Studies on structural, morphological and electrical properties of Ce_(0.8)Ln_(0.2)O_(2-δ) (Ln = Y~(3+), Gd~(3+), Sm~(3+), Nd~(3+) and La~(3+)) solid solutions prepared by citrate complexation method

摘要

A modified sol-gel method which is also known as citrate complexation is used here to prepare Ce_(0.8)Ln_(0.2) O_(2-δ) (Ln = Y~(3+), Gd~(3+), Sm~(3+), Nd~(3+) and La~(3+)) solid solutions for their proposed application in intermediate-temperature solid oxide fuel cells (IT-SOFCs) as electrolytes. All the samples exhibit the fluorite type crystalline structure without any phase segregation, characteristics of CeO_2, as revealed in XRD pattern. The lattice parameters and densities calculated based on the oxygen vacancy model agreed well with the experimental (Archimedes method) values. The formation of solid solution is also confirmed by Raman spectroscopy. The microstructural features of the samples are recorded by using FE-SEM/TEM. The ionic conductivities of various Ln-doped samples at 623 K as obtained from electrochemical impedance measurement are as follows: Ce_(0.8)Sm_(0.2)O_(2-δ) > Ce_(0.8)Gd_(0.2)O_(2-δ)> Ce_(0.8)Nd_(0.2)O_(2-δ) > Ce_(0.8)La_(0.2)O_(2-δ) > Ce_(0.8)Y_(0.2)O_(2-δ). The activation energy for total conductivity are found to be 0.86, 0.87, 0.89, 0.96 and 1.02 eV for Sm, Gd, Nd, La and Y doped ceria, respectively. The relationship between the dopant radius, chemical compo sition, lattice parameters, morphology and electric properties are discussed here.