engleski

Electrical transport in phosphate glasses containing MoO3 and WO3

Phosphate glasses containing transition metal oxides such as MoO3 and WO3 are well-known for their semiconducting nature with polaronic conduction mechanism. Also, these glasses can accommodate a relatively high amount of alkali and silver oxides which give rise to ionic conductivity. Such a large compositional and preparation variability enables tuning of the types and mechanisms of the electrical conduction and makes these materials attractive for application in modern electrochemical devices. In this contribution, we discuss various factors that influence electrical transport in these glasses from simple binary WO3/MoO3-P2O5 systems to complex ones containing variable amounts of alkali/silver oxides. Interestingly, WO3 and MoO3 can play very different roles in the electrical conduction in these materials. While polaronic conductivity in MoO3-P2O5 glasses depends strongly on the amount of MoO3 and fraction of molybdenum ions in different oxidation states, in phosphate glasses containing WO3 it is governed mainly by the features of the glass structure, in particular clustering of tungsten units which facilitates the transport of polarons. In combination with alkali oxides, WO3 and MoO3 can actively contribute to the electrical conductivity via polaronic transport, hence giving rise to the mixed ion-polaron conductivity. On the other hand, these oxides can influence the conductivity without introducing the polaronic conduction - by forming mixed phosphate–tungstate and phosphate–molybdate units in the glass network which facilitate the transport of alkali ions in a similar manner to in the classical mixed glass-former effect.

phosphate glasses ; electrical conductivity

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