earth element.

[0031] Here, the Group 2 element of the periodic table is any one element selected from beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

[0032] In addition, the lanthanide element is any one element selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0033] Under the same temperature conditions, as the value of x approaches 0, the resistivity of the semiconductor material constituting the oxygen gas detection unit 13 decreases and the difference in resistivity of the semiconductor material depending on temperature tends to increase.

[0034] In general, the electrical conductivity σ [S / m] of a resistive oxygen gas sensor at a given temperature is expressed as the oxygen partial pressure P O2 It is known that the dependence on [air pressure] can be expressed as follows using the factor m:

[0035]

number

[0036] In formula (1), the value of factor m varies depending on the type of defect in the semiconductor oxide (semiconductor material), the impurity concentration, the measurement temperature, etc. According to formula (1), at a given temperature, the smaller the absolute value of factor m (>0) is, the better the responsiveness (sensitivity) of the oxygen gas sensor is.

[0037] Therefore, if the absolute value of factor m changes little when the temperature of the measurement environment changes, it can be said that the temperature dependency is small. Therefore, the smaller the absolute value of factor m in formula (1) is, and the smaller the change in the value of factor m due to temperature change, the more sensitive and stable the resistance-type oxygen gas sensor is.

[0038] The factor m can be calculated as follows using the oxygen partial pressure P1 in the atmospheric gas surrounding the semiconductor material, the resistance value R1 of the semiconductor material at the oxygen partial pressure P1, the oxygen partial pressure P2, and the resistance value R2 of the semiconductor material at the oxygen partial pressure P2.

[0039]

number

[0040] As described above, in view of the relationship between the value of x in the composition formula and the value of the factor m, it is preferable that the value of x satisfies 0.4≦x≦0.8.

[0041] If the value of x in the composition formula is less than 0.4, the temperature range in which the change in the value of factor m can be kept small shifts to the higher temperature side, while if the value of x in the composition formula is more than 0.8, the temperature range in which the change in the value of factor m can be kept small narrows.

[0042] From the viewpoint of not shifting the temperature region in which the amount of change in the value of the factor m can be kept small to the high temperature side and not narrowing the temperature region in which the amount of change in the value of the factor m can be kept small, a more preferable range of the value of x in the composition formula is 0.4≦x≦0.6.

[0043] From the above viewpoint, it is preferable that the value of x in the composition formula satisfies 0.4≦x≦0.8, and the value of the factor m calculated by formula (2) satisfies 3.8≦m≦6.0.

[0044] According to equations (1) and (2), at a given temperature, the smaller the absolute value of factor m (>0), the better the responsiveness (sensitivity) of the oxygen gas sensor. However, if the value of factor m is less than 3.8, the temperature range in which the oxygen gas sensor effectively functions appears on the high temperature side beyond the practical range, reducing its practicality.

[0045] Furthermore, when the value of the factor m exceeds 6.0, the temperature dependency becomes significant, narrowing the temperature range in which the sensor can be effectively used as an oxygen gas sensor, thereby reducing its practical applicability.

[0046] The temperature region in which the change in the value of factor m becomes small varies depending on the value of x, and therefore the preferred value of factor m is determined according to the value of x.

[0047] The above formula is RE(Ba 2-x ,RE x )CuO y In the semiconductor material represented by the formula, it is preferable to use La, Nd, or Sm, which has a large solid solubility limit of x, as the rare earth element RE, from the viewpoint of easily adjusting the value of x to the above range. A combination of a plurality of rare earth elements may also be used. A semiconductor material obtained by adding RE2BaCuO5 to Nd123 may also be used.

[0048] <Effects of the First Embodiment> The resistance-type oxygen gas sensor 1 according to the first embodiment has a composition formula of RE(Ba 2-x ,RE x )CuO y The oxygen gas detector 13 is mainly made of a semiconductor material represented by the formula (wherein RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5).

[0049] In the above semiconductor material, by appropriately selecting the rare earth element RE and the values ​​of x and y from the above ranges, it is possible to prepare a semiconductor material in which the change in resistivity due to temperature change is small in a specific temperature range.

[0050] Therefore, the resistance-type oxygen gas sensor 1 having the oxygen gas detection section 13 mainly made of the above semiconductor material can reduce the temperature dependency of the response compared to conventional resistance-type oxygen gas sensors.

[0051] Furthermore, according to the resistance-type oxygen gas sensor 1, the temperature range in which the change in resistivity of the semiconductor material becomes small can be set to a lower temperature range than that of conventional resistance-type oxygen gas sensors by appropriately selecting the rare earth element RE and the value of x in the semiconductor material forming the oxygen gas detection part 13. Therefore, it is possible to provide a resistance-type oxygen gas sensor 1 that can exhibit good responsiveness as an oxygen gas sensor in a temperature range lower than that of conventional resistance-type oxygen gas sensors.

