JP2013199396A - Conductive oxide sintered body, thermistor element, and temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive oxide sintered body having properties such as B constant of 1,000-2,000 K, a thermistor element using the sintered body, and a temperature sensor using the thermistor element.SOLUTION: A conductive oxide sintered body 10 is represented by general formula: M1M2M3AlO, wherein M1 represents at least one of the group 3 elements except La; M2 represents at least one of the group 2 elements; M3 represents at least one of the groups 4, 5, 6, 7 and 8 elements; a is 0.18<a<0.50; and b is 0.05<b<0.40.

Description

  The present invention relates to a conductive oxide sintered body having conductivity and a resistance value that varies with temperature, a thermistor element using the same, and a temperature sensor using the same.

Conventionally, a conductive oxide sintered body that has conductivity and whose resistance value (specific resistance) varies depending on temperature, a thermistor element that performs temperature measurement using the sintered body, and a temperature using this thermistor element Sensors are known. For example, in Patent Document 1, at least one element of Group 3A elements (Group 3 elements) excluding La is M1, and at least one element of Group 2A elements (Group 2 elements) is M2. When at least one of the 4A, 5A, 6A, 7A and 8A group elements (Group 4, 5, 6, 7 and 8 elements) is M3, the general formula is M1 _a M2 _b in _{M3 c Al d Cr e O f} , d satisfies the condition conductive sintered oxide, such as 0.400 ≦ d ≦ 0.800 is disclosed. This conductive oxide sintered body has a temperature gradient constant (B constant) in the temperature range of −40 to 900 ° C. in the range of 2000 to 3000K.

JP 2006-315946 A

  As described above, the conductive oxide sintered body described in Patent Document 1 has a characteristic that the B constant is 2000 to 3000K. For this reason, by connecting a resistance voltage dividing circuit in which a thermistor element using this and a pull-up fixed resistor having an appropriate resistance value are connected in series to a constant voltage (for example, +5 Vdc), for example, a temperature of −40 to 600 ° C. In the entire range, the temperature of the thermistor element can be appropriately measured with high sensitivity.

Here, the case where the above-described resistance voltage dividing circuit is used will be examined in detail.
For example, when the temperature is measured using a thermistor element having a B constant of 2500 K (reference resistance value of 1 kΩ at a reference temperature of 100 ° C.) and a resistance voltage dividing circuit configured with a pull-up fixed resistor (1 kΩ) conforming thereto. The graph of the change of the output voltage in the temperature range of -40-600 degreeC is shown with a broken line in FIG.
Also, a resistance comprising a 1500 K thermistor element (reference resistance value 1 kΩ at a reference temperature of 100 ° C.) and a pull-up fixed resistance (1 kΩ) in which the B constant is in the range of 1000 to 2000 K lower than the range of 2000 to 3000 K. A graph of the change in the output voltage in the temperature range of −40 to 600 ° C. when the temperature is similarly measured using the voltage dividing circuit is shown by a solid line in FIG. 3.
In the graph shown in FIG. 3, the resistance voltage dividing circuit using a thermistor element having a B constant of 2500 K (broken line) shows the slope of the graph in the temperature range of about 20 to 240 ° C. (that is, the voltage per unit temperature change). While the change: V / deg) is large, the slope of the graph in the temperature range of −40 to 20 ° C. and 240 to 600 ° C. is small. Therefore, in a resistance voltage dividing circuit using a thermistor element having a B constant in the range of 2000 to 3000K, good sensitivity (unit temperature change) at any temperature within the temperature range of 640 deg (−40 to 600 ° C.). (Voltage change per unit: V / deg) is not always obtained. That is, it can be seen that the sensitivity (slope of the above-described graph) decreases near the lower limit (around −40 ° C.) and the upper limit (around 600 ° C.) of the temperature range.

  On the other hand, in the solid line graph, the inclination of the graph in the temperature range of −40 to 20 ° C. and 240 to 600 ° C. is larger than the inclination of the broken line graph in the temperature range. For this reason, if a thermistor element having a characteristic of 1000 to 2000 K lower than the range of 2000 to 3000 K is used as the B constant, the average sensitivity in the entire temperature range of −40 to 600 ° C. is lowered, but near the lower limit of the temperature range. Sensitivity can be relatively increased even near (−40 ° C.) and near the upper limit (around 600 ° C.). That is, it can be seen that it may be preferable to use a thermistor element having a characteristic of B constant of 1000 to 2000K.

