engleski

Low potassium mobility in iron pyrophosphate glasses

Structural and electrical properties of glasses of the molar composition xK2O−(40−x/2)Fe2O3−(60−x/2)P2O5, x = 0–36 mol%, are investigated by Raman, Mössbauer and Impedance spectroscopy. All glasses show pyrophosphate structure with a growing tendency for depolymerization with increasing K2O content. The DC conductivity changes in a non- monotonic fashion, exhibiting a broad flat maximum as K2O gradually substitutes Fe2O3 and P2O5. The observed conductivity trend could be related to the changes in the number density of polarons which depends on Fe2O3 and fraction of ferrous ions, indicating dominant polaronic conduction mechanism in all glasses. Interestingly, a relatively small addition of K2O, up to 12 mol%, has a positive effect on the polaronic transport due to slight modifications of glass network. Potassium ions are weakly mobile in iron pyrophosphate glass network and have a negligible contribution to the electrical transport even when their molar fraction is as high as 36 mol%.

Iron phosphate glasses ; Pyrophosphate structure ; Electrical conductivity ; Polaronic transport ; Impedance spectroscopy

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