A non-stoichiometric rare earth zirconate ceramic and a method of making the same

Abstract

The application belongs to the field of zirconate ceramic materials, and particularly relates to a rare earth zirconate ceramic and a preparation method thereof. 1‑x Yb x ) 2+y Zr 2‑y‑ z Hf z O 7‑0.5y , wherein 0

Description

TECHNICAL FIELD

[0001] The application belongs to the field of zirconate ceramic materials, and particularly relates to a rare earth zirconate ceramic and a preparation method thereof. BACKGROUND

[0002] As a kind of complex structure oxide material, rare earth zirconate (RE2Zr2O7, RE = La~Lu, Y) has the characteristics of good temperature resistance and high chemical stability; its thermal conductivity is 2.1 W / (m·K) at 1200℃, which is only 2 / 3 of that of traditional yttria-stabilized zirconia ceramic. If the thermal conductivity can be further reduced and the mechanical properties can be improved through component regulation, the rare earth zirconate ceramic is expected to replace the traditional system and become a new generation of thermal barrier coating material.

[0003] The thermal barrier coating is generally a double-layer structure coating composed of an intermediate metal bonding layer and a ceramic thermal barrier layer, and its excellent thermal barrier performance mainly depends on the surface ceramic layer material. The low thermal conductivity, high temperature resistance and corrosion resistance of the ceramic material can effectively protect the alloy substrate, which also puts forward strict requirements on the selection of the ceramic layer material: high melting point, low thermal conductivity, thermal expansion coefficient matching with the substrate, high fracture toughness, high strain limit, no phase change at high temperature, good corrosion resistance and low sintering rate. Y2O3-ZrO2 (YSZ) with a mass fraction of 6wt.%~8wt.% is widely used in the past few decades due to its high melting point, high temperature oxidation resistance, good high temperature chemical stability, low and stable thermal conductivity, and thermal expansion coefficient close to metal materials. However, with the development of higher performance of aero-engines, the new generation of engines generally requires the turbine inlet temperature to be above 1600℃, and the traditional YSZ material may have phase change failure and serious sintering when the working temperature is above 1250℃. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a rare earth zirconate ceramic and a preparation method thereof. The rare earth zirconate ceramic of the present application can maintain the stability of the phase structure at 1600℃ for 30h, which can meet the needs of thermal barrier coating materials with continuously increasing temperature resistance requirements.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The present application provides a rare earth zirconate ceramic, whose chemical formula is (Gd 1-x Yb x ) 2+y Zr 2-y-z Hf z O 7-0.5y , wherein 0 < x < 0.3, -0.15 < y < 0.15, and y is not equal to 0, and 0 < z < 0.6.

[0007] Preferably, the chemical formula of the rare earth zirconate ceramic is 0.1≤x≤0.25, -0.1≤y≤0.1, and 0≤z≤0.4.

[0008] Preferably, the chemical formula of the rare earth zirconate ceramic includes (Gd 0.7 Yb 0.3 ) 2.15 Zr 1.65 Hf 0.2 O 6.925 , (Gd 0.85 Yb 0.15 ) 1.95 Zr 1.45 Hf 0.6 O 7.025 , (Gd 0.9 Yb 0.1 ) 2.1 Zr 1.5 Hf 0.4 O 6.95 , (Gd 0.85 Yb 0.15 ) 1.95 Zr 2.05 O 7.025 , or (Gd 0.75 Yb 0.25 ) 1.85 Zr 1.75 Hf 0.4 O 7.075 .

[0009] The application further provides a preparation method of the rare earth zirconate ceramic.

[0010] The oxide raw material is mixed with anhydrous ethanol for first ball milling and first drying, and the obtained mixture is pre-fired to obtain a pre-fired powder;

[0011] The pre-fired powder is mixed with anhydrous ethanol for second ball milling and second drying, and the obtained powder is granulated and molded to obtain a green body;

[0012] The green body is degreased and sintered to obtain the rare earth zirconate ceramic.

[0013] Preferably, the rotating speed of the first ball milling is 300-400 r / min, and the time is 12-24 h.

[0014] Preferably, the pre-firing temperature is 1100-1400 ℃, and the time is 2-6 h.

[0015] Preferably, the rotating speed of the second ball milling is 250-450 r / min, and the time is 24-48 h.

[0016] Preferably, the forming method is dry pressing forming, the pressure of the dry pressing forming is 5-10 MPa, and the pressure maintaining time is 1-3 min.

