A multi-principal component dopant for zirconium oxide
By modifying zirconia with equimolar ratio multi-principal component dopants, the problems of instability and low conductivity of zirconia materials at high temperatures were solved, the fracture toughness and oxygen ion conductivity were improved, and the dopant control process was simplified.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2022-03-22
- Publication Date
- 2026-07-17
AI Technical Summary
Existing zirconia materials are unstable at high temperatures, have low oxygen ion conductivity, and insufficient fracture toughness, making it difficult to meet the high-performance requirements of thermal barrier coatings and solid oxygen fuel cells. Multi-component doping also makes performance optimization difficult.
A mixture of various rare earth oxides and transition metal oxides in equimolar or near-equimolar ratios was used as a multi-principal component dopant. Tetragonal/cubic phase doped zirconium oxide was obtained by solid-state sintering. The amount and type of dopant elements were controlled to simplify performance optimization.
This improved the fracture toughness, high-temperature stability, and oxygen ion conductivity of doped zirconia, simplified the complexity of dopant addition, and achieved an overall performance improvement.
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Figure CN114538922B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a multi-principal component dopant for zirconium oxide, belonging to the field of materials. Background Technology
[0002] Zirconia doped with yttrium oxide (YSZ) is currently widely used in thermal barrier coatings, solid oxygen fuel cell electrolytes, and structural ceramics. However, persistent problems such as high-temperature instability, low oxygen ion conductivity, and low fracture toughness have limited the further application of this material. Among these, Yttrium-doped yttrium oxide (YSZ), a traditional thermal barrier coating material, possesses a high melting point, low thermal conductivity (2–3 W / m·K), and a fracture toughness of 3.0 ± 0.5 MPa·m. 1 / 2 Meanwhile, the instability at high temperatures (≥1200℃) makes YSZ unsuitable for meeting the advancements in engine technology and the higher thermal efficiency requirements of gas turbines and aero engines. To address this, researchers have developed novel thermal barrier coating materials (rare earth zirconates, cerates, stannates, etc.) with lower thermal conductivity and higher temperature resistance. Among them, La2Zr2O7 exhibits excellent high-temperature stability, and its dense material has a thermal conductivity of only 1.56 W / m·K. However, its low fracture toughness makes it difficult to apply directly. Therefore, modifying and doping YSZ remains the primary means of improving the performance of thermal barrier coatings.
[0003] Previous studies have shown that while increasing the dopant content can effectively improve the stability of YSZ, it also significantly reduces the material's fracture toughness. To improve the overall performance of YSZ, researchers have used different stabilizers to dope and modify it (monological doping, binary doping, and ternary doping). Among these, rare earth ions with small ionic radii (such as Sc) are used as dopants. 3+ Yb 3+ Doping with zirconia can reduce the tetragonal phase distortion of YSZ and improve the phase stability of the doped zirconia, but at the expense of the material's fracture toughness. Doping with Gd₂O₃ can reduce the thermal conductivity of YSZ, improving the material's fracture toughness and anti-sintering properties, but it reduces the stability of the t′ phase, which to some extent sacrifices the material's high-temperature phase stability. In summary, this type of multi-component doped zirconia often sacrifices other properties while improving one, making it difficult to obtain thermal barrier coating materials with excellent overall performance.
[0004] In solid oxygen fuel cell (SOFC) electrolyte materials, although 12 mol% Sc2O3-doped ZrO2 (ScSZ) exhibits the highest oxygen ion conductivity, the high economic cost of Sc2O3 and the rapid aging rate of ScSZ electrolyte limit its widespread use. Considering all factors, yttrium-doped zirconium oxide (operating temperature range: 950℃~1000℃) remains the commercially preferred electrolyte material. To reduce the cost of SOFCs, minimize thermal mismatch between components, and improve the stability of electrode materials, it is typically necessary to lower the operating temperature of SOFCs to 650℃-800℃. Doping modification remains a crucial approach to achieving mid-temperature operation of SOFCs and improving the oxygen ion conductivity of electrolyte materials. Traditional YSZ materials exhibit oxygen ion conductivity of 19 and 44 mS / cm at 800 and 900℃, respectively. (ZrO2) 1-x-y (Sc2O3) x (Y2O3) y The ionic conductivity of Y-TZP (x = 0.003 - 0.045, y = 0.005 - 0.03) at 900℃ is only 40 mS / cm; the ionic conductivity of 0.5 mol% Sm₂O₃-doped Y-TZP at 800℃ is only 20 mS / cm. -1 .
