CN112960980B - Ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material and preparation method thereof - Google Patents
Ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material and preparation method thereof Download PDFInfo
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Abstract
The invention provides an ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material and a preparation method thereofThe chemical composition of the thermal barrier coating is (RE) 1‑x A x ) 2 (Zr 1‑y B y ) 2 O 7 Wherein A is 3+ Substituted RE position, substituted ion A 3+ Has an ionic radius smaller than that of the original ion RE 3+ Forming a resonator strong scattering phonon effect; b is 4+ Substitution of Zr site, substitution of ion B 4+ Has an ionic radius larger than that of the original ion Zr 4+ Forming a lattice softening effect; RE is any rare earth element, the doping element A is yttrium or scandium or bismuth or indium or any lanthanide element, and the doping element B is cerium. The total-temperature-domain thermal conductivity of the fully-compact ceramic block prepared by the co-doped modified pyrochlore thermal barrier coating material provided by the invention is 1.0-1.10W/mK, and the material has wide application prospect in the field of high-temperature thermal barrier coatings.
Description
Technical Field
The invention relates to a preparation technology of a high-temperature resistant ceramic material with ultralow thermal conductivity, in particular to an ultralow thermal conductivity co-doped modified pyrochlore thermal barrier coating material and a preparation method thereof.
Background
Thermal Barrier Coating (TBC) refers to a ceramic Coating system with excellent Thermal insulation properties deposited on the surface of a high temperature resistant alloy component, such as an aircraft engine hot end component. The application of the high-temperature-resistant thrust-weight ratio thrust bearing can obviously reduce the working temperature of the base body, protect the metal base body from being eroded by high-temperature fuel gas, prolong the high-temperature working life of the metal base body and further improve the thrust force and the thrust-weight ratio of an aeroengine. Thermal barrier coating materials need to have low thermal conductivity, high melting point, high chemical stability, a coefficient of thermal expansion matched to that of the metal substrate, and good resistance to sintering. The thermal barrier coating material has excellent temperature resistance and excellent thermal insulation performance, and is the core performance requirement of the thermal barrier coating material.
With the development of a new generation of aeroengine, the thrust and thrust-weight ratio of the new generation of aeroengine is continuously improved, so that the temperature of the front inlet of a turbine of the new generation of aeroengine is continuously improved, for example, the temperature of the front inlet of the turbine of the currently researched four generation of aeroengine exceeds 1500 ℃, while the temperature of the front inlet of the turbine of the five generation of aeroengine exceeds 1700 ℃, but the service temperature of the traditional t' -YSZ thermal barrier coating is generally considered not to exceed 1200 ℃, the application requirements are difficult to meet, and a high-temperature thermal barrier coating material with more excellent temperature resistance needs to be developed. Currently, rare earth zirconates RE 2 Zr 2 O 7 Is considered by the academia as the most promising high-temperature thermal barrier coating material. It has the following advantages: 1) Excellent heat resistance, pyrochlore/fluorite type cubic phase rare earth zirconate RE 2 Zr 2 O 7 Generally, a single phase is maintained from room temperature to its melting point, and its melting point is generally close to or even exceeds 2000 ℃; 2) The thermal conductivity is relatively low; 3) A lower oxygen transmission rate, which is advantageous for retarding the growth of thermally grown oxide layer (TGO), which is advantageous for extending its lifetime; 4) Pyrochlore/fluorite type cubic phase rare earth zirconate RE 2 Zr 2 O 7 The material has a very open crystal lattice, that is, the RE site (or called A site) and the Zr site (or called B site) can be replaced by atoms with similar chemical properties, so that the thermophysical properties (i.e. thermal conductivity, thermal expansion coefficient and the like) can be further designed and regulated, thereby better meeting the requirements of the thermal barrier coating on the material properties.
The open lattice structure of the rare earth zirconate provides freedom for the design and performance optimization of the material. In view of the extreme importance of the thermal insulation performance of the thermal barrier coating material, namely, the improvement of the thermal insulation performance is directly related to the improvement of the front inlet temperature of the turbine, so that the thrust and thrust-weight ratio of the aircraft engine are improved. Accordingly, there is a continuing need in the industry for high temperature thermal barrier coating materials having ultra-low thermal conductivity.
