1. Laboratory of Functional Molecular Materials, School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo 255000, China;
2. State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
In the present study, high-quality apatite-type La9.33Ge6O26 powders are successfully synthesized by a facile molten-salt synthesis method (MSSM) at low temperatures, using LiCl, LiCl/NaCl mixture (mass ratio 1:1) as molten salt, respectively. Experimental results indicate that the optimal mass ratio between reactant and molten salt is 1:2, and LiCl/NaCl mixed molten-salt is more beneficial for forming high-quality La9.33Ge6O26 powders than LiCl individual molten-salt. Comparing with the conventional solid-state reaction method (SSRM), the synthesis temperature of apatite-type La9.33Ge6O26 powders using the MSSM decreases more than 350℃, which can effectively avoid Ge loss in the preparation process of precursor powders. Furthermore, the powders obtained by the MSSM are homogeneous, non-agglomerated and well crystallized, which are very favorable for gaining dense pellets in the premise of avoiding Ge loss. On the basis of high-quality precursor powders, the dense and pure ceramic pellets of La9.33Ge6O26 are gained at a low temperature of 1100℃ for 2 h, which exhibit higher conductivities (σ850℃(LiCl)=2.3×10-2 S·cm-1, σ850℃(LiCl/NaCl)=4.9×10-2 S·cm-1) and lower activation energies (Ea(LiCl)=1.02 eV, Ea(LiCl/NaCl)=0.99 eV) than that synthesized by the SSRM.
(Theory of diffusion and ionic conduction in solids)
Fund:
Project supported by the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2016FB16, ZR2015AQ010, and ZR2016AQ08) and the Shandong University of Technology at Zibo and Zibo City Integration Development Project, China (Grant No. 2016ZBXC205).
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