Improved ionic conductivity in NdGdZr₂O₇: influence of Sc³⁺ substitution

Abstract

Aliovalent Sc³⁺ doped pyrochlores NdGdZr_2−xSc_xO_7−δ (0.0 ≤ x ≤ 0.15) have been prepared by gel-combustion method followed by high temperature sintering. Detailed structural characterization of these compounds has been carried out using X-ray diffraction and Raman spectroscopy, which together have established the retention of pyrochlore structure of these compositions till x = 0.15 Sc³⁺ incorporation. Both X-ray diffraction and Raman results have also indicated the presence of local lattice distortion with net cell contraction upon Sc³⁺ incorporation in these solid solutions. Micro structural studies have revealed highly dense end products with uniform grain distribution and homogeneous compositions at grain size level. Ionic conductivity characterization of system been carried out from 473 to 573 K. A significant improvement in the total ionic conductivity of this series has been observed which has been explained in terms of additional oxygen vacancies created upon Sc³⁺ incorporation and enhanced lattice disorder.