Naslov
Nature of mixed electrical transport in Ag2O– ZnO–P2O5 glasses containing WO3 and MoO3 studied by impedance spectroscopy

Autori
Pavić, Luka ; Nikolić, Juraj ; Šantić, Ana ; Pajić, Damir ; Mošner, Petr ; Koudelka, Ladislav ; Moguš-Milanković, Andrea

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

Izvornik
Borates & Phosphates 2017 : Book of abstracts / - Sheffield : Society of Glass Technology, 2017, 82-82

Skup
Borate & Phosphate 2017

Mjesto i datum
Oxford, Ujedinjeno Kraljevstvo, 24.07.2017. - 28.07.2017

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Glass ; Impedance spectroscopy ; Phosphates ; Silver ions

Sažetak
Phosphate-based glasses containing mobile silver ions and transition metal oxides (TMO) such as WO3 and MoO3 exhibit mixed electronic- ionic conductivity. In general, glass systems with mixed conduction behaviour are especially attractive due to their potential applications as cathode materials for batteries, memory switching, and electrical threshold devices. Electronic (polaronic) conduction is achieved by small polaron hopping mechanism and electrical conductivity depends on the overall amount of TMO and fraction of TM ions in different valence states, whereas ionic conductivity depends on the concentration and mobility of silver ions. The understanding of the charge carriers transport phenomenon in mixed conducting glasses is a challenging task due to a variety of parameters that influence each type, possible mutual interactions among ions and polarons as well as complexity of glass structure. The aim of this study was to investigate the nature of electrical transport and changes with type and content of TMO in glasses containing Ag2O. Glasses from two series, namely xTMO–(30−0.5x)Ag2O–(30−0.5x)ZnO– 40P2O5 (TMO=MoO3/WO3, 0≤x≤60 mol%), were electrically characterized by impedance spectroscopy (IS) in wide frequency and temperature range. Moreover, their structural features were studied by Raman spectroscopy, while EPR and SQUID measurements were employed to determine the fraction of tungsten and molybdenum ions in different valence states. The results of IS measurements revealed gradual changes in nature of electrical transport with increase in TMO content. TMO-free glass shows pure ionic conductivity of 3x10-9 (Ωcm)-1 at RT due to highly mobile Ag ions. In both series, electrical conductivity of glasses is decreasing for about 3 to 4 orders of magnitude with gradual exchange of Ag2O by TMO content. For WO3 series, a clear minimum in conductivity is observed at approximately x=30 mol% whereas with further addition of WO3 conductivity starts to increase due to an increase in polaronic contribution. These results suggests a distinct transition from predominantly ionic (up to x=30 mol%) to predominantly polaronic transport (x>30 mol%) in this glass series. In contrast, for MoO3 series conductivity is decreasing in the whole mixed Ag-TMO compositional range (up to x=50 mol%) indicating that the nature of electrical transport is dominated by ionic component due to highly mobile silver ions without a significant contribution of polaronic mechanism. Furthermore, two extremes in both compositional ranges are binary 60TMO–40P2O5 (mol%) which are pure polaronic conductors. Both glasses show increase in conductivity with extraordinary high value of 4.6×10-6 (Ωcm)-1 at RT for 60WO3–40P2O5 glass, in particular. Changes in electrical mechanism, in both series, are discussed in details in terms of possible origins: a) structural influence on different migrating paths for electrons (polarons) and/or ions and their mutual interactions and b) ion-polaron effect. Obtained results represent novel view on the correlation between structure and electrical behaviour in these mixed ion-polaron glass systems.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

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