[0017] Preferably, the temperature of the glue discharging is 550-650 ℃, and the holding time is 1-2 h.

[0018] Preferably, the temperature of the sintering is 1500-1700 ℃, and the holding time is 5-10 h.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The present application provides a rare earth zirconate ceramic, the chemical formula of which is (Gd 1-x Yb x ) 2+y Zr 2-y-z Hf z O 7-0.5y , wherein 0 < x ≤ 0.3, -0.15 < y < 0.15, and y is not equal to 0, and 0 ≤ z ≤ 0.6. The rare earth zirconate ceramic of the present application is a non-stoichiometric gadolinium zirconate-based ceramic. When the components deviate from the normal stoichiometric ratio, additional interstitial cations or cation vacancy defects are generated, and the microstructure generated by the defects greatly strengthens the phonon scattering in the heat conduction process, thereby significantly reducing the thermal conductivity of the material. Meanwhile, through ytterbium doping or ytterbium and hafnium co-doping, the materials play a role in optimizing the thermal and mechanical properties in different lattice positions, thereby meeting the needs of thermal barrier coating materials with continuously increasing temperature resistance requirements.

[0021] The present application innovatively combines non-stoichiometric ratio and A-site (or A / B-site) ion doping, so that the thermal physical properties of the ceramic are excellent, and the ceramic has excellent high-temperature phase structure stability. The rare earth zirconate ceramic of the present application has a stable single-phase fluorite structure, and has the advantages of low high-temperature thermal conductivity, high relative density, high hardness, etc. Moreover, the preparation method of the rare earth zirconate ceramic of the present application is simple and convenient for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1 The XRD patterns of the ceramics of Examples 1-5 are shown in the following table:

[0024] Figure 2 The thermal conductivity-temperature relationship curves of the ceramics of Examples 1-5 are shown in the following table:

[0025] Figure 3 Coefficient of thermal expansion of the ceramic of Example 1-5 as a function of temperature;

[0026] Figure 4 Vickers hardness of the ceramic of Example 1-5;

[0027] Figure 5 Young's modulus of the ceramic of Example 1-5;

[0028] Figure 6 Fracture toughness of the ceramic of Example 1-5;

[0029] Figure 7 Thermal conductivity of the ceramic of Example 4 compared to Gd2Zr2O7;

[0030] Figure 8 XRD pattern of the ceramic of Example 4 after high temperature treatment at 1600°C for different times. DETAILED DESCRIPTION

[0031] The present application provides a rare earth zirconate ceramic, with the chemical formula (Gd 1-x Yb x ) 2+y Zr 2-y-z Hf z O 7-0.5y , wherein 0 < x < 0.3, -0.15 < y < 0.15, and y is not equal to 0, 0 < z < 0.6.

[0032] In the present application, the materials and equipment used are commercially available unless otherwise specified.

[0033] In the present application, in the chemical formula, preferably: 0.1 < x < 0.25, more preferably 0.15 < x < 0.2.

[0034] In the present application, in the chemical formula, preferably: -0.1 < y < 0.1, more preferably y = -0.05.

[0035] In the present application, in the chemical formula, preferably: 0 < z < 0.4, specifically preferably 0, 0.2 or 0.4.

[0036] In the present application, the chemical formula of the rare earth zirconate ceramic preferably includes (Gd 0.7 Yb 0.3 ) 2.15 Zr 1.65 Hf 0.2 O 6.925 , (Gd 0.85 Yb 0.15 ) 1.95 Zr 1.45 Hf0.6 O 7.025 、(Gd 0.9 Yb 0.1 ) 2.1 Zr 1.5 Hf 0.4 O 6.95 、(Gd 0.85 Yb 0.15 ) 1.95 Zr 2.05 O 7.025 or (Gd) 0.75 Yb 0.25 ) 1.85 Zr 1.75 Hf 0.4 O 7.075 .

[0037] In this invention, the rare-earth zirconate ceramic is a non-stoichiometric rare-earth gadolinium zirconate-based ceramic with a single-phase fluorite structure. It utilizes the additional interstitial cations or cation vacancy defects generated when the composition deviates from the normal stoichiometric ratio, and the resulting microstructure, to significantly enhance phonon scattering during heat conduction, thereby significantly reducing the material's thermal conductivity. Furthermore, the thermal and mechanical properties of the material are optimized through ytterbium doping or ytterbium-hafnium co-doping. However, if other rare-earth elements are selected for doping, some performance improvements may be accompanied by a decrease in other performance characteristics; for example, Ce doping may reduce the stability of the ceramic.

