“…Regarding now the final product, the only impurity that can be detected is the band at 1,226 cm −1 associated to NASICON. Indeed, lantern units building the Li 3 Fe 2 (PO 4 ) 3 lattice give rise to infrared bands in the range 1,150-1,250 cm −1 [30], which are attributed to the stretching vibrations of terminal PO 3 units because the NASICONlike phase shows the same vibrational modes that observed in R(PO 3 ) 3 metaphosphates (R=Ga, In, Y, Sm, Gd, Dy) in the range 1,230-1,280 cm −1 [31]. For the case of the sample heated at T s =400°C, this result corroborates the observation of this impurity phase on the XRD spectra.…”