Microstructure and Mechanical Properties of ZrO₂-Sc₂O₃-Y₂O₃-La₂O₃ Ceramics AITranslate

［1］（杨宏波，王源升，王轩，武强. 燃气轮机在海洋环境下的热腐蚀与防护技术研究进展 ［J］. 表面技术，2020，49（1）：163.）

H B Yang，Y S Wang，X Wang，Q Wu. Research progress on hot corrosion and protection technology of gas turbine in marine environment ［J］. Surface Technology，2020，49（1）：163.

［2］（陆天龙，冯晶，种晓宇. 基于有限元模拟的RETaO4热障涂层隔热性能研究 ［J］. 稀有金属，2024，48（1）：50.）

T L Lu，J Feng，X Y Chong. Thermal insulation properties of RETaO4 thermal barrier coatings based on finite element simulation ［J］. Chinese Journal of Rare Metals，2024，48（1）：50.

［3］Belmonte M. Advanced ceramic materials for high temperature applications ［J］. Advanced Engineering Materials，2006，8（8）：693.

［4］（郭磊，孟诗钧，叶福兴，冯佳燚. 高熵陶瓷在热障涂层与环境障涂层中的研究进展 ［J］. 稀有金属，2023，47（11）：1525.）

L Guo，S J Meng，F X Ye，J Y Feng. Research progress of high entropy ceramic in fields of thermal barrier coatings and environmental barrier coating ［J］. Chinese Journal of Rare Metals，2023，47（11）：1525.

［5］（张红松，陈晓鸽，徐强，王富耻，刘玲. 热障涂层用氧化物稳定的ZrO2陶瓷材料研究现状 ［J］. 中国陶瓷，2008，44（3）：5.）

H S Zhang，X G Chen，Q Xu，F C Wang，L Liu. Research status of oxide-stabilized ZrO2 ceramic materials for thermal barrier coatings ［J］. China Ceramics，2008，44（3）：5.

［6］（郭洪波，宫声凯，徐惠彬. 先进航空发动机热障涂层技术研究进展 ［J］. 中国材料进展，2009，28（9）：18.）

H B Guo，S K Gong，H B Xu. Research progress of advanced aeroengine thermal barrier coating technology ［J］. Progress of Materials in China，2009，28（9）：18.

［7］Zhou S L，Shen S B，Chen Y Y，Zhang Z，Wu S J. Fast synthesis of novel micron porous particles of Gd，Yb and Y-stabilized zirconia to prepare TBCs with low thermal conductivity ［J］. Materials Chemistry and Physics，2021，259：124018.

［8］Rahaman M N，Gross J R，Dutton R E，Wang H. Phase stability，sintering，and thermal conductivity of plasma-sprayed ZrO2-Gd2O3 compositions for potential thermal barrier coating applications ［J］. Acta Materialia，2006，54：1615.

［9］Matsumoto M，Aoyama K，Matsubara H，Takayama K，Banno T，Kagiya Y，Sugita Y. Thermal conductivity and phase stability of plasma sprayed ZrO2-Y2O3-La2O3 coatings ［J］. Surface & Coatings Technology，2005，（1）：194.

［10］Matsumoto M，Yamaguchi N，Matsubara H. Low thermal conductivity and high temperature stability of ZrO2-Y2O3-La2O3 coatings produced by electron beam PVD ［J］. Scripta Materialia，2004，50（6）：867.

［11］（苏正夫，刘怀菲，王雅雷. La2O3和Y2O3掺杂ZrO2复合材料的高温相稳定性、抗烧结性及热导率 ［J］. 复合材料学报，2015，32（5）：1381.）

Z F Su，H F Liu，Y L Wang. High temperature phase stability，sintering resistance and thermal conductivity of La2O3 and Y2O3 doped ZrO2 composites ［J］. Acta Materiae Compositae Sinica，2015，32（5）：1381.

［12］Song X W，Xie M，Mou R D，Zhou F，Jia G X，An S L. Influence of the partial substitution of Y2O3 with Ln2O3 （Ln=Nd，Sm，Gd） on the phase structure and thermophysical properties of ZrO2-Nb2O5-Y2O3 ceramics ［J］. Acta Materialia，2011，59：3895.

［13］Huang M Z，Liu X Y，Feng Y J，Wan C L，Pan W，Yang J，Zhao X H. Structure and properties of nonstoichiometric Y1-xNbxO1.5+x for thermal barrier coatings ［J］. Journal of the European Ceramic Society，2021，41：526.

