Structural and electrical properties of (Ba1−xSrx)(Zr0.9M0.1)O3, M=Y, La, solid solutions

Abstract

The aim of the work was to study the structural and electrical properties of the (Ba 1− x Sr x )(Zr 0.9 Y 0.1 )O 3 and (Ba 1− x Sr x )(Zr 0.9 Y 0.1 )O 3 solid solutions. The powders of different strontium content ( x = 0, 0.03, 0.05 and 0.1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. Some parameters describing stability and transport properties of the perovskite structure, such as tolerance factor, specific free volume and global instability index, were calculated. It was found that the introduction of strontium into both solid solutions caused the increase of specific free volume and global instability index—these structures became a little less stable but, on the other hand, better ionic conductor. All samples were cubic perovskite and the substitution of strontium for barium caused the decrease of respective lattice parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H 2 and/or H 2 O at the temperature from 300 to 800 °C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. In general, the electrical conductivity was higher in wet atmospheres which contained oxygen, being in accordance with the model of a proton transport in the perovskite structure which assumed the presence of the oxygen vacancy. The solid solution containing 5 mol.% of strontium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres.