Chemical Stability of (Sm_1-xLa_x)₂Zr₂O₇ and Al₂O₃ at High Temperature

Abstract:

Due to its high melting point, low thermal conductivity, and good phase stability at high-temperature, rare earth zirconates material (A₂B₂O₇) will be one of the candidate materials used for the thermal barrier coating. At high temperature, the chemical stability between rare earth zirconates and TGO layer (mainly Al₂O₃) affects much the performance of coating, so the study of the chemical stability is of great significance. In this paper, (Sm_1-xLa_x)₂Zr₂O₇(x=0, 1) were prepared by the co-precipitation method and the chemical stability between (Sm_1-xLa_x)₂Zr₂O₇(x=0, 1) and Al₂O₃ was investigated at the temperature of 1 200 ° C,1 300 ° C, 1 400 ° C, 1 500 ° C, 1 600 ° C respectively for 8 h¡¢24 h. The microstructures were analyzed by scanning electron microscope (SEM) and the crystallographic phases were determined by X-ray diffraction (XRD). The results showed that the chemical reaction occurred between Sm₂Zr₂O₇ and Al₂O₃ above 1 200 ° C producing SmAlO₃. With the heating temperature increased, the content of SmAlO₃ increased. The chemical reaction between La₂Zr₂O₇ and Al₂O₃ began at 1 200 ° C producing LaAlO₃ and ZrO₂. LaAl₁₁O₁₈ appeared at 1 300 ° C. As the increase of heating temperature, the content of LaAlO₃ and ZrO₂ with tetragonal phase reduced gradually in the heated samples, and the content of LaAl₁₁O₁₈ and ZrO₂ with monoclinic phase increased gradually in the heated samples. With the increase of heating temperature, the doping amount decreases in ZrO₂ with tetragonal phase, the structure of ZrO₂ with tetragonal phase tend to be more complete. So ZrO₂ with tetragonal phase transformed to ZrO₂ with monoclinic phase in cooling process easily, which leads to the increase of ZrO₂ with monoclinic phase in the heated samples. As the time of heating temperature prolonged, the kinds of reaction products didn t change, but the amount of reaction products increased.

• Periodical: Key Engineering Materials (Volumes 602-603)
• Pages: 340-344
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.602-603.340
• Online since: March 2014
• Authors: Lin Ru Cui*, Shi Zhen Zhu, Qiang Xu, Ling Liu, Zhuang Ma
• Keywords: Chemical Stability, Material of Thermal Barrier Coatings, Rare-Earth Zirconates

References

[1] W. Belle, G. Marijnissen, A.V. Lieshout, The Evolution of Thermal Barrier Coatings Status and Upcoming Solutions for Today's Key Issues, Surface and Coatings Technology 120 (1999) 61-67.

DOI: 10.1016/s0257-8972(99)00342-4

[2] W. Pan, C.L. Wan, Q. Xu, Thermal Diffusivity of Samarium-Gadolinium Zirconate Solid Solutions, Thermochimica Acta. 455 (2007) 16-20.

DOI: 10.1016/j.tca.2006.12.001

[3] H. Yokokawa, T. Horita, N. Sakai, T. Kawada, M. Dokiya, Chemical thermodynamic stabilities of electrode/electrolyte interfaces of high temperature electrochemical cells, Solid State Ionics 78 (1995) 203–210.

DOI: 10.1016/0167-2738(95)00092-k

[4] W. Ma, S.K. Gong, H.F. Li, H.B. Xu, Novel thermal barrier coatings based on La2Ce2O7/8YSZ double-ceramic-layer systems deposited by electron beam physical vapor deposition, Surface & Coatings Technology 202 (2008) 2704–2708.

DOI: 10.1016/j.surfcoat.2007.09.047

[5] Z. H. Xu, L.M. He, R.D. Mu, S.M. He, Double-ceramic-layer thermal barrier coatings based on La2(Zr0. 7Ce0. 3)2O7/La2Ce2O7 deposited by electron beam-physical vapor deposition, Applied Surface Science 256 (2010) 3661–3668.

DOI: 10.1016/j.apsusc.2010.01.004