  The present invention has been made in view of such problems, and is a conductive oxide sintered body having a B constant of 1000 to 2000K, a thermistor element using the same, and a temperature sensor using the same. Is to provide.

In one embodiment of the present invention, at least one element of Group 3 elements excluding La is M1, and at least one element of Group 2 elements is M2, and Group 4, Group 5, When at least one element selected from the group, group 7 and group 8 is M3, it is represented by the general formula M1 _1-a M2 _a M3 _1-b Al _b O ₃ , and a is 0.18 <a It is a conductive oxide sintered body where <0.50 and b is 0.05 <b <0.40.

  The conductive oxide sintered body described above has a characteristic that the B constant in the temperature range of −40 to 600 ° C. is 1000 to 2000K.

  Furthermore, in the conductive oxide sintered body described above, the element M3 may be a conductive oxide sintered body containing at least Mn among Mn, Fe, and Cr.

  In the conductive oxide sintered body described above, since the element M3 contains at least Mn among Mn, Fe, and Cr, the B constant in the above range can be easily obtained stably, and the heat resistance of the conductive oxide sintered body can be obtained. Therefore, it is possible to obtain a conductive oxide sintered body that ensures the property and hardly changes even when exposed to a high temperature environment for a long time.

  Furthermore, in any one of the conductive oxide sintered bodies described above, the element M1 may be a conductive oxide sintered body containing at least one of Y, Yb, and Nd.

  In the conductive oxide sintered body described above, since the element M1 contains at least one of Y, Yb, and Nd, the conductive oxidation having the characteristic that the B constant in the temperature range of −40 to 600 ° C. is 1000 to 2000K. A sintered product can be obtained stably.

  Furthermore, in any one of the conductive oxide sintered bodies described above, the element M2 may be a conductive oxide sintered body containing at least one of Sr, Ca, and Mg.

  In the conductive oxide sintered body described above, since the element M2 contains at least one of Sr, Ca, and Mg, the conductive oxidation having the characteristic that the B constant in the temperature range of −40 to 600 ° C. is 1000 to 2000K. A sintered product can be obtained stably.

  Furthermore, another aspect of the present invention is a thermistor element using any one of the above-described conductive oxide sintered bodies.

  In the thermistor element described above, any one of the conductive oxide sintered bodies described above is used. For this reason, it can be set as the thermistor element whose B constant in the temperature range of -40-600 degreeC is 1000-2000K, and the sensitivity in the lower limit (-40 degreeC) vicinity and upper limit (600 degreeC) vicinity of the above-mentioned temperature range is obtained. An improved thermistor element can be obtained.

  Furthermore, another embodiment of the present invention is a temperature sensor using the thermistor element described above.

  Since the above-described temperature sensor uses the above-described thermistor element, the B constant in the temperature range of −40 to 600 ° C. can be a temperature sensor of 1000 to 2000 K, and the lower limit (−40 ° C. ) And a temperature sensor with improved sensitivity near the upper limit (600 ° C.).

It is explanatory drawing explaining the thermistor element (electroconductive oxide sintered compact) concerning embodiment. It is explanatory drawing explaining the temperature sensor concerning embodiment. It is a graph which shows the change of the output voltage in the temperature range of -40-600 degreeC when measuring temperature using the resistance voltage dividing circuit containing a thermistor element.

Example 1
Next, Example 1 of the embodiment of the present invention will be described.
First, the production of the conductive oxide sintered body 10 according to Example 1 will be described. As raw material _{powders, Y 2 O 3, SrCO 3} , MnO 2, Al 2 O 3, Cr 2 O 3 ( both having a purity of 99% or more commercially available) using a composition formula _{Y 1-a Sr a (Mn} , Cr) _1-b Al _b O ₃ When a and b are the number of moles shown in Table 1, they are weighed, and these raw material powders are wet-mixed and dried to obtain a raw material powder mixture. It was adjusted. The ratio of Mn and Cr in parentheses was adjusted at the ratio shown in Table 1. Subsequently, this raw material powder mixture was calcined for 2 hours at 1400 ° C. in an air atmosphere to obtain a calcined powder having an average particle diameter of 1 to 2 μm. Thereafter, wet mixing and pulverization were performed using a resin pot and high-purity alumina cobblestone using ethanol as a dispersion medium.

