Na+ ion conductors of glass-ceramics in the system Na1+xAlxGe2-xP3O12(0.3 ≤ x ≤ 1.0)

New sodium-ion conducting glass-ceramics composed of Na1+xAlxGe2-xP3O12(0.3 <= x <= 1.0) crystalline conducting phase with NASICON-type structure were successfully prepared by heat-treating the parent glass. The products were characterized with DSC, XRD, SEM, FTIR and electrochemical impedance spectroscopy techniques. The results showed that all these compounds were isomorphous with NaGe2P3O12, showing characteristic PO4 vibrational bands. The conductivities of the glass-ceramics were higher than those of the corresponding sintered ceramics and two orders of magnitude higher than the parent glass. Among the series studied, the composition of x = 0.8 exhibits the highest conductivity of sigma = 3.8 x 10(-4) S/cm at 300 degrees C (E-a = 0.54 eV). In addition, the reasons for the enhancement of the conductivity in glass-ceramics were discussed in view of the microstructure morphology dependent upon the heating conditions. (C) 2008 Elsevier B.V. All rights reserved.