Preparation and characterization of Li1 + xAlyScx − yTi2 − x(PO4)3 (x = 0.3, y = 0.1, 0.15, 0.2) ceramics

The powder of Li1 + xAlyScx − yTi2 − x(PO4)3 with x = 0.3 and y = 0.1, 0.15, 0.2 has been prepared by solid state reaction and the ceramics have been sintered. The results of X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy up to 109 Hz are presented. At room temperature the compounds belong to the rhombohedral symmetry (space group R3̅c). Ti 2p, P 2p, O 1s, Sc 2p, Al 2p, and Li 1s core level XP spectra's were fitted. The values of binding energies of core level XP spectra's, splitting energies of Ti 2p3/2–Ti 2p1/2, Sc 2p3/2–Sc 2p1/2, P2p3/2–P2p1/2 spin-orbit doublets, and amount of the elements with different binding energies were found to be dependent on stoichiometric factor y. The elemental compositions are defined by EDX. Impedance spectroscopy study in the frequency range 10 Hz–3 GHz have shown three relaxation dispersion regions of electrical properties and the processes are thermally activated. The high frequency dispersion region may be attributed to the relaxation processes in bulk, while lower dispersion regions are related to the processes in grain boundaries and blocking Pt electrodes.

► Compounds belong to the rhombohedral symmetry, typical for NASICON.
► The typical values of parameters obtained from XP spectra, were found to be dependent on stoichiometry.
► XPS suggested that elements could be in several oxidation states.
► XPS has shown that Li ions can occupy two different positions.
► The bulk ionic conductivity is not dependent on stoichiometry.
► Two relaxation dispersion regions of electrical properties were found and the processes are thermally activated.