The dielectric relaxation behavior induced by sodium migration in the Na2CoSiO4 structure within a three-dimensional Co–O–Si framework

Abstract

The disodium cobalt(II) orthosilicate material (NCS) has been synthesized using improved solid-state (NCS-SS) and co-precipitation (NCS-CP) methods of synthesis. The Rietveld refinement of the XRD pattern of Na₂CoSiO₄ has demonstrated an orthorhombic crystal system with the space groups Pna2₁ and Pbca for NCS-SS and NCS-CP respectively. The elemental mapping of microstructures by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) showed the porous morphology and the homogenous particles of the Na₂CoSiO₄ powders. Their dielectric properties were measured in the frequency and temperature ranges of 0.1–10⁶ Hz and 383–613 K respectively. Different dielectric relaxation phenomena associated with the Na⁺-ion migration through different paths were displayed in relation with the temperature and frequency. The decrease and increase in the dielectric properties were found to be dependent on the formation of short-range ordered structure formed after the migration of Na⁺-ions. In the present work, an attempt has been made to study the relation between the structural properties and the dielectric process. Thus, interesting insights into the transport behavior of Na⁺-ions in different chemical environments were obtained. This in turn provides an effective procedure to probe the relationship between the diffusion pathway of Na⁺-ions and the dielectric response.