[0005] In the aforementioned multi-component doped YSZ system, the dopants are often treated as independent variables, resulting in extremely complex combinations of their amounts. This poses a significant challenge to controlling the overall performance of the doped zirconia system. Furthermore, the performance disadvantages caused by multi-component doping have been a long-standing drawback. Therefore, the key to obtaining high-performance doped zirconia lies in optimizing and improving the overall performance of zirconia through doping modification while simultaneously reducing the difficulties caused by the diversity of dopant addition amounts. Summary of the Invention
[0006] The problem this invention aims to solve is to provide a multi-principal-component dopant for zirconia. Compared to previous traditional YSZ and multi-component doped YSZ systems, the multi-principal-component doped zirconia of this invention exhibits superior fracture toughness, high-temperature stability, and ideal oxygen ion conductivity. Furthermore, the amount of each dopant component added in the multi-principal-component doped zirconia is essentially fixed, avoiding the difficulties caused by variations in the amount added, which hinder the optimization / control of the overall performance of the doped zirconia.
[0007] The objective of this invention is achieved through the following technical solution.
[0008] A multi-principal component dopant (nRe) for zirconium oxide uses a mixture of various rare earth oxides and transition metal oxides as the multi-principal component dopant (nRe). Tetragonal / cubic phase doped zirconium oxide is obtained by solid-state sintering, exhibiting superior fracture toughness, high-temperature stability, and ideal oxygen ion conductivity. The molar ratio of the dopant to zirconium oxide is x:100-x, where x satisfies: 5≤x≤15.
[0009] The multi-principal component dopant (nRe) is a mixture of various (≥5) rare earth oxides and transition metal oxides; the multi-principal component dopant and the transition metal oxide are in an equimolar ratio or a near equimolar ratio (the relative content variation range is ±5%).
[0010] The rare earth oxides are lanthanide rare earth oxides; the transition metal oxides include Sc2O3 and Y2O3.
[0011] The lanthanide rare earth oxides include: Lu2O3, Yb2O3, Tm2O3, Er2O3, Ho2O3, Dy2O3, Tb2O3, Gd2O3, Eu2O3, Sm2O3, Nd2O3, Pr2O3, and La2O3.
[0012] Beneficial effects:
[0013] 1. This invention employs a mixture of multiple (≥5) rare earth oxides / transition metal oxides in equimolar or near-equimolar ratios as a multi-principal component dopant (nRe), and obtains tetragonal / cubic doped zirconia (nReSZ) through solid-state sintering. Due to its larger tetragonal grain size, through the martensitic transformation toughening mechanism and the ferroelastic domain orientation energy absorption mechanism, this type of material exhibits superior fracture toughness compared to traditional YSZ and multi-component doped YSZ.
[0014] 2. This invention employs a mixture of multiple (≥5) rare earth oxides / transition metal oxides in equimolar or near-equimolar ratios as a multi-principal component dopant (nRe), and obtains tetragonal / cubic doped zirconia (nReSZ) through solid-state sintering. Utilizing the hysteresis diffusion effect, multi-principal component doping effectively suppresses the segregation of dopant elements at high temperatures, significantly improving the high-temperature stability of doped zirconia at 1300℃ compared to traditional YSZ.
[0015] 3. This invention employs a mixture of multiple (≥5) rare earth oxides / transition metal oxides in equimolar or near-equimolar ratios as a multi-principal component dopant (nRe), and obtains cubic phase-doped zirconia (nReSZ) through solid-state sintering. By controlling the oxygen ion migration channel radius, the oxygen ion conductivity of nReSZ at 800 and 900℃ is increased to 27 and 55 mS / cm, respectively.
[0016] 4. In the multi-principal component dopant (nRe) disclosed in this invention, each rare earth / transition metal oxide is in an equimolar or near-equimolar ratio (relative content variation range of ±5%). A high-performance doped zirconium oxide system can be obtained simply by controlling the dopant (nRe) content and the type of rare earth / transition metal oxide, simplifying the complexity of traditional multi-component doping. Attached Figure Description
[0017] Figure 1 Surface morphology (a) and EBSD (b) of 6 mol% multi-principal component dopant (nRe = Lu2O3, Yb2O3, Dy2O3, Gd2O3, Y2O3) doped zirconium oxide (nReSZ);
[0018] Figure 2 Fracture toughness and Vickers hardness of zirconia (nReSZ) doped with 5.8, 6, and 8 mol% multi-principal component dopants (nRe = Lu2O3, Yb2O3, Dy2O3, Gd2O3, Y2O3) (a) and the content of tetragonal phases that can undergo phase transformation (b).
[0019] Figure 3 XRD patterns of 5.8, 6, and 8 mol% multi-principal component dopants (nRe = Lu2O3, Yb2O3, Dy2O3, Gd2O3, Y2O3) doped zirconium oxide (nReSZ) and 8YSZ polished surfaces (a), and XRD patterns of the surfaces after heat treatment at 1300℃ for 50 h (b).