  Next, the obtained slurry was dried at 80 ° C. for 2 hours to obtain a thermistor synthetic powder. Thereafter, 20 parts by weight of a binder mainly composed of polyvinyl butyral is added to 100 parts by weight of the thermistor synthetic powder, mixed and dried. Furthermore, it granulated through the sieve of a 250 micrometer mesh, and the granulated powder was obtained. In addition, as a binder which can be used, it is not specifically limited to the above-mentioned polyvinyl butyral, For example, polyvinyl alcohol, an acrylic binder, etc. are mentioned. The amount of the binder is usually 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on the total amount of the calcined powder. Moreover, when mixing with a binder, it is preferable that the average particle diameter of the thermistor synthetic powder is 2.0 μm or less, whereby uniform mixing is possible.

  Using the granulated powder described above, uniaxial press molding at 20 MPa by a mold molding method, followed by molding at 150 MPa by a cold isostatic pressing (CIP) method, cylindrical molding with a diameter of 9 mm and a height of 10 mm Got the body. Then, this molded object was baked by hold | maintaining at 1500 degreeC for 2 hours by an atmospheric condition, and the electroconductive oxide sintered compact was obtained. Next, each conductive oxide sintered body was polished to form a cylindrical shape having a diameter of 6 mm and a height of 5 mm, and platinum electrodes were formed on both end faces by a screen printing method.

Using the obtained conductive oxide sintered body, resistance values (R (−40) and R (600)) at temperatures of −40 ° C. and 600 ° C. were measured by a direct current four-terminal method in an air atmosphere. The specific resistances ρ (−40) and ρ (600) were calculated from the resistance values, and the B constant (B (−40 to 600)) was calculated according to the following formula (1).
B (−40 to 600) = ln [ρ (600) / ρ (−40)] / [1 / T (600) −1 / T (−40)] (1)
Note that T (−40) = 233K and T (600) = 873K.
These results are shown in Table 1.

(Examples 2-7, Comparative Examples 1-6)
In addition, the present inventors use the same elements as the conductive oxide sintered body of Example 1 described above, but have different combinations of molar ratios (a, b) described in the composition formula. To 7 and Comparative Examples 1 to 6 were prepared.
In addition, each conductive oxide sintered compact of these Examples 2-7 and Comparative Examples 1-6 is the same raw material powder as Example 1, and each of Examples 2-7 of Table 1 and Comparative Examples 1-6. After weighing according to the molar ratio (a, b) in the column, it is produced in the same manner as in Example 1.
However, among these Examples 2 to 7 and Comparative Examples 1 to 6, in Comparative Examples 2, 4 and 6, a dense conductive oxide sintered body was not obtained without being sufficiently baked (this specification) And “unsintered” in Table 1).

In each of the conductive oxide sintered bodies of Examples 2 to 7 and Comparative Examples 1, 3, and 5, the resistance value (R (−40), R (600)) was measured, specific resistance (ρ (−40), ρ (600)) was calculated, and B constant (B (−40 to 600)) was calculated.
These results are shown in Table 1.

According to Table 1, the conductive oxide sintered bodies of Examples 1 to 7 and Comparative Examples 1 to 6 represented by the composition formula Y _1-a Sr _a (Mn, Cr) _1-b Al _b O ₃ Among the Examples 1 and 2 and Comparative Example 2 in which a = 0.20, the B constant of the conductive oxide sintered bodies of Examples 1 and 2 in which b = 0.25 and 0.30 is (−40 to 600) = 1922K and 1960K, which are in the range of 1000 to 2000K. On the other hand, Comparative Example 2 in which b = 0.00 was “unsintered”.
In addition, among Examples 3 to 5 and Comparative Example 3 in which a = 0.25, the B constant of Comparative Example 3 of the conductive oxide sintered body in which b = 0.50 is a large value exceeding 2000K. It became. On the other hand, the B constants of Examples 3 to 5 of the conductive oxide sintered bodies with b = 0.25, 0.30, and 0.38 are all B (−40 to 600) = 1000 to 2000K. It was within the range.
In addition, among Examples 6 and 7 and Comparative Examples 4 and 5 in which a = 0.30, the B constant of Comparative Example 5 of the conductive oxide sintered body in which b = 0.50 exceeded 2000K. The B constants of Examples 6 and 7 of the conductive oxide sintered bodies with b = 0.15 and 0.30 were all B (−40 to 600) = 1000 to 2000K. It was within the range. Note that Comparative Example 4 in which b = 0.00 was “unsintered”.

