KR20090081506A - Ceramic material of pyrochlore crystal structure with low thermal conductivity and manufacturing method of the same - Google Patents

Abstract

A pyrochlore crystal structured ceramic material and a manufacturing method thereof are provided to show low thermal conductivity of 1.3~1.6 W/mK while preventing a rapid decrease in thermal expansion coefficient within a temperature range of 200~400°C. A pyrochlore crystal structured ceramic material has a pyrochlore crystal structure of A2B2O7 and a composition of LaaY2-aCe2O7(0<a<2 and the a is an actual number). In the structure, the A site consists of a rare earth element including at least La and Y; and the B site is Ce. The A site additionally contains an element of Gd and the composition of La2-aGda+b-2Y2-bCe2O7(the a and b are actual numbers and satisfy the inequality of 0<a<2 and 0<b<2).

Description

Ceramic material of pyrochlore crystal structure with low thermal conductivity and manufacturing method of the same

The present invention relates to a ceramic material and a method of manufacturing the same, and more particularly, the abnormal phenomenon in which the thermal expansion coefficient rapidly decreases in the 200-400 ° C. range while having low thermal conductivity can be suppressed, thereby preventing peeling of the thermal barrier coating layer. A low thermal conductivity ceramic material having a pyrochlore crystal structure and a method of manufacturing the same.

The actual operating temperature of the gas turbine using heat shield coating is 1100 ℃ ~ 1200 ℃, when exposed to high temperature atmosphere, the surface of the metal material is easy to oxidize. Superalloys developed for use at high temperatures, such as gas turbines, also suffer from long-term endurance at temperatures above 1000 ° C. Therefore, in order to improve the life of the metal material exposed to high temperature, it is necessary to coat with a material having excellent heat shielding properties.

Thermal Barrier Coating (TBC) material requirements include not only low thermal conductivity for heat shielding but also phase stability at high temperatures, high thermal expansion coefficient approaching the thermal expansion coefficient of the metal base material, and suppressing the increase in thermal conductivity at high temperatures. Low sintering properties and the like (R. Vassen, X. Cao, F. Tietz, D. Basu, and D. St, "Zirconates as New Materials for Thermal Barrier Coating", J. Am. Ceram. Soc., 83, [8] 2023-2028 (2000)), (DR Clarke and CG Levi, "Materials Design for the Next Generation Thermal Barrier Coatings", Annu. Rev. Mater. Res., 33, 383-417 (2003)) ).

Currently, 7-8 wt% YSZ (Y ₂ O ₃ -stabilized zirconia) is widely used as a material for TBC (Thermal Barrier Coating). However, if the material is kept at a high temperature for a long time, the sintering proceeds to increase the density of the TBC, increase the thermal conductivity, and also cause a crack in the TBC layer during the cooling / heating cycle due to the volume change due to the phase transformation (( S. Rangaraj and K. Kokini, "Fracture in Single-Layer Zirconia (YSZ) -Bond Coat Alloy (NiCoCrAlY) Composite Coatings under Thermal Shock", Acta Materialia, 52, 455465 (2004)), (F. Tang and JM Schoenung , "Evolution of Young's Modulus of Air Plasma Sprayed Yttria-Stabilized Zirconia in Thermally Cycled Thermal Barrier Coatings", Scripta Materialia, 54, 1587-92 (2006)).

Recently, various attempts have been made to solve the problems of YSZ and to develop materials having lower thermal conductivity. Among them, many studies have been conducted to reduce thermal conductivity by adding rare earth elements such as La ₂ O ₃ and Y ₂ O ₃ to YSZ ((M. Matsumoto, N. Yamaguchi, and H. Matsubara, "Low Thermal Conductivity and Temperature Stability). of ZrO ₂ -Y ₂ O ₃ -La ₂ O ₃ Coatings Produced by Electron Beam PVD ", Scripta Materialia, 50, 867-871 (2004)), (M. Matsumoto, H. Takayama, D. Yokoe, K. Mukai , H. Matsubara, Y. Kagiya, and Y. Sugita, "Thermal Cycle Behavior of Plasma Sprayed La ₂ O ₃ , Y ₂ O ₃ Stabilized ZrO ₂ Coatings", Scripta Materialia, 54, 203539 (2006)).

