Patent Application
20250087391
The present invention relates to a temperature sensor element that includes a heat sensitive body such as a thermistor, in which electrical characteristics change in response to a temperature change.
A temperature sensor element includes: for example, a thermistor that is formed of an electroconductive oxide sintered body; a coating layer that coats a periphery of the thermistor; and a pair of lead-out wires that are connected to the thermistor and are led out in penetration through the coating layer.
When the temperature sensor element is used in a reducing gas atmosphere, the reducing gas intrudes into the thermistor through an interface between the coating layer and the lead-out wire. The thermistor is an oxide, and is accordingly reduced by a reducing gas that has intruded thereinto, which may decrease the temperature detection accuracy of the temperature sensor element.
In order to solve the above problem, in Patent Literature 1, a second coating layer is provided in addition to a first coating layer that coats the periphery of the thermistor, the second coating layer surrounding an extending portion of the lead-out wire on the outer surface of the first coating layer and being formed mainly containing an oxygen-supplying oxide. The oxygen-supplying oxide in Patent Literature 1 contains at least one oxide of Cr, Mn, Fe, Co, Ni, Ce and Pr. In Patent Literature 1, the second coating layer containing an oxygen-supplying oxide can suppress a reduction reaction under exposure of the thermistor to a strong reducing atmosphere even when a gap exists at an interface between the lead-out wire and the first coating layer.
However, in Patent Literature 1, there is a concern that an oxygen-supplying oxide may be depleted when the temperature sensor element is continuously used in a strong reducing atmosphere for a long time.
For this reason, an object of the present invention is to provide a temperature sensor element that has an enhanced wettability of an interface between a lead-out wire and a first coating layer, and thereby can suppress a reduction reaction of a heat sensitive body, even after a long time usage in a strong reducing atmosphere.
A temperature sensor element according to the present invention includes: a heat sensitive body of which the electric resistance changes according to a temperature; a first coating layer that covers a periphery of the heat sensitive body; a pair of lead-out wires that are connected to the heat sensitive body and also are led out in penetration through the first coating layer, toward a rear end side; a second coating layer that covers a periphery of the pair of lead-out wires which are led out in penetration through the first coating layer; and a third coating layer that covers peripheries of the first coating layer and the second coating layer.
The second coating layer in the present invention includes a mixture of glass and at least one of chromium oxide, manganese oxide, ruthenium oxide powder, iridium oxide powder and platinum oxide.
In the present invention, it is preferable that the lead-out wire includes: a core wire that is formed from platinum; and a plated coating layer that is formed from one or both of titanium oxide and ruthenium oxide, and covers a periphery of the core wire.
In the present invention, it is preferable that the core wire is formed from a platinum alloy containing iridium.
In addition, in the present invention, it is preferable that the first coating layer includes a first oxide powder or a mixture of a first oxide powder and glass; and the third coating layer includes a mixture of a third oxide powder and glass.
In the present invention, it is preferable that the first oxide powder is formed of a powder of a thermistor constituting the heat sensitive body.
In addition, in the present invention, the second coating layer can be configured to cover the periphery of the pair of lead-out wires which are led out in penetration through the first coating layer, and also to cover the first coating layer in between the first coating layer and the third coating layer.
Furthermore, in the present invention, the second coating layer can be configured to limitedly cover the periphery of the pair of lead-out wires which are led out in penetration through the first coating layer so that the first coating layer and the third coating layer are in direct contact with each other.
Furthermore, the present invention provides a temperature sensor equipped with the temperature sensor element described above.
According to the present invention, a temperature sensor element is provided that has an enhanced wettability between a lead-out wire and a second coating layer provided on a periphery of the lead-out wire, and thereby can suppress a reduction reaction of a heat sensitive body, even after a long time usage in a strong reducing atmosphere.
Embodiments of the present invention will be described below with reference to the accompanying drawings.
A temperature sensor element 1 according to one embodiment of the present invention will be described with reference to the drawings.
As shown in
The temperature sensor element 1 is provided with the second coating layer 25 between the first coating layer 20 and the third coating layer 30, and the second coating layer 25 is made to have a wettability enhancement effect which will be described in detail later. The temperature sensor element 1 can reduce a rate of change in the electric resistance value of the heat sensitive body 11 to a small value, in a reducing atmosphere, for example, an atmosphere containing hydrogen.