Note that the B constant of the conductive oxide sintered body of Comparative Example 1 (a = 0.15) in which the value of a is smaller than that of Example 2 (a = 0.20) described above exceeds 2000K. . From this, it can be seen that the B constant of the conductive oxide sintered body having a of 0.18 or less is a value exceeding 2000K.
Moreover, the thing of the comparative example 6 (a = 0.60) made larger than Example 7 (a = 0.30) was unsintered. From this, it can be seen that the conductive oxide sintered body having a of 0.50 or more is not sufficiently baked.

Further, regarding b, each of the conductive oxide sintered bodies of Comparative Examples 2 and 4 in which b = 0.00 was “unsintered”. From this, it can be seen that the conductive oxide sintered body not containing aluminum as a constituent element is not sufficiently baked regardless of a.
Furthermore, about the value of b, the electroconductive oxide sintered compact of the comparative example 3 (b = 0.50) made larger than Example 4 (b = 0.30), and Example 7 (b = 0.0). In any of the conductive oxide sintered bodies of Comparative Example 5 (b = 0.50) larger than 30), the B constant exceeds 2000K. From this, it can be seen that the B constant of the conductive oxide sintered body having b of 0.40 or more is a value exceeding 2000K.

  From the above, each conductive oxide sintered body of Examples 1 to 7 in which a is 0.18 <a <0.50 and b is 0.05 <b <0.40 is −40 to 600 ° C. It can be seen that the B constant in the temperature range is in the range of B (−40 to 600) = 1000 to 2000K.

(Examples 8 to 10)
In Examples 1 to 7 (and Comparative Examples 1 to 6) described above, among the conductive oxide sintered bodies represented by the general formula Y _1-a Sr _a M3 _1-b Al _b O ₃ , the element M3 The example which made Mn and Cr into was shown. On the other hand, in Examples 8 to 10, a conductive oxide sintered body in which the element M3 was Mn alone or Mn and Fe was investigated.
In Examples 8 and 9, Cr ₂ O ₃ was not used among the raw material powders used in Example 1, and in Example 10, Fe ₂ O ₃ was used instead of Cr ₂ O _3. The raw material powder was weighed according to the molar ratio (a, b) in each column of Examples 8 to 10 in Table 1, and produced in the same manner as Example 1. In Examples 8 to 10, all became dense conductive oxide sintered bodies.
About each conductive oxide sintered compact of the above-mentioned Examples 8-10, after calculating a specific resistance ((rho) (-40), (rho) (600)) similarly to Example 1, B constant (B (-40) ~ 600)) was calculated (see Table 1).

According to Table 1, the general formula _{Y 1-a Sr a M3 1} -b Al b O 3 in an element M3, in addition to Examples 1 to 7 described above with Mn and Cr, the element M3 Mn only, or It can be seen that the conductive oxide sintered bodies of Examples 8 to 10 using Mn and Fe also have a B constant in the range of B (−40 to 600) = 1000 to 2000K. From this, Example 1 in which M3 contains at least Mn among Mn, Fe, and Cr, a is 0.18 <a <0.50, and b is 0.05 <b <0.40. It can be seen that each of the conductive oxide sintered bodies of 10 to 10 has a B constant of B (−40 to 600) = 1000 to 2000K.

(Examples 11 to 13)
In Examples 1 to 7, the element M1 is Y in the conductive oxide sintered body represented by the general formula M1 _1-a Sr _a (Mn, Cr) _1-b Al _b O ₃ . An example is shown. On the other hand, in Examples 11 to 13, a conductive oxide sintered body in which the element M1 is only Nd or Y and Yb was investigated.
As the raw material powder, in Example 11, Nd ₂ O ₃ was used instead of Y ₂ O ₃ in the raw material powder used in Example 1, and in Examples 12 and 13, it was used in Example 1. Yb ₂ O ₃ was used in addition to the raw material powder. Each raw material powder was weighed according to the molar ratio (a, b) in each column of Examples 11 to 13 in Table 1, and produced in the same manner as Example 1. In Examples 11 to 13, all became dense conductive oxide sintered bodies.
For each of the conductive oxide sintered bodies of Examples 11 to 13, the specific resistance (ρ (−40), ρ (600)) is calculated in the same manner as in Example 1, and the B constant (B (−40 to 600) is calculated. )) Was calculated (see Table 1).

