Synthesis and electrical properties of Li1-xMxTi2-x(PO4)3 (where M = Sc, Al, Fe, Y; x=0.3) superionic ceramics

Compounds of the system Li1+xMxTi2-x (PO4)(3) (where M = Sc, Al, Fe, Y; x = 0.3) were synthesized by a solid-state reaction and studied by X-ray diffraction. The ceramic samples were sintered and investigated by complex impedance spectroscopy in the frequency range 10(6)-1.2x10(9) Hz in the temperature range 300-600 K. Two relaxation dispersions related to the fast Li+ ion transport in bulk and grain boundaries were found. The activation energies of the bulk conductivity and relaxation frequency were obtained from the slops of Arrhenius plots. The values of the activation energies of the bulk ionic conductivity and relaxation frequency were found to be very similar in all the materials investigated. That can be attributed to the fact that the temperature dependences of the bulk conductivity are caused only by the mobility of the fast Li+ ions, while the number of charge carriers remains constant with temperature.