Note that, in some cases, the temperature sensor element 1 is used in a state of being accommodated in a protective pipe made from a metal excellent in heat resistance and oxidation resistance, such as stainless steel or Ni superalloy, though the specific description is omitted here.
Hereinafter, each element of the temperature sensor element 1 will be described, and then an operation and effects of the temperature sensor element 1 will be described.
A thermistor sintered body is used for the heat sensitive body 11. A thermistor is an abbreviation of a thermally sensitive resistor, and is a metal oxide that measures a temperature by utilizing its property that an electric resistance value changes according to a temperature.
The thermistor is classified into a negative temperature coefficient (NTC) thermistor and a positive temperature coefficient (PTC) thermistor, and any of the thermistors can be used in the present invention.
The oxide sintered body can be used for the heat sensitive body 11, which includes manganese oxide (Mn3O4) that has a spinel structure which is typical for an NTC thermistor, as a basic composition. The oxide sintered body can be used for the heat sensitive body 11, which has a composition of MxMn3-xO4 that is obtained by addition of an M element (one or more of Ni, Co, Fe, Cu, Al and Cr) to the basic composition. Furthermore, one or more of V, B, Ba, Bi, Ca, La, Sb, Sr, Ti and Zr can be added.
In addition, the oxide sintered body can be used for the heat sensitive body 11, which includes a composite oxide having a perovskite structure that is typical for an NTC thermistor, for example, YCrO3, as a basic composition. The sintered body most typical as the NTC thermistor has a Y2O3 phase and at least one of a Y(Cr, Mn)O3 phase, a YCrO3 phase and a YMnO3 phase.
The heat sensitive body 11 formed of the thermistor sintered body is manufactured through the steps of: weighing raw material powders; mixing the raw material powders; drying the raw material powders; calcining the raw material powders; mixing and pulverizing the calcined raw material powders; drying and granulating the calcined raw material powders; and compacting and sintering the resultant. Each process will be described below while using a thermistor sintered body having the Y2O3 phase and the Y(Cr, Mn)O3 phase, as an example.
Raw material powders containing yttrium oxide (Y2O3) powder, chromium oxide (Cr2O3) powder, manganese oxide (MnO, Mn2O3, Mn3O4 or the like) powder and calcium carbonate (CaCO3) powder are weighed so as to form the above-described chemical composition.
Note that, in the present embodiment, the powder is composed of a plurality of particles.
The Y2O3 powder contributes to the formation of the Y2O3 phase; and the Y2O3 powder, the Cr2O3 powder and the manganese oxide powder (Mn3O4 powder) contribute to the formation of the Y(Cr, Mn)O3 phase. The CaCO3 powder functions as a sintering aid, and in addition, dissolves in the Y(Cr, Mn)O3 phase in a form of Ca, and contributes to lowering of the B constant.
The raw material powder to be used has a purity of 98% or higher, preferably 99% or higher, and more preferably 99.9% or higher, in order that a thermistor sintered body having high characteristics is obtained.
In addition, the particle size of the raw material powder is not limited as long as calcination proceeds, but can be selected from a range of 0.1 to 6.0 μm in terms of particle size (d50).
The Y2O3 powder, the Cr2O3 powder, the Mn3O4 powder and the CaCO3 powder are each weighed by a predetermined amount, and are mixed. The mixing can be performed, for example, by a procedure of converting the mixed powder into a slurry state by addition of water, and mixing the slurry by a ball mill. For the mixing, a mixer other than a ball mill can also be used.
It is preferable to dry and granulate the slurry after the mixture, with a spray dryer or other equipment, and to form a mixed powder for calcination.
The mixed powder for calcination after drying is calcined. By the calcination, a calcined body having a composite structure of the Y2O3 phase and the Y(Cr, Mn)O3 phase is obtained from the Y2O3 powder, the Cr2O3 powder, the Mn3O4 powder and the CaCO3 powder.