Disclosure of Invention
The invention aims to provide an ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material based on cubic-phase pyrochlore rare earth zirconate RE 2 Zr 2 O 7 By adopting the lattice regulation and control technology, appropriate doped ions are introduced into the RE position and the Zr position simultaneously, so that the thermal conductivity of the thermal barrier coating is obviously reduced, the thermal insulation performance of the thermal barrier coating at the service temperature is effectively improved, and the thrust and thrust-weight ratio of the aircraft engine are finally improved.
In order to achieve the purpose, the invention provides an ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material which has the following chemical composition: (RE) 1-x A x ) 2 (Zr 1-y B y ) 2 O 7 ，
Wherein A is 3+ Substituted REPosition, substituted ion A 3+ Has an ionic radius smaller than that of the original ion RE 3+ ，B 4+ Substitution of Zr site, substitution of ion B 4+ Has an ionic radius larger than that of the original ion Zr 4+ ；
When substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the small is not more than 5%, 0<x is less than or equal to 0.5; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the particle size is 10-15%, 0<x is less than or equal to 0.4; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When it is smaller than 20%, 0<x<0.05；
The substituted ion B 4+ Of Zr is larger than the original ion 4+ 15 to 20 percent larger, and the value of y is 0<y≤0.4；
After substitution, the ratio of the RE site ion radius to the Zr site ion radius is between 1.46 and 1.78;
RE is any rare earth element, and the doping element A is yttrium or scandium or bismuth or indium or any lanthanide element.
Further, the doping element a may be any one of lanthanoids of 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), and may also be any one of yttrium (Y), scandium (Sc), bismuth (Bi), and indium (In); the RE is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and scandium; the doping element B is cerium.
Further, the ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material is prepared into a 100% density ceramic block, and the full-temperature-range thermal conductivity of the ceramic block is 1.0-1.10W/m K.
Further, the thermal barrier coating prepared from the ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material by adopting a plasma spraying process is suitable for the temperature of room temperature to 1700 ℃.
The invention also provides a preparation method of the ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material, which comprises the following steps of:
step one, A 2 O 3 ,RE 2 O 3 ,ZrO 2 ,BO 2 Weighing the powder according to the molar ratio of (1-x) x (1-y) y, performing high-energy ball milling on the powder in a high-energy ball milling tank by using distilled water as a medium, freeze-drying the obtained powder slurry, and calcining the powder slurry at high temperature to enable the mixed oxides to fully react to generate the required component (RE) 1-x A x ) 2 (Zr 1-y B y ) 2 O 7 ；
Step two, fully crushing the components obtained in the step one in a mortar, then carrying out high-energy ball milling, and freeze-drying the obtained slurry to obtain well-dispersed powder;
and step three, cold press molding and sintering the powder obtained in the step two to prepare the ultralow-thermal-conductivity modified pyrochlore thermal barrier coating material with the density of more than 99%.
Furthermore, in the step one, the calcining temperature is 1300-1500 ℃, and the calcining time is 20-24 hours.
Furthermore, in the first step and the second step, the rotation speed of the high-energy ball mill is 300-500 r/min, and the ball milling time is 10-24 hours.
Further, in the third step, the cold press molding pressure is 50-200 MPa, the sintering temperature is 1500-1700 ℃, and the heat preservation time is 1-3 hours.
The invention has the following beneficial effects:
the invention provides an ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material based on cubic-phase pyrochlore rare earth zirconate RE 2 Zr 2 O 7 The lattice regulation technology, namely, appropriate doping ions are introduced into the RE site and the Zr site simultaneously, so that the thermal conductivity of the material can be obviously reduced. The RE bit doping is to introduce doping ions with smaller sizes (or weaker combination with the surroundings) at the RE bit so as to introduce harmonic oscillator resonance scattering phonon effect; the Zr site doping refers to introducing doping ions (including but not limited to Ce) with larger size at the Zr site 4+ ) A softening lattice effect is formed. The softening lattice effect of introducing larger-sized dopant ions at Zr site is mainly based on ZrO 6 Octahedron forms skeleton of cubic pyrochlore phase and has larger sizeIon B 4+ The introduction of (2) weakens the B-O bonding strength, namely, the pyrochlore crystal framework is softened, so that a softening lattice effect is formed. After the harmonic oscillator is introduced into the RE position, the non-resonance of lattice vibration is increased; meanwhile, large-size doping ions are introduced into the Zr position to form a softening lattice effect, and under the superposition of the two effects, the co-doped pyrochlore is enabled to have extremely low thermal conductivity k of a high-temperature lattice platform region min (i.e., high temperature lattice thermal conductivity). Wherein the high temperature lattice platform region thermal conductivity k min And (E/Ma gamma) 0.5 In proportion, where E is the modulus of elasticity of the crystal, M and a 3 The average atomic mass and the volume in the crystal are respectively, and gamma is a parameter for representing the vibration and non-resonance of the crystal lattice. The above shows that proper doping ions are introduced into the RE site and the Zr site simultaneously to form the cubic phase pyrochlore rare earth zirconate RE 2 Zr 2 O 7 The thermal barrier coating has lower thermal conductivity at high temperature, which obviously is beneficial to further improving the thermal insulation performance of the thermal barrier coating at high service temperature.