According to Table 1, the general formula _{M1 1-a Sr a (Mn} , Cr) 1-b Al b in O ₃ in the element M1, a conductive oxide sintered body of Examples 1 to 7 described above with Y In addition, the conductive oxide sintered bodies of Examples 11 to 13 using Nd or Y and Yb as the element M1 also have a B constant in the range of B (−40 to 600) = 1000 to 2000K. It became. Therefore, an example in which the element M1 contains at least one of Y, Yb, and Nd, a is 0.18 <a <0.50, and b is 0.05 <b <0.40. It can be seen that each of the conductive oxide sintered bodies of 1 to 7 and Examples 11 to 13 has a B constant of B (−40 to 600) = 1000 to 2000K.

(Examples 14 to 16)
In Example 1-7 described above, the general formula _{Y 1-a M2 a (Mn} , Cr) 1-b Al b O 3 of conductive oxide sintered body was expressed in, the element M2 was Sr An example is shown. On the other hand, in Examples 14 to 16, a conductive oxide sintered body in which the element M2 is only Ca, or Sr and Ca or Mg was investigated.
As the raw material powder, in Example 14, CaCO ₃ was used instead of SrCO ₃ among the raw material powders used in Example 1, and in Examples 15 and 16, the raw material powder used in Example 1 was used. In addition, CaCO ₃ (or MgO in Example 16) was used. Each raw material powder was weighed according to the molar ratio (a, b) in each column of Examples 14 to 16 in Table 1, and produced in the same manner as in Example 1. In Examples 14 to 16, all became dense conductive oxide sintered bodies.
For each of the conductive oxide sintered bodies of Examples 14 to 16, the specific resistance (ρ (−40), ρ (600)) was calculated in the same manner as in Example 1, and the B constant (B (−40 to 600) was further calculated. )) Was calculated (see Table 1).

According to Table 1, the general formula _{Y 1-a M2 a (Mn} , Cr) 1-b Al b in O ₃ in the element M2, conductive oxide sintered body of Examples 1 to 7 described above with Sr In addition, each conductive oxide sintered body of Examples 14 to 16 using only Ca, Sr and Ca or Mg as the element M2 also has a B constant of B (−40 to 600) = 1000 to 2000K. It was within the range. Therefore, an example in which the element M2 includes at least one of Sr, Ca, and Mg, a is 0.18 <a <0.50, and b is 0.05 <b <0.40. It can be seen that each of the conductive oxide sintered bodies of 1 to 7 and Examples 14 to 16 has a B constant of B (−40 to 600) = 1000 to 2000K.

From the above results, the general formula M1 _1-a M2 _a M3 _1-b Al _b O ₃ (where the element M1 is at least one of the Group 3 elements excluding La and the element M2 is at least of the Group 2 elements) One element and the element M3 are represented by at least one element selected from Group 4, Group 5, Group 6, Group 7, and Group 8 elements, and a is 0.18 <a <0. 50, each conductive oxide sintered body 10 of this embodiment (Examples 1 to 16) satisfying b <0.05 <b <0.40 has a B constant in a temperature range of −40 to 600 ° C. B (−40 to 600) = 1000 to 2000K.
Note that at least Mn is preferably included as the element M3 among Mn, Fe, and Cr. In addition, the element M1 may include at least one of Y, Yb, and Nd. Furthermore, the element M2 may contain at least one of Sr, Ca, and Mg.

Next, the thermistor element 1 according to the present embodiment will be described with reference to FIG.
This thermistor element 1 includes a conductive oxide sintered body 10 according to Examples 1 to 16 described above, and a pair of electrode wires 11 made of a Pt—Rh alloy extending from the conductive oxide sintered body 10. , 12 (see FIG. 1).
For this reason, it can be set as the thermistor element 1 whose B constant in the temperature range of -40-600 degreeC is B (-40-600) = 1000-2000K, and the lower limit (-40 degreeC) vicinity and upper limit (600 of temperature range) Thermistor element 1 with improved sensitivity in the vicinity of [° C.] can be obtained.