In calcination, the mixed powder for calcination is charged into, for example, a crucible, and a temperature range of 800 to 1300° C. is maintained in the atmosphere. If the calcination temperature is lower than 800° C., the formation of the composite structure is insufficient, and if the calcination temperature exceeds 1300° C., there is a possibility that the density of the sintered body decreases and the stability of the resistance value decreases. Because of this, the holding temperature of the calcination is set in the range of 800 to 1300° C.
The holding time period in the calcination should be appropriately set according to the holding temperature, and a purpose of the calcination can be achieved by a holding time period of about 0.5 to 100 hours, in the case of the above temperature range.
The powder after the calcination is mixed and pulverized. The mixing and pulverization can be performed by adding water to form a slurry and using a ball mill, as in the case before the calcination.
It is preferable to dry and granulate the powder after the pulverization, by a spray dryer or other equipment.
The granulated powder after the calcination is compacted into a predetermined shape.
For compaction, there can be used a press compaction with the use of a die, and in addition, a cold isostatic press (CIP: Cold Isostatic Press).
The higher the density of the compacted body is, the higher density the sintered body easily obtains; and accordingly, it is desirable to enhance the density of the compacted body as highly as possible. For this purpose, it is preferable to use the CIP which can obtain the high density.
Next, the obtained compacted body is sintered.
Sintering is performed by maintaining a temperature range of 1400 to 1650° C. in the atmosphere. If the sintering temperature is lower than 1400° C., the composite structure is not sufficiently formed, and if the temperature exceeds 1650° C., the sintered body is melted or causes a reaction with a crucible for the sintering or the like. A holding time period in the sintering should be appropriately set according to a holding temperature, and a dense sintered body can be obtained with a holding time period of about 0.5 to 200 hours, in the case of the above temperature range.
It is preferable for the obtained thermistor sintered body to be subjected to annealing so as to stabilize its thermistor characteristics. Annealing is performed by maintaining the temperature at, for example, 1000° C. in the atmosphere.
As shown in
The electrodes 13 and 13 are formed as thick films or thin films. The electrodes 13 and 13 of the thick films are formed in such a manner that a paste that has been produced by mixing of platinum powder and an organic binder is applied onto both front and back surfaces of the thermistor sintered body, the paste is dried, and then the resultant is sintered. In addition, the thin film electrode can be formed by vacuum deposition or sputtering.
The heat sensitive body 11 on which the electrodes 13 and 13 are formed is worked into a predetermined dimension.
The connection electrodes 17 and 17 are composed of metal films which are formed on the surfaces of the electrodes 13 and 13, respectively. The connection electrodes 17 and 17 are also composed of a noble metal, typically platinum (Pt).
As shown in
The lead-out wires 15 and 15 are connected to the electrodes 13 and 13 in the following way.
Paste containing platinum powder which forms connection electrodes 17 and 17 is applied to one end side of each of the lead-out wires 15 and 15, in advance. The platinum paste is dried in a state in which the sides of the lead-out wires 15 and 15 coated with the platinum paste are brought into contact with the electrodes 13 and 13, respectively, and then the platinum powder is sintered.
Next, the first coating layer 20 will be described.
The first coating layer 20 has a function to become a buffer material for alleviating a stress generated by thermal expansion of the third coating layer 30 from being directly applied to the heat sensitive body 11. In other words, the first coating layer 20 receives the thermal stress from the third coating layer 30.
In addition, the first coating layer 20 fixes connection portions between the heat sensitive body 11 and the lead-out wires 15 and 15, and thereby realizes stable electrical and mechanical connections.
The first coating layer 20 according to the present embodiment is formed of a mixture of glass and oxide powder (first oxide powder), in one preferable embodiment.
In the first coating layer 20, the glass functions as a binding agent that binds the oxide powders to each other and allows the first coating layer 20 to maintain its shape.
A ratio of the glass to the oxide powder is not limited as long as the desired coefficient of linear expansion is obtained and the glass functions as the binding agent.
As the glass constituting the first coating layer 20, one or both of crystalline glass and amorphous glass can be used, but it is preferable to use crystalline glass which is stable at high temperature. As the crystalline glass, for example, a composition can be applied which includes 30 to 60 wt % of SiO2, 10 to 30 wt % of CaO, 5 to 25 wt % of MgO, and 0 to 15 wt % of Al2O3.
