Naslov
Electrical transport in sodium phosphate glasses containing tungsten and molybdenum oxides

Autori
Šantić, Ana ; Pavić, Luka ; Koudelka, Ladislav ; Mošner, Petr ; Moguš-Milanković, Andrea

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

Izvornik
Abstract book of the XVI European Ceramic Society Conference / - Torino : AIM Group International Florence Office, 2019, 448-448

Skup
16th Conference & Exhibition of the European Ceramic Society (ECerS 2019)

Mjesto i datum
Torino, Italija, 16.06.2019. - 20.06.2019

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
oxide glasses ; electrical conductivit ; , structure

Sažetak
Oxide glasses containing Li2O or Na2O in combination with transition metal oxide (TMO) have recently emerged as promising candidates for cathode materials in battery technologies. Such glasses exhibit mixed ion-polaron conductivity with the ionic contribution being dependent on the concentration and mobility of the alkali (Li+/Na+) ions whereas polaronic conductivity follows the small polaron hopping mechanism and depends on the amount of TMO and a relative fraction of TM ions in different valence states. In this study, we report the influence of WO3 and MoO3 on the transport of sodium ions in phosphate glasses. Two series of glasses of molar composition 40Na2O-xWO3-(60-x)P2O5 and 40Na2O-xMoO3-(60-x)P2O5, x = 0, 10, 20, 30, 40, 50 mol%, were prepared by melt quenching. Electrical properties of glasses were measured by impedance spectroscopy over a wide temperature and frequency range. Raman spectroscopy was used for structural characterization, whereas the fractions of tungsten and molybdenum ions in different valence states were determined by EPR spectroscopy. The DC electrical conductivity of glasses changes non-linearly as P2O5 is gradually replaced by WO3/MoO3 exhibiting maximum at 40 mol% WO3 (1.6 x 10-8 S/cm at 303 K) and 30 mol% MoO3 (2.2 x 10-9 S/cm at 303 K). Raman spectra reveal that with the addition of WO3/MoO3, octahedral WO6/MoO6 units enter the phosphate network, gradually depolymerize metaphosphate chains and form tungstate/molybdate network. We propose that the observed conductivity enhancement of approximately four orders of magnitude originates from the modification of glass structure which has a favourable effect on the mobility of sodium ions rather than the contribution of polaronic transfer between tungsten or molybdenum ions in different valence states. Indeed, EPR study revealed that the fraction of W5+/Wtot and Mo5+/Motot is less than 1% which suggest that the polaronic conductivity in these glasses is small. In conclusion, we show that the mixed-glass former effect can be extended to the glass systems where the conventional glass forming oxide (P2O5) is replaced by the conditional one (WO3/ MoO3).

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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