Lithium-Ion Mobility in Quaternary Boro-Germano-Phosphate Glasses

J Phys Chem B. 2016 Apr 28;120(16):3978-87. doi: 10.1021/acs.jpcb.6b01424. Epub 2016 Apr 13.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Boron Compounds / chemistry*
  • Electric Conductivity
  • Germanium / chemistry*
  • Glass / chemistry*
  • Ions / chemistry
  • Lithium / chemistry*
  • Magnetic Resonance Spectroscopy
  • Phosphates / chemistry*
  • Spectrum Analysis, Raman
  • Temperature
  • Transition Temperature

Substances

  • Boron Compounds
  • Ions
  • Phosphates
  • Germanium
  • boron oxide
  • germanium oxide
  • Lithium