[0052] Furthermore, in the above composition formula, by making the value of x satisfy 0.4≦x≦0.8, the temperature range in which the amount of change in resistivity due to temperature change is small can be set to between 450°C and 800°C, and a resistance-type oxygen gas sensor 1 is obtained that can exhibit oxygen gas detection ability in a lower temperature range than conventional resistance-type oxygen gas sensors.

[0053] In particular, when the value of x is in the vicinity of x=0.6, it is possible to reduce the temperature dependence of the resistance value in the vicinity of 700° C. to 800° C. This also makes it possible to reduce the temperature dependence of the resistivity in the vicinity of 700° C. to 800° C.

[0054] In addition, since the resistivity of the oxygen gas detection section 13 is 0.035 Ωcm or more and 0.21 Ωcm or less, the overall size of the resistance-type oxygen gas sensor 1 can be kept within a specified size while maintaining oxygen gas detection ability, so the resistance-type oxygen gas sensor 1 can be made smaller.

[0055] In addition, the resistance-type oxygen gas sensor 1 has an electric conductivity σ [S / m] of the oxygen gas detection section 13 that is greater than the oxygen partial pressure P O2 The relation σ∝P, which is proportional to the 1 / m power of [atmospheric pressure] O2 1 / mWhen the value of m satisfies 3.8≦m≦6.0, the temperature range in which the oxygen gas sensor exhibits effective function can be set within a practical range.

[0056] [Second embodiment] <Configuration of Resistance-Type Oxygen Gas Sensor> Fig. 3 is a plan view illustrating a resistance-type oxygen gas sensor 2 according to a second embodiment of the present invention. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. The same components as those in the resistance-type oxygen gas sensor 1 are designated by the same reference numerals and detailed description thereof will be omitted.

[0057] Similar to the resistance-type oxygen gas sensor 1 of the first embodiment, the resistance-type oxygen gas sensor 2 has a substrate 10, a first electrode 11, a second electrode 12, and an oxygen gas detection unit 13, and further has a heater electrode 14.

[0058] The heater electrode 14 is for heating the oxygen gas detection unit 13. In this embodiment, the heater electrode 14 is formed in a rectangular loop shape on the surface of the substrate 10, and the oxygen gas detection unit 13 is laminated after the heater electrode 14 is formed.

[0059] A resistance heating type heat generating element that utilizes resistance loss can be used as the heater electrode 14. When a voltage is applied to both ends of the heater electrode 14, a current flows and the heater electrode 14 generates heat.

[0060] This enables the heater electrode 14 to quickly heat the oxygen gas detection unit 13 to a temperature range where the semiconductor material exhibits good oxygen gas responsiveness, and also enables the oxygen gas detection unit 13 to be maintained at a temperature where it exhibits good oxygen gas responsiveness.

[0061] The resistance-type oxygen gas sensor 2 also includes a temperature compensating section 23. The temperature compensating section 23 compensates for temperature changes in the oxygen gas detecting section 13. It is preferable that the material forming the temperature compensating section 23 has a temperature dependency close to that of the oxygen gas detecting section 13.

[0062] Furthermore, the temperature compensation section 23 may be made of a material having a resistivity close to that of the oxygen gas detection section 13, and may be made of a conductive material or a semiconductor material. Furthermore, it is preferable that the temperature compensation section 23 be made of a conductive material whose resistivity changes in response to temperature changes, similar to that of the oxygen gas detection section 13.

[0063] In this embodiment, the temperature compensation section 23 is made of a semiconductor material that is the main component of the oxygen gas detection section 13, that is, a semiconductor material having a composition formula of RE(Ba 2-x ,RE x )CuO y (wherein RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5).

[0064] Furthermore, the resistance-type oxygen gas sensor 2 has a heater electrode 24 between the temperature compensation section 23 and the substrate 10 for heating the temperature compensation section 23 so that the temperature of the temperature compensation section 23 becomes equal to the temperature of the oxygen gas detection section 13 .

[0065] The heater electrode 24 is formed from the same material as the heater electrode 14, and in this embodiment, the heater electrode 24, like the heater electrode 14, is formed in a rectangular loop shape on the surface of the substrate 10, and a temperature compensation section 23 is formed thereon.

[0066] Moreover, in this embodiment, the resistance-type oxygen gas sensor 2 has a shielding layer 25, which is impermeable to oxygen gas, on the surface of the temperature compensation section 23. The temperature compensation section 23 is covered with the shielding layer 25 so as not to come into contact with oxygen gas.

[0067] 5 is a circuit diagram illustrating a resistance-type oxygen gas sensor according to the second embodiment. A resistance-type oxygen gas sensor 2 equipped with a temperature compensation section 23 has a circuit configuration as shown in FIG.

