Microstructural Evolution in a CeO2-Gd2O3 System
Abstract Microstructural evolution in a CeO2-Gd2O3 system at atomic and nanoscale levels with increasing Gd concentration has been comprehensively investigated by transmission electron microscopy. When the Gd concentration was increased from 10 to 80 at.%, the phase transformation from ceria with fluorite structure to solid solution with C-type structure was not a sudden change but an evolution in the sequence of clusters, domains, and precipitates with C-type structure in the fluorite-structured matrix. Moreover, the ordering of aggregated Gd cations and oxygen vacancies in these microstructural inhomogeneities developed continuously with increasing Gd concentration. This microstructural evolution can be further described based on the development of defect clusters containing Gd cations and oxygen vacancies.
Influence of microstructural characteristics on ionic conductivity of ceria based ceramic solid electrolytes
Abstract Solid electrolyte powders based on gadolium-doped and samaria-codoped ceria of compositions Ce 0.8 Gd 0.2−x Sm x O 1.9 (x = 0.00; 0.01; 0.03; 0.05) were sintered using the polymeric precursor method (Pechini). The X-ray diffractometry results confirmed the formation of a single crystalline phase, that is, a solid solution. Test specimens were compacted using uniaxial cold pressing followed by two-stage sintering. Relative densities were higher than 96% of theoretical density in all the samples. Ionic conductivity was determined using impedance spectroscopy, obtaining values of 10 −2  S cm −1 at 700 °C, with the best results for codoped electrolytes, primarily the Ce 0.8 Gd 0.15 Sm 0.05 O 1.9. system. This study aimed at correlating ionic conductivity variations of codoped electrolytes with microstructural alterations (on a nanometric scale) resulting from the addition of codopants. Energy dispersive spectroscopy (EDS) was used to analyze the grain boundary compositions of the electrolytes produced and assess possible dopant segregation in these regions. Interplanar spacings corresponding to the crystallographic planes of the cubic (fluorite-type) phase were identified using high-resolution transmission electron microscopy (HRTEM) images. Extra diffraction spots and diffuse stains were observed in the doped and codoped electrolytes, using selected area electron diffraction (SAED), confirming the presence of amorphous nanodomains at the atomic level. However, the codoped system exhibited diffraction patterns with no diffuse stains, indicating that codoping favored obtaining nanodomain-free regions. These regions displayed better structural homogeneity, which may explain the enhanced ionic conductivity in codoped systems.
Simulation Analysis of Local Heat Treatment Formability of an Aerospace Aluminum Alloy Frame Parts
Wang Zhijian1,a, Guo Fangyu1,b, Shang Xiaofeng1,c, Song Hongwu2,d, Wang Ling3,e and Wang Jiale1,f 1School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China 2Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China 3Shenyang aircraft industry company, Shenyang 110134, China aWangzhijian1974@sina.com, b1486121506@qq.com, c1009074102@qq.com dhwsong@imr.ac.cn, ew_ling2008@aliyun.com, f1591897439@qq.com