Abstract
Coatings based on lanthanum, neodymium, samarium, and gadolinium zirconates have been grown by atmospheric plasma spraying of powders, and their composition and structure have been investigated by scanning electron microscopy, chemical analysis, and X-ray diffraction. The results demonstrate that the chemical composition of the coatings differs from the compositions of the powders they were prepared from. During plasma spraying of Ln2Zr2O7-based powders, the rare-earth oxide vaporizes more rapidly than zirconia. The difference in composition between the powders and coatings decreases as the atomic number of the rare earths increases in going from La to Gd. We have studied the processes that take place in the coatings during heat treatment at a temperature of 1250°C. It has been shown that the major phase in the La2Zr2O7-, Nd2Zr2O7-, and Sm2Zr2O7-based coatings undergoes a defect fluorite–pyrochlore structural phase transition. The La2Zr2O7-based coatings have been found to contain ∼5 wt % t-ZrO2 in addition to the major phase. The Gd2Zr2O7-based coating retained a defect fluorite structure.
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Miller, R.A., Thermal barrier coatings for aircraft engines: history and directions, J. Therm. Spray Technol., 1997, vol. 6, no. 1, pp. 35–42.
Levi, C., Emerging materials and processes for thermal barrier systems, Curr. Opin. Solid State Mater. Sci., 2004, vol. 8, pp. 77–91.
Cao, X.Q., Vassen, R., and Stoever, D., Ceramic materials for thermal barrier coatings, J. Eur. Ceram. Soc., 2004, vol. 24, no. 1, pp. 1–10.
Cao, X.Q., Application of rare earths in thermal barrier coating materials, J. Mater. Sci. Technol., 2007, vol. 23, no. 1, pp. 15–35.
Vassen, R., Jarligo, M., Steinke, T., Mack, D., and Stoever, D., Overview on advanced thermal barrier coatings, Surf. Coat. Technol., 2010, vol. 205, pp. 938–942.
Cao, X.Q., Vassen, R., Jungen, W., Schwartz, S., Tietz, F., and Stoever, D., Thermal stability of lanthanum zirconate plasma-sprayed coating, J. Am. Ceram. Soc., 2001, vol. 84, no. 9, pp. 2086–2090.
Xu, Z., Zhong, X., Zhang, J., and Zhang, Y., Effects of deposition conditions on composition and thermal cycling life of lanthanum zirconate coatings, Surf. Coat. Technol., 2008, vol. 202, pp. 4714–4720.
Chen, H., Gao, Y., Tao, S., Liu, Y., and Luo, H., Thermophysical properties of lanthanum zirconate coating prepared by plasma spraying and the influence of post annealing, J. Alloys Compd., 2009, vol. 486, pp. 391–399.
Mauer, G., Sebold, D., Vassen, R., and Stoever, D., Improving atmospheric plasma spraying of zirconate thermal barrier coatings based on particle diagnostics, J. Therm. Spray Technol., 2012, vol. 21, pp. 363–371.
Mazilin, I.V., Baldaev, L.Kh., Drobot, D.V., Akhmetgareeva, A.M., Zhukov, A.O., and Khismatullin, A.G., Thermal and thermophysical properties of lanthanum zirconate-based thermal barrier coatings, Perspekt. Mater., 2013, no. 7, pp. 21–30.
Jacobson, N.S., Thermodynamic properties of some metal oxide–zirconia systems, NASA Technical Memorandum, NASA-TM-102351, 1989.
Shlyakhtina, A.V., Synthesis and properties of oxygenion-conducting rare-earth pyrochlores, Doctoral (Chem.) Dissertation, Moscow, 2010.
Fukan, F., Kuznetsov, A.K., and Keler, E.K., Rareearth zirconates and their physicochemical properties: I. Lanthanum, neodymium, and cerium zirconates, Izv. Akad. Nauk SSSR, Ser. Khim., 1962, no. 7, pp. 1151–1157.
Lee, Y.H., Sheu, H.S., Deng, J.P., and Kao, H.C.I., Preparation and fluorite–pyrochlore phase transformation in Gd2Zr2O7, J. Alloys Compd., 2009, vol. 487, pp. 595–598.
Tabira, Y., Withers, R.L., Minervini, L., and Grimes, R.W., Systematic structural change in selected rare earth oxide pyrochlores as determined by wide-angle CBED and a comparison with the results of atomistic computer simulation, J. Solid State Chem., 2000, vol. 153, pp. 16–25.
Wang, C., Zinkevich, M., and Aldinger, F., Phase diagrams and thermodynamics of rare-earth-doped zirconia ceramics, Pure Appl. Chem., 2007, vol. 79, no. 10, pp. 1731–1753.
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Original Russian Text © I.V. Mazilin, L.Kh. Baldaev, D.V. Drobot, E.Yu. Marchukov, A.M. Akhmetgareeva, 2016, published in Neorganicheskie Materialy, 2016, Vol. 52, No. 9, pp. 1004–1009.
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Mazilin, I.V., Baldaev, L.K., Drobot, D.V. et al. Composition and structure of coatings based on rare-earth zirconates. Inorg Mater 52, 939–944 (2016). https://doi.org/10.1134/S0020168516090119
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DOI: https://doi.org/10.1134/S0020168516090119