Furthermore, in order to increase the amount of oxygen vacancy and to secure high temperature phase stability, research on pyrochlore phases such as La ₂ Zr ₂ O ₇ is underway, and the lowest thermal conductivity is 1.3. Results of W / mK (1000 ° C.) have recently been reported (H. Lehmann, D. Pitzer, G. Pracht, R. Vassen, and D. St, "Thermal Conductivity and Thermal Expansion Coefficients of the Lanthanum Rare-Earth). -Element Zirconate System ", J. Am. Ceram. Soc., 86, [8] 133844 (2003)), (NP Bansal and D. Zhu, "Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings", Materials Science and Engineering, A459, 192-195 (2007)) ).

The technical problem to be achieved by the present invention is low thermal conductivity of the pyrochlore crystal structure that can suppress the separation of the heat shield coating layer because the abnormal phenomenon that the coefficient of thermal expansion is rapidly reduced in the 200 ~ 400 ℃ section while having low thermal conductivity To provide a ceramic material.

Another technical problem to be achieved by the present invention is a low heat conductivity and low heat of the pyrochlore crystal structure that can suppress the separation of the heat shield coating layer does not occur abnormal phenomenon that the thermal expansion coefficient is rapidly reduced in the 200 ~ 400 ℃ section The present invention provides a method for manufacturing a conductive ceramic material.

The present invention has a pyrochlore crystal structure, wherein in the A ₂ B ₂ O ₇ composition of the pyrochlore crystal system, the A site is composed of rare earth elements containing at least La and Y, and the B site is composed of Ce elements. A low thermal conductivity ceramic material having a pyrochlore crystal structure having a composition of La _a Y _{2 -a} Ce ₂ O ₇ , wherein 0 <a <2 and a is a real number.

The low thermal conductivity ceramic material of the pyrochlore crystal structure is configured to further include a Gd element at the A site, and La _{2 - a} Gd _{a + b-2} Y _{2- b} Ce ₂ O ₇ (where a and b are It is a real number and can have a composition of 0 <a <2 and 0 <b <2.

The content of the Y element may be less than 50 mol%.

It is preferable that the low thermal conductivity ceramic material of the pyrochlore crystal structure has a value of thermal conductivity of less than 2.0 W / mK at 1000 ° C.

The present invention also provides an oxide powder containing at least La ₂ O ₃ and Y ₂ O ₃ as a source raw material of an element to be added to the A site in the A ₂ B ₂ O ₇ composition of the pyrochlore crystal structure, and the B site Charging CeO ₂ oxide powder as a source raw material of the element to be added to the ball mill, wet mixing with a solvent, stirring and drying the slurry mixed by the ball mill to prevent precipitation, and drying the dried slurry. Pulverizing and pulverizing, charging and shaping the pulverized powder into a mold, and sintering the molded specimen to form La _a Y _2-a Ce ₂ O ₇ (where 0 <a <2 and a is a real number). It provides a method for producing a low thermal conductivity ceramic material of the pyrochlore crystal structure comprising the step of forming a ceramic material of the pyrochlore crystal structure having a composition of).

The source material of the element to be added to the A site further comprises a Gd ₂ O ₃ oxide powder, the ceramic material of the pyrochlore crystal structure is La _{2 - a} Gd _{a + b-2} Y _{2- b} Ce ₂ O ₇ (where a and b are real numbers and have a composition of 0 <a <2, 0 <b <2).

According to the present invention, while having a low thermal conductivity of 1.3 ~ 1.6 W / mK, the abnormal phenomenon in which the thermal expansion coefficient rapidly decreases in the 200 ~ 400 ℃ section can be effectively eliminated A ₂ B ₂ O which can suppress the peeling of the thermal barrier coating layer _A low thermal conductivity material having a _seventh -phase pyrochlore phase can be obtained.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen.

The pyrochlore crystal system (A ₂ B ₂ O ₇ ) is a new material emerging as a heat shielding material because of its excellent thermal phase stability, low thermal diffusion coefficient, and excellent mechanical properties at high temperatures.

Y on pyrochlore₂O₃ Research is underway to lower the thermal conductivity by adding additional rare earth elements such as ZrO.₂CeO similar to pyrochlore₂Research on pyrochlore phase is also underway. La₂Ce₂O₇The stable presence of pyrochlore on pyrochlore has also been investigated for its applicability as a thermal barrier coating as a low thermal expansion material. But presented La₂Ce₂O₇The low thermal conductivity composition is ZrO₂Unlike the system, anomalous phenomenon of thermal expansion coefficient was observed in which the thermal expansion coefficient rapidly decreased around 200-400 ℃. Such rapid reduction of the coefficient of thermal expansion must be improved because it can induce peeling of the thermal barrier coating layer from a metal base material having a relatively large coefficient of thermal expansion.

