Alkali ion charge transport has been studied in a series of mixed glass former lithium borophosphate glasses of composition 0.33Li 2 O + 0.67[xB 2 O 3 + (1 -x)P 2 O 5 ]. The entire concentration range, 0.0 ≤ x ≤ 1.0, from pure glassy Li 2 P 4 O 11 to pure glassy Li 2 B 4 O 7 has been examined while keeping the molar fraction of Li 2 O constant. Electrical conductivity measurements and nuclear magnetic resonance techniques such as spin relaxometry, line shape analysis, and stimulated-echo spectroscopy were used to examine the temperature and frequency dependence of the Li + ion motion over wide ranges of time scale and temperature. By accurately determining motional time scales and activation energies over the entire composition range the ion dynamics and the charge transport are found to be fastest if the borate and the phosphate fractions are similar. The nonlinear variation of the charge conduction, the most notable feature of the mixed glass former effect, is discussed in terms of the composition dependence of network former units which determine the local glass structure. Electrical conductivity measurements and nuclear magnetic resonance techniques such as spin relaxometry, line shape analysis, and stimulated-echo spectroscopy were used to examine the temperature and frequency dependence of the Li + ion motion over wide ranges of time scale and temperature. By accurately determining motional time scales and activation energies over the entire composition range the ion dynamics and the charge transport are found to be fastest if the borate and the phosphate fractions are similar. The nonlinear variation of the charge conduction, the most notable feature of the mixed glass former effect, is discussed in terms of the composition dependence of network former units which determine the local glass structure.

Glasses with varying compositions of constituent network formers but constant mobile ion content can display minima or maxima in their ion transport which are known as the negative or the positive mixed glass former effect, MGFE, respectively. Various nuclear magnetic resonance (NMR) techniques are used to probe the ion hopping dynamics via the (23)Na nucleus on the microscopic level, and the results are compared with those from conductivity spectroscopy, which are more sensitive to the macroscopic charge carrier mobility. In this way, the current work examines two series of sodium borosilicate and sodium borophosphate glasses that display positive and negative MGFEs, respectively, in the composition dependence of their Na(+) ion conductivities at intermediate compositions of boron oxide substitution for silicon oxide and phosphorus oxide, respectively. A coherent theoretical analysis is performed for these glasses which jointly captures the results from measurements of spin relaxation and central-transition line shapes. On this basis and including new information from (11)B magic-angle spinning NMR regarding the speciation in the sodium borosilicate glasses, a comparison is carried out with predictions from theoretical approaches, notably from the network unit trap model. This comparison yields detailed insights into how a variation of the boron oxide content and thus of either the population of silicon or phosphorus containing network-forming units with different charge-trapping capabilities leads to nonlinear changes of the microscopic transport properties.