Phase equilibria in the CaO-TaO2.5-YO1.5 system and its implication for YTaO4 reactivity with CMAS |
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| Affiliation: | 1. School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China;2. Centre of Excellence for Advanced Materials, Dongguan 523808, China;1. Shi-Changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;2. School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China;3. AECC Guizhou Liyang Aviation Power Co., Ltd., Guizhou 550014, China;4. Department of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang 110142, China;1. KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium;2. KU Leuven, Department of Oral Health Sciences, BIOMAT-Biomaterials Research Group & UZ Leuven (University Hospitals Leuven), Dentistry, Kapucijnenvoer 7 Block A, B-3000 Leuven, Belgium;1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China;2. Engineering Laboratory of Advanced Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China;3. Qianwan Institute of CNiTECH, Ningbo 315336, China;4. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Phase equilibria in the CaO-TaO2.5-YO1.5 system were experimentally investigated and the isothermal section at 1400 °C was constructed. Ten three-phase equilibrium fields were determined, and the solid solution regions of the binary compounds were analyzed. The Ca4Ta2O9 in the ternary system is marked as (YO3/2)x(Ca2/3Ta1/3O3/2)1?x. Its maximum solubility is the formula of Ca2YTaO6. The solubilities of CaO in the M′-YTaO4 and fluorite phases reach up to about 2.0 mol% and 8.9 mol%, respectively. A ternary pyrochlore-type phase was found, which was expressed as the chemical formula of Ca0.5–0.5xY0.75xTa0.5–0.25xO1.75. The morphology of pyrochlore was polygonal, and it was the only reaction product when the YTaO4 oxides were corroded by the molten silicate (CMAS). Since the CaO is the main reactant, the CaO-TaO2.5-YO1.5 phase diagram was used to successfully explain the corrosion behavior of YTaO4. The current experimental phase diagram is important to understand the CMAS degradation of the thermal barrier coatings. |
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| Keywords: | Phase equilibria Solid solution Pyrochlore CMAS Yttrium tantalate |
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