[0068] The resistor Rs shown in FIG. 5 corresponds to the oxygen gas detection unit 13. The reference resistor R0 corresponds to the temperature compensation unit 23. DCis the applied voltage to the resistive oxygen gas sensor 2, and V out is the voltage applied to the reference resistor R0. In this circuit configuration, the resistance R of the oxygen gas detection unit 13 is calculated by the following equation (3): S can be sought.

[0069]

number

[0070] In equation (3), the resistance R s Considering the temperature dependence of resistance R s If the rate of change is n, equation (3) can be expressed as equation (4) below.

[0071]

number

[0072] In particular, when the oxygen gas detection unit 13 and the temperature compensation unit 23 are made of the same material and the temperature compensation unit 23 is shielded from oxygen gas by providing a shielding layer 25 as in this embodiment, n in formula (4) is cancelled out. Therefore, the above circuit configuration can reduce the fluctuation in resistivity of the oxygen gas detection unit 13 due to temperature changes.

[0073] <Effects of the second embodiment> According to the resistance-type oxygen gas sensor 2 of the second embodiment, by providing a temperature compensation section 23 that compensates for temperature changes in the oxygen gas detection section 13, the effect of reducing the temperature dependence of the responsiveness to oxygen gas can be further enhanced compared to conventional resistance-type oxygen gas sensors.

[0074] In the resistance-type oxygen gas sensor 2, a material having a resistivity close to that of the oxygen gas detection section 13 is used, which is a semiconductor material that is a main component of the oxygen gas detection section 13, that is, a material having a composition formula of RE(Ba 2-x ,RE x )CuO y(wherein RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5), and a shielding layer 25 that does not allow oxygen gas to pass through is formed on the surface of the temperature compensation section 23, so that oxygen gas is not adsorbed to the temperature compensation section 23.

[0075] Therefore, particularly when the temperature compensating section 23 is made of the same semiconductor material as the oxygen gas detecting section 13, only the change in resistivity due to the temperature change can be offset.

[0076] This makes it possible to eliminate noise caused by temperature changes in the resistance-type oxygen gas sensor 2, thereby improving the accuracy of oxygen gas detection.

[0077] [Manufacturing method of resistive oxygen gas sensor] Next, a description will be given of a method for manufacturing the resistance-type oxygen gas sensor 1. Fig. 6 is a flow chart showing a method for manufacturing the oxygen gas detection unit 13 of the first and second embodiments.

[0078] In step S1 of FIG. 6, oxides of metal elements constituting the composition of the semiconductor material are mixed to form a compound having a composition formula of RE(Ba 2-x ,RE x )CuO y The ingredients are weighed out so as to obtain the desired amount, and then mixed together.

[0079] If the rare earth element RE is yttrium, Y2O3 is used, and if it is lanthanum, La2O3 is used. To introduce barium into the composition formula, BaCO3 is used, and to introduce copper, CuO is used. Furthermore, when any element in the composition formula is to be replaced by calcium as a group 2 element, CaCO3 is introduced. RE2BaCuO5 may be further added to the mixture thus obtained.

[0080] In step S2, the raw materials mixed in step S1 are pulverized. The pulverization method may be a method using a ball mill, a solid phase method such as a bead mill using beads as the pulverization medium, or a liquid phase method. In this embodiment, a ball mill mixing and pulverization method using zirconia as the pulverization medium and water as the solvent can be suitably used.

[0081] In step S3, the mixture of powders of the raw materials obtained by mixing and pulverizing in step S2 is calcined. As an example of the calcination conditions, the mixture is heated in air at a temperature of 880° C. to 970° C. for a predetermined time.

[0082] In this embodiment, from the viewpoint of adjusting the reactivity and grain size of the semiconductor material, the heating temperature is preferably 900° C. to 935° C., and it is more preferable to perform heat treatment in the atmosphere at 900° C. for 5 hours.

[0083] Next, in step S4, a pasting process is performed. In the pasting process, a vehicle made of a binder resin and a solvent is prepared, and the mixture calcined in step S3 is added to this vehicle to prepare a paste.

[0084] In the pasting, for example, a binder resin such as methyl cellulose, ethyl cellulose, polyvinyl alcohol (PVA), and a solvent that dissolves these binder resins can be used. In this embodiment, ethyl cellulose can be used as the binder resin, and terpineol can be used as the solvent.

[0085] In step S5, the paste is molded into a predetermined shape. In this embodiment, the paste obtained by pasting is printed on the surface of the base material 10 shown in FIG. 1 by screen printing or thin film printing to form a rectangular pattern (oxygen gas detection unit 13 shown in FIG. 1) having a predetermined size.

[0086] Subsequently, in step S6, the molded body of the oxygen gas detection unit 13 formed in step S5 is sintered. The sintering temperature can be set to 900° C. to 1000° C. The optimum value of this sintering temperature can be appropriately selected depending on the composition formula of the semiconductor material.

[0087] As an example, firing is performed in air for one hour at 950° C. After the firing process, an annealing process may be further performed.