The present invention can be used as a heat shield coating material for improving the heat resistance and life of the base metal, which is a metal used in a gas turbine, and has a stabilized pyrochlore crystal structure in which the thermal expansion coefficient is not reduced rapidly around 200-400 ° C. Present a ceramic material. Low thermal conductivity ceramic material with heat shielding function to protect base metal which is metal at high temperature, has pyrochlore structure, site A in general composition of A ₂ B ₂ O ₇ of pyrochlore A material consisting of rare earth elements containing at least La (lanthanum) and Y (yttrium) elements at (site) and Ce (cerium (cerium) element at site B is presented. . The low thermal conductivity ceramic material of the pyrochlore crystal structure according to the preferred embodiment of the present invention may be configured to further include a Gd (gadolinium) element at the A site. Ceramic material of the claws control the crystal structure in a pie according to an embodiment of the present invention are _{La a Y 2 -a Ce 2 O} 7 The composition of (and where, 0 <a <2, a is a real number Im) or La _{2 - a} Gd _{a + b-2} Y _{2 -b} Ce ₂ O ₇ (where a and b are real and have a composition of 0 <a <2, 0 <b <2).

The ceramic material of the pyrochlore crystal structure according to the preferred embodiment of the present invention is a stable material having excellent high temperature characteristics and no phase deformation. The ceramic material of the pyrochlore crystal structure according to the preferred embodiment of the present invention has an average thermal expansion coefficient of about 9.20 × 10 ^{−6 to} 11.8 × 10 ⁻⁶ / K from room temperature to 1000 ° C., and thermal conductivity at 1000 ° C. Figure 1.3-1.6W / mK is less than 2W / mK can be used as a material for heat shield coating.

Hereinafter, a method of manufacturing a ceramic material having a pyrochlore crystal structure according to a preferred embodiment of the present invention will be described.

Weighing an oxide powder containing an element to be added to the A site and an oxide powder containing an element to be added to the B site so as to have an A ₂ B ₂ O ₇ composition having a pyrochlore crystal structure. do. The element to be added to the A site may be La (lanthanum) and Y (yttrium) elements or La (lanthanum), Y (yttrium) and Gd (gadolinium) elements, and as an oxide which is a source material of these elements, La ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ can be used. The element to be added to the B site may be a Ce (cerium; cerium) element, and CeO ₂ may be used as an oxide that is a source material of the element.

Oxide powder, which is a source material containing an element to be added to the A site, and oxide powder, which is a source material containing an element to be added to the B site, are charged into a ball milling machine and wetted with a solvent. Mix. The ball mill is rotated at a constant speed to mechanically grind and uniformly mix the source raw materials.

The balls used for ball milling may use balls made of ceramics such as zirconia, and the balls may be all the same size or may be used with balls having two or more sizes. Grind to the size of the target particles by adjusting the size of the ball, milling time, rotation speed per minute of the ball mill. For example, in consideration of the particle size, the size of the ball can be set in the range of about 1 mm to 10 mm, and the rotational speed of the ball mill can be set in the range of about 50 to 500 rpm. Ball milling is performed for 1 to 100 hours in consideration of the target particle size and the like.

By ball milling, the source raw materials are ground to finely sized particles, have a uniform particle size distribution, and are mixed evenly.

A drying process is performed while stirring using a magnetic bar so that the mixed slurry is not precipitated. The drying process can be weight-dried for 24 hours in an oven at 80 ℃.

The dried slurry is pulverized to prepare a powder. The grinding can be carried out using alumina induction.

The pulverized powder is charged into a mold and molded. The molding may be carried out by charging into a mold having a diameter of 16 mm, first uniaxially molding for 1 minute at a pressure of 50 MPa, and then cold isostatic pressing (Cold Isostatic Pressing) for 1 minute at a pressure of 150 MPa.

The molded specimen is sintered to form a ceramic material of pyrochlore crystal structure. Preferably, the sintering is carried out at a temperature of about 1300 ° C to 1600 ° C for about 1 hour to 3 hours. The sintering step can be carried out by heating up to a sintering temperature at a heating rate of 10 ° C./min, sintering for a predetermined time (for example, about 1 hour to 3 hours), and quenching to room temperature.

