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Effect of controlled crystallization on polaronic transport in phosphate‐based glass‐ceramics
Author(s) -
Pavić Luka,
Nikolić Juraj,
Graça Manuel P.F.,
Costa Benilde F.O.,
Valente Manuel A.,
Skoko Željko,
Šantić Ana,
MogušMilanković Andrea
Publication year - 2020
Publication title -
international journal of applied glass science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 34
eISSN - 2041-1294
pISSN - 2041-1286
DOI - 10.1111/ijag.13618
Subject(s) - crystallization , materials science , polaron , electrical resistivity and conductivity , phase (matter) , analytical chemistry (journal) , conductivity , ceramic , mineralogy , chemical engineering , composite material , chemistry , electron , physics , electrical engineering , organic chemistry , chromatography , quantum mechanics , engineering
The effect of induced crystallization on changes in electrical transport of two types of glass‐ceramics, pure polaron conductive 40Fe 2 O 3 ‐60P 2 O 5 (F40) (mol%) and predominantly polaronic 5Li 2 O‐5ZnO‐40P 2 O 5 ‐50WO 3 (Li‐50W) (mol%) was investigated. F40 glass‐ceramics produced at low heat‐treatment temperatures contain single‐phase Fe 3 (P 2 O 7 ) 2 whereas at higher temperatures two more phases Fe 4 (P 2 O 7 ) 3 and Fe(PO 3 ) 3 are formed. Structural modifications strongly depend on the crystallization temperature and time. The appearance of crystalline phases studied by Mössbauer spectroscopy exhibits changes in Fe 2+ /Fe tot ratio in crystalline/glassy phases. The detailed analysis of different iron sites allows their correlation with changes in electrical conductivity as crystallization progresses. Depending on the course of crystallization, the contribution of each phase to the overall conductivity is determined by the frequency dependence of Z ʺ(ω) and M ʺ(ω). DC conductivity shows a sharp decrease as Fe 3 (P 2 O 7 ) 2 phase appears and consequently glass matrix remains impoverished in Fe 2+ ‐Fe 3+ pairs. In the multiphase systems prepared at higher crystallization temperatures, the overall electrical conductivity increases although the continuous grain boundaries along different crystalline grains play a limiting factor. In contrast, the slight conductivity change in Li‐50W glass‐ceramics upon crystallization is a result of remaining W 5+ ‐W 6+ pairs in the residual glassy phase. Independence of electrical transport on Li + ions confirms predominantly polaronic transport in Li‐50W glass‐ceramics.