On the way to understand the keys for the stabilization of the conductive phase in doped- NASICON-type materials

A family of doped-NASICON-type structures according to the chemical compositions: Li1.2 Zr1.9M0.1(PO4)3 [with M = Ca2+, Mg2+, Zn2+]; Li1.1 Zr1.9Y0.1(PO4)3 and Li1.0 Zr1.9Ce0.1(PO4)3 have been synthesized by solid state reaction. The modification on the thermal treatment proposed in this work makes possible to obtain a high purity phase confirmed by XRD, SEM, microRaman-confocal and FTIR. Rietveld refinement evidences how the LZP lattice parameters are affected by each of those five different dopant cations incorporated into the pristine structure. Impedance spectroscopy proves how the relationship radius - charge of each dopant-ion affects the ionic conductivity. Unravelling that the partial replacement of Zr4+ in the LZP by a dopant improves the conductivity behavior. When the dopant cation has a lower charge and a larger size than the Zr4+ the developed structure favours the lithium-ion mobility at room temperature and the lithium conductivity increases.