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The Role of Point Defects in the Mechanical Behavior of Doped Ceria Probed by Nanoindentation
Author(s) -
Korobko Roman,
Kim Seong K.,
Kim Sangtae,
Cohen Sidney R.,
Wachtel Ellen,
Lubomirsky Igor
Publication year - 2013
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201301536
Subject(s) - materials science , nanoindentation , dopant , creep , doping , vacancy defect , crystallographic defect , elastic modulus , oxygen , composite material , ionic bonding , crystallography , ion , chemistry , optoelectronics , organic chemistry
The influence of dopant size and oxygen vacancy concentration on the room temperature elastic modulus and creep rate of ceria doped with Pr 4+ , Pr 3+ , Lu 3+ , and Gd 3+ , is investigated using a nanoindentation technique. Measurements are conducted with both fast (15 mN s −1 ) and slow (0.15 mN s −1 ) loading modes, including a load‐hold stage at 150 mN of 8 s and 30 s, respectively. Based on the data obtained using the fast loading mode, it is found that: 1) the dopant size is a primary determinant of the elastic modulus—the larger dopants (Pr 3+ and Gd 3+ ) produce lower unrelaxed moduli which are independent of the oxygen vacancy concentration. 2) The rearrangement of point defects is the major source of room temperature creep observed during load‐hold. Pr 3+ ‐ and Gd 3+ ‐doped ceria display the higher creep rates: due to their large size, they repel oxygen vacancies (V O ), thereby promoting the formation of O 7 –Ce Ce –V O complexes that are capable of low temperature rearrangement. Lower creep rates are observed for Pr 4+ ‐ and Lu 3+ ‐doped ceria: the former has no vacancies and the latter, immobile vacancies. 3) Nanoindentation is a practical technique for identifying materials with labile point defects, which may indicate useful functionality such as high ionic conductivity, large electrostriction, and inelasticity.