SYNTHESIS AND CHARACTERIZATION OF (Ba1-хSrx)7Nb4MoO20 POWDERS FOR PROTON-CONDUCTING SOLID OXIDE FUEL CELLS

This work reports on the preparation and characterization of Sr2+-doped Ba7Nb4MoO20 powders prepared by a solid-state synthesis as promising materials for solid oxide fuel cells. The influence of synthesis parameters and strontium content (x = 0; 0.05; 0.10; 0.15; 0.20) on the phase composition and properties of (Ba1-xSrx)7Nb4MoO20 powders was studied. The results of the phase analysis show that (Ba1-xSrx)7Nb4MoO20 (x = 0; 0.05; 0.10) powders with a minimum amount of secondary phases can be obtained after at least three repeated synthesis cycles at 1060–1080 оС for 10 h. According to the laser diffraction analysis, the synthesized powders comprise particles with a polydisperse size distribution spreading from 0.05 μm to 12 μm and average particle size of 2.1 μm. Electron microscopy observations support these findings and demonstrate that the particles and their aggregates have rounded irregular shape. Moreover, it was found that the morphology and particle size of the powder does not depend on the strontium content. Doping (Ba1-xSrx)7Nb4MoO20 with 15 mol.% and 20 mol.% Sr2+ leads to the formation of a significant amount of secondary phases due to exceeding the solubility limit of strontium, thus making these compositions unsuitable for use in solid oxide fuel cells.