The ceramic material of the pyrochlore crystal structure according to the preferred embodiment of the present invention may be a composition of La _a Y _{2 -a} Ce ₂ O ₇ (where 0 <a <2 and a is a real number) or La _{2 − a} Gd _{a + b-2} Y _{2 -b} Ce ₂ O ₇ (where a and b are real and have a composition of 0 <a <2, 0 <b <2) and have an average thermal expansion from room temperature to 1000 ° C The coefficient is about 9.20 × 10 ^{−6 to} 11.8 × 10 ⁻⁶ / K, and the thermal conductivity at 1000 ° C. is about 1.3 to 1.6W / mK, which is smaller than 2W / mK.

As a ceramic material of pyrochlore crystal structure to improve the heat resistance and life of the base metal, which is a metal, a source of element to enter the A site in the pyrochlore crystal system (A ₂ B ₂ O ₇ ) The thermal properties were analyzed by sintering at a constant temperature for a predetermined time using CeO ₂ as a source material of elements to enter La ₂ O ₃ , Y ₂ O ₃ or Gd ₂ O ₃ , B sites. Hereinafter, a high temperature thermal characteristic analysis method of the ceramic material of the pyrochlore crystal structure of the present invention will be described in detail.

The invention is described in more detail with reference to the following examples and comparative examples, which are not intended to limit the invention.

Table 1 summarizes the characteristics of the composition corresponding to the example of La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system.

Composition (mol%) Average thermal expansion coefficient at room temperature to 1000 ℃ (10 ^-6 / K) 200 ~ 400 ℃ thermal expansion coefficient or more Thermal conductivity (1000 ℃) CeO ₂ Gd ₂ O ₃ La ₂ O Y ₂ O ₃ Example 1 _{La 1 .5 Y 0 .5 Ce 2} O 7 66.7 - 25 8.3 9.2 radish 1.4 Example 2 _{La 1 .0 Y 1 .0 Ce 2} O 7 66.7 - 16.65 16.65 11.7 radish 1.5 Example 3 _{La 0 .5 Y 1 .5 Ce 2} O 7 66.7 - 8.3 25 11.7 radish 1.6 Example 4 _{La 0 .5 Gd 1 .0 Y 0} .5 Ce 2 O 7 66.67 16.67 8.33 8.33 11.8 radish 1.5 Example 5 _{La 1 .0 Gd 0 .5 Y 0} .5 Ce 2 O 7 66.67 8.34 16.66 8.33 11.8 radish 1.6 Example 6 _{La 0 .5 Gd 0 .5 Y 1} .0 Ce 2 O 7 66.68 8.34 8.34 16.65 11.8 radish 1.5

Table 2 summarizes the composition corresponding to the comparative example of La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system.

Composition (mol%) Average thermal expansion coefficient at room temperature to 1000 ℃ (10 ^-6 / K) 200 ~ 400 ℃ thermal expansion coefficient or more Thermal conductivity (1000 ℃) CeO ₂ Gd ₂ O ₃ La ₂ O Y ₂ O ₃ Comparative Example 1 La ₂ Ce ₂ O ₇ 66.7 - 33.3 - 10.8 U 1.3 Comparative Example 2 _{La 1 .5 Gd 0 .5 Ce 2} O 7 66.7 8.3 25 - 10.0 U 1.5 Comparative Example 3 _{La 0 .5 Gd 1 .5 Ce 2} O 7 66.7 25 8.3 - 11.1 U 1.6 Comparative Example 4 Gd ₂ Ce ₂ O ₇ 66.7 33.3 - - 11.5 radish 1.8 Comparative Example 5 Y ₂ Ce ₂ O ₇ 66.7 - - 33.3 11.5 radish 2.1

Table 1 and Table 2 separately indicate the average coefficient of thermal expansion and the presence or absence of abnormalities in the room temperature ~ 1200 ℃ of Examples and Comparative Examples.

Examples 1 to 6 and Comparative Examples 1 to 5 are as ions enter into the A site (site) of the claws language family (A ₂ B ₂ O ₇₎ as a pie using the La ^{3 +,} Gd ^{3 +,} or Y ^{+ 3,} and B It is a composition using Ce ⁴⁺ as ions to enter the site.

The source raw materials are weighed to have the composition of Table 1 and Table 2. Weighing is made to have the composition shown in Table 1 based on the molecular weight, the content ratio, and the molar ratio of the composition of the source raw material.