[0038] The non-stoichiometric rare earth zirconate ceramic of this invention has a relative density greater than 98%, a hardness of 11.99–12.74 GPa, and a coefficient of thermal expansion of 10.33–10.82 × 10⁻⁶. -6 K -1 The thermal conductivity at room temperature is 1.48–1.93 W / (m·K), and the thermal conductivity at 1200℃ is 1.68–1.94 W / (m·K).

[0039] This invention also provides a method for preparing the rare earth zirconate ceramics described in the above technical solution, comprising the following steps:

[0040] The oxide raw material is mixed with anhydrous ethanol and subjected to a first ball milling and a first drying. The resulting mixture is then pre-calcined to obtain a pre-calcined powder.

[0041] The pre-calcined powder is mixed with anhydrous ethanol and subjected to a second ball milling and a second drying. The resulting powder is then granulated and shaped to obtain a green body.

[0042] The blank is debinded and sintered to obtain the rare earth zirconate ceramic.

[0043] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0044] The oxide raw material is mixed with anhydrous ethanol to perform first ball milling and first drying, and the obtained mixture is pre-fired to obtain a pre-fired powder.

[0045] In the present application, the oxide raw material comprises zirconium oxide and rare earth oxide, the rare earth oxide preferably comprises gadolinium oxide and ytterbium oxide, and when z is not equal to 0, it further comprises hafnium oxide.

[0046] In the present application, the zirconium oxide is preferably nano zirconium oxide, the particle size of the nano zirconium oxide is preferably 20-50 nm, and the purity is preferably greater than 99.9%. The zirconium oxide and the gadolinium oxide in the rare earth oxide are the matrix material, and together form the basic gadolinium zirconate ceramic structure.

[0047] In the present application, the rare earth oxide is preferably nano rare earth oxide, the particle size of the nano rare earth oxide is preferably 20-50 nm, and the purity is preferably greater than 99.9%. The ytterbium oxide and the hafnium oxide in the rare earth oxide optimize the gadolinium zirconate ceramic, and play a role in optimizing the thermal and mechanical properties of the material in different lattice positions.

[0048] In the present application, the molar ratio of the rare earth oxide and the zirconium oxide in the component is adjusted, and the molar ratio is controlled to be greater than 1 or less than 1, so as to realize the deviation of the stoichiometric ratio.

[0049] In the present application, the mass ratio of the oxide raw material and anhydrous ethanol is preferably 1:2.

[0050] In the present application, the rotation speed of the first ball milling is preferably 300-400 r / min, the time is preferably 12-24 h, more preferably 15-20 h, and more preferably 18 h. The temperature of the first drying is preferably 60℃, and the time is preferably 24 h. The rotation speed and the time of the first ball milling in the present application can make the raw materials uniformly mixed.

[0051] In the present application, the temperature of the pre-firing is preferably 1100-1400℃, more preferably 1250-1350℃, and more preferably 1300℃, and the time is preferably 2-6 h, more preferably 2.5-4 h, and more preferably 3 h. The temperature rising program of the pre-firing comprises: rising from room temperature to 1000℃ at a temperature rising rate of 5-10℃ / min, and then rising to the temperature of the pre-firing at a temperature rising rate of 2-4℃ / min. In the pre-firing process, the raw materials are preliminarily reacted to synthesize zirconate.

[0052] After obtaining the pre-fired powder, the pre-fired powder is mixed with anhydrous ethanol to perform second ball milling and second drying, and the obtained powder is granulated and formed to obtain a green body.

[0053] In the present application, the rotation speed of the second ball milling is preferably 250-450 r / min, more preferably 300-400 r / min, and the time is preferably 24-48 h, more preferably 36 h. The temperature of the second drying is preferably 60℃, and the time is preferably 24 h.

[0054] In the present application, the obtained powder is mixed with a polyvinyl alcohol solution before granulation. The method for the granulation is not particularly limited in the present application, and any method commonly used by those skilled in the art can be used to obtain granules with uniform particle size (0.15-0.25 mm). The concentration of the polyvinyl alcohol solution is preferably 8-10 wt.%, and the mass ratio of the polyvinyl alcohol solution to the powder is preferably 3:10-3:20.

