Enhancement of sodium ion conductivity in phosphate-based glass-ceramics by chemical substitution approach

Abstract

A NASICON-type sodium-ion conducting material was synthesized via the glass-ceramic route by investigating the zinc doped Na 2 O–Al 2 O 3 –TiO 2 –P 2 O 5 system. The glasses and glass-ceramics corresponding to the formula Na 2+x Al 1-x Zn x Ti(PO 4 ) 3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1), labeled as (NAZTP-G x ) and (NAZTP-GC x ) respectively, were characterized using different techniques. Differential Scanning Calorimetry (DSC) measurements were carried out to identify the characteristic temperatures, the glass transition (T g ) and the crystallization temperature (T c ). X-ray Diffraction (XRD) analysis of the glass-ceramics confirmed the formation of a solid solution Na 2+x Al 1-x Zn x Ti(PO 4 ) 3 NASICON phase, Theoretical calculations employing the Perdew–Burke–Ernzerhoff generalized gradients approximation (PBE-GGA) model supported the potential substitution of aluminum by zinc in the octahedral site in the NASICON-phase. Further structural insights were obtained through Infrared (IR) and Raman spectroscopies . Scanning electron microscopy (SEM) analysis revealed a distinct flower-like shape of the formed crystallites in the glass-ceramic NAZTP-GC 0.2 . Electrical characterization using electrochemical impedance spectroscopy (EIS) demonstrated that the NAZTP-GC 0.2 sample exhibited the highest ionic conductivity at 300 °C, reaching 4.1 × 10 −5 (Ω −1 cm −1 ) with an activation energy of 0.25 eV. The DC polarization was performed on the NAZTP-GC 0.2 glass-ceramic, revealing that the ions are the main charge carriers in the sample. This comprehensive analysis provides valuable insights into the partial zinc doping of NASICON glass-ceramics, offering potential for improved performance as solid electrolytes in various applications. • Elaboration of sodium ion conducting phosphate glasses. • Synthesis of glass-ceramics with a NASICON-like structure. • The optimal zinc dopping in the glass-ceramics enhances the conductivity.