The formation of the strontium zirconates SrZrO3, Sr4Zr3O10, Sr3Zr2O7 and Sr2ZrO4, and of the lanthanum zirconates La2Zr2O7 and La2-xYZr2O7 at 1450-degrees-C was investigated by x-ray powder diffraction and DTA. Three different routes of synthesis were tested. In the Sr-zirconate system, single phase orthorhombic SrZrO3 and somewhat impure, tetragonal Sr2ZrO4 were observed, whereas the formation of ordered Ruddlesden-Popper phases, SrnZrn-1O3n-2, where n = 4 and 3, could not be verified. The conductivity of La2Zr2O7 was 3.7 X 10(-6) S/cm at 750-degrees-C and 3.8 x 10(-5) S/cm at 1000-degrees-C. The conductivity of the Sr-zirconates increases with increasing Sr/Zr ratio. Samples with a nominal composition corresponding to Sr2ZrO4 have a conductivity of 7.5 x 10(-5) and 5.9 x 10(-4) S/cm at 750 and 1000-degrees-C, respectively. For all samples one observes low activation energies for ionic conduction (0.5-0.65 eV). Formation of pyrochlore structure La2-xYZr2O7 from YSZ and La2O3 at 1450-degrees-C was demonstrated.
|Journal||Solid State Ionics|
|Publication status||Published - 1992|