[0088] Next, in step S7, rectangular electrode patterns (first electrode 11 and second electrode 12) are formed on both ends of the oxygen gas detection unit 13 using an electrode material by a film deposition method such as screen printing or sputtering.

[0089] Next, in step S8, the first electrode 11 and the second electrode formed in step S7 are heated and baked. The baking conditions can be appropriately selected depending on the electrode material and thickness to be used, but it is preferable that the baking temperature is 1000° C. or less in order to suppress the progress of a reaction due to excessive sintering or overheating of the oxygen gas detection unit 13. In the present embodiment, as an example, the baking process is performed in air at 700° C. for 20 minutes.

[0090] According to the above steps, the resistance-type oxygen gas sensor 1 shown in FIGS. 1 and 2 can be manufactured.

[0091] 3 and 4, heater electrodes 14 and 24 are formed at predetermined positions on the substrate 10 prior to forming the electrode pattern in step S7, and then the oxygen gas detection unit 13 is disposed on the substrate 10 in step S5. In the same step, the temperature compensation unit 23 can be formed at a position adjacent to the oxygen gas detection unit 13 using a semiconductor material fabricated in the same steps as steps S1 to S4. Thereafter, the first electrode 21 and the second electrode 22 are formed so as to cover the electrode connection portions. Then, after baking in step S8, a shielding layer 25 can be disposed so as to cover the temperature compensation unit 23.

[0092] [Oxygen sensor device] The resistance-type oxygen gas sensors 1 and 2 described using Figures 1-4 can be applied to oxygen sensor devices such as a monitoring device that monitors the oxygen concentration in a specific environment, or a management device that monitors the oxygen concentration in a specific environment and adjusts the oxygen concentration.

[0093] 7 is a configuration diagram for explaining the oxygen sensor device 30. The oxygen sensor device 30 includes an oxygen gas sensor 31 located in the measurement environment 100, a heater control unit 32, an oxygen concentration adjustment unit 34, and a processing unit 35, and is a device that can measure the oxygen concentration in a specific environment (measurement environment 100) and adjust the oxygen concentration.

[0094] In this embodiment, the oxygen gas sensor 31 corresponds to the resistance-type oxygen gas sensor 2 described with reference to FIGS.

[0095] The heater control unit 32 controls the heater electrodes 14, 24 provided in the oxygen gas sensor 31 to provide a predetermined amount of heat so that the oxygen gas sensor 31 (resistance-type oxygen gas sensor 2) reaches an appropriate operating temperature.

[0096] The oxygen concentration adjustment unit 34 is connected to an oxygen gas generation source (not shown), and is configured to be able to introduce oxygen gas from the oxygen gas generation source into the measurement environment 100 so that the oxygen concentration in the measurement environment 100 becomes a predetermined concentration.

[0097] The processing unit 35 converts the sensor output value from the oxygen gas sensor 31 into an oxygen concentration, and, if necessary, sends a control signal to the oxygen concentration adjusting unit 34 to adjust the oxygen concentration in the measurement environment 100 .

[0098] This allows the oxygen sensor device 30 to detect the oxygen concentration in the measurement environment 100 and adjust the oxygen concentration in the measurement environment 100.

[0099] The oxygen sensor device 30 may be provided with a display unit such as a liquid crystal panel that displays the oxygen concentration and other information for operation. It may also be provided with an operation unit having various operation switches for inputting information required for setting measurement conditions and managing the oxygen concentration. Note that a touch panel provided on the display unit may be used instead of mechanically configured operation switches.

[0100] In this embodiment, the configuration of the oxygen sensor device is not limited to this. Also, the oxygen sensor device 30 may be a computer, and the processing unit 35 may be configured by the CPU of the computer. Also, the processing unit 35 may be configured by multiple microcomputers.

[0101] [Other embodiments] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above-mentioned embodiments.

[0102] The first electrode 11 and the second electrode 12 can be formed on the substrate 10 by a thick film method, a thin film method, or a coating device equipped with a dispenser. The shapes of the first electrode 11 and the second electrode 12 are not limited to rectangular. They may be so-called comb-shaped electrodes. In order to increase the resistance value, the first electrode 11 and the second electrode 12 are preferably rectangular.

[0103] In this embodiment, the oxygen gas detection unit 13 may have a rectangular shape, or may have a so-called meandering shape, serpentine shape, etc. From the viewpoint of achieving both miniaturization and high resistance of the resistance-type oxygen gas sensors 1 and 2, the meandering shape is more preferable.

[0104] In this embodiment, the heater electrodes 14, 24 can be formed on the substrate 10 in the same manner as the first electrode 11 and the second electrode 12. The shapes of the heater electrodes 14, 24 are not limited to those shown in Figures 3 and 4. They can be appropriately set to a so-called comb shape, meandering shape, serpentine shape, or the like.

