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Sympozjum Wydziau Fizyki 17 kwietnia 2008 Transport adunku elektrycznego w amorficznych, nanokrystalicznych i kompozytowych przewodnikach elektronowych i jonowych Jerzy E.Garbarczyk, Wojciech Wrbel Zakad Joniki Ciaa Staego Wydzia Fizyki PW

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Motywacja Cel poznawczy Badanie transportu adunku elektrycznego w mao poznanych formach fazy skondensowanej Cel aplikacyjny Zastosowania w urzdzeniach do konwersji i magazynowania energii (baterie litowo-jonowe, ogniwa paliwowe, sensory gazowe, superkondensatory) Sympozjum Wydziau Fizyki 17 kwietnia 2008

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Prezentacje Jerzy E.Garbarczyk Nowe nanomateriay i kompozyty oparte na szklistych przewodnikach elektronowych i jonowych Wojciech Wrbel Korelacja midzy elektrycznymi i mechanicznymi waciwociami cieczy szkotwrczych Sympozjum Wydziau Fizyki 17 kwietnia 2008

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Novel nanomaterials and composites based on electronic and ionic conductive glasses

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Outline Advantages and disadvantages of ionic and electronic conductive glasses Novel nanomaterials based on lithium-vanadate-phosphate (LVP) glasses Novel nanomaterials based on lithium-iron-phosphate (LFP) glasses Novel composites based on ionically conductive glasses Summary

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Advantages and disadvantages of conductive glasses Advantages simple processing possibility of forming various shapes isotropy and homogeneity absence of grain boundaries high ionic conductivity at room temperature (up to 10 -2 S/cm for AgI based conducting glasses) high electronic conductivity at above 300C (up to 10 -3 S/cm for vanadia rich glasses) inherent ability to nanocrystallization (this study) possibility of considerable modification of the composition and electrical properties

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Example: vanadia-based glasses V 2 O 5 main glass former, source of electronic conduction via V 4+ V 5+ hopping of small polarons P 2 O 5 supporting glass former Li 2 O glass modifier, source of mobile Li + ions Ag 2 O glass modifier, source of mobile Ag + ions AgI dopant, main source of mobile Ag + ions Mixed ionic-electronic conductivity in systems: Li 2 O - V 2 O 5 - P 2 O 5 (Li + /e - ) AgI - Ag 2 O - V 2 O 5 - P 2 O 5 (Ag + /e - )

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses or

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Model of the electrical charge transport in Li 2 O-V 2 O 5 -P 2 O 5 glasses

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or

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Isotherms of the total electrical conductivity in Li 2 O-V 2 O 5 -P 2 O 5 glasses V 2 O 5 -rich glasses ionic electronic mixed P.Jozwiak, J.Garbarczyk, Solid State Ionics 176 (2005) 2163 H.Takahashi, T.Karasawa, T.Sakuma, J.E.Garbarczyk, ICPSSI-2, Yokohama, 2007

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Total electrical conductivity at 100C vs. composition in AgI-Ag 2 O-V 2 O 5 -P 2 O 5 glasses J.E.Garbarczyk, P.Machowski et al. Mol.Phys.Rep. 35 (2003) 139. electronic ionic

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Total electrical conductivity at 100C vs. composition in AgI-Ag 2 O-V 2 O 5 -P 2 O 5 glasses electronic ionic electronic ionic J.E.Garbarczyk, P.Machowski et al. Mol.Phys.Rep. 35 (2003) 139.

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Advantages and disadvantages of conductive glasses (cont.) Disadvantages metastability composition and structure less known than those of the crystalline materials low glass transition temperature of the best ion conductive glasses (for AgI-doped glasses 60C < T g < 100C) low fracture toughness moderate electronic conductivity at 20C of glassy cathode materials

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Aims of our studies preparation of new nanomaterials derived from conductive glasses exhibiting better electrical properties and thermal stability than the initial glasses preparation of new glassy-crystalline composites exhibiting improved mechanical properties compared to the glasses