Source raw materials weighed to have the compositions of Tables 1 and 2 were charged to a ball mill and ethanol was wet mixed for 4 hours in a planetary mill using 3 mm zirconia balls as solvent.

The mixture was stirred and dried using a magnetic bar to prevent precipitation of the mixed slurry, followed by constant drying in an oven at 80 ° C. for 24 hours, and then pulverized using alumina induction to prepare a powder.

The mixed powder was charged into a mold having a diameter of 16 mm, first uniaxially formed at a pressure of 50 MPa for 1 minute, and further subjected to isostatic pressing (Cold Isostatic Pressing) at 150 MPa for 1 minute.

The molded specimens were each heated to a temperature increase rate of 10 ° C./min up to 1600 ° C., and then sintered for 2 hours and cooled to room temperature.

1 is a graph showing the results of X-ray diffraction (XRD) phase analysis of a La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system.

The relative density of the sintered test piece was calculated using the Archimedes method. In order to analyze the crystal structure of the sintered specimens, the specimens sintered at 1600 ° C. for 2 hours using a high-power X-ray diffractometer (D / max-2500 / PC, Rigaku, Japan) were used. The diffraction pattern was observed up to 20 ° to 70 ° at a scan rate of 4 ° C./min at 40 kV and 200 Hz. It can be seen that a pyrochlore phase was produced as shown in FIG. 1.

In Table 1 and Table 2, the thermal conductivity of Examples 1-6 and Comparative Examples 1-5 is shown.

Compared to _{the; (YSZ Y 2 O 3 -stabilized} zirconia) (Nitin, P. Padture Examples 1 to 6 shows a thermal conductivity of 1.4 ~ 1.6 W / mK, Y 2 O 3 is often used in the conventional addition of zirconia , Klemens, G. Paul, J. Am. Ceram. Soc., 80, (1997) 1018-1020).

On the other hand, Comparative Examples 1 to 5 showed thermal conductivity of 1.3 to 2.1 W / mK and higher values than Examples 1 to 6.

Thermal conductivity was calculated by multiplying the specific heat value measured by differential scanning calorimeter (DSC), theoretical density and thermal diffusivity according to American Society for Testing Materials (ASTM) E1461. In consideration of the density was corrected using the following equation (1).

In Equation 1, k _measured means measured thermal conductivity, Φ means porosity, k _true means thermal conductivity of the actual material.

Specific heat was measured by the following method. Based on ASTM (American Society for Testing Materials) E1269, a sintered body of a circular disk having a diameter of 6 mm and a thickness of 0.6 to 0.7 mm was prepared, and a differential scanning calorimeter (DSC) (DSC) Specific heat was measured to 1200 degreeC using the temperature increase rate of 10 degree-C / min using 404C, Netzsch, Germany. As a result of specific heat measurement, it was obtained that it had a value of 0.57-0.70 J / gK at 1200 degreeC.

Thermal diffusivity was measured by the following method. In order to measure the thermal diffusivity, a sintered compact of a circular disk having a diameter of 12.7 mm and a thickness of 2.0 mm was manufactured, and the upper and lower surfaces were polished using diamond having a diameter of 1 m. Graphite was coated on both sides in order to prevent the reflection of the laser from the specimen surface and to help the absorption into the test specimen, and thermal diffusivity was measured using a passion water meter (LFA427, Netzsch, Germany). As a result of thermal diffusivity measurement, it was concluded that it has a value of 0.6 ~ 0.7mm ² / s at 1000 ℃.

On the other hand, Figure 2 shows the thermal expansion coefficient (thermal expansion coefficient (TEC)) according to the temperature (temperature) of Example 1 and Comparative Examples 1 to 3.

In Example 1, there is no abnormal phenomenon such as the thermal expansion coefficient is decreased in particular according to the temperature, while in Comparative Examples 1 to 3, an abnormal phenomenon of the thermal expansion coefficient is shown in the thermal expansion coefficient is rapidly reduced in the 200 ~ 400 ℃ section. That is, the anomaly of thermal expansion coefficient appearing in La ₂ Ce ₂ O ₇ was effectively removed by the addition of Y ^{3 +} . However, in this Comparative Example 2, and anomalies in the thermal expansion coefficient may be substituted for Gd ^{+ 3} is La ^{+ 3,} as shown at 3 to 75 mol% did not improve effectively.

