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Crystallization processes in superionic AgI-Ag2O-P2O5 ([Ag2O]/[P2O5] = 3) glasses

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Nowiński J. L. , Mroczkowska M. , Garbarczyk J. E. , Wasiucionek M.

Materials Science Poland

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2006

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tom Vol. 24, No. 1

161--167

EN

Crystallization processes in superionic AgI-Ag2O-P2O5 ([Ag2O]/[P2O5] = 3) glasses were investigated by X-ray, DSC, SEM, and impedance spectroscopy. It was found that the crystallization process depended on the total concentration of the AgI dopant in the material and on the thermal treatment of the glass. During quenching of the glass melt, the following phases are successively formed with increasing total AgI concentration: pure glass without detectable (XRD) traces of crystalline phases, glasses containing ß-AgI and some other, unidentified crystallites precipitated on the surface, and finally a composite material, namely a glass matrix in which ß/gamma-AgI inclusions are embedded. Glasses containing x < 50 mol % of AgI do not crystallize during annealing. Two bulk crystallization processes were identified in solid glasses with 50 < x < 75 mol %. During annealing, the initial product of crystallization transforms to the final one. There is an evidence that crystallization is preceded by a pre-crystallization stage, in which the glass matrix becomes inhomogeneous, forming nano-sized volumes.

2

Evaluation of transference numbers in mixed conductive lithium vanadate-phosphate glasses

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Jozwiak P. , Garbarczyk J. E. , Wasiucionek M.

Materials Science Poland

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2006

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tom Vol. 24, No. 1

148--153

EN

A method for evaluating the transference numbers in mixed electronic-ionic glasses of the Li2O-V2O5-P2O5 system is proposed and tested, basing on the analysis of temperature dependences of the total conductivity of these glasses. The method consists of representing experimental non-Arrhenius temperature dependences of the total conductivity by a sum of two Arrhenius-like contributions. The latter ones were tentatively attributed to the electronic and ionic partial conductivities.

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The thermal stability, local structure and electrical properties of lithium-iron phosphate glasses

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Jóźwiak P. , Garbarczyk J. E. , Wasiucionek M. , Gorzkowska I. , Gendron F. , Mauger A. , Julien C.

Materials Science Poland

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2009

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tom Vol. 27, No. 1

307--318

EN

Amorphous analogues of lithium-iron phosphates (LFP), which are promising cathode materials for Li ion batteries, were prepared by the standard press-quenching method and their thermal stability, as well as structural and electrical properties, were studied for the first time. The glass transition temperature, Tg, determined by the differential thermal analysis (DTA) is composition-dependent and lies in the 492-523 °C range. The local structure, studied by the FTIR absorption spectroscopy, and the thermal stability are found to be almost insensitive to the lithium content. Studies on the electrical properties, carried out by impedance spectroscopy, have shown that the total electrical (predominantly polaronic) conductivity at 450 °C approaches 10-2 Socm-1. The room temperature conductivity of samples after their nanocrystallization (induced by annealing at the temperature of the beginning of crystallization) was higher by a factor of 4-10 (depending on composition) than that of the as-received glass. Therefore, nanocrystallization seems to be a promising way to enhance the electrical conductivity of amorphous lithium-iron phosphates.

4

Nanokrystalizacja szkieł o wysokiej przewodności elektrycznej.

75%

Garbarczyk J. E. , Nowiński J. L. , Wasiucionek M. , Jóźwiak P. , Latuch J. , Wnętrzewski B.

Archiwum Nauki o Materiałach

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2003

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tom T. 24, nr 4

583-596

PL

W pracy przedstawiono wyniki badań nanomateriałów szklisto-krystalicznych na bazie szkieł układów AgI-Ag2O-V2O5, AgI-Ag2O-P2O5 i Li2O-V2O5-P2O5. Nanomateriały otrzymywano dwoma metodami - przez wygrzewanie wyjściowych szkieł w temperaturze zbliżonej do temperatury krystalizacji, oraz przez ultraszybkie chłodzenie roztopionych mieszanin zawierających dużą nadwyżkę jednego ze składników (AgI), która przy typowej szybkości chłodzenia prowadziłaby do masowej krystalizacji próbki. Stwierdzono, że wygrzewanie wyjściowych szkieł w temperaturze krystalizacji, wyznaczonej z pomiarów DSC, prowadzi do wyraźnej poprawy przewodności elektrycznej materiałów. Podwyższeniu ulega także górna granica temperatury, w której właściwości próbek są stabilne. Obserwowana wyraźna korelacja między temperaturami, w których mają miejsce zmiany przewodnictwa elektrycznego i wyznaczonymi z termogramów DSC temperaturami przejścia szklistego i krystalizacji jednoznacznie wskazuje na wpływ struktury materiału na transport ładunku elektrycznego. Badania rentgenograficzne potwierdziły amorficzność wyjściowych szkieł oraz pozwoliły prześledzić proces tworzenia się krystalitów w matrycy szklistej w trakcie nanokrystalizacji. Rozmiary powstałych ziaren krystalicznych wynosiły od 20 nm do ponad 100 nm (zależnie od składu i etapu procesu nanokrystalizacji). Zaproponowano model opisujący związek między ilością i wielkością krystalitów w nanomateriałach układu Li2O-V2O5-P2O5 a obserwowanymi zmianami przewodności elektrycznej.

EN

Results of studies of glass-crystalline nanomaterials based on glasses of the AgI-Ag2O-V2O5, AgI-Ag2O-P2O5 and Li2O-V2O5-P2O5 systems are presented. These nanomaterials were prepared by two methods: annealing of initial glasses at crystallization temperature and ultrafast quenching of molten mixtures containing an excess of one component (AgI). It was found that the annealing of glasses at crystallization temperature (determined from DSC thermograms) leads to a considerable increase in electrical conductivity of the annealed materials. Also the upper thermal stability limit of the samples increases. The correlation between temperatures at which conductivity of the samples undergo noticeable changes and glass transition and crystallization temperatures, determined from DSC scans, indicate the influence of material's structure on transport of electrical charges. X-ray diffraction studies confirmed amorphous state of as-obtained glasses and showed the formation of crystallites during nanocrystallization. Dimensions of these crystallites were from 20 nm to above 100 nm. A model explaining the effect of concentration and dimensions of crystallites on observed changes of electrical conductivity was proposed.