In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 shows the thermal conductivity curves of example 3 and comparative examples 1 to 3 as a function of temperature;
figure 2 shows the thermal conductivity versus temperature curves for example 3 and comparative examples 1, 4 and 5.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
The invention provides an ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material which comprises the following chemical components: (RE) 1-x A x ) 2 (Zr 1-y B y ) 2 O 7 ，
Wherein A is 3+ Substituted RE position, substituted ion A 3+ Has an ionic radius smaller than that of the original ion RE 3+ ，B 4+ Substitution of Zr site, substitution of ion B 4+ Has an ionic radius larger than that of the original ion Zr 4+ ；
When substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the small is not more than 5%, 0<x is less than or equal to 0.5; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the grain size is 10-15%, 0<x is less than or equal to 0.4; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When it is smaller than 20%, 0<x<0.05；
Substituted ion B 4+ Has an ionic radius larger than that of the original ion Zr 4+ When the size is 15% -20%, the value of y is as follows: 0<y≤0.4；
After substitution, the ratio of the average ionic radius of the RE site to the average ionic radius of the Zr site is between 1.46 and 1.78; the average ionic radius of RE sites is the original ion RE 3+ And a substituent ion A 3+ Average ionic radius of Zr site is original ion Zr 4+ And a substituent ion B 4+ Average ionic radius of (a).
RE is any rare earth element, and the doping element A is yttrium or scandium or bismuth or indium or any lanthanide element.
Further, the doping element a may be any one of lanthanoids of 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), and may also be any one of yttrium (Y), scandium (Sc), bismuth (Bi), and indium (In). Doping element B includes but is not limited to Ce 4+ 。
Example 1:
low-thermal-conductivity Y-and Ce-codoped modified La 2 Zr 2 O 7 Pyrochlore ((La) 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 X = y = 0.1) a method for producing a solid solution, comprising the steps of:
(1) Y with particle size not more than 10 μm 2 O 3 ,La 2 O 3 ,ZrO 2 ,CeO 2 Weighing the powder according to a preset proportion, ball-milling the powder in a high-energy ball-milling tank at a speed of 400r/min for 24 hours by using distilled water as a medium, freeze-drying the obtained powder slurry, and calcining the powder slurry at 1500 ℃ for 24 hours to ensure that the mixed oxides fully react to generate the required component (La) 0.9 Y 0.1 ) 2 (Zr 0.9 Ce 0.1 ) 2 O 7 ；
(2) Fully crushing the obtained components in a mortar, then carrying out ball milling for 24 hours at the speed of 400r/min by using distilled water as a medium, and freeze-drying the obtained slurry to obtain well-dispersed powder;
(3) Finally, the obtained powder is subjected to cold press molding under the pressure of 100MPa, and then is sintered at 1500 ℃ for heat preservation for 2 hours to prepare the ceramic block body with the density of more than 99%.
Example 2:
low-thermal-conductivity Y-and Ce-codoped modified La 2 Zr 2 O 7 Pyrochlore (La) 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 The same procedure as in example 1 was repeated, except that x =0.2 and y =0.3 were used for the preparation of the solid solution.
Example 3:
low-thermal-conductivity Y-and Ce-codoped modified La 2 Zr 2 O 7 Pyrochlore (La) 1-x Y x ) 2 (Zr 1-y Ce y ) 2 O 7 The solid solution was prepared by the same method as in example 1 except that x = y = 0.3.
