Novel insights into electrical transport mechanism in ionic‐polaronic glasses

Transformation of electrical transport from ionic to polaronic in glasses, which are a potential class of new cathode materials, has been investigated in four series containing WO 3 /MoO 3 and Li + /Na + ions, namely: x WO 3 –(30−0.5 x )Li 2 O–(30−0.5 x )ZnO–40P 2 O 5 , x WO 3 –(30−0.5 x )Na 2 O–(30.5 x )ZnO–40P 2 O 5 , x MoO 3 –(30−0.5 x )Li 2 O–(30−0.5 x )ZnO–40P 2 O 5 , and x MoO 3 –(30−0.5 x )Na 2 O–(30−0.5 x )ZnO–40P 2 O 5 , 0 ≤ x ≤ 60, (mol%). This study reports a detailed analysis of the role of structural modifications and its implications on the origin of electrical transport in these mixed ionic‐polaron glasses. Raman spectra show the clustering of WO 6 units by the formation of W–O–W bonds in glasses with high WO 3 content while the coexistence of MoO 4 and MoO 6 units is evidenced in glasses containing MoO 3 with no clustering of MoO 6 octahedra. Consequently, DC conductivity of tungstate glasses with either Li + or Na + exhibits a transition from ionic to polaronic showing a minimum at about 20‐30 mol% of WO 3 as a result of ion‐polaron interactions followed by a sharp increase for six orders of magnitude as WO 3 content increases. The formation of WO 6 clusters involved in W‐O‐W linkages for tungsten glasses plays a key role in significant increase in DC conductivity. On the other hand, DC conductivity is almost constant for glasses containing MoO 3 suggesting an independent ionic and polaronic transport pathways for glasses containing 10‐50 mol% of MoO 3 .