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Title: Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts

Abstract

The effects of TaO2.5 additions to Y4Zr3O12 (YZO) on its interactions with calcium-magnesium alumino-silicate (CMAS) melts are investigated herein. YZO is a candidate material for the protection of novel ZrO2-YO1.5-TaO2.5 based thermal barrier coatings (TBCs) against CMAS attack, but thermochemical considerations dictate that YZO contain TaO2.5 for interfacial compatibility. Oxides based on Y4Zr3-xTaxO12+0.5x (x = =0, 0.7, 1.4) were mixed with various ternary and quinary silicate compositions ranging in Ca:Si ratio from 0.35 to 1.13 and equilibrated at 1300 °C. The results show that all combinations form the desired apatite phase except for the mixture of the higher Ta5+ content with the lowest Ca:Si melt. It is found that the addition of Ta5+ increases the capture of Y3+ by the reprecipitated fluorite, decreasing the amount available to form apatite and eventually suppressing it at low Ca:Si. The effect is ascribed to the attractive interactions between Y3+ and Ta5+ in solid solution, similar to that found in tetragonal zirconia, but with concurrent incorporation of anion vacancies associated with excess Y3+ that stabilize the cubic form. As the Ca2+ content of the melt increases, so does the amount of Ca2+ incorporated in fluorite. The latter also interacts attractively with Ta5+ and leadsmore » to a reduction of captured Y3+ in fluorite as the Ca content in the reacting deposit increases. This serves to increase the amount of Y3+available in the melt to form apatite in TBC-CMAS interactions.« less

Authors:
ORCiD logo [1];  [2];  [2];  [2];  [2];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of California, Santa Barbara, CA (United States)
  2. Univ. of California, Santa Barbara, CA (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); US Department of the Navy, Office of Naval Research (ONR)
OSTI Identifier:
1601623
Report Number(s):
LA-UR-19-25329
Journal ID: ISSN 1359-6454
Grant/Contract Number:  
89233218CNA000001; DMR 1720256; DMR 1105672; N00014-16-1–2702
Resource Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 185; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Thermal barrier coating (TBC); Calcium-magnesium alumino-silicates (CMAS); Rare-earth oxide; Phase equilibria

Citation Formats

Abdul-Jabbar, Najeb Mohammed, Fernandez, Abel N., Jackson, Richard Wesley, Park, Daesung, Summers, William D., and Levi, Carlos G. Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts. United States: N. p., 2019. Web. https://doi.org/10.1016/j.actamat.2019.11.060.
Abdul-Jabbar, Najeb Mohammed, Fernandez, Abel N., Jackson, Richard Wesley, Park, Daesung, Summers, William D., & Levi, Carlos G. Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts. United States. https://doi.org/10.1016/j.actamat.2019.11.060
Abdul-Jabbar, Najeb Mohammed, Fernandez, Abel N., Jackson, Richard Wesley, Park, Daesung, Summers, William D., and Levi, Carlos G. Fri . "Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts". United States. https://doi.org/10.1016/j.actamat.2019.11.060. https://www.osti.gov/servlets/purl/1601623.
@article{osti_1601623,
title = {Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts},
author = {Abdul-Jabbar, Najeb Mohammed and Fernandez, Abel N. and Jackson, Richard Wesley and Park, Daesung and Summers, William D. and Levi, Carlos G.},
abstractNote = {The effects of TaO2.5 additions to Y4Zr3O12 (YZO) on its interactions with calcium-magnesium alumino-silicate (CMAS) melts are investigated herein. YZO is a candidate material for the protection of novel ZrO2-YO1.5-TaO2.5 based thermal barrier coatings (TBCs) against CMAS attack, but thermochemical considerations dictate that YZO contain TaO2.5 for interfacial compatibility. Oxides based on Y4Zr3-xTaxO12+0.5x (x = =0, 0.7, 1.4) were mixed with various ternary and quinary silicate compositions ranging in Ca:Si ratio from 0.35 to 1.13 and equilibrated at 1300 °C. The results show that all combinations form the desired apatite phase except for the mixture of the higher Ta5+ content with the lowest Ca:Si melt. It is found that the addition of Ta5+ increases the capture of Y3+ by the reprecipitated fluorite, decreasing the amount available to form apatite and eventually suppressing it at low Ca:Si. The effect is ascribed to the attractive interactions between Y3+ and Ta5+ in solid solution, similar to that found in tetragonal zirconia, but with concurrent incorporation of anion vacancies associated with excess Y3+ that stabilize the cubic form. As the Ca2+ content of the melt increases, so does the amount of Ca2+ incorporated in fluorite. The latter also interacts attractively with Ta5+ and leads to a reduction of captured Y3+ in fluorite as the Ca content in the reacting deposit increases. This serves to increase the amount of Y3+available in the melt to form apatite in TBC-CMAS interactions.},
doi = {10.1016/j.actamat.2019.11.060},
journal = {Acta Materialia},
number = C,
volume = 185,
place = {United States},
year = {2019},
month = {11}
}

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