Examples of the oxide powders constituting the first coating layer 20 include aluminum oxide (Al2O3), magnesium oxide (MgO), calcium oxide (CaO), yttrium oxide (Y2O3), and zirconium oxide (ZrO2). In addition, as this oxide powder, a thermistor powder constituting the heat sensitive body 11 can be used.
As the thermistor powder, a powder can be used which has a composition equivalent to that of the thermistor sintered body constituting the heat sensitive body 11. The equivalent composition means that both of the thermistor powders contained in the heat sensitive body 11 and in the first inner layer form have the above-described chemical composition of Cr, Mn, Ca and Y, excluding oxygen, which is included in a composition range of Cr: 3 to 15 mol %, Mn: 5 to 15 mol %, and Ca: 0.5 to 8 mol %. The case is also included where the thermistor powder and the thermistor sintered body constituting the heat sensitive body 11 have the same composition.
The first coating layer 20 according to the present embodiment is allowed to be formed of only the oxide powder, in another preferable embodiment.
Next, the third coating layer 30 will be described.
It is a main function of the third coating layer 30 to provide airtightness for hermetically sealing of the heat sensitive body 11 from the surrounding atmosphere. The third coating layer 30 imparts a mechanical strength for protecting the heat sensitive body 11 from external force.
The third coating layer 30 can be composed of an oxide powder similar to that of the first coating layer 20. The third coating layer 30 may also be formed of a mixture of the glass similar to that of the first coating layer 20 and an oxide powder (third oxide powder). A usable oxide powder includes one or more of aluminum oxide (Al2O3), magnesium oxide (MgO), yttrium oxide (Y2O3), calcium oxide (CaO), zirconium oxide (ZrO2), strontium oxide (SrO), titanium oxide (TiO) and lanthanum oxide (La2O3).
The third coating layer 30 can obtain a necessary thickness and state by one layer of the third coating layer 30, which is formed by one time of operation, but the third coating layer 30 can also be formed to have a plurality of layers. When the third coating layer 30 is formed of a plurality of layers, each layer may have an equal thickness or an unequal thickness to the others.
Next, the second coating layer 25 will be described.
The second coating layer 25 is provided between the first coating layer 20 and the third coating layer 30, and covers the first coating layer 20 and also covers the outer circumferential surface of the lead-out wire 15 which is led out from the first coating layer 20. The periphery of the second coating layer 25 covering the lead-out wire 15 is covered with the third coating layer 30.
It is understood that the second coating layer 25 has enhanced wettability with the lead-out wire 15, and thereby is brought into close contact with the boundary face with the lead-out wire 15, while the temperature sensor element 1 is used in a high temperature range. Due to the enhancement of the wettability, minute gaps between the lead-out wire 15 and the second coating layer 25 are reduced, and thereby the reduction resistance of the temperature sensor element 1 is enhanced.
The second coating layer 25 is composed from a mixture of glass and at least one of chromium oxide (Cr2O3) powder, manganese oxide (Mn3O4) powder, ruthenium oxide (RuO2) powder, iridium oxide (IrO2) powder, and platinum oxide (PtO2) powder, in order to improve the wettability with the lead-out wire 15, which is understood to be the reason why the second coating layer 25 can improve the wettability of glass with respect to the lead-out wire 15. In the present embodiment, chromium oxide, manganese oxide, ruthenium oxide, iridium oxide and platinum oxide are referred to as wettability improving oxides.
