Elaboration and ionic conduction of apatite-type lanthanum silicates doped with Ba, La10−xBax(SiO4)6O3−x/2 with x = 0.25–2

The main task in SOFC research is the reduction of the working temperature down to the range 700–800 °C. Apatite ceramics are interesting alternative SOFC electrolytes because of their open structure including tunnels for the diffusion of oxide ions and their good chemical stability. This study reports the influence of barium doping on the microstructural and electrochemical properties of the apatite phase La10−xBax(SiO4)6O3−x/2 with x = 0.25–2. This doping range allows theoretical stoichiometric and overcharged apatite (more than two oxide ions in the tunnel). X-ray diffraction results on fired pellets show total insertion of the barium in the apatite lattice with a linear increase of the lattice parameters following the barium rate. Ionic conductivities are measured under air by impedance spectroscopy between 400 and 900 °C. The results are compared with apatite phases doped with calcium and strontium on the La site.