Example 4:
nd-and Ce-codoped modified La with low thermal conductivity 2 Zr 2 O 7 Pyrochlore (La) 1-x Nd x ) 2 (Zr 1-y Ce y ) 2 O 7 (x = y = 0.1) method for producing a solid solution. By Nd 2 O 3 Powder replacement of Y 2 O 3 The powder was otherwise the same as in example 1.
Example 5:
a kind of lowerThermal conductivity Nd-and Ce-codoped modified La 2 Zr 2 O 7 Pyrochlore (La) 1-x Nd x ) 2 (Zr 1-y Ce y ) 2 O 7 The preparation method of the solid solution is the same as that of example 4 except that x = y = 0.2.
Example 6:
nd-and Ce-codoped modified La with low thermal conductivity 2 Zr 2 O 7 Pyrochlore (La) 1-x Nd x ) 2 (Zr 1-y Ce y ) 2 O 7 The solid solution was prepared by the same method as in example 4 except that x = y = 0.3.
Comparative example 1: (undoped La) 2 Zr 2 O 7 )
Comparative example 1 is different from example 1 in that it does not contain any doping element, and the others are the same as example 1.
Comparative example 2: (use only A-site Y doping)
Comparative example 2 differs from example 3 in that Y-site doping is applied only to the A site, and B-site doping is not applied, and the other example is the same as example 3, namely (La) 0.7 Y 0.3 ) 2 Zr 2 O 7 。
Comparative example 3: (doping with only B-site Ce)
Comparative example 3 differs from example 3 in that only the B site is doped with Ce and not the A site is doped with Y, otherwise the method is the same as example 3, i.e. La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 。
Comparative example 4:
in comparative example 4, the B site was substituted for Zr with a small size of a strongly bonded Hf, the same as in example 3, i.e., (La) 0.7 Y 0.3 ) 2 (Zr 0.7 Hf 0.3 ) 2 O 7 。
Comparative example 5:
in comparative example 5, the B site was substituted for Zr with small size strongly bonded Ti, which was otherwise the same as in example 3, i.e. (La) 0.7 Y 0.3 ) 2 (Zr 0.7 Ti 0.3 ) 2 O 7 。
FIG. 1 shows the thermal conductivity curves of example 3 and comparative examples 1 to 3 as a function of temperature. By contrast, the following can be found: by introducing small-sized doped ions into the A site of pyrochlore, and by utilizing the special crystal structure of the pyrochlore and the local resonance of the pyrochlore in an abnormally large 'atom cage' in crystal lattices, phonons are strongly scattered, the thermal conductivity in a medium and low temperature range can be effectively reduced, namely the thermal conductivity of the corresponding pyrochlore solid solution loses the temperature dependence. In fact, in ceramic materials, the heat transfer is achieved by lattice vibrations; and the quantization of lattice vibrations is a phonon. The phonon free path determines the thermal conductivity of the material. For ceramic materials with point defects, the phonon free path (Λ) can be generally expressed by the following formula:
Λ -1 ＝Λ U -1 +Λ D -1 +Λ rattler -1 (1)
wherein, Λ U ,Λ D ,Λ rattler The mean free path generated by phonon-phonon inverse scattering, phonon-point defect scattering and phonon-resonator scattering respectively. When no point defect is present in the material, its thermal conductivity depends on the mean free path generated by phonon-phonon back-scattering (i.e. Λ) U ) And Λ U ∝ω -2 T -1 (where ω is the phonon vibration frequency and T is the temperature). It can be seen that U Inversely proportional to temperature, this also explains that the thermal conductivity of most ceramic materials generally decreases with increasing temperature when point defects are not present, i.e., la in FIG. 1 2 Zr 2 O 7 Thermal conductivity-temperature curve; while mean free for point defect-phonon scattering Cheng D Which is dependent only on the phonon vibration frequency, i.e. Λ D ∝ω -4 This is due to the analogy of point defects-phonon scattering to rayleigh scattering, which also explains that the thermal conductivity-temperature curve of doped solid solutions becomes relatively flat in the presence of point defects, which corresponds to La in fig. 1 2 (Zr 0.7 Ce 0.3 ) 2 O 7 Thermal conductivity-temperature curve; while mean free Cheng for resonator-phonon scattering rattler Can be represented by the following formula:
Λ rattler ＝C(ω R 2 -ω 2 ) 2 /ω 2 (2)
wherein C is a constant, ω R Is the resonant frequency. Represented by formula (2), Λ rattler Is also only related to the phonon vibration frequency and is not related to the temperature, and can strongly scatter phonon frequency at omega R Nearby phonons, which are seen to be a strong source of phonon scattering. In the presence of strong phonon scattering source, the total phonon free path of the material is determined by the phonon free path generated by the strong phonon scattering source, i.e. in formula (1), Λ rattler -1 Is decisive and is temperature independent, which even masks Λ U -1 So that the thermal conductivity-temperature curve in the presence of the resonator in the crystal lattice can be approximated as a straight line parallel to the temperature axis, i.e., corresponding to (La) in FIG. 1 0.7 Y 0.3 ) 2 Zr 2 O 7 And (La) 0.7 Y 0.3 ) 2 (Zr 0.7 Ce 0.3 ) 2 O 7 Thermal conductivity-temperature curve of (a).
