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Origin of Darkening in 8 wt% Yttria—Zirconia Plasma‐Sprayed Thermal Barrier Coatings
Author(s) -
Ingo Gabriel Maria
Publication year - 1991
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/j.1151-2916.1991.tb06891.x
Subject(s) - thermal barrier coating , yttria stabilized zirconia , materials science , cubic zirconia , zirconium , x ray photoelectron spectroscopy , oxide , plasma , thermal , impurity , analytical chemistry (journal) , mineralogy , chemical engineering , metallurgy , chemistry , ceramic , thermodynamics , chromatography , engineering , physics , organic chemistry , quantum mechanics
The origins of darkening of 8 wt% Y 2 O 3 ‐ZrO 2 air plasmasprayed (APS) and low‐pressure plasma‐sprayed (LPPS) thermal barrier coatings (TBC) have been studied using X‐ray photoelectron spectroscopy. The change of valence states of zirconium, due to the reduction of ZrO 2 to Zr 2 O 3 , was responsible for darkening of TBC. Quantification of Zr 3+ oxide was related both to the black color of TBC and to the spraying technologies and parameters. Furthermore, impurity (Fe, Al, Si, and Na) segregation and exsolution phenomena were monitored as a function of the air thermal treatment (up to 1473 K) and it was demonstrated not to be the origin of darkening.