title: Lithium-Ion Mobility in Quaternary Boro-Germano-Phosphate Glasses.
abstract: Effect of the structural changes, electrical conductivity, and dielectric properties on the addition of a third glass-former, GeO2, to the borophosphate glasses, 40Li2O-10B2O3-(50 - x)P2O5-xGeO2, x = 0-25 mol %, has been studied. Introduction of GeO2 causes the structural modifications in the glass network, which results in a continuous increase in electrical conductivity. Glasses with low GeO2 content, up to 10 mol %, show a rapid increase in dc conductivity as a result of the interlinkage of slightly depolymerized phosphate chains and negatively charged [GeO4](-) units, which enhances the migration of Li(+) ions. The Li(+) ions compensate these delocalized charges connecting both phosphate and germanium units, which results in reduction of both bond effectiveness and binding energy of Li(+) ions and therefore enables their hop to the next charge-compensating site. For higher GeO2 content, the dc conductivity increases slightly, tending to approach a maximum in Li(+) ion mobility caused by the incorporation of GeO2 units into phosphate network combined with conversion of GeO4 to GeO6 units. The strong cross-linkage of germanium and phosphate units creates heteroatomic P-O-Ge bonds responsible for more effectively trapped Li(+) ions. A close correspondence between dielectric and conductivity parameters at high frequencies indicates that the increase in conductivity indeed is controlled by the modification of structure as a function of GeO2 addition.
authors.affiliation: Ruđer Bošković Institute , Division of Materials Chemistry, 10000 Zagreb, Croatia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Moguš-Milanković
authors.affiliation: Ruđer Bošković Institute , Division of Materials Chemistry, 10000 Zagreb, Croatia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Sklepić
authors.affiliation: Department of General and Inorganic Chemistry, University of Pardubice, Faculty of Chemical Technology , 53210 Pardubice, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Mošner
authors.affiliation: Department of General and Inorganic Chemistry, University of Pardubice, Faculty of Chemical Technology , 53210 Pardubice, Czech Republic.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Koudelka
authors.affiliation: Department of General and Inorganic Chemistry, University of Pardubice, Faculty of Chemical Technology , 53210 Pardubice, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Kalenda
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D004553:Electric Conductivity; D005857:Germanium / Q000737:chemistry*; D005898:Glass / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010710:Phosphates / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013696:Temperature; D044366:Transition Temperature
chemical_list: D001896:Boron Compounds; D007477:Ions; D010710:Phosphates; D005857:Germanium; C042168:boron oxide; C040516:germanium oxide; D008094:Lithium