Structure and lithium-ion mobility in Li1.5M0.5Ge1.5(PO4)3 (M = Ga, Sc, Y) NASICON glass-ceramics

This work reports structural and lithium-ion mobility studies in NASICON single- or multiple phase Li1+xMxGe2-x(PO4)(3) (M = Ga3+, Sc3+, Y3+) glass-ceramics using solid-state NMR techniques, X-ray powder diffraction, and impedance spectroscopy. X-ray powder diffraction data show the successful incorporation of Ga3+ and Sc3+ into the Ge4+ octahedral sites of the NASICON structure at the levels of x = 0.5 and 0.4, respectively. The glass-to-crystal transition was further characterized by multinuclear NMR and electrical conductivity measurements. Among the studied samples, the gallium-containing glass-ceramic presented the highest DC conductivity, 1.1 x 10(-4) S/cm at room temperature, whereas for the Sc-containing samples, the maximum room temperature conductivity that could be reached was 4.8 x 10(-6) S/cm. No indications of any substitution of Ge4+ by Y3+ could be found.