Here, the present inventors have fractured and analyzed a temperature sensor element that includes the lead-out wire 15 formed from platinum and the first coating layer 20 containing the thermistor powder. As a result, the state has been observed in which the thermistor powder strongly adheres to the lead-out wire 15. This is understood to be based on the fact that the wettability of the glass to the lead-out wire 15 has been enhanced by the inclusion of the thermistor powder. As technologies for improving a bonding strength and the wettability between a metal material and an oxide material including glass, there are a mechanical bonding technique for enhancing a mechanical bonding strength and a chemical bonding technique for enhancing a chemical bonding strength. In order to enhance a bonding effect of glass, the surface of the lead-out wire 15 has been subjected to machine work, and an enhancement effect for the reduction resistance has been checked, but a satisfactory result has not been obtained. However, materials which are widely used as chemical bonding materials include transition metal oxides (Mn—O, Cr—O, Fe—O, Ti—O, and the like); and a powder material of the thermistor in the present invention contains yttrium oxide (Y2O3) and Y—Ca—Cr—Mn oxide. For this reason, the present inventors have made the second coating layer 25 contain simple oxides of chromium oxide and manganese oxide, in Example which will be described later, and thereby, have checked the effect on the reduction resistance in a high temperature range. As a result, it has been confirmed that the reduction resistance has been enhanced in any of the oxide powders. The optimum size and amount of the additive particles has been examined by observation of the fractured surface; and the enhancement of the wettability has been exhibited at the time when the glass has been subjected to firing treatment. As a result, not only the glass but also the thermistor powder adheres to the lead-out wire 15, and can suppress the intrusion of a reducing gas, particularly hydrogen, along the lead-out wire 15.
In order to find other oxides besides chromium oxide and manganese oxide, which can achieve the enhancement of the reduction resistance, a search for materials that form a strong bond on the surface of the lead-out wire has been conducted. The reduction resistance has been checked with the use of the following oxides which have higher heat resistance and stronger bonding force with oxygen than chromium oxide and manganese oxide, i.e.: ruthenium oxide which is used for a high temperature metal material as one of chemical bonding materials; in addition, indium oxide or the like, which is used for an on-vehicle spark plug as a material having a high bonding force to oxygen, in other words, having high reduction resistance; platinum oxide or the like, which uses an anchor effect by a mechanical bonding technique. As a result, as will be clear from the Example which will be described later, it has been confirmed that the reduction resistance is improved by a mixture of glass and at least one of ruthenium oxide powder, iridium oxide powder and platinum oxide powder.
As described above, the second coating layer 25 is composed from a mixture of glass and a reduction-resistance improving oxide powder that includes at least one of chromium oxide powder, manganese oxide powder, ruthenium oxide powder, iridium oxide powder, and platinum oxide powder. As the glass in the second coating layer 25, a glass similar to that of the first coating layer 20 can be used.
A content of the oxide powder which improves the reduction resistance by improvement of the wettability in the second coating layer 25 is selected from a range of 0.5 to 30% by mass, and the balance is glass. If the content is less than 0.5% by mass, an effect of the improvement of the reduction resistance is insufficient in some cases; and if the content exceeds 30% by mass, the amount of glass relatively decreases, and the airtightness of the coating itself results in decreasing.
The content of the reduction-resistance improving oxide powder is preferably in a range of 1 to 25% by mass, and the content of the reduction-resistance improving oxide powder is more preferably in a range of 2 to 20% by mass.
Next, a method for manufacturing the temperature sensor element 1 will be described.
As shown in
For the first coating layer 20, a paste is prepared in which, for example, the previously described oxide powder, preferably, the thermistor powder and the crystalline glass powder are mixed with a solvent. After the paste has been formed on the heat sensitive body 11, the paste is dried, then the glass component is subjected to firing treatment at, for example, 1200° C.; and thereby the first coating layer 20 is formed.
For forming the paste on the heat sensitive body 11, a dipping method is suitably applied in which the thermistor element is dipped in the paste from the heat sensitive body 11 side to a predetermined range of the lead-out wire 15, and the resultant is pulled out from the paste. The same applies to the second coating layer 25 and the third coating layer 30.
When the first coating layer 20 is formed of a plurality of layers, dipping is performed a plurality of times; and then the resultant is dried, and is subjected to firing treatment, for example, at 1200° C. In addition, when the first coating layer 20 is formed of a plurality of layers, a boundary between the adjacent coating layers can be visually recognized, and the adjacent coating layers are bonded to each other with a force of a degree that can secure the function of the first coating layer 20. This is also applied to the second coating layer 25 and the third coating layer 30 in the same manner.
For the second coating layer 25, a paste is prepared in which a powder of a reduction-resistance improving oxide and a crystalline glass powder are mixed with a solvent. After the paste has been formed on the first coating layer 20, the paste is dried, then the glass component is subjected to firing treatment, for example, at 1200° C., and the second coating layer 25 is formed.