[0020] Figure 4 Thermal conductivity (a) and coefficient of thermal expansion (b) of zirconia (nReSZ) doped with 5.8, 6, and 8 mol% multi-principal component dopants (nRe = Lu2O3, Yb2O3, Dy2O3, Gd2O3, Y2O3);
[0021] Figure 5 Impedance spectra of 8 mol% zirconium oxide (nReSZ) doped with multi-principal component dopants (nRe = Lu2O3, Yb2O3, Dy2O3, Sc2O3, Y2O3) at 800℃ and 900℃.
[0022] Figure 6 Fracture toughness and Vickers hardness of 5.5 mol% multi-principal component dopant (nRe = Lu2O3, Yb2O3, Dy2O3, Gd2O3, Sc2O3, Y2O3) doped zirconia (nReSZ). Detailed Implementation
[0023] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:
[0024] Example 1:
[0025] Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, and Y₂O₃ were mixed in an equimolar ratio as multi-principal component dopants (nRe). (Lu2O3) :n (Yb2O3) :n (Dy2O3) :n (Gd2O3) :n (Y2O3) =1:1:1:1:1), where nRe = 5.8, 6, and 8 mol%. The corresponding oxide powders were weighed according to the above ratios. Ethanol was used as the grinding medium, and the mixed powders were ground and mixed for 12 hours using a planetary ball mill (250 r / min). The resulting slurry was placed in a 60℃ oven for 10 hours. The dried powder was sieved, granulated, and formed into a green body using a dry pressing method. The green body was then subjected to cold isostatic pressing (200 MPa) for 2 minutes to further increase its density. The green body was then sintered at 1550℃ for 4 hours under normal pressure to obtain multi-principal component doped zirconia (nReSZ) with dopant (nRe) addition amounts of 5.8, 6, and 8 mol%. The nReSZ surface was polished and hot-etched, and its microstructure and phase composition were analyzed using SEM and EBSD. The polished ReSZ surface and the ground powder were characterized by XRD to analyze the content of the tetragonal phase capable of phase transformation.
[0026] Appendix Figure 1 The left image shows the surface morphology (EBSD) of 6 mol% multi-principal component dopant (nRe = Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, Y₂O₃). (See right image for details.) Figure 2 Schematic diagrams showing the fracture toughness and Vickers hardness of zirconia (nReSZ) doped with 5.8, 6, and 8 mol% multi-principal component dopants (nRe = Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, Y₂O₃). Figure 2 a) and the content of tetragonal phase that can undergo phase transformation ( Figure 2 b). From the appendix Figure 2 (a) It can be seen that when nRe = 5.8 mol%, the fracture toughness of nReSZ reaches a maximum of 10.96 MPa·m. 1 / 2 Analysis suggests this is due to its large t-phase grain size and high tetragonal phase content capable of phase transformation.
[0027] Example 2:
[0028] Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, and Y₂O₃ were mixed in an equimolar ratio as multi-principal component dopants (nRe). (Lu2O3) :n (Yb2O3) :n (Dy2O3) :n (Gd2O3) :n (Y2O3)=1:1:1:1:1), where nRe = 5.8, 6, 8 mol%. The corresponding oxide powders were weighed according to the above ratios. Ethanol was used as the grinding medium, and the mixed powders were ground and mixed for 12 hours using a planetary ball mill (250 r / min). The resulting slurry was placed in a 60℃ oven for 10 hours. The dried powder was sieved, granulated, and formed into a green body using a dry pressing method. The green body was then subjected to cold isostatic pressing (200 MPa) for 2 minutes to further increase its density. The green body was then sintered at 1550℃ for 4 hours under normal pressure to obtain multi-principal component doped zirconia (nReSZ) with dopant (nRe) addition amounts of 5.8, 6, and 8 mol%. The nReSZ surface was polished and placed in a tube furnace at 1300℃ for 50 hours. XRD was used to characterize the phase changes before and after the 1300℃ heat treatment, with 8YSZ used as a control group. nReSZ was fabricated into circular wafers with a diameter of 12.7 mm, a thickness of 1 mm, and a surface finish of ≤1 μm, and its thermal conductivity was characterized using a laser thermal conductivity meter. nReSZ was also fabricated into 11 mm × 4 mm × 4 mm rectangles, and their coefficient of thermal expansion was characterized.
