Naslov
Structure and electrical properties of Cr2O3-Fe2O3-P2O5 and Cr2O3-PbO-Fe2O3-P2O5 glasses and glass-ceramics

Autori
Šantić, Ana ; Moguš-Milanković, Andrea ; Skoko, Željko ; Day, Delbert E.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Acta Crystallographica Section A / Ban, Nenad ; Luić, Marija - Zagreb : European Crystallographic Association, 2015, S309-s309

Skup
29th European Crystallographic Meeting (ECM29)

Mjesto i datum
Rovinj, Hrvatska, 23.08.2015. - 28.08.2015

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Glass-ceramics; Electrical conductivity

Sažetak
Iron phosphate glasses are electronically conducting glasses with polaronic conduction mechanism where conduction takes place by electrons hopping from Fe2+ to Fe3+. Consequently, polaron transport directly depends on Fe2+/Fetot ratio and overall Fe2O3 content. On the other hand, electronic conduction in iron phosphate glass-ceramics depends on (micro)structure, size, shape, distribution and nature of the crystalline phase(s). The aim of the present study was to investigate structure and electrical properties of iron phosphate glasses and glass-ceramics containing PbO and Cr2O3 as a nucleating agent. For that purpose two series of glasses, (43.3-x)PbO-(13.7+x)Fe2O3-43.0P2O5 (0≤x≤30 mol%) and xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5 (0≤x≤10 mol%), were prepared by melt quenching technique. The structural changes in glasses were investigated using X-ray diffraction analysis (XRD), Raman and Mössbauer spectroscopies and scanning electron microscopy whereas electrical properties were investigated by impedance spectroscopy. The Raman spectra and XRD of PbO-Fe2O3-P2O5 compositions showed that melt underwent partial crystallization when Fe2O3 content is ≥33.7 mol%. With increasing molar O/P ratio and fraction of Fe2+ ions, the length of phosphate units decreases which causes a higher crystallization tendency of the melt. For fully amorphous glasses with < 33.7 mol% Fe2O3, electrical conductivity increases with the increase of Fe2+/Fetot indicating polaronic transport. On the other hand, the electrical conductivity of the partially crystallized samples decreases despite the increase in Fe2+ fraction which can be attributed to a massive crystallization of several crystalline phases: Fe7(PO4)6, Fe3(P2O7)2, Fe2Pb3(PO4)4 and FePO4. However, the electrical conductivity of partially crystallized sample with 33.7 mol% Fe2O3 is still considerably high which is related to the fast conduction at the interfaces between crystallites and glassy phase. The structural studies on the Cr2O3-PbO-Fe2O3-P2O5 glasses showed that the compositions containing up to 4 mol% Cr2O3 formed fully amorphous samples while compositions containing 8 and 10 mol% Cr2O3 partially crystallized during cooling to Fe7(PO4)6, Fe2Pb3(PO4)4 and Cr2Pb3(PO4)4. The electrical conductivity within this series is a function of the Fe2+/Fetot ratio and passes through a maximum at 0.48 which indicates that the conduction process is controlled entirely by the polaron transfer between iron sites.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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