Influence of K+ substitution on germanium doped strontium silicate (Sr3-3xK3xSi3-3yGe3yO9-δ; 0 ≤ x ≤ 0.20, y=0.1) for application as solid electrolyte

Abstract

The different alkali metal substitution strategies of the strontium meta-silicate based ion conductors have been enormously cross-examined to synthesize cost-effective novel electrolyte for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs). In the present investigation, crystal structure, phase formation, microstructure, total conductivity and stability of the Potassium and Germanium incorporated Sr3Si3O9 based system, Sr3-3xK3xSi3-3yGe3yO9-δ (0 ≤ x ≤ 0.20, y = 0.1), is examined for their application as solid electrolyte for electrochemical devices such as ITSOFCs. These samples have been made via solid state reaction route. X-ray Rietveld refinement method was used for the structural investigation. Raman and FT-IR spectroscopy were performed to examine the phase formation and absorption of light by the bonds of vibrating molecules to provide molecular characteristics and vibrational modes of the molecules. The X-ray Photoelectron Spectroscopy study was used to validate the characteristic valence states of the constituting elements. Thermo-gravimetric analysis was performed to inspect the thermal stability and weight changes in the compounds during heating process. In the SEM and EDS mapping, an amorphous phase of K2Si2O5 can be visualized which seems to segregate along grain boundaries and this amorphous complexion augmented with K+ dopant concentration. AC Electrical impedance spectroscopy studies suggest that the ionic conduction in Sr3-3xK3xSi3-3yGe3yO9-δ could be from the oxide ions along with mobility of K+ ions of the glassy phase. In this study, we also tried to get the optimal doping condition with compositions to minimize numerous concern of the system.