[0029] Appendix Figure 3 Represented as XRD patterns of nReSZ and 8YSZ polished surfaces ( Figure 3 a) and surface XRD after heat treatment at 1300℃ for 50h ( Figure 3 b). By Figure 3 (b) It can be seen that, compared with the traditional 8YSZ, nReSZ did not exhibit the m-phase after heat treatment at 1300℃ for 50 hours, demonstrating excellent high-temperature stability. (Appendix) Figure 4 The graph (a) shows the thermal conductivity (5.8), thermal expansion coefficient (b) for nReSZ at 6.8, 5.8, and 8 mol%. Figure 4 As can be seen from (a) and 4(b), the thermal conductivity of nReSZ is close to that of traditional 8YSZ, and the thermal expansion coefficient of nReSZ is close to or even higher than that of traditional 8YSZ.
[0030] Example 3:
[0031] Lu₂O₃, Yb₂O₃, Dy₂O₃, Sc₂O₃, and Y₂O₃ were mixed in an equimolar ratio as multi-principal component dopants (nRe). (Lu2O3) :n (Yb2O3) :n (Dy2O3) :n (Sc2O3) :n (Y2O3)=1:1:1:1:1), where nRe = 8 mol%. The corresponding oxide powders were weighed according to the above ratio. Ethanol was used as the grinding medium, and the mixed powders were ground and mixed for 12 hours using a planetary ball mill (250 r / min). The obtained slurry was placed in a 60℃ oven for 10 hours. The dried powder was sieved, granulated, and formed into a green body using a dry pressing method. The green body was then subjected to cold isostatic pressing (200 MPa) for 2 minutes to further increase its density. The green body was then sintered at 1550℃ for 4 hours under normal pressure to obtain multi-principal component doped zirconia (nReSZ) with an nRe dopant (nRe) content of 8 mol%. The surface of nReSZ was polished, baked, and its ionic conductivity was analyzed by impedance spectroscopy.
[0032] Appendix Figure 5 The impedance spectra of nReSZ at 800℃ and 900℃ are used to determine the total resistance of the sample and calculate the oxygen ion conductivity of the doped zirconium oxide using formula (1). It was found that the oxygen ion conductivity of nReSZ at 800℃ and 900℃ is 27 and 55 mS / cm, respectively.
[0033]
[0034] Where R represents resistance, A represents cross-sectional area, and l represents sample thickness.
[0035] Example 4:
[0036] Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, Sc₂O₃, and Y₂O₃ were mixed in an equimolar ratio as multi-principal component dopants (nRe). (Lu2O3) :n (Yb2O3) :n (Dy2O3) :n (Gd2O3) :n (Sc2O3) :n (Y2O3) =1:1:1:1:1:1), where nRe = 5.5 mol%. The corresponding oxide powders were weighed according to the above ratio. Ethanol was used as the grinding medium, and the mixed powders were ground and mixed for 12 hours using a planetary ball mill (250 r / min). The resulting slurry was placed in a 60℃ oven for 10 hours. The dried powder was sieved, granulated, and formed into a green body using a dry pressing method. The green body was then subjected to cold isostatic pressing (200 MPa) for 2 minutes to further increase its density. The green body was then sintered at 1550℃ for 4 hours under normal pressure to obtain multi-principal component doped zirconia (nReSZ) with a dopant (nRe) content of 5.5 mol%. The surface of the nReSZ was polished, and the fracture toughness and Vickers hardness of the material were characterized by indentation.
[0037] Appendix Figure 6Figure (a) shows the fracture toughness and Vickers hardness of zirconia (nReSZ) doped with 5.5 mol% of multi-principal component dopants (nRe = Lu₂O₃, Yb₂O₃, Dy₂O₃, Gd₂O₃, Sc₂O₃, Y₂O₃). As shown in Figure (a), when nRe = 5.5 mol%, the fracture toughness of nReSZ reaches 10.05 MPa·m. 1 / 2 .
[0038] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A multi-principal-component doped zirconium oxide, characterized in that: Lu₂O₃, Yb₂O₃, Dy₂O₃, Sc₂O₃, and Y₂O₃ were mixed in an equimolar ratio as multi-principal component dopants, with a molar ratio of 1:1:1:1:1, and the content of the multi-principal component dopants was 8 mol%. The corresponding oxide powders were weighed according to the above ratio, and ethanol was used as the grinding medium. The mixed powders were ground and mixed for 12 hours using a planetary ball mill at a speed of 250 r / min. The resulting slurry was placed in a 60℃ oven and kept warm for 10 hours. The dried powder was then sieved, granulated, and formed into a green blank using a dry pressing method. The green blank density was further increased by cold isostatic pressing for 2 minutes at a pressure of 200 MPa. The green blank was then sintered at 1550℃ for 4 hours under normal pressure to obtain multi-principal component doped zirconium oxide with an dopant content of 8 mol%. Tetragonal / cubic doped zirconium oxide was obtained by solid-state sintering.