Naslov
Structure-electrical properties relationship in polaronic WO3-P2O5 and MoO3-P2O5 glasses

Autori
Renka, Sanja ; Pavić, Luka ; Kalenda, Petr ; Mošner, Petr ; Koudelka, Ladislav ; Šantić, Ana

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

Izvornik
CMD2020GEFES, Scientific Program / - , 2020, 89-89

Skup
2020 Joint Conference of the Condensed Matter Divisions of EPS (CMD) and RSEF (GEFES)

Mjesto i datum
Madrid, Španjolska, 31.08.2020. - 04.09.2020

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Glasses ; Electrical properties ; Scaling ; Raman spectroscopy

Sažetak
Phosphate glasses containing transition metal oxides (TMO) such as MoO3, WO3, V2O5 and Fe2O3 are semiconducting materials that exhibit polaronic conductivity as a result of electron hopping from lower oxidation state to higher oxidation state of metal ion forming so-called small polaron. Unlike in conventional semiconductors, this type of conductivity strongly depends on the amount of TMO and fraction of reduced TM-ions. However, this study shows that electrical properties of phosphate glasses containing WO3 and MoO3 are determined by structural features of glass. Since these materials have potential application in various electrochemical devices, understanding of structure-electrical properties relationship is essential for their development. Electrical properties of two glass series, xWO3-(100-x)P2O5 and xMoO3-(100-x)P2O5, x=40–80 mol%, were studied by impedance spectroscopy (IS) in a wide frequency (0.01 Hz – 106 Hz) and temperature (303 K – 513 K) range, whereas Raman spectroscopy was used to observe structural changes with the addition of WO3 and MoO3. Electron paramagnetic resonance (EPR) was also used to determine the fraction of metal ions in different oxidation states. Surprisingly, the study showed significantly higher electrical conductivity of WO3 containing glasses, and a decrease in conductivity above 60 mol% of both TMO (Figure 1a). The ESR measurements could not explain the former result since the fraction of W5+ was found to be considerably lower than Mo5+ within entire compositional range (Figure 1b). This suggests a high influence of glass structure. Indeed, Raman spectra revealed significant differences between two glass series. While MoO6 and MoO4 polyhedra tend to incorporate uniformly in phosphate network, WO6 octahedra are more prone to clustering by forming continuous W5+–O–W6+–O–W5+- bridges thus facilitating the transport of polarons. However, at a high amount of WO3 local structure is more „crystal-like“ and conductivity drastically decreases. On the other hand, in MoO3 series, polaronic conductivity increases with the amount of MoO3 and decreases due to the decrease in the Mo5+/Motot content (Figure 1a). In the second step, scaling properties of conductivity spectra were investigated by the Summerfield and Sidebottom scaling procedures. It was shown that the conduction mechanism does not change with temperature in all glasses except W-80 probably due to the “crystal-like” transport. Furthermore, Summerfield scaling was found not to be valid only in Mo-40 and Mo-50 glasses which suggests possible changes in polaron number density and/or characteristic hopping distance of polarons with temperature.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

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