Ionic conductivity and structural characterization of Na1.5Nb0.3Zr1.5(PO4)(3) with NASICON-type structure

The NASICON-type Na1.5Nb0.3Zr1.5(PO4)(3) was prepared by solid state reaction of Nb2O5 and the precursor gamma-NaHZr(PO4)(2) at 700 degrees C. The EPR spectra showed a signal with a g factor of 1.984 assigned to Nb (IV) species in octahedral oxygen environments. The X-ray powder diffraction pattern obtained with monochromatic radiation was indexed on the basis of a rhombohedral cell, the hexagonal parameters being a(H) = 8.8061(2) and c(H) = 22.7638(7) Angstrom. The Na+ ion conduction was measured by the complex impedance method (frequency range: 0.1-10(5) Hz; temperature range: 20-500 degrees C) on four pellets previously sintered at 450, 750, 900 and 1000 degrees C. The conductivity data are discussed in relation to the sintering temperature. An activation energy of 0.60 eV for the movement of Na+ ions in the NASICON framework has been found.