Molten-salt Synthesis And Characterization Of Apatite La_9.33Ge₆O₂₆ Electrolyte

In the recent decades, the Solid Oxide Fuel Cell obtained the worldwideattention because of its high energy efficiency, clean energy conversion and thepotential for developing fuel cell devices[1-5].In contrast to a vacancy mechanismcommonly observed for fuorite-and perovskite-type oxide ion conductors, ATLGhas a unique interstitial conduction mechanism.Therefore, ATLG exhibits a higherionic conductivity at intermediate temperature (500°C-800°C).In this background,We studied the preparation of apatiteLa9.33Ge6O26electrolyte. The preparation ofATLG is commonly used by the conventional solid state synthesis method, whilethis method needs high temperature that limits their preparations, particularly thepreparations of ATLG. In this paper, We preparate La9.33Ge6O26material powderthrough the method of molten salt synthesis to reduce the synthesis temperature, andimprove the performance of powder. By comparing the solid state synthesis methodand molten-salt synthesis method, can outstand the superiority of the preparation ofLa9.33Ge6O26material powder by molten-salt synthesis method.We use LiCl and LiCl/NaCl(the mass ratio of LiCl and NaCl is1:1) as eutecticsalt. Simultaneously，their crystal structure, morphology and electrical property weremeasured and analyzed. We successfully prepared pure apatite structure La9.33Ge6O26material powder at750°C and600°C by molten-salt synthesis method, respectivelyusing LiCl and LiCl/NaCl(the mass ratio of LiCl and NaCl is1:1)mixture as eutecticsalt. Compared with the solid state synthesis method, the temperature decreased byat least500°C. The as-prepared La9.33Ge6O26powders are homogeneous, nano-size,less agglomerated and well crystallized particles, which are favorable to obtain thehigh dense pellets; Compared with the conventional methods, dense pellets havebeen successfully sintered at a relatively low temperature of1100°C, which inhibitsthe vaporization of Ge; The pellets exhibit a higher conductivity with a value of4.7×10-2Scm-1at850°C, due to the high density and the avoidance of impurity La2GeO5; The main problems such as Ge loss, agglomeration and bad crystallinityencountered in the conventional preparations have been effectively solved via themolten-salt synthesis method. However, the problem of the mass ratio and thesynthesis temperature exsit in the process of the preparation of La9.33Ge6O26materialpowder by the molten-salt synthesis method. In addtion, the increase of sinteringtime can play a positive aspect in the character of secondary sintering syntheticceramic electrolyte, in the terms of idensity, grain plumpness, performance and so on.