Issue 17, 2009

Nearly constant loss effects in borate glasses

Abstract

Different nearly constant loss phenomena are investigated in borate glasses with compositions xNa2O·(1−x)B2O3, for 0 ≤x≤ 0.3. The ionic conductivities caused by these effects are studied in wide ranges of temperature and frequency, spanning 4.3 K to 573 K and 100 mHz to 1 MHz, respectively. In a first step, we show how to identify the nearly constant loss (NCL) in 0.3Na2O·0.7B2O3 glass. In the procedure, the scaling property of the conductivity caused by ordinary hopping is used to remove this component from the total conductivity as measured as a function of temperature at fixed frequency. The resulting NCL component is seen to be proportional to frequency and to display no temperature dependence. In a second step, a broad-band relaxation process is shown to exist in amorphous boron oxide and in sodium borate glasses with x≤ 0.1. It is most probably due to the presence of traces of water, with hydrogen ions behaving as reorienting and interacting local dipoles. In a third step, we propose a simple formal treatment of the NCL phenomenon, tracing it back to a large number of interacting ions, each of them moving locally. The key aspect is a “see-saw-type” time dependence of their individual single-particle double-well potentials, which is due to their Coulomb interactions. The individual ion does, therefore, not require thermal activation and is thus kept in motion even at cryogenic temperatures.

Graphical abstract: Nearly constant loss effects in borate glasses

Article information

Article type
Paper
Submitted
15 Dec 2008
Accepted
06 Feb 2009
First published
10 Mar 2009

Phys. Chem. Chem. Phys., 2009,11, 3158-3167

Nearly constant loss effects in borate glasses

D. M. Laughman, R. D. Banhatti and K. Funke, Phys. Chem. Chem. Phys., 2009, 11, 3158 DOI: 10.1039/B822561N

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