Enhancement of the ionic conductivity of lanthanum silicate-based apatites was

examined with emphasis on optimizing the La composition and the Mg doping

level at the same time. La10Si5.8Mg0.2O26.8 and La9.8Si5.7Mg0.3O26.4 showed the

highest level of the ionic conductivities among apatite silicates, 8.8 and 7.4 x

102S/cm at 800C, respectively, with a very low level of activation energy (0.42 to

0.43eV). Their conductivities were higher than yttria stabilized zirconia below

900C and even comparable to Sr and Mg doped lanthanum gallate below 550C.

Structural investigation by Rietveld analysis of the powder X-ray diffraction pattern revealed significant enlargement of the bottleneck triangle sizes of the

conduction channel with the Mg doping.

Ionic Conductivity and Fuel Cell Properties of Apatite-Type Lanthanum Silicates

Doped with Mg and Containing Excess Oxide Ions. H.Yoshioka, Y.Nojiri,

S.Tanase: Solid State Ionics, 2008, 179[38], 2165-9