[0105] The heater electrode 14 may be formed on the surface of the substrate 10 opposite to the surface on which the oxygen gas detection unit 13 is formed, as long as it can heat and maintain the temperature of the oxygen gas detection unit 13 at a predetermined temperature.

[0106] Instead of using the heater electrode 24, the heater electrode 14 may be wired on the substrate 10 so that the oxygen gas detection unit 13 and the temperature compensation unit 23 can be heated by a single heater electrode 14.

[0107] The resistance-type oxygen gas sensor 2 in Figures 3 and 4 does not need to be provided with the heater electrodes 14 and 24 if the oxygen gas detection unit 13 and the temperature compensation unit 23 can be kept at approximately the same temperature by the heat transfer of the substrate 10.

[0108] In this embodiment, instead of using the temperature compensation unit 23, data for compensating for the change in resistivity of the oxygen gas detection unit 13 with respect to temperature may be input from outside the resistance-type oxygen gas sensor 2. For example, a profile of the change in resistivity of the oxygen gas detection unit 13 with respect to temperature is prepared in a memory or the like, and the resistivity corresponding to the temperature applied to the oxygen gas detection unit 13 is selected and offset by calculation. This makes it possible to eliminate noise due to temperature changes.

[0109] In the manufacturing method of the resistance-type oxygen gas sensor according to this embodiment, in addition to the above-mentioned printing method, a press pressure may be applied to the granulated powder to produce a press-molded body by a hydrostatic press method, a hot press method, a doctor blade method, a uniaxial press method, etc. In this case, in the manufacturing process, the press-molded body is diced and cut and processed into a predetermined shape and size. EXAMPLES

[0110] A specimen based on the resistance-type oxygen gas sensor 1 according to the embodiment of the present invention was prepared, and the obtained specimen was subjected to various measurements and evaluated as an oxygen gas sensor. A method for preparing the specimen and its evaluation will be described below.

[0111] [Preparation of specimen] <Resistance-type oxygen gas sensor> The composition formula is RE(Ba 2-x ,RE x )CuO y (where RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5), neodymium (Nd) was used as the rare earth element. Semiconductor materials A, B, C, and D were prepared by changing the values ​​of the substitution amounts x and y. Furthermore, resistive oxygen gas sensor specimens 1-4 were fabricated using each semiconductor material by the method shown in FIG. 6.

[0112] In the following, in the above composition formula, the material prepared so that x = 0 is referred to as semiconductor material A, the material prepared so that x = 0.4 is referred to as semiconductor material B, the material prepared so that x = 0.6 is referred to as semiconductor material C, and the material prepared so that x = 0.8 is referred to as semiconductor material D.

[0113] According to the manufacturing method of FIG. 6, oxides of neodymium (Nd), barium (Ba), and copper (Cu) constituting the semiconductor material AD, i.e., Nd2O3, BaCO3, and CuO, are 2-x ,Nd x )CuO y The components were weighed and mixed so as to obtain the desired x and y values ​​for the test specimen. The y value varies in the range of y=6 to 7.5 depending on the oxide added to adjust the x value.

[0114] The mixing and grinding method was a ball mill method using zirconia as a grinding medium and water as a solvent.

[0115] The resulting mixture of raw material powders was then calcined in air at 900° C. for 5 hours, thereby obtaining a semiconductor material AD.

[0116] Next, a vehicle was prepared using ethyl cellulose as a binder resin and terpineol as a solvent. The mixture (semiconductor material AD) after the calcination treatment was added to the vehicle and kneaded.

[0117] Next, the vehicle containing the mixture was printed by screen printing onto an alumina substrate as the base material 10 to form the rectangular pattern of the oxygen gas detection unit 13 shown in Fig. 1. The sizes of the alumina substrate and the oxygen gas detection unit 13 are as follows:

[0118] Size of the base material 10: length 6.3 mm x width 3.1 mm x thickness 0.5 mm Size of the oxygen gas detector 13: length 5.8 mm x width 0.25 mm x thickness 0.02 mm (however, this is the size after printing and drying)

[0119] Next, the alumina substrate and the molded body of the oxygen gas detection part 13 formed on the alumina substrate by printing were heated in the atmosphere at 950° C. for 1 hour to carry out a binder removal process.

[0120] Next, using silver (Ag) paste as the electrode material for the first electrode 11 and the second electrode 12, rectangular electrode patterns were formed by a printing method on both ends of the oxygen gas detection unit 13 formed by printing on the alumina substrate.

[0121] Next, after the electrode pattern was formed, a baking treatment was carried out in the atmosphere at 700° C. for 20 minutes.

[0122] Through the above steps, a resistive oxygen gas sensor specimen 1-4 was obtained.

[0123] <Hot spot type oxygen gas sensor> Among the above-mentioned semiconductor materials AD, the semiconductor materials A (x=0) and C (x=0.6) were used to fabricate hot spot type oxygen gas sensor specimens 5 and 6.

