Peculiarities of ionic transport of oxygen vacancy conducting superionic ceramics

Abstract

The powder of Zr_0.92Y_0.08O₂ (YSZ), Ce_0.9Gd_0.1O_2–δ (GDC) and Sm_0.15Ce_0.85O_2–δ (SDC) compounds from the company Fuel Cell Materials were used for sintering of ceramic samples in air at temperature T = 1673 K. The surface of the prepared ceramics was studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results of the performed XPS investigations revealed that cerium exists as Ce³⁺ and Ce⁴⁺ in both the Ce_0.9Gd_0.1O_2–δ and Sm_0.15Ce_0.85O_2–δ ceramics. XPS spectra of O 1s of all the investigated materials demonstrated two peaks corresponding to oxygen O(1) in crystal lattice and to adsorbed oxygen O(2). Measurements of complex impedance, electric conductivity, dielectric permittivity, and tanδ of dielectric losses were carried out in frequency range 10⁶–1.2⋅10⁹ Hz at temperatures ranging from 300 K to 700 K. Relaxation dispersion of the electric parameters has been found for all the compounds. The dispersion is caused by the oxygen vacancy (V_O^••) transport in grains of the ceramic samples.
Keywords: YSZ, GDC, SDC ceramics, solid oxide fuel cells, ionic conductivity
PACS: 81.15.Jj, 66.30.Dn, 82.47.Ed, 73.61.-r