Effect of Anelastic Relaxation of Defect Complexes on Mechanical Properties of Stabilized Zirconias

Wednesday, May 14, 2014: 11:00
Bonnet Creek Ballroom IV, Lobby Level (Hilton Orlando Bonnet Creek)
P. Gao (Department of Mechanical Engineering, Texas A&M University), A. Bolon (Department of Materials Science & Engineering, Texas A&M University), E. Lara-Curzio (Materials Science and Technology Division, Oak Ridge National Laboratory), and M. Radovic (Department of Materials Science and Engineering, Texas A&M University, Department of Mechanical Engineering, Texas A&M University)
Stabilized zirconias with high ionic conductivity are currently essential electrolyte materials for solid oxide fuel cells (SOFCs). Study of mechanical properties of oxide ceramics is significant to reliability and durability of SOFCs which work under harsh environment including high temperature, mechanical stress, electric fields, etc. In this paper, we report on the temperature dependent elastic properties of two stabilized zirconias, namely Yttria Stabilized Zirconia (YSZ) and Scandia-Ceria Stabilized Zirconia (SCZ). The elastic properties were studied using Resonant Ultrasound Spectroscopy (RUS), Dynamic Mechanical Analysis (DMA) and Cyclic Compression Testing. It was found that elastic moduli change with temperature in non-linear manner with large peaks in the mechanical loss coefficients (or mechanical damping) at different temperatures. A strong mechanical damping or attenuation is related to the stress induced anelastic relaxation due to hopping of the oxygen vacancies in dopant-vacancy defect complexes. Effects of applied stress, stress frequency, electric field and temperature on the changes of elastic moduli are discussed in more details in this paper.