[0124] A hot spot oxygen gas sensor is a sensor that utilizes the fact that the semiconductor material used as the gas detection section of the oxygen gas sensor develops a heat generating region called a hot spot when a voltage is applied. Since the current is constant at the hot spot regardless of the applied voltage, the adsorption of oxygen gas to the hot spot can be detected as a change in the current value.

[0125] In this embodiment, in the dicing in step S6 shown in FIG. 6, a linear body having a square cross section of 0.3 mm×0.3 mm×7 mm was formed.

[0126] Next, the linear bodies of semiconductor materials A and C obtained by dicing were heated in air at 950° C. for 1 hour to remove the binder.

[0127] Subsequently, the ends of the linear body after the binder removal treatment were dip-coated with silver (Ag) and dried at 150° C. for 10 minutes to form electrode connectors at both ends of the linear body.

[0128] Subsequently, a silver (Ag) wire having a diameter of 0.1 mm was attached to the connection portion by wire bonding, and the connection portion was dried at 150° C. for 10 minutes.

[0129] Next, the linear semiconductor material having the electrodes attached by wire bonding as described above was subjected to a baking treatment in air at 670°C for 20 minutes to obtain hot spot type oxygen gas sensor specimens 5 and 6.

[0130] [Evaluation method] <Measurement of resistance and resistivity of semiconductor materials> Each of the above test pieces 1 to 4 connected to a multimeter was placed in a chamber capable of changing the temperature, and the resistance value (Ω) detected in each test piece was measured while changing the temperature in the chamber.

[0131] In addition, the resistivity (Ωcm) was calculated based on the shape of the semiconductor material used in each specimen. The measurement results of the resistance value are shown in Figure 8, and the results of the resistivity are shown in Figure 9.

[0132] <Calculation of temperature dependence of oxygen gas responsiveness> For the specimens 1-4, the factor m, which represents the dependency on the oxygen partial pressure in the atmospheric gas, was calculated based on the above-mentioned formula (2).

[0133] In this example, the atmospheric temperature surrounding the specimens 1-4 was changed, and the factor m was calculated for each predetermined temperature using the resistance value R1 (Ω) when the oxygen partial pressure P1 was 0.21 (atmosphere) and the resistance value R2 (Ω) when the oxygen partial pressure P2 was 0.01 (atmosphere), and the change in factor m due to temperature change was plotted. The result of the temperature dependency of factor m is shown in FIG. 10.

[0134] <Oxygen gas response measurement> The oxygen gas responsiveness was measured using specimens 1 and 3, which were selected based on the calculation results of the temperature dependence of the oxygen gas responsiveness. In this measurement, first, the atmospheric gas was changed to air (P O2 = 0.21 atm) and after 6 minutes, oxygen gas (P O2 =0.01 atm) and then after 6 minutes, air (P O2 = 0.21 atm) was fed into the specimens, and the change in resistance during this time was measured. The results of oxygen gas response are shown in Figures 11 and 12.

[0135] <Comparison between resistive oxygen gas sensor and hot spot oxygen gas sensor> The sensor sensitivity was compared between specimen 1, a resistive oxygen gas sensor using semiconductor material A (x=0), and specimen 5, a hot spot type oxygen gas sensor using semiconductor material A (x=0).The sensor sensitivity was also compared between specimen 3, a resistive oxygen gas sensor using semiconductor material C (x=0.6), and specimen 6, a hot spot type oxygen gas sensor using semiconductor material C (x=0.6).

[0136] For resistive oxygen gas sensor specimens 1 and 3, the sensor sensitivity was measured when the sensor was held at 500° C. The results are shown in Table 2.

[0137] [Evaluation Results] <Resistance and resistivity results for semiconductor materials> Fig. 8 is a diagram showing the relationship between the temperature change and the resistance change of the specimen 1-4, and Fig. 9 is a diagram showing the relationship between the temperature change and the resistivity change of the specimen 1-4.

[0138] 8 and 9, the measurement results of specimen 1 using semiconductor material A (x=0) are shown by a dashed line, the measurement results of specimen 2 using semiconductor material B (x=0.4) are shown by a dotted line, the measurement results of specimen 3 using semiconductor material C (x=0.6) are shown by a solid line, and the measurement results of specimen 4 using semiconductor material A (x=0.8) are shown by a dashed double-dashed line.

[0139] FIG. 8 shows that the temperature dependence of the resistance value in the specimen 1 using the semiconductor material A (x=0) can be reduced as the x value increases.

[0140] This is Nd(Ba 2-x ,Nd x )CuO y (where 0≦x≦0.8, y is 6.0≦y≦7.5), the divalent barium (Ba) site is replaced with trivalent neodymium (Nd), reducing the hole carriers and causing the semiconductor properties to offset the original metallic properties.

