New approach to improve the conductivity of apatite-type lanthanum germanate La sub(9.33)Ge sub(6)O sub( 26) as electrolyte for IT-SOFCs

Apatite-type La sub(9.33)Ge sub(6)O sub( 26) powders have been successfully synthesized by a facile molten-salt synthesis method, using NaCl as a eutectic salt. The morphology, structure and phase composition of the powders were examined. The results demonstrated that the apatite-type La sub(9.33)Ge sub(6)O sub( 26) powders are homogeneous, nano-size, non-agglomerated and well crystallized particles, which are favorable to obtain highly dense pellets. Compared with the conventional methods, dense pellets have been successfully sintered at a relatively low temperature of 1100 degree C, which inhibits the vaporization of GeO sub(2). The pellets exhibit a higher conductivity with a value of 2.4 10 super(-2) S cm super(-1) at 850 degree C, due to the high density and the avoidance of impurity La sub(2)GeO sub(5). The main problems such as Ge volatility, agglomeration and crystallinity encountered in the conventional methods have been effectively solved viathe molten-salt synthesis method. In addition, the related mechanism is also discussed in the present paper.