Ion dynamics in combustion synthesized Na 3Cr 2(PO 4) 3 crystallites

Abstract

Phase pure Na 3Cr 2(PO 4) 3 crystallites of 41 nm are synthesized by novel solution combustion technique. Characterization methods like X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis spectroscopy, Thermo gravimetric, differential thermal analysis and scanning electron microscopy with energy dispersive X-ray analysis are utilized to validate the structure and phase purity. These crystallites are stable in room temperature rhombohedral phase of R 3 ¯ c symmetry. Fascination of the material is because of its structural stability and high conductivity. Due to its structural stability, present study depicts the ion dynamics in the crystal lattice by analyzing the conductivity relaxation process. Interpretations from impedance representation fortify these conclusions and the dc conductivity activation energy is found to be 0.70 ± 0.02 eV. Almost same value of activation energy for conductivity relaxation from modulus and conductivity representations show that while conducting and relaxing, ion has to overcome the same energy barrier. The conductivity and modulus isotherms are shown to be collapsed to a master curve upon appropriate scaling of the axes; indicating the temperature independent relaxation mechanism. It is evident that the scaling of conductivity and modulus spectra provides the same information on ion dynamics of this material.