[0141] In particular, in the case of specimen 3 using the semiconductor material C (x=0.6), the temperature dependence of the resistance value in the vicinity of 700° C. to 800° C. is small, and accordingly, the temperature dependence of the resistivity is also small.

[0142] From this, Nd(Ba 2-x ,Nd x )CuO y In this case, it is expected that a semiconductor material with x in the vicinity of 0.6 can be suitably used as an oxygen gas sensor that is less affected by temperature.

[0143] In general, NdBa2Cu3O y has a low resistivity, and when a film-like oxygen gas sensor element such as the oxygen gas detection unit 13 shown in Fig. 1 is formed, the resistance value is several tens of Ω. Furthermore, if the resistance value is 100 Ω or less, it is easily affected by the wiring resistance, which makes it difficult to accurately measure the resistance value of the oxygen gas sensor element itself.

[0144] In response to this, for example, by forming the oxygen gas sensor element in a meandering pattern, the resistance value of the oxygen gas sensor element can be increased to a certain extent, making it easier to detect the resistance value of the oxygen gas sensor element itself.

[0145] However, due to technical limitations in the printing accuracy of the printing method used to form the oxygen gas sensor element in film form, it was difficult to form the oxygen gas sensor element in a film thickness that would increase the resistance value of the oxygen gas sensor element by 10 times or more.

[0146] In contrast, as shown in FIG. 8, when semiconductor materials B, C, and D are used, that is, Nd(Ba 2-x ,Nd x )CuO y It was found that when x is in the range of 0.4 to 0.8, the resistance value can be adjusted in a high range of about 100 Ω to 400 Ω.

[0147] This is Nd(Ba 2-x ,Nd x )CuO yIn this case, a semiconductor material satisfying 0.4≦x≦0.8 and 6.0≦y≦7.5 is shown to be a semiconductor material that can be suitably used for an oxygen gas sensor.

[0148] <Results of temperature dependence of oxygen gas response> FIG. 10 is a graph showing the temperature dependence of factor m, which represents the oxygen partial pressure dependence.

[0149] In Figure 10, the measurement results of specimen 1 using semiconductor material A (x = 0) are shown by a dashed line, the measurement results of specimen 2 using semiconductor material B (x = 0.4) are shown by a dotted line, the measurement results of specimen 3 using semiconductor material C (x = 0.6) are shown by a solid line, and the measurement results of specimen 4 using semiconductor material A (x = 0.8) are shown by a dashed line.

[0150] As shown in FIG. 10, in the case of the specimen 1 to which the semiconductor material A (x=0) was applied, the factor m became small in the vicinity of 600° C. to 800° C., and it was found that good oxygen gas responsiveness was exhibited in this temperature range.

[0151] It was found that as x increases, the value of factor m tends to increase in the low temperature range (near 400°C) and in the high temperature range (above 800°C).

[0152] This is Nd(Ba 2-x ,Nd x )CuO y (where x=0.6, y is 6.0≦y≦7.5), the amount of hole carriers increases or decreases as the amount of trivalent neodymium (Nd) substituted with divalent barium (Ba) changes, and the amount of hole carriers increases or decreases accordingly. 2- This is thought to be due to changes in the absorption and release properties of the material.

[0153] The temperature range in which the change in factor m in FIG. 10 is within 0.1 is shown in Table 1 below.

[0154] [Table 1]

[0155] According to FIG. 10 and Table 1, it was found that specimen 3, which uses semiconductor material C (x=0.6), exhibits oxygen gas responsiveness as an oxygen gas sensor from a low temperature range of about 450°C, and that a wide temperature range can be selected in which the amount of change in the value of factor m can be kept small.

[0156] Therefore, Nd(Ba 2-x ,Nd x )CuO y It was found that a semiconductor material with x in the vicinity of 0.6 has oxygen gas responsiveness that is less susceptible to temperature fluctuations, making it possible to realize a highly accurate and stable oxygen gas sensor.

[0157] <Oxygen gas response results> Fig. 11 is a diagram showing the oxygen gas responsiveness of specimen 1. Fig. 12 is a diagram showing the oxygen gas responsiveness of specimen 3. In Fig. 11, the results of the responsiveness test performed with the ambient temperature of specimen 1 set to 600°C are shown by a dotted line, and the results of the responsiveness test performed with the ambient temperature set to 500°C are shown by a solid line. In Fig. 12, the results of the responsiveness test performed with the ambient temperature of specimen 3 set to 600°C are shown by a dotted line, and the results of the responsiveness test performed with the ambient temperature set to 500°C are shown by a solid line.

[0158] In both Figures 11 and 12, the resistance values ​​of specimens 1 and 3 when the atmospheric gas was air were R air The resistance value of specimens 1 and 3 when the atmospheric gas was oxygen gas was R gas In addition, R gas / R air was used as an index of oxygen gas responsiveness (hereinafter referred to as sensor sensitivity).