［14］（吴煦，牟仁德，王开军. 三元共掺杂对YSZ热障涂层热物理性能的影响 ［J］. 航空材料学报，2019，39（2）：49.）

X Wu，R D Mu，K J Wang. Influence of ternary co-doping on thermo-physical properties of YSZ thermal barrier coatings ［J］. Journal of Aeronautical Materials，2019，39（2）：49.

［15］Zhou S L，Shen S B，Chen Y Y，Zhang Z，Wu S J. Fast synthesis of novel micron porous particles of Gd，Yb and Y-stabilized zirconia to prepare TBCs with low thermal conductivity ［J］. Materials Chemistry and Physics，2021，259（4）：124018.

［16］（王晶，钱凌翼，郭云珊，Richard Wheatley，侯向辉，刘宇阳. R2O3+Er2O3稳定ZrO2的新型TBC材料 ［J］. 稀有金属，2018，46（7）：853.）

J Wang，L Y Qian，Y S Guo，W Richard，X H Hou，Y Y Liu. R2O3+Er2O3 stabilized ZrO2 for TBC application ［J］. Chinese Journal of Rare Metals，2018，46（7）：853.

［17］Jones R L，Reidy R F，Mess D. Scandia，yttria-stabilized zirconia for thermal barrier coatings ［J］. Surface & Coatings Technology，1996，82（1-2）：70.

［18］（范薇，白宇，王玉，雷丽军，张翼. 钪钇共稳二氧化锆热障涂层结构设计与热冲击失效行为研究 ［J］. 热加工工艺，2022，51（10）：69.）

W Fan，Y Bai，Y Wang，L J Lei，Y Zhang. Structural design and thermal shock failure behavior of scandiumand yttrium co-stabilized zirconia thermal barrier coatings ［J］. Hot Working Technology，2022，51（10）：69.

［19］Jones R L. Some aspects of the hot corrosion of thermal barrier coatings ［J］. Journal of Thermal Spray Technology，1997，6（1）：77.

［20］Jones R L. The development of hot-corrosion-resistant zirconia thermal barrier coatings ［J］. Materials at High Temperatures，1991，9（4）：228.

［21］Fan W，Bai Y，Wang Z Z. Effect of point defects on the thermal conductivity of Sc2O3-Y2O3 co-stabilized tetragonal ZrO2 ceramic materials ［J］. Journal of the European Ceramic Society，2019，39：2389.

［22］Fan W，Bai Y，Liu Y F. Corrosion behavior of Sc2O3-Y2O3 co-stabilized ZrO2 thermal barrier coatings with CMAS attack ［J］. Ceramics International，2019，45：15763.

［23］Chen C，Liang T Q，Guo Y，Chen X Y，Man Q Y，Zhang X H，Zeng J M，Ji V. Effect of scandia content on the hot corrosion behavior of Sc2O3 and Y2O3 co-doped ZrO2 in Na2SO4+V2O5 molten salts at 1000 ℃ ［J］. Corrosion Science，2019，158：108094.

［24］Fan W，Wang Y Q，Liu Y F，Bai Y，Wang Y，Liu Q. Mechanical properties durability of Sc2O3-Y2O3 co-stabilized ZrO2 thermal barrier materials for high temperature application ［J］. Coatings，2022，12：155.

［25］Leoni M，Jones R L，Scardi P. Phase stability of scandia-yttria-stabilized zirconia TBCs ［J］. Surface and Coatings Technology，1998，108-109：107.

［26］Wan C L，Qu Z X，Du A B，Pan W. Order-disorder transition and unconventional thermal conductivities of the （Sm1-xYbx）2Zr2O7 Series ［J］. International Journal of Applied Ceramic Technology，2011，94（2）：592.

Basic Information:

DOI：10.13373/j.cnki.cjrm.XY24040016

Chinese Library Classification Number:TQ174.75

Citation Information:

It has long been recognized that plasma-sprayed （PS） or electron beam physical vapor deposited （EB-PVD） ceramic coatings could insulate engine parts from internal hot combustion gases. The ceramic coatings were tried as a means for reducing metal surface temperatures of，and providing corrosion protection for，gas turbine and air engine turbine blades. To be practical，it must be able to withstand several thousand hours of engine operation at gas temperatures as high as about 1900~2000 ℃ without spalling，cracking，or excessively eroding. In this regard，thermal barrier coating （TBC） ceramics required toprocessinclude （1） superior thermal insulating performance，（2） high thermal stability at both room temperature and service temperature，and （3） close thermal expansion coefficient to the metallic substrates，among which superior thermal insulating performance plays the most vital role for TBCs. 7%±1%Y₂O₃-stabilized zirconia （8YSZ） ceramics，and higher melting point，currently appear to have considerable potential as thermal barriers or corrosion-resistant coatings for application to gas turbine components. However，the practical application of 8YSZ，as the state-of-the-art TBC and current industry standard，is largely restricted by the tetragonal-to-monoclinicphase transformation，high temperature accelerated sintering，and the almost translucent to high-temperature thermal radiation during the prolonged high-temperature service above 1200 ℃. The phase structure of deposited or sprayed YSZ coating transforms from the metastable tetragonal prime phase to the tetragonal phase and the cubic phase. Subsequently，the tetragonal phase further transforms into the monoclinic phase during cooling，resulting in not only a volume expansion but also the degradation of the fracture toughness，and ultimately results in delamination，spallation，and failure of TBCs. In this view，to meet the requirement for higher efficiency and thrust-weight ratios of turbine engines，a barrage of efforts was made to explore novel candidate TBC ceramic materials with superb comprehensive performance at elevated temperatures. Three mainstream strategies have been proposed to overcome such drawbacks over past decades：（1） development of a advanced structural TBC ceramic material with higher temperature resistance such as rare earth zirconates，rare earth phosphate，perovskites and rare earth hexaaluminates，and （2） multi-element modification and optimization of YSZ materials，such as gadolinia （Gd₂O₃），neodymia （Nd₂O₃），erbia （Er₂O₃），scandia （Sc₂O₃），Lanthanum oxide （La₂O₃），and ytterbia （Yb₂O₃），by regulating the lattice defects such as oxygen vacancies and substitutional solute atoms in the material. Compared with YSZ，among these candidates for TBCs，A₂B₂O₇ ceramics with pyrochlore and/or fluorite crystal structure，such as RE₂Zr₂O₇ （RE=La，Sm，Gd，Dy，Er，and Yb），are more promising to be used as high-temperature TBC materials，owing to their improved high-temperature phase stability and simultaneous lower thermal conductivity. However，their relatively low thermal expansion coefficient （TEC） may lead to a large expansion mismatch with substrates for various applied areas. Fortunately，it has been found that rare earth oxides doping，such as Gd₂O₃，Nd₂O₃，Er₂O₃，Sc₂O₃，La₂O₃，and Yb₂O₃，can not onlystrengthen the thermal insulation performance of YSZ but also significantly increase its high-temperature stability. Numerous oxygen vacancies and crystal lattice distortion of zirconia induced by the addition of dopants alter the coordination number of Zr atoms and increase the potential energy of the transformation of the tetragonal phase，thus enhancing the phase stability at higher service temperatures. Hence，rare-earth multi-doping of zirconia ceramics is a feasible and effective strategy to achieve the multiple goals of regulating phase stability and thermal properties. Given that the traditional 8YSZ yttria partially stabilized zirconia for use as thermal barrier coating cannot meet the application demands of long-term stable service above 1200 ℃. Driven by the urgent demand for enhanced efficiency and decreased energy consumption，rare-earth multi-doped zirconia ceramics with low thermal conductivity have raised wide interest for thermal barrier coatingapplications. In this regard，this work proposed a novel La₂O₃-Sc₂O₃-Y₂O₃ co-doped ZrO₂ thermal barrier coating ceramic material prepared by the conventional solid-state reaction. The effects of La₂O₃ addition on the microstructural and mechanical properties，such as elastic modulus，Vickers hardness，and fracture toughness of high-temperature solid-phase synthesized ceramic materials，were investigated by means of X-ray diffraction （XRD），field emission scanning electron microscopy （SEM），and Vickers hardness tests. The results showed that the relative density of ZrO₂-Sc₂O₃-Y₂O₃ ceramics sintered at 1450 ℃ for 3.5 h was more than 98%，and the tetragonal phase was a dominant structure of zirconia. The elastic modules decreased from 200 to154 GPa with an increase in La₂O₃ doping content from 0.1% to 0.5%，and Vickers hardness and fracture toughness of La₂O₃-Sc₂O₃-Y₂O₃ co-doped ZrO₂ ceramics were 13~14 GPa and 6.5~7.0 MPa·m^1/2，respectively，which were comparable to that of traditional 8YSZ ceramic. The fracture behavior on the fracture surfaces was found to be a mixed mode of intergranular and transgranular fracture. This research provides theoretical support for rare-earth-doped modified YSZ thermal barrier coating materials.