Furthermore, as for the third coating layer as well, the third coating layer 30 is formed on the second coating layer 25 with the use of the glass paste for the outer layer, which has been prepared by mixing of the oxide powder, the glass powder and the solvent in the same way as in the above description.
Next, a temperature sensor element 2 according to a second embodiment will be described with reference to
The temperature sensor element 2 will be described below in comparison with the temperature sensor element 1. As shown in
In other words, in the temperature sensor element 2, the first coating layer 20 and the third coating layer 30 are in direct contact with each other, and the second coating layer 27 is provided only on the outer peripheries of the lead-out wires 15 and 15. Accordingly, the cross section of a portion at which the second coating layer 27 is provided has a structure in which the lead-out wire 15, the second coating layer 27, and the third coating layer 30 are arranged in this order from the inside or the center, similarly to that of the first embodiment. Except for this point, as shown in
The temperature sensor element 2 having the above cross-sectional structure around the lead-out wire 15 can enhance the reduction resistance, similarly to that of the temperature sensor element 1 of the first embodiment.
It is difficult to form the second coating layer 27 by dipping. For example, the second coating layer 27 is formed in such a manner that a paste is applied to the region by a liquid quantitative discharge device which is referred to as a dispenser, and the paste is then dried and fired.
Next, one example of the present invention will be described on the basis of specific Example.
The temperature sensor element 1 was manufactured that included the first coating layer 20, the second coating layer 25 and the third coating layer 30, which would be described below, and a rate of change in a resistance value was measured.
Raw material powders having the following particle sizes (d50) were prepared of which the mixing ratios were shown in the following, and a heat sensitive body 11 was manufactured according to the above-described steps. The calcination was performed under conditions of 1300° C. for 24 hours, and the sintering was performed under conditions of 1500° C. for 24 hours, both in the atmosphere.
The electrode 13, the lead-out wire 15 and the connection electrode 17 were all formed from platinum (pt), and the thermistor element 3 was produced by the procedure described in the embodiment.
On the thermistor element 3 described above, the first coating layer 20, the second coating layer 25 and the third coating layer 30 were formed.
For the first coating layer 20, crystalline glass was used as glass, and a thermistor powder which had the same composition as that of the heat sensitive body 11 was used. A mass ratio of the crystalline glass to the thermistor powder was controlled to 20:80. In addition, for a paste for the first coating layer 20, an organic binder was used as a binder, and a single precursor layer was formed by dipping. After that, the precursor layer was dried and subjected to heat treatment for firing, and the first coating layer 20 according to the Example was formed.
For the second coating layer 25, crystalline glass, yttrium oxide (Y2O3) powder, chromium oxide (Cr2O3) powder and manganese oxide (Mn3O4) powder were used. The particle size is the same as that used in the production of the heat sensitive body 11. A mass ratio of the crystalline glass to the reduction-resistance improving oxide powder was as shown in Table 1. Yttrium oxide (Y2O3) powder is an oxide powder which is conventionally used in a portion corresponding to the second coating layer 25. Note that as shown in
For the third coating layer 30, crystalline glass and Y2O3 of the third oxide powder were used. A mass ratio of the crystalline glass to the Y2O3 as the third oxide powder is 80:20.
The second coating layer 25 and the third coating layer 30 were formed in the following way. The second coating layer 25 and the third coating layer 30 according to the Example were formed in such a manner that a precursor layer of the second coating layer 25 was formed by dipping a thermistor element 3 in a paste for the second coating layer 25, a precursor layer of the third coating layer 30 was formed by dipping the resultant in a paste for the third coating layer 30, and then, the resultant was dried and subjected to heat treatment for firing.
Rates of changes in electric resistance values were measured under the following conditions, with the use of 4 types of temperature sensor elements (Sample Nos. 1 to 4) shown in Table 1. The measurement results are shown in Table 1.
The rate of change in the electric resistance value was measured under the second measurement conditions which were the same as the first measurement conditions except that the holding temperature was 1050° C.
As shown in Table 1, it is understood that due to the use of chromium oxide or manganese oxide as an oxide powder of the second coating layer 25, the rate of change in the electric resistance value in the high temperature range of 900° C. and 1050° C. can be reduced, and the reduction resistance enhances. In particular, the effect of enhancement of the reduction resistance by chromium oxide is remarkable.
