engleski

Potassium mobility/transport in niobium phosphate glasses - the influence of structure

Niobium phosphate glasses belong to the important class of oxide glasses and have been investigated fora wide range of applications, such as the waste form for radioactive waste immobilization, glass fibers and optical lenses, electrodes, as potential solid electrolytes for batteries. In this study structural and electrical properties of glasses with composition xNb2O5-(100-x)[0.45K2O- 0.55P2O5], x=10-50 mol% were investigated by Raman and impedance spectroscopies. Glasses were synthesized by microwave heating of starting chemicals NH4H2PO4, Nb2O5, and KOH in a microwave oven with a nominal power of 1100 W for 30 min. The melt was quenched in the air by pouring it into steel molds and was annealed for 3 h at 773 K. From the Raman spectra, it can be observed that phosphate network gets progressively depolymerized as Nb2O5 content increases replacing the metaphosphate groups by octahedral [NbO6]7−. This indicates that niobium oxide acts as a conditional glass- former. The DC conductivity decreases with a decrease in K2O suggesting that it depends on the concentration of potassium ions. However, a non-linear dependence indicates that potassium mobility is also dependent on structural changes in the glass network i.e. stronger cross-linkage in the niobium rich glass hinders the dynamics/transport of K+ ions. All glasses obey both Summerfield and Sidebottom scaling procedures of conductivity spectra indicating that the conductivity mechanism does not change with the temperature.

Glasses ; Electrical properties ; Niobium ; Raman spectroscopy

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