On the other hand, as in Comparative Example 4, the anomalous phenomenon of the coefficient of thermal expansion disappeared in Gd ₂ Ce ₂ O ₇ having no Gd of 100 mol%, that is, no La (lanthanum). However, in this case, the thermal conductivity of 1000 ° C. is 1.8 W · mK, which is higher than that of Examples 1 to 6 of the present invention. Therefore, even when the excess of Gd to control the thermal expansion coefficient abnormal phenomenon of La ₂ Ce ₂ O ₇ It can be seen that it is not suitable as a heat shield coating material because the thermal conductivity, which is the core property of the low thermal conductivity ceramic material increases. The same applies to the case of Y ₂ Ce ₂ O ₇ of Comparative Example 5. Anomalous thermal expansion coefficient is not found, but thermal conductivity is high.

In the comparative examples, not only the phenomenon of thermal expansion coefficient abnormality but also the measurement of specific heat was observed. 3 is a graph showing specific heat at room temperature to 1200 ° C. of a La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system. In FIG. 3, the specific heat of the composition to which Gd ^{3 +} and Y ^{3 +} is added tends to increase slowly with temperature, whereas Comparative Example 1 to which La ^{3 +} is added has a peak of change in specific heat near 270 ° C. Was observed. This is similar to the abnormal phenomenon of the coefficient of thermal expansion of Comparative Example 1 shown in FIG.

In Examples 4, 5 and 6, even when Gd was added to La ₂ Ce ₂ O ₇ , when Y was further added at 25 mol% or more, the abnormal phenomenon of the coefficient of thermal expansion shown in Comparative Examples 2 to 3 disappeared. have. Nevertheless, it can be seen that the thermal conductivity has a value of 1.5 W / mK similar to La ₂ C ₂ O ₇ .

As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment, A various deformation | transformation by a person of ordinary skill in the art within the scope of the technical idea of this invention is carried out. This is possible.

1 is a graph showing the results of X-ray diffraction (XRD) phase analysis of a La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system.

2 is a graph showing a thermal expansion coefficient (TEC) according to the temperature (temperature) of Example 1 and Comparative Examples 1 to 3.

3 is a graph showing specific heat at room temperature to 1200 ° C. of a La ₂ Ce ₂ O ₇ -Gd ₂ Ce ₂ O ₇ -Y ₂ Ce ₂ O ₇ ternary system.

Claims (6)

In the A ₂ B ₂ O ₇ composition of the pyrochlore crystal system, the A site is composed of rare earth elements containing at least La and Y, and the B site is composed of Ce elements, _A low thermal conductivity ceramic material having a pyrochlore crystal structure, having a composition of _a Y _{2 -a} Ce ₂ O ₇ , wherein 0 <a <2 and a is a real number. The method of claim 1, wherein the A site is configured to further include a Gd element, La _{2 -a} Gd _{a + b-2} Y _2-b Ce ₂ O ₇ (where a and b are real, 0 <a A low thermal conductivity ceramic material having a pyrochlore crystal structure, having a composition of <2, 0 <b <2. The low thermal conductivity ceramic material of claim 1, wherein the content of the Y element is less than 50 mol%. The low thermal conductivity ceramic material of claim 1, wherein the thermal conductivity at 1000 ° C. has a value of less than 2.0 W / mK. An oxide powder containing at least La ₂ O ₃ and Y ₂ O ₃ as a source raw material to be added to the A site in the A ₂ B ₂ O ₇ composition of the pyrochlore crystal structure, and a source of the element to be added to the B site Charging CeO ₂ oxide powder as a raw material into a ball mill and wet mixing with a solvent; Stirring and drying the slurry mixed by the ball mill to prevent precipitation; Pulverizing and drying the dried slurry; Charging the ground powder to a mold and molding; And Sintering the molded specimen to form a ceramic material of a pyrochlore crystal structure having a composition of La _a Y _{2 -a} Ce ₂ O ₇ , where 0 <a <2 and a is a real number A method for producing a low thermal conductive ceramic material having a pyrochlore crystal structure. The method of claim 5, wherein the source material of the element to be added to the A site further comprises a Gd ₂ O ₃ oxide powder, the ceramic material of the pyrochlore crystal structure is La _{2 - a} Gd _{a + b-2} Y _{2 -b} Ce ₂ O ₇ (where a and b are real numbers and have a composition of 0 <a <2, 0 <b <2), manufacturing a low thermal conductivity ceramic material having a pyrochlore crystal structure Way.

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