[0055] In the present application, the method for the molding is preferably dry pressing, and the pressure of the dry pressing is preferably 5-10 MPa, and the pressure holding time is preferably 1-3 min. In specific embodiments of the present application, the pressure holding time is 2 min at 6 MPa, 1 min at 7 MPa, 3 min at 5 MPa, or 2 min at 8 MPa.

[0056] After obtaining the green body, the green body is degreased and sintered to obtain the rare earth zirconate ceramic.

[0057] In the present application, the temperature of the degreasing is preferably 550-650℃, more preferably 600-630℃, the holding time is preferably 1-2 h, and the heating rate from room temperature to the degreasing temperature is preferably 0.5-2℃ / min, more preferably 1-1.5℃ / min. In specific embodiments of the present application, the holding time is 2 h at 550℃ with a heating rate of 1℃ / min, 1 h at 650℃ with a heating rate of 0.5℃ / min, 1 h at 600℃ with a heating rate of 2℃ / min, 1 h at 630℃ with a heating rate of 1.5℃ / min, or 1 h at 600℃ with a heating rate of 1℃ / min. The degreasing removes the organic matter.

[0058] In the present application, the sintering temperature is preferably 1500-1700°C, more preferably 1550-1650°C, and even more preferably 1600°C, the holding time is preferably 5-10h, more preferably 8h, and the heating rate from the degassing temperature to the sintering temperature is preferably 5-10°C / min, more preferably 8°C / min. In a specific embodiment of the present application, the holding time is 10h at 1550°C with a heating rate of 5°C / min, 10h at 1600°C with a heating rate of 5°C / min, 8h at 1650°C with a heating rate of 8°C / min, 5h at 1700°C with a heating rate of 5°C / min, or 10h at 1500°C with a heating rate of 10°C / min. In the sintering procedure of the present application, the bulk shrinks to form a dense non-stoichiometric rare earth zirconate ceramic.

[0059] In order to further illustrate the present application, the rare earth zirconate ceramic and the preparation method thereof provided by the present application are described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present application.

[0060] Example 1

[0061] 109.11g of nano gadolinium oxide, 50.84g of nano ytterbium oxide, 16.84g of nano hafnium oxide, 81.32g of nano zirconium oxide, and 516.22g of anhydrous ethanol were mixed for 12h of ball milling, and a uniform mixture was obtained after drying; the mixture was placed in a box furnace and calcined at 1300°C for 3h to obtain a non-stoichiometric rare earth zirconate ceramic (Gd 0.7 Yb 0.3 ) 2.15 Zr 1.65 Hf 0.2 O 6.925 The non-stoichiometric rare earth zirconate pre-sintered powder was mixed with anhydrous ethanol and ball milled at a rotation speed of 450r / min for 24h, and a pre-sintered powder was obtained by drying at 60°C. The pre-sintered powder was mixed with a polyvinyl alcohol aqueous solution, granulated, and dry-pressed into a green body under a pressure of 6MPa for 2min. The green body was degassed at 550°C for 2h with a heating rate of 1°C / min, and then sintered at 1550°C for 10h with a heating rate of 5°C / min to obtain a non-stoichiometric rare earth zirconate ceramic.

[0062] The non-stoichiometric rare earth zirconate ceramic (Gd 0.7 Yb 0.3 ) 2.15 Zr 1.65 Hf 0.2 O 6.925The phase structure of the non-stoichiometric rare earth zirconate ceramic is single-phase fluorite structure, the relative density is 98.76%, the hardness is 11.99 GPa, the Young's modulus is 236 GPa, the fracture toughness is 1.29 MPa·m 1 / 2 , the thermal expansion coefficient is 10.71×10 -6 K -1 , the room temperature thermal conductivity is 1.93 W / (m·K), and the thermal conductivity at 1200℃ is 1.94 W / (m·K).

[0063] Example 2

[0064] 120.17g of nano gadolinium oxide, 23.05g of nano ytterbium oxide, 50.52g of nano hafnium oxide, 71.47g of nano zirconium oxide and 530.42g of anhydrous ethanol are mixed for 24h ball milling, and a uniform mixture is obtained after drying; the mixture is placed in a box furnace and calcined at 1250℃ for 4h to obtain (Gd 0.85 Yb 0.15 ) 1.95 Zr 1.45 Hf 0.6 O 7.025 The non-stoichiometric rare earth zirconate pre-sintered powder is mixed with anhydrous ethanol and ball milled at a speed of 300r / min for 48h, and the pre-sintered powder is obtained by drying at 60℃, mixed with polyvinyl alcohol aqueous solution for granulation, and dry pressed into a green body under a pressure of 7MPa for 1min, then the green body is heated at a rate of 0.5℃ / min to 650℃ for 1h to remove the binder, and the green body after binder removal is heated at a rate of 5℃ / min to 1600℃ for 10h to obtain the non-stoichiometric rare earth zirconate ceramic.