Five types of temperature sensor elements (Sample Nos. 5 to 9) which were produced in the same way as in the first Example, except that the oxide powder in the second coating layer 25 was changed to each of those shown in Table 2, were used for measurement of the rates of changes in the electric resistance values under the first measurement condition and the second measurement condition in the first Example. The results are shown in Table 2.
As shown in Table 2, it is understood that the rate of change in the electric resistance value in a high temperature range can be reduced and the reduction resistance enhances in an oxide (TiO2) of titanium which is a transition metal element similar to Cr and Mn, and an oxide (Al2O3) of aluminum which is a metallic element. However, in the case of surface modification with the use of a transition metal oxide, the effect results in decreasing in a temperature range exceeding 1000° C. Therefore, it is understood that in the oxides (IrO2 and RuO2) of iridium and ruthenium, which are the same noble metal elements as platinum constituting the lead-out wire 15, and further the oxide (PtO2) of platinum, the rate of change in the electric resistance value can be reduced in the high temperature range and the reduction resistance enhances. In particular, the oxide of the noble metal element has a large effect of enhancement of the reduction resistance, as compared with the oxide of a metal element.
Next, with the use of two types of the temperature sensor elements (Sample Nos. 10 and 11) in which the lead-out wires 15 were plated with ruthenium and titanium that were confirmed to have the effect of enhancement of the reduction resistance in the above Examples, respectively, for the purpose of enhancing the wettability of the lead-out wire 15 side with respect to the glass, the rates of changes in the electric resistance values were measured under the first measurement condition and the second measurement condition in the first Example. The measurement results are shown in Table 3. Note that the temperature sensors of Sample Nos. 10 and 11 have the same structure as the temperature sensor of sample No. 1 except that the plating coating is formed.
As shown in Table 3, it is understood that the reduction resistance is enhanced by formation of a layer that is formed from an element which exhibits an effect of improvement of the wettability of the lead-out wire 15 side with respect to the glass.
With the use of a sensor element (sample No. 12) having a lead-out wire 15 that was formed from a platinum alloy containing 20% by mass of iridium which was confirmed to have an effect of enhancement of the reduction resistance in the above Examples, for the purpose of enhancing the wettability of the lead-out wire 15 side, the rates of changes in the electric resistance values were measured under the first measurement condition and the second measurement condition in the first Example. The measurement results are shown in Table 4. Note that the temperature sensor of sample No. 12 has the same structure as the temperature sensor of sample No. 1 except that the lead-out wire 15 is formed from the platinum alloy.
As shown in Table 4, it is understood that the reduction resistance is enhanced by the lead-out wire 15 which contains an element that exhibits an effect of improvement of the wettability.
With the use of a temperature sensor element (sample No. 13) in which the sample No. 7 of the second Example containing iridium oxide powder in the second coating layer 25 was combined with the sample No. 12 of the fourth Example in which the lead-out wire 15 was formed from the platinum alloy containing 20% by mass of iridium, the rates of changes in the electric resistance values were measured under the first measurement condition and the second measurement condition in the first Example. The measurement results are shown in Table 5.
As shown in Table 5, due to both the lead-out wire 15 and the second coating layer 25 which had each the function of improvement of the wettability of the interface, a high enhancement effect of the reduction resistance was obtained.
Next, the first coating layer 20 in contact with the lead-out wire 15 was examined. Specifically, with the use of a temperature sensor element (sample No. 14) having a first coating layer 20 that did not contain the glass but contained 10% by mass of chromium oxide, the rates of changes in the electric resistance values were measured under the first measurement condition and the second measurement condition in the first Example. The measurement results are shown in Table 6. Note that the temperature sensor element of sample No. 14 has the same structure as that of sample No. 1 except for the first coating layer 20.
As shown in Table 6, also when the first coating layer 20 had the function of improvement of the wettability of the interface, a high enhancement effect of the reduction resistance was obtained.
In the above, the preferable embodiments of the present invention have been described, but the configurations described in the above embodiments can be selected or replaced with other configurations, as long as the gist of the invention does not deviate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-102373 | Jun 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/023373 | 6/23/2023 | WO |