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Novel nanomaterials based on lithium-vanadate-phosphate (LVP) glasses It is known that nanostructured materials exhibit attractive properties, often dramatically different than those of the crystalline or amorphous counterparts. Effect of nanocrystallization on ionic conductivity St. Adams, K.Hariharan, J.Maier, Solid State Ionics 86-88 (1996) 503. AgI-rich glasses of the system AgI-Ag 2 O-M x O y Effect of nanocrystallization on electronic and mixed conductivity J.E.Garbarczyk, P.Jozwiak et al. Solid State Ionics 175 (2004) 691. V 2 O 5 -rich glasses of the system Li 2 O-V 2 O 5 -P 2 O 5 a) 15Li 2 O70V 2 O 5 15P 2 O 5 b) 90V 2 O 5 10P 2 O 5

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DSC Nanocrystallization of the 90V 2 O 5 10P 2 O 5 glass

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SEM picture of a 90V 2 O 5 10P 2 O 5 sample after nanocrystallization at T c 340C

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20 nm visible nanocrystallites of V 2 O 5 covered by a glassy phase

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SEM picture and XRD pattern of a 90V 2 O 5 10P 2 O 5 sample after massive crystallization at 540C - orthorhombic V 2 O 5

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SEM picture of a 90V 2 O 5 10P 2 O 5 sample after massive crystallization at 540 o C (another fragment) orthorhombic V 2 O 5 crystallites

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Discussion of the results on vanadia-based nanomaterials Mott theory of electron hopping in disordered systems R average distance between hopping centers C fraction of hopping sites occupied by electrons N concentration of hopping centres inverse localization length of the electron wave function r p radius of a small polaron for T > / 2 Debye temperature

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Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization V2O5V2O5 20 nm

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Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization V2O5V2O5 20 nm higher concentration of V 4+ -V +5 pairs

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Discussion of the results on vanadia-based nanomaterials Samples after nanocrystallization Easy conduction paths interface regions between nanocrystallites and glassy phase. Higher concentration of V 4+ -V 5+ pairs in these regions than inside grains. V2O5V2O5 20 nm high concentration of V 4+ -V +5 pairs easy conduction path +

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Discussion of the results (cont.) Sample after massive crystallization There is no intermediate glassy phase. The electrical transport between grains is partly blocked by the presence of grain boundaries.

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Novel nanomaterials based on lithium-iron-phosphate (LFP) glasses Crystalline lithium-iron-phosphates (olivines) Nanocrystallization of glassy samples - SEM Cooperation with Prof. Christian Julien, Univ. P.et M.Curie, Paris, France (local structure) A.Ait Salah, P.Jozwiak, J.Garbarczyk, Ch.Julien et al. Journal of Power Sources 140 (2005) 370.

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Zwizki interkalowane - przykady Oliwiny i zwizki pokrewne

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Crystalline lithium-iron-phosphates Crystalline olivine-type phases - LiFePO 4 and FePO 4 as well as Li x FePO 4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries. These cathode materials are: highly stable (thermally and electrochemically), inexpensive, environment friendly. Furthermore they exhibit: high specific capacity (170 mAh/g), high discharge voltage (3.5 V vs. Li).

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Crystalline lithium-iron-phosphates Crystalline olivine-type phases - LiFePO 4 and FePO 4 as well as Li x FePO 4 solid solutions - are under intensive studies worldwide as the most competitive cathode materials for Li-ion rechargeable batteries. These cathode materials are: highly stable (thermally and electrochemically), inexpensive, environment friendly. Furthermore they exhibit: high specific capacity (170 mAh/g), high discharge voltage (3.5 V vs. Li). Unfortunately they have one serious deficiency very low electrical conductivity - ca. 10 -10 Scm 1 at 25C.

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Crystalline olivines (cont.) Many efforts have been undertaken to improve their electrical properties by: introduction of carbon additives, doping with supervalent cations, various synthesis routes. Our alternative approach nanocrystallization of glassy analogs of olivines: step 1:preparation of vitreous analogs of these materials, step 2: turning these glasses into nanomaterials by an appropriate thermal treatment.

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Electrical properties after partial nanocrystallization (sample of x = 0)

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SEM picture after partial nanocrystallization for sample of x = 0

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Electrical properties after partial nanocrystallization (sample of x = 0.4) t (530C)=1.110 -2 S/cm t (50C)= 1.810 -8 S/cm t (50C)=7.610 -8 S/cm 4 times

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SEM micrograph after crystallization for sample of x = 0.4

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Novel composites based on ionically conductive glasses Motivation Ag + - ion conductive glasses exhibit high electrical conductivity (up to 10 -2 Scm -1 at 25C), but some of their mechanical properties may cause problems with samples machining (e.g. cutting and polishing) and limit eventual prospective applications. In order to minimize this drawback we propose new composites based on silver-ion conductive glasses.

