Transport property and Raman spectra of nanocrystalline solid solutions Ce0.8Nd0.2O2-delta with different particle size

Nanocrystalline solid solutions Ce0.8Nd0.2O2-delta with different grain siz e were synthesized by a sol-gel method. XRD measurements showed that the pr oduct obtained by sintering the fresh gel at 200 degreesC crystallized in a single fluorite structure and the grain size was calculated to be ca. 7.2 nm by Scherrer formula. The grain size for the solid solutions grew with th e increase of sintering temperature. The first-order Raman spectra of the s olid solutions exhibited two peaks. The strong band F(2)g mode at ca. 470 c m(-1) was assigned to the symmetric breathing mode of oxygen atoms around c erium ions, while the weak band at ca. 580 cm(-1) to the presence of oxygen vacancies. Accompanying with grain growth from 7.2 to 65.1 nm, the F-2g mo de shifted ca. 9 cm(-1) towards higher frequencies, while the half-height w idth became narrower. The ionic conductivity for the solid solution Ce0.8Nd 0.2O2-delta was sigma (500 degreesC) = 2 65 x 10(-3) S cm(-1), and the acti vation energy was 0.82 eV. (C) 2001 Elsevier Science B.V. All rights reserv ed.