[0159] As shown in Figs. 11 and 12, in the test piece 1 to which the semiconductor material A (x = 0) with a large temperature dependency of the factor m was applied, the sensor sensitivity (R gas / R air ) will be improved.

[0160] On the other hand, in the case of specimen 3, which uses semiconductor material C (x = 0.6) with a small temperature dependency of factor m, the sensor sensitivity (R gas / R air ) is only slightly improved, but the sensor sensitivity due to the difference in ambient temperature (R gas / R air ) was small, and it was found that it is possible to realize an oxygen gas sensor element with small temperature dependence.

[0161] <Comparison of resistance-type oxygen gas sensor and hot spot-type oxygen gas sensor> The sensor sensitivity was measured using the resistance-type oxygen gas sensor, as explained in the above section "Results of oxygen gas responsiveness" (R gas / R air ) was used.

[0162] In the hot spot oxygen gas sensor, the sensor sensitivity is calculated from the change in the current I. Therefore, unlike the resistance type oxygen gas sensor, the hot spot oxygen gas sensor has a small resistance value when oxygen gas is introduced into the atmosphere (air). Therefore, for ease of comparison, the I air / I gas He expressed it as follows.

[0163] The sensor sensitivity results for specimens 1, 3, 5, and 6 are shown in Table 2.

[0164] [Table 2]

[0165] In a current detection type sensor, as the value of x in the above composition formula of the semiconductor material approaches 0, the sensitivity to oxygen gas increases, but the temperature dependency of the semiconductor material tends to become greater.

[0166] From Table 2, it was found that the resistance-type oxygen gas sensor (specimens 1 and 3) is capable of adjusting the semiconductor material to obtain stable high sensitivity in the low temperature range around 500°C compared to the hot spot-type oxygen gas sensor (specimens 5 and 6).

[0167] Furthermore, from Table 2, it was found that the resistance-type oxygen gas sensor (specimens 1 and 3) could improve the sensor sensitivity compared to the hot spot-type oxygen gas sensor (specimens 5 and 6). [Explanation of symbols]

[0168] 1,2 Resistive oxygen gas sensor 10 Base material 11,21 First electrode 12,22 Second electrode 13 Gas detection unit 14,24 Heater electrode 25 Shielding layer 30 Oxygen sensor device 31 Oxygen gas sensor 32 Heater control section 34 Oxygen concentration adjustment unit 35 Processing section 100 Measured environment

Claims

1. A resistance-type oxygen gas sensor having an oxygen gas detection portion made of ceramic for detecting oxygen gas, a heater electrode for heating the oxygen gas detection unit; The oxygen gas detection unit is The composition formula is RE(Ba ２－ｘ , R.E. ｘ ) Cu ３ O ｙ (wherein RE is a rare earth element, x is 0.4≦x≦1.2, and y is 6.0≦y≦7.5). The semiconductor material represented by the formula Resistive type oxygen gas sensor.

2. 2. The resistance-type oxygen gas sensor according to claim 1, In the composition formula, x satisfies 0.4≦x≦0.8, Resistive type oxygen gas sensor.

3. 3. The resistance-type oxygen gas sensor according to claim 1, The resistivity of the oxygen gas detection portion is 0.035 Ω cm or more. Resistive type oxygen gas sensor.

4. 4. The resistance-type oxygen gas sensor according to claim 1, The electrical conductivity σ [S / m] of the oxygen gas detection section is Ｏ２ The relation σ∝ that is proportional to the 1 / m power of [atmospheric pressure] １／ｍ In the above, the value of m satisfies 3.8≦m≦6.

0. Resistive type oxygen gas sensor.

5. 5. The resistance-type oxygen gas sensor according to claim 1, The oxygen gas detection unit has a porous structure and is formed as a film having a predetermined thickness. Resistive type oxygen gas sensor.

6. 6. The resistance-type oxygen gas sensor according to claim 1, Further comprising a temperature compensation unit that compensates for a temperature change of the oxygen gas detection unit. Resistive type oxygen gas sensor.

7. 7. The resistance-type oxygen gas sensor according to claim 6, The temperature compensation unit is a main component of the oxygen gas detection unit. The composition formula is RE(Ba ２－ｘ , R.E. ｘ ) Cu ３ O ｙ (wherein RE is a rare earth element, x is 0≦x≦1.2, and y is 6.0≦y≦7.5). A semiconductor material represented by Resistive type oxygen gas sensor.

8. 8. The resistance-type oxygen gas sensor according to claim 6, The temperature compensation unit is shielded from the oxygen gas. Resistive type oxygen gas sensor.

9. 9. A resistance-type oxygen gas sensor according to claim 1, The rare earth element is at least one element selected from lanthanum (La), neodymium (Nd), and samarium (Sm); Resistive type oxygen gas sensor.

10. A resistive oxygen gas sensor comprising the resistive oxygen gas sensor according to any one of claims 1 to 9. Oxygen sensor device.

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