Determination of the nature of the co-doping effect on the structure, mechanical properties and ionic conductivity of SOFC electrolyte based on YSZ

Abstract

In this work, the influence of additives of rare earth and transition metals on the process of formation of the structure, mechanical and electrical properties of the SOFC electrolyte material based on zirconia was studied in order to identify the key technological and physical parameters affecting this process.A strong influence of the type of doping impurity on the lattice parameter of synthesized particles and sintered ceramics, on the strength and density of ceramics, and on the activation energy of ionic conductivity along grain boundaries was found. The effect of the type of additive on the value of ionic conductivity by grain volume in sintered ceramics was not detected.It was shown that the dopants effects on the ionic conductivity of zirconia electrolyte material in the indirect mode. The ionic radius of the dopants are determines the level of stability of the substitutional solid solution, and the diffusion of the impurity to the grain boundaries during sintering. It has been established that the more the ionic radius of the impurity differs from the equivalent ionic radius of the cation, the greater the activation energy of ionic conductivity along grain boundaries is observed. This depends on the degree of contamination of the grain boundaries with various impurities, which can diffuse to the grain boundaries and segregate there due to a violation of the Hume-Rothery rule. At the same time, the activation energy of ionic conductivity over the grain volume changes insignificantly, which indicates that the conductivity over the grain volume depends strongly on the number of oxygen vacancies, the concentration of which weakly depends on the ionic radius of the impurity.