[0065] The (Gd 0.85 Yb 0.15 ) 1.95 Zr 1.45 Hf 0.6 O 7.025 The phase structure of the non-stoichiometric rare earth zirconate ceramic is single-phase fluorite structure, the relative density is 98.76%, the hardness is 11.99 GPa, the Young's modulus is 236 GPa, the fracture toughness is 1.29 MPa·m 1 / 2 , the thermal expansion coefficient is 10.71×10 -6 K -1 , the room temperature thermal conductivity is 1.93 W / (m·K), and the thermal conductivity at 1200℃ is 1.94 W / (m·K).

[0066] Example 3

[0067] The 137.03 g nanometer gadolinium oxide, 16.55 g nanometer ytterbium oxide, 33.68 g nanometer hafnium oxide, 73.93 g nanometer zirconium oxide and 522.37 g anhydrous ethanol are mixed for 18 h ball milling, and a uniform mixture is obtained after drying; the mixture is placed in a box furnace and calcined at 1400℃ for 2 h to obtain (Gd 0.9 Yb 0.1 ) 2.1 Zr 1.5 Hf 0.4 O 6.95 The non-stoichiometric rare earth zirconate pre-fired powder is mixed with anhydrous ethanol and ball milled at a speed of 250 r / min for 48 h, dried at 60℃ to obtain a pre-fired powder, mixed with polyvinyl alcohol aqueous solution to granulate, and dry pressed at 10 MPa for 1 min, then the green body is heated at a rate of 2℃ / min to 600℃ for 1 h to remove the binder, and then heated at a rate of 8℃ / min to 1650℃ for 8 h to obtain a non-stoichiometric rare earth zirconate ceramic.

[0068] The (Gd 0.9 Yb 0.1 ) 2.1 Zr 1.5 Hf 0.4 O 6.95 The phase structure of the non-stoichiometric rare earth zirconate ceramic is single-phase fluorite structure, the relative density is 98.88%, the hardness is 12.74 GPa, the Young's modulus is 225 GPa, the fracture toughness is 1.04 MPa·m 1 / 2 , the thermal expansion coefficient is 10.33×10 -6 K -1 , the room temperature thermal conductivity is 1.74 W / (m·K), and the thermal conductivity at 1200℃ is 1.84 W / (m·K).

[0069] Example 4

[0070] The 120.17 g nanometer gadolinium oxide, 23.05 g nanometer ytterbium oxide, 101.04 g nanometer zirconium oxide and 488.52 g anhydrous ethanol are mixed for 20 h ball milling, and a uniform mixture is obtained after drying; the mixture is placed in a box furnace and calcined at 1350℃ for 2.5 h to obtain (Gd 0.85 Yb 0.15 ) 1.95 Zr 2.05 O 7.025The non-stoichiometric rare earth zirconate pre-sintered powder is mixed with anhydrous ethanol and ball milled at a rotating speed of 400 r / min for 36 h, dried at 60 ℃ to obtain the pre-sintered powder material, mixed with a polyvinyl alcohol aqueous solution to granulate, dry-pressed to form a green body at 5 MPa for 3 min, then the green body is heated at a temperature increasing speed of 1.5 ℃ / min at 630 ℃ for 1 h to remove the binder, and then the binder-removed green body is heated at a temperature increasing speed of 5 ℃ / min at 1700 ℃ for 5 h to obtain the non-stoichiometric rare earth zirconate ceramic.

[0071] The (Gd 0.85 Yb 0.15 ) 1.95 Zr 2.05 O 7.025 The phase structure of the non-stoichiometric rare earth zirconate ceramic is a single-phase fluorite structure, the relative density is 98.77%, the hardness is 12.64 GPa, the Young's modulus is 225 GPa, the fracture toughness is 1.02 MPa·m 1 / 2 , the thermal expansion coefficient is 10.82×10 -6 K -1 , the thermal conductivity at room temperature is 1.48 W / (m·K), and the thermal conductivity at 1200 ℃ is 1.68 W / (m·K).

[0072] Example 5

[0073] 100.59 g of nano gadolinium oxide, 36.45 g of nano ytterbium oxide, 33.68 g of nano hafnium oxide, 86.25 g of nano zirconium oxide, and 513.94 g of anhydrous ethanol are mixed and ball milled for 15 h, and after drying, a uniform mixture is obtained; the mixture is placed in a box furnace and calcined at 1100 ℃ for 6 h to obtain (Gd 0.75 Yb 0.25 ) 1.85 Zr 1.75 Hf 0.4 O 7.075 The non-stoichiometric rare earth zirconate pre-sintered powder is mixed with anhydrous ethanol and ball milled at a rotating speed of 400 r / min for 36 h, dried at 60 ℃ to obtain the pre-sintered powder material, mixed with a polyvinyl alcohol aqueous solution to granulate, dry-pressed to form a green body at 5 MPa for 3 min, then the green body is heated at a temperature increasing speed of 1.5 ℃ / min at 630 ℃ for 1 h to remove the binder, and then the binder-removed green body is heated at a temperature increasing speed of 5 ℃ / min at 1700 ℃ for 5 h to obtain the non-stoichiometric rare earth zirconate ceramic.

[0074] The (Gd 0.75 Yb 0.25 ) 1.85 Zr 1.75 Hf 0.4 O7.075 The phase structure of the non-stoichiometric rare earth zirconate ceramic is a single-phase fluorite structure, the relative density is 98.48%, the hardness is 12.70 GPa, the Young's modulus is 243 GPa, the fracture toughness is 1.08 MPa·m 1 / 2 , the thermal expansion coefficient is 10.58*10 -6 K -1 , the room temperature thermal conductivity is 1.79 W / (m·K), and the thermal conductivity at 1200 DEG C is 1.94 W / (m·K).

[0075] It can be seen from the above examples that the preparation method provided by the application is simple, the non-stoichiometric rare earth zirconate ceramic prepared has a small high-temperature thermal conductivity, a high density and a large hardness, and the thermal and mechanical properties of the zirconate ceramic material are comprehensively improved, instead of only improving a certain aspect of performance, so that the needs of ceramic materials for thermal barrier coatings can be met.

[0076] Figure 1 The XRD patterns of the ceramics of examples 1-5 are shown in the figure, and 1#-5# in the figure correspond to examples 1-5, respectively. The ceramics of examples 1-5 are all single-phase fluorite structures, and no other impurities exist.

[0077] Figure 2 The thermal conductivity-temperature relationship curves of the ceramics of examples 1-5 are shown, which show that the thermophysical properties of the gadolinium zirconate-based ceramics are successfully optimized. The thermal conductivity of yttria-stabilized zirconia (YSZ) at 800 DEG C is 2.3 W / (m·K), and the thermal conductivity of the rare earth zirconate ceramic prepared in the examples of the application at 800 DEG C is less than 1.7 W / (m·K), so compared with yttria-stabilized zirconia, the thermal conductivity of the non-stoichiometric rare earth zirconate ceramic of the application is greatly reduced.

[0078] Figure 3 The thermal expansion coefficient-temperature relationship curves of the ceramics of examples 1-5 are shown, which show that the thermal expansion coefficients of the ceramics of examples 1-5 in the application are relatively large, and the values of the thermal expansion coefficients at 1200 DEG C are all greater than 10.3*10 -6 K -1 , and some are close to 11*10 -6 K -1 .

[0079] Figure 4 The Vickers hardness of the ceramics of examples 1-5 is shown, which shows that the Vickers hardness of the example ceramics is relatively large, and most of them are greater than 12 GPa, which is beneficial to the use at high temperature.

[0080] Figure 5 The Young's modulus of the ceramics of examples 1-5 is shown, which shows that the Young's modulus of the example ceramics is relatively small, and most of them are below 230 GPa, which is beneficial to the long-term use at high temperature and prolongs the service life.

[0081] Figure 6 The fracture toughness of the ceramics of Examples 1-5 is greater than 1 MPa·m 1 / 2 , which is beneficial for long-term work at high temperature and reduces the occurrence of cracks.

