The effect of Ba doping upon the microstructural and electrochemical properties of the apatite phase, La10−xBax(SiO4)6O3−x/2 with x = 0.25 to 2, was reported. This doping range permitted theoretical stoichiometric and overcharged apatite (more than 2 oxide ions in the tunnel). X-ray diffraction results on fired pellets revealed total insertion of the Ba in the apatite lattice, with a linear increase in the lattice parameters following the Ba rate. Ionic conductivities were measured in air by using impedance spectroscopy at between 400 and 900C. The results were compared with apatite phases doped with Ca and Sr on the La sites.

Elaboration and Ionic Conduction of Apatite-Type Lanthanum Silicates Doped with Ba, La10−xBax(SiO4)6O3−x/2 with x = 0.25–2. A.Vincent, S.B.Savignat, F.Gervais: Journal of the European Ceramic Society, 2007, 27[2-3], 1187-92