Publication detail

Electrical transport in mixed ion-polaron glasses

Year: 2019

Type of publication: článek v odborném periodiku

Name of source: Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B

Publisher name: Society of Glass Technology

Place: Sheffield

Page from-to: 97-103

Titles:

Language	Name	Abstract	Keywords
cze	Elektrická vodivost ve směsných iontově-polaronových sklech	Směsná iontově polaronový přenos náboje byl studován ve dvou řadách fosfátových skel obsahujících Na2O a WO3/MoO3 o složení xWO(3) -(30-0.5x)Na2O-(30-0.5x)ZnO-40P(2)O(5) a xMoO(3)-(30-0.5x)Na2O-(30-0.5x)ZnO-40P(2)O(5), 0 <= x <= 60(mol%). Změny v mechanismu vodivosti se složením byly analyzovány v korelaci se zm,ěnami struktury a změnami oxidačního stavu molybdenu a wolframu. Ramanova spektra ukázala na tvorbu klastrů z celků WO(6 ) s tvorbou vazeb W-O-W u skel s vysokým obsahem WO3 zatímco ve sklech s molybdenem docházelo ke koexistenci celků MoO4 a MoO6. Výrazný rozdíl ve vodivosti byl pozorován zejména u skel s vysokým obsahem WO3 and MoO3. While for glasses containing MoO3 the conductivity remains almost constant up to 50 mol% of MoO3, it constantly increases for almost six orders of magnitude for glasses with up to 60 mol% of WO3. Chování DC vodivosti u skel s MoO3 ukazuje na přechod od iontové k polaronové vodivosti. Výrazně vyšší vodivost skel s vysokým, obsahem WO3 je zapříčiněna vysokým příspěvkem polaronové vodivosti na rozdíl od skel s MoO3. Tvorba můstků W-O-W-W totiž značně usnadňuje polaronový transport.	Fosfátová skla; iontová vodivost; polaronový transport; Ramanova spektra
eng	Electrical transport in mixed ion-polaron glasses	Mixed ionic-polaronic transport has been investigated in two series of glasses containing Na2O and WO3/MoO3, namely xWO(3) -(30-0.5x)Na2O-(30-0.5x)ZnO-40P(2)O(5) and xMoO(3)-(30-0.5x)Na2O-(30-0.5x)ZnO-40P(2)O(5), 0 <= x <= 60(mol%). The changes in the conduction mechanism with the systematic alternation of the glass composition have been analysed in correlation to the structural modifications and variations of molybdenum and tungsten in different oxidation states. Raman spectra revealed the clustering of WO(6 )units by the formation of W-O-W bonds in glasses with increasing WO3 content while the co-existence of MoO4 and MoO6 units is evidenced in glasses containing MoO3. In particular, the dominant molybdenum coordination in glasses with highest MoO3 content is four suggesting the absence of clustering of molybdate units. The DC conductivity of glasses with <= 20 mol% of WO3 and <= 30 mol% of MoO3 is almost identical due to the dominance of ionic conductivity. In this compositional region, the introduction of tungstate and molybdate units in the glass structure increases the mobility of sodium ions and compensates the decrease in sodium number density. The significant difference in conductivity is observed for glasses with higher WO3 and MoO3 content. While for glasses containing MoO3 the conductivity remains almost constant up to 50 mol% of MoO3, it constantly increases for almost six orders of magnitude for glasses with up to 60 mol% of WO3. The behaviour of DC conductivity for glasses containing MoO3 suggests the transition from ionic to polaronic conduction mechanisms which transport pathways are independent of each other. On the other hand, significantly higher conductivity of glasses with higher amounts of WO3 originates from a huge polaronic contribution, much larger than in a case of MoO3. Such a high conductivity is a consequence of the clustering of tungstate units which forms continuous W-O-W-O-W bridges which significantly facilitate polaronic transport.	Phosphate glasses; ionic conductivity; polaron transport; Raman spectra

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