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High‐Temperature Aging of Plasma Sprayed Quasi‐Eutectoid LaYbZr 2 O 7 –Part II : Microstructure & Thermal Conductivity
Author(s) -
Ren Xiaorui,
Zhao Meng,
Wan Chunlei,
Zheng Yixin,
Pan Wei
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13673
Subject(s) - microstructure , materials science , thermal barrier coating , eutectic system , sintering , grain growth , yttria stabilized zirconia , annealing (glass) , thermal conductivity , grain boundary , composite material , grain size , cubic zirconia , ceramic , metallurgy
LaYbZr 2 O 7 ceramic thermal barrier coatings ( TBC ) of meta‐stable structure were prepared by an air plasma spraying process. Their microstructure and associated thermal transport properties evolution during high‐temperature annealing at 1300°C were characterized. The as‐sprayed LaYbZr 2 O 7 TBC s underwent a fast crystallization and a quasi‐eutectoid transformation during annealing, resulting in a biphase composite consisting of La‐rich pyrochlore phase and Yb 2 Zr 2 O 7 fluorite phase with coherent phase boundaries. Due to the diffusion barriers between the two phases as well as the low interface energy of the coherent boundaries, sintering and grain growth of materials was significantly refrained. Therefore, a final thermal dynamically stable microstructure with a grain size of ~300 nm and a total porosity about 5% could be maintained even after long‐term aging at a high temperature of 1300°C. Resulting from this stable microstructure, an ultralow thermal conductivity of 1.3 W·(m·K) −1 could be obtained even after 216 h high‐temperature aging, which is much lower than that of the state‐of‐art 7 wt% yttria‐stabilized zirconia TBC s. Both the high phase and microstructure stability and the extremely low thermal conductivities could be particularly beneficial for TBC material in gas turbine applications.