Double NASICON-type cell: ordered Nd3+ distribution in Li0.2Nd0.8/3Zr2(PO4)3

Abstract

The NASICON compound Li_0.2Nd_0.8/3Zr₂(PO₄)₃, synthesized by a sol–gel process, has been structurally characterized by TEM and powder diffraction (neutron and X-ray). It crystallizes in the space groupR (No. 148): at room temperature, the Nd³⁺ ions present an ordered distribution in the [Zr₂(PO₄)₃]⁻ network which leads to a doubling of the classical c parameter (a = 8.7160(3) Å, c = 46.105(1) Å). Above 600 °C, Nd³⁺ diffusion occurs leading at 1000 °C to the loss of the supercell. This reversible cationic diffusion in a preserved 3D [Zr₂(PO₄)₃]⁻ network is followed through thermal X-ray diffraction. Ionic conductivity measurements have been undertaken by impedance spectroscopy, while some results concerning the sintering of the NASICON compound are given.