Although the thermal conductivity-temperature curve can be made parallel to the temperature axis (i.e., does not change with temperature) by introducing smaller sized dopant ions at the a-site, a strong phonon scattering source, the resonator, in the pyrochlore lattice, its plateau value k min But is more affected by the B-site doping. Thermal conductivity high temperature plateau value (k) min ) The phonon mean free path of the ceramic material gradually approaches to the atomic mean spacing Lambda in the crystal lattice after the ceramic material exceeds a certain temperature 0 Its volumetric heat capacity C V Also gradually approaches its limit value (3 k) B /a 3 ) Wherein k is B Is Boltzmann constant, a 3 Is the average atomic size in the lattice, in particular k min Can be represented by the following formula:
where v is the average speed of sound. Since the parameters a, v, etc. are almost independent of temperature, the thermal conductance of the high temperature plateau regionRate k min It can be considered independent of temperature. In fact, k min Determines the lattice thermal conductivity of the ceramic material at high temperature, and has outstanding significance for high-temperature service materials such as thermal barrier coatings and the like. Further, k is min Can be expressed as:
wherein E is the elastic modulus of the crystal lattice, M is the average atomic mass in the crystal lattice, and gamma is Gr ü neisen constant (representing the non-resonance property of the vibration of the crystal lattice). E and M in formula (4) can be further regulated and controlled through doping.
Since the pyrochlore lattice can be seen as the formation of the framework by the stacking of BO6 octahedra sharing vertices, a 3+ The BO6 octahedron determines the elastic modulus of pyrochlore crystal lattices to a certain extent, and the bonding strength of B-O bonds has a large influence on the elastic modulus of the crystal lattices. As shown in FIG. 2, under the premise of introducing 30% of Y doping into both A sites of pyrochlore lattices, 30% of different doping elements including Ce, hf and Ti are doped into B sites, and significantly different k is obtained min The value is obtained. This is mainly based on the introduction of different doping elements in the B site, resulting in different effects on the elastic modulus of the pyrochlore lattice. Since the B-O bond is typically an ionic bond, the bond energy is determined by the following formula:
E∝M a /r 0 4 (5) Wherein M is a Is Madelung constant, r 0 Is the ion spacing. When doped with introduced phase ratio Zr 4+ Larger ions, e.g. Ce 4+ ，r 0 Significantly increased, E is significantly decreased (i.e., the lattice becomes soft); in contrast, when doping is introduced compared to Zr 4+ Smaller ions, e.g. Hf 4+ And Ti 4+ Then r is 0 Decreasing, E increases (i.e., lattice hardening). Therefore, large-size doping ions are introduced into the B site of pyrochlore to realize the softening effect of the crystal lattice, and the method is very critical to reducing the thermal conductivity of the crystal lattice in a high-temperature platform region.
