The Role of Point Defects in the Mechanical Behavior of Doped Ceria Probed by Nanoindentation. (2nd July 2013)

• Record Type: Journal Article
• Authors: Korobko, Roman; Kim, Seong K.; Kim, Sangtae; Cohen, Sidney R.; Wachtel, Ellen; Lubomirsky, Igor
• Is Part Of: Advanced functional materials. Volume 23:Number 48(2013)
• Page Start: 6076
• Page End: 6081
• Publication Date: 2013-07-02
• Subjects: Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201301536
• Languages: English
• ISSNs: 1616-301X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The influence of dopant size and oxygen vacancy concentration on the room temperature elastic modulus and creep rate of ceria doped with Pr<sup>4+</sup>, Pr<sup>3+</sup>, Lu<sup>3+</sup>, and Gd<sup>3+</sup>, is investigated using a nanoindentation technique. Measurements are conducted with both fast (15 mN s<sup>−1</sup>) and slow (0.15 mN s<sup>−1</sup>) 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<sup>3+</sup> and Gd<sup>3+</sup>) 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<sup>3+</sup>‐ and Gd<sup>3+</sup>‐doped ceria display the higher creep rates: due to their large size, they repel oxygen vacancies (V<sub>O</sub>), thereby promoting the formation of O<sub>7</sub>–Ce<sub>Ce</sub>–V<sub>O</sub> complexes that are capable of low temperature rearrangement. Lower creep rates are observed for Pr<sup>4+</sup>‐ and Lu<sup>3+</sup>‐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.</p> </abstract>