A Study of Ionic Conductivity and Free Volume in Sodium Glass

The motivation of this research project is to investigate a property of a sodium glass ((0.6-0.08y)Na₂S+(0.4+0.08y)[(1-y)[(1-x)SiS₂+xPS_5/2]+yNaPO₃], x = 0.00 - 0.35, y = 0.15 - 0.35 ) to advance the idea of creating a sodium-ion battery for solar and wind farms. The hypothesis is that the free volume (v) is related to the ionic conductivity (σ) of the glass by the power law ((σ-σ₀ )/σ₀)=((v-v₀)/v₀)³. The free volume is the unoccupied space between the particles that make up the glass, and the conductivity is the glass’s ability to conduct electricity. The free volume was computed by a Python program developed with data from Olsen et al.; the molar free volume was approximately 15 cubic centimeters. Then, phosphorus and oxygen ratios were calculated, and the glasses were grouped into categories based on these ratios since there is a belief that the conductivity is related to these ratios. Then, the free volume ratios and conductivity were plotted against each other. This preliminary analysis revealed no evidence for cubic power law behavior in this system.