Thermal analyses of yttrium-doped barium zirconate with phosphor pentoxide, boron oxide and zinc oxide addition

Yttrium-doped barium zirconate (BZY), one of the protonic conductors considered to be used as solid electrolyte in solid oxide fuel cells (SOFC) operating at temperatures lower than the one found in conventional oxide-ion SOFCs, still presents some challenges to reach high density and high electrical conductivity: the difficulty to sinter at temperatures well below its melting point and the blocking of the conducting species at the grain boundaries. We describe an experimental sequence to prepare powders and to obtain highly dense BZY ceramic pellets with enhanced electrical conductivity, using either phosphor pentoxide (P2O5), boron oxide (B2O3) or zinc oxide (ZnO) as sintering aid. The reactions leading to sintering ceramic pellets with densities higher than 94% of the theoretical density and improved electrical performance are monitored by thermal analyses. BZY with the addition of 5 mass% P2O5 or 2 mass% ZnO shows a tenfold enhancement of the electrical conductivity.