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Novel composites based on ionically conductive glasses (cont.) Glassy components: AgI-Ag 2 O-B 2 O 3 AgI-Ag 2 O-P 2 O 5 AgI-Ag 2 O-V 2 O 5 Ceramic powder components: Diamond (1-2 m) -Al 2 O 3 (2 m) ZrO 2 (1 and/or 10 m) Composites prepared in 50 - 50 % vol fractions B 2 O 3, P 2 O 5, V 2 O 5 glass formers Ag 2 O glass modifier AgI dopant

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High-pressure route of preparation of the composites Facility at the Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw

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High-pressure route of preparation of the composites (cont.) 100-200C 100-250C 3-8 GPa

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SEM and XRD studies Obrazek SEM (fosforanowe z diamentem, boranowe z alumina) Glass: 40AgI30Ag 2 O30P 2 O 5 Diamond powder (1-2 m) Synthesis: p = 3 GPa, T = 250C as-prepared after annealing at 200C M.Zgirski, J.Garbarczyk et al., Solid State Ionics, 176 (2005) 2141

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SEM studies (cont.) 50AgI33Ag 2 O17B 2 O 3 : -Al 2 O 3 (2 m) - a phase view Al 2 O 3 Glass

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SEM studies (cont.) 55AgI30Ag 2 O15B 2 O 3 : ZrO 2 (1 m) - a phase view ZrO 2

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Electrical properties of composites above room temperature 40AgI30Ag 2 O30P 2 O 5 : diamond 200 =1.610 -2 Scm -1 27 =110 -4 Scm -1 E=0.34 eV E=0.54 eV TgTg glass

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Electrical conductivity of composites at low temperatures M.Foltyn, M.Wasiucionek, J.E.Garbarczyk et al.., Solid State Ionics, 179 (2008) 38

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Mechanical properties - Vickers microhardness xAgI(100-x)(0.67Ag 2 O0.33B 2 O 3 ) composites (with -Al 2 O 3 ) glasses

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Electrical properties of composites (cont.) Lower specific conductivity of the composites can be compensated by a possibility of preparing thinner samples. Mechanically sound membranes of ca 100 m thickness can be fabricated. sheet of paper - edge composite 1. (ca 100 m) composite 2. (ca 300 m)

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Summary Conductive glasses can be promising starting materials to prepare attractive composites and nanostructured materials. The annealing of the V 2 O 5 rich glasses (LVP) to T c leads to their nanocrystallization. The resulting nanomaterials exhibit much higher electronic conductivity (10 -1 S/cm at 300C), lower activation energy and better thermal stability than the initial glasses.

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Summary (cont.) Electrical properties of lithium-iron-phosphate (LFP) glasses are similar to crystalline olivines. It was found that thermal nanocrystallization of LFP glasses leads to the conductivity enhancement,

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Summary (cont.) Electrical properties of lithium-iron-phosphate (LFP) glasses are similar to crystalline olivines. It was found that thermal nanocrystallization of LFP glasses leads to the conductivity enhancement,...therefore it seems to be a promising way for electrical conductivity improvement of amorphous lithium-iron-phosphates. A prospective high-pressure method was used to produce silver ion conductive composites based on AgI doped glasses with good electrical and mechanical properties.

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Zesp badawczy Marek Wasiucionek Pawe Jwiak Jan L.Nowiski Marek Foltyn Irena Gorzkowska Wydzia Chemiczny PW Bogdan Paosz Unipress (IWC PAN) Stanisaw Gierlotka Unipress (IWC PAN)

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R. Bacewicz, M. Wasiucionek, A. Twarg, J. Filipowicz, P. Jwiak, J.E. Garbarczyk, J. Mat. Sci. 40 (2005) 4267-4270.

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Electrical properties of composites above room temperature 40AgI40Ag 2 O20B 2 O 3 : -Al 2 O 3 M.Foltyn, M.Wasiucionek, J.Garbarczyk et al. J.Power Sources 173 (2007) 795 =1.610 -2 =2.510 -3