[0082] Comparative Example 1

[0083] 145 g of nanometer gadolinium oxide, 98.57 g of nanometer zirconium oxide, and 487.14 g of anhydrous ethanol were mixed and ball-milled for 20 h, and a uniform mixture was obtained after drying. The mixture was placed in a box furnace and calcined at 1350 DEG C for 2.5 h to obtain a Gd2Zr2O7 stoichiometric pre-fired powder. The pre-fired powder was mixed with anhydrous ethanol and ball-milled at a speed of 400 r / min for 36 h, and was dried at 60 DEG C to obtain a pre-fired powder. The pre-fired powder was mixed with a polyvinyl alcohol aqueous solution, granulated, and dry-pressed at 5 MPa for 3 min. The green body was then degassed at a temperature increasing rate of 1.5 DEG C / min at 630 DEG C for 1 h, and then degassed at a temperature increasing rate of 5 DEG C / min at 1700 DEG C for 5 h to obtain a gadolinium zirconate ceramic with a stoichiometric ratio.

[0084] The preparation method of Comparative Example 1 is the same as that of Example 4, and the Gd2Zr2O7 stoichiometric ceramic prepared has a single-phase pyrochlore structure, a relative density of 97%, a hardness of 11.04 GPa, a Young's modulus of 219 GPa, a fracture toughness of 1.53 MPa·m 1 / 2 , and a thermal expansion coefficient of 11.24 x 10 -6 K -1 , a room temperature thermal conductivity of 2.10 W / (m·K), and a thermal conductivity of 1.72 W / (m·K) at 1200 DEG C.

[0085] The thermal conductivities of Gd2Zr2O7 and the A-site doped and non-stoichiometric ceramic of Example 4 are compared as shown in Figure 7 It can be seen that the non-stoichiometric rare earth zirconate ceramic of the present application has a large decrease in thermal conductivity at a low temperature stage below 600 DEG C compared with a traditional stoichiometric ceramic, and the mechanical properties of the ceramic are increased. The non-stoichiometric ceramic of the present application has a stable single-phase fluorite structure and does not have a phase structure transition.

[0086] Figure 8The XRD patterns of the example 4 ceramic treated at 1600℃ for different time, the example 4 ceramic can keep the stable phase structure at 1600℃ for 30h, that is, the example 4 ceramic can be used at 1600℃, which shows that the ceramic has excellent thermophysical properties and high temperature phase structure stability. The stoichiometric Gd2Zr2O7 ceramic in the comparative example has a transformation from pyrochlore phase to fluorite phase at about 1550℃.

[0087] The present application combines the non-stoichiometric ratio and A-site (or A / B-site co-doped) ion doping, optimizes the thermophysical properties of the rare earth zirconate ceramic, and the rare earth zirconate ceramic has excellent high temperature phase structure stability.

[0088] Although the above embodiment has described the present application in detail, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the embodiments of the present application without creative labor, which all belong to the protection scope of the present application.

Claims

1. A method for producing a rare earth zirconate ceramic, characterized by, The method comprises the following steps: mixing the oxide raw material with anhydrous ethanol to perform first ball milling and first drying, pre-sintering the obtained mixture to obtain pre-sintered powder; mixing the pre-sintered powder with anhydrous ethanol to perform second ball milling and second drying, granulating and forming the obtained powder to obtain a green body; performing degumming and sintering on the green body to obtain a rare earth zirconate ceramic; The rare earth zirconate ceramic has a chemical formula of (Gd 1-x Yb x ) 2+y Zr 2-y-z Hf z O 7-0.5y wherein 0.1≤x≤0.25, -0.1≤y≤0.1, and y is not equal to 0, 0≤z≤0.

4. the pre-sintering temperature is 1100-1400 DEG C, and the time is 2-6h; the sintering temperature is 1500-1700 DEG C, and the holding time is 5-10h.

2. The production method according to claim 1, characterized by, The rare earth zirconate ceramic has a chemical formula of (Gd 0.9 Yb 0.1 ) 2.1 Zr 1.5 Hf 0.4 O 6.95 or (Gd 0.85 Yb 0.15 ) 1.95 Zr 2.05 O 7.025 .

3. The preparation method according to claim 1, characterized in that, the first ball milling speed is 300-400r / min, and the time is 12-24h.

4. The preparation method according to claim 1, characterized in that, the second ball milling speed is 250-450r / min, and the time is 24-48h.

5. The preparation method according to claim 1, characterized in that, the forming method is dry pressing, and the dry pressing pressure is 5-10MPa, and the pressure holding time is 1-3min.

6. The method of claim 1, wherein, the degumming temperature is 550-650 DEG C, and the holding time is 1-2h.

Images