Preparation and characterization of NASICON type Li + ionic conductors

Abstract

The new scandium/aluminium co-doped NASICON phases Li1 +xAl ySc x-yTi 2-x(PO 4) 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 °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 Sc 3+ caused elongation of a- and c- axes for all the compounds when compared with undoped LiTi 2(PO 4) 3. The compound Li 1.3Sc 0.3Ti 1.7(PO 4) 3 showed a maximum of a08.5504(7), c020.986(3) Å at room temperature and exhibited highest coefficient of thermal expansion. The highest ionic conductivity (σ), 7.28 × 10 -4 S cm -1 was observed for Li 1.3Sc 0.3Ti 1.7(PO 4) 3, two orders of magnitude higher than for the undoped phase. © Springer-Verlag 2012.