Preparation and characterization of NASICON type Li+ ionic conductors

The new scandium/aluminium co-doped NASICON phases Li1 + x Al (y) Sc (x -aEuro parts per thousand y) Ti2 -aEuro parts per thousand x (PO4)(3) (x = 0.3, y = 0,0.1,0.2,0.3) were prepared by mechanical milling followed by annealing of the mixtures at 950 A degrees C. X-ray diffraction of all samples showed the formation of NASICON structure with space group R-3c along with a minor impurity. Rietveld refinement of the X-ray data was performed to identify the structural variation. Doping with Sc3+ caused elongation of a- and c- axes for all the compounds when compared with undoped LiTi2(PO4)(3). The compound Li1.3Sc0.3Ti1.7(PO4)(3) showed a maximum of a = 8.5504(7), c = 20.986(3) at room temperature and exhibited highest coefficient of thermal expansion. The highest ionic conductivity (sigma), 7.28x10(-4) S cm(-1) was observed for Li1.3Sc0.3Ti1.7(PO4)(3), two orders of magnitude higher than for the undoped phase.