It should be noted that patent document CN102070335a adopts Ce dopingModified La 2 Zr 2 O 7 A reduction in thermal conductivity (down to 1.5W/m · K) and an increase in the coefficient of thermal expansion of the thermal conductivity are achieved. The invention adopts a mode of co-doping A site and B site, small-size doped ions are introduced into the A site, large-size doped ions are introduced into the B site, and the doping of the A site introduces a resonator phonon scattering effect (namely a strong phonon scattering source), so that the thermal conductivity in a medium and low temperature range is obviously reduced, and the thermal conductivity after doping is not changed along with the change of temperature; through the doping of the B site, softening effect (namely, the elastic modulus of the crystal lattice is obviously reduced) is generated on the pyrochlore crystal lattice, and the obvious reduction of the thermal conductivity of the crystal lattice in the high-temperature platform region is realized. Through the two functions, the preparation of the ultralow-thermal-conductivity co-doped modified pyrochlore rare earth zirconate material is realized, and the thermal conductivity can be as low as 1.1W/m.K. It is worth noting that since the successful introduction of the resonator mainly depends on an abnormally large atomic cage in a pyrochlore crystal structure, the ultralow thermal conductivity in the whole temperature range is realized by co-doping the A site and the B site, and the ratio of the RE site average ionic radius to the Zr site average ionic radius is required to be between 1.46 and 1.78 after doping, namely the ratio is in the pyrochlore phase stability interval.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. An ultra-low thermal conductivity co-doped modified pyrochlore thermal barrier coating material is characterized in that,
has the following chemical composition: (RE) 1-x A x ) 2 (Zr 1-y B y ) 2 O 7 ，
Wherein A is 3+ Substituted RE position, substituted ion A 3+ Has an ionic radius smaller than that of the original ion RE 3+ ，B 4+ Substituted in Zr position, substituted ion B 4+ Has an ionic radius larger than that of the original ion Zr 4+ ；
When substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the size is less than or equal to 5 percent, x is more than 0 and less than or equal to 0.5; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the size is 10 to 15 percent, x is more than 0 and less than or equal to 0.4; when substituting the ion A 3+ Ion radius ratio of (2) to the original ion RE 3+ When the size is more than 20%, x is more than 0 and less than 0.05;
the substituted ion B 4+ Of Zr is larger than the original ion 4+ 15 to 20 percent of the total weight of the powder, and the value of y is more than 0 and less than or equal to 0.4;
after substitution, the ratio of the RE site ion radius to the Zr site ion radius is 1.46-1.78, and the obtained material is pyrochlore phase;
RE is any rare earth element, and the doping element A is yttrium or scandium or bismuth or indium or any lanthanide element; the doping element B is cerium;
the full-temperature-range thermal conductivity of the 100% density ceramic block prepared from the ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material is 1.0-1.10W/mK;
the thermal barrier coating prepared from the ultralow-thermal-conductivity co-doped modified pyrochlore thermal barrier coating material by adopting a plasma spraying process is suitable for the temperature from room temperature to 1700 ℃.
2. The ultra-low thermal conductivity co-doped modified pyrochlore thermal barrier coating material of claim 1, wherein RE is any one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium; the doped element A is any one lanthanide element of cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, or any one of yttrium, scandium, bismuth and indium.
3. A method for preparing the ultralow thermal conductivity co-doped modified pyrochlore thermal barrier coating material according to claim 1 or 2, comprising the following steps:
step one, A 2 O 3 ，RE 2 O 3 ，ZrO 2 ，BO 2 The powder is prepared according to the molar ratio of (1-x) toWeighing x to (1-y) to y, high-energy ball milling in a high-energy ball milling tank with distilled water as medium, freeze drying the obtained powder slurry, calcining to make the mixed oxides fully react to generate the required component (RE) 1-x A x ) 2 (Zr 1-y B y ) 2 O 7 ；
Step two, fully crushing the components obtained in the step one in a mortar, then carrying out high-energy ball milling, and freeze-drying the obtained slurry to obtain well-dispersed powder;
and step three, cold press molding and sintering the powder obtained in the step two to prepare the ultralow-thermal-conductivity modified pyrochlore thermal barrier coating material with the density of more than 99%.
4. The preparation method according to claim 3, wherein in the first step, the calcination temperature is 1300-1500 ℃, and the calcination time is 20-24 hours.
5. The preparation method of claim 3, wherein in the first step and the second step, the rotation speed of the high-energy ball mill is 300-500 r/min, and the ball milling time is 10-24 hours.
6. The preparation method of claim 3, wherein in the third step, the cold press molding pressure is 50-200 MPa, the sintering temperature is 1500-1700 ℃, and the heat preservation time is 1-3 hours.
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