Extreme Materials

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Corrosion performance of high-entropy (Ho_0.2Er_0.2Tm_0.2Yb_0.2Lu_0.2)₂Si₂O₇ environmental barrier coating material under CMAS conditions at 1500 ℃

Zhang Zhenya, Yuan Shuai, Zhu Zihao, Gao Wei, Meng Yifan, Xue Zhaolu, Xiang Tengfei, Shen Yizhou, Yan Kai, Gyawali Gobinda, Zhang Shihong

Extreme Materials, DOI: 10.1016/j.exm.2026.01.001

Num.	O	Ca	Si	Ho	Er	Tm	Yb	Lu	RE:Ca	Product
#1	61.85	4.65	14.34	3.87	4.02	3.69	3.82	3.76	4.12	Ca₂RE₈(SiO4)₆O₂
#2	60.99	4.18	15.42	4.65	4.65	2.70	3.94	3.48	4.65	Ca₂RE₈(SiO4)₆O₂
#3	65.79	3.81	13.79	3.76	3.70	2.65	3.36	3.05	4.34	Ca₂RE₈(SiO4)₆O₂
#4	51.94	6.00	17.81	6.45	5.94	3.75	4.05	3.83	4.01	Ca₂RE₈(SiO4)₆O₂

Table 3 Atomic ratios (at%) of the corresponding points in Fig. 8

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Fig.1 Schematic diagram of preparation of (5RE_0.2)₂Si₂O₇ powder and bulk.
Fig.2 XRD patterns (a), Rietveld refinement of XRD pattern (b), Raman spectrum (c), and crystal structure (d) of high-entropy (5RE_0.2)₂Si₂O₇
Table 1 Crystal structure parameters of high-entropy (5RE_0.2)₂Si₂O₇ and individual RE₂Si₂O₇
Fig. 3 Microstructure, EDS maps, and elemental composition of high-entropy (5RE_0.2)₂Si₂O₇ ceramic
Fig. 4 Heat capacity (a), thermal diffusivity coefficient (b), and thermal conductivity (c) of high-entropy (5RE_0.2)₂Si₂O₇ ceramic
Table 2. Thermal conductivity of (5RE_0.2)₂Si₂O₇ and each single principal RE₂Si₂O₇
Fig. 5 TG/DSC curves of high-entropy (5RE_0.2)₂Si₂O₇ from room temperature to 1500 °C
Fig. 6 Schematic diagram of microhardness of high-entropy (5RE_0.2)₂Si₂O₇
Fig.7 XRD patterns of the molten CMAS corrosion of (5RE_0.2)₂Si₂O₇ pellets for different times at 1500℃
Fig.8 Surface morphologies of the molten CMAS corrosion of (5RE_0.2)₂Si₂O₇ pellets for various durations at 1500 °C
Fig. 9 Cross-sectional microstructures of the molten CMAS corrosion of (5RE_0.2)₂Si₂O₇ pellets for different times at 1500 °C.
Table 4 Atomic ratios (at%) of the corresponding points in Fig. 9
Fig. 10 Cross-sectional microstructures and EDS maps of (5RE_0.2)₂Si₂O₇ and Yb₂Si₂O₇ pellets after CMAS corrosion for 20 h at 1500 ℃
Fig.11 Reaction layer thickness in (5RE_0.2)₂Si₂O₇ ceramic (a), and average apatite formation rate (μm/h^0.5) vs. corrosion time ^0.5 (h^0.5) for Yb₂Si₂O₇ ceramic (b) pellets during CMAS corrosion for different times at 1500 ℃

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