Next, a temperature sensor 100 using the above-described thermistor element 1 will be described with reference to FIG.
The temperature sensor 100 includes a thermistor element 1 and a casing 110 that houses the thermistor element 1 (see FIG. 2). Among these, the housing 110 includes a cylindrical main body 111 and a cylindrical protrusion 112 having a diameter smaller than that of the main body 111 and protruding from the main body 111. The protrusion 112 has the thermistor element 1 disposed on the inside thereof, and can measure the temperature around the protrusion 112.
Note that the temperature sensor 100 according to the present embodiment (Examples 1 to 16) is, for example, as shown in FIG. 2, the temperature of the exhaust gas EG discharged from the vehicle engine (not shown) and flowing through the exhaust pipe EP. Used to measure In this case, the main body 111 of the housing 110 is fixed to the wall of the exhaust pipe while the protruding portion 112 of the housing 110 is disposed inside the exhaust pipe EP (see FIG. 2).

  Since the temperature sensor 100 according to the present embodiment (Examples 1 to 16) uses the thermistor element 1, the B constant in the temperature range of −40 to 600 ° C. is B (−40 to 600) = 1000. The temperature sensor 100 of 2000K can be obtained, and the temperature sensor 100 with improved sensitivity near the lower limit (−40 ° C.) and the upper limit (600 ° C.) of the temperature range can be obtained.

In the above, the present invention has been described with reference to the embodiments (Examples 1 to 16). However, the present invention is not limited to the above-described Examples and the like, and can be appropriately changed without departing from the gist thereof. Needless to say, it can be applied.
For example, when the conductive oxide sintered bodies of Examples 1 to 16 were produced, the compounds containing each element were exemplified as the raw material powder. In addition to the exemplified compounds, oxides of each element, carbonate, hydroxide Compounds such as products and nitrates may also be used. In particular, oxides and carbonates are preferably used.
Further, in the examples, Y, Y and Yb, or Nd is used as M1 composed of at least one element among the Group 3 elements excluding La. A group element may be used, or Y, Yb, and Nd may be used together. Further, in the examples, Sr, Ca, Sr and Ca, or Sr and Mg are used as M2 composed of at least one element among the Group 2 elements. However, other Group 2 elements may be used, or Sr, Ca and Mg may be used together. Furthermore, as M3 which consists of at least 1 sort (s) of elements in Group 4, Group 5, Group 6, Group 7 and Group 8, Mn, Mn and Cr, or Mn and Fe in the examples An example using is shown. However, other elements such as Group 4, Group 5, Group 6, Group 7 and Group 8 may be used, or Mn, Cr and Fe may be used together.
In addition, within the range that does not impair the characteristics required for the conductive oxide sintered body, thermistor element or temperature sensor, such as the sinterability and B constant of the conductive oxide sintered body, , Na, K, Ga, Si, C, Cl, S, etc. may be contained.

1 Thermistor element 10 Conductive oxide sintered body 100 Temperature sensor

Claims (6)

At least one element of Group 3 elements excluding La is M1,
At least one element of group 2 elements is M2,
When at least one element among Group 4, Group 5, Group 6, Group 7 and Group 8 elements is M3,
Represented by the general formula M1 _1-a M2 _a M3 _1-b Al _b O ₃ ,
a is 0.18 <a <0.50,
A conductive oxide sintered body in which b is 0.05 <b <0.40. The conductive oxide sintered body according to claim 1,
The element M3 is
A conductive oxide sintered body containing at least Mn among Mn, Fe and Cr. The conductive oxide sintered body according to claim 1 or 2, wherein
The element M1 is
A conductive oxide sintered body containing at least one of Y, Yb, and Nd. The conductive oxide sintered body according to any one of claims 1 to 3, wherein
The element M2 is
A conductive oxide sintered body containing at least one of Sr, Ca, and Mg. The thermistor element which uses the electroconductive oxide sintered compact of any one of Claims 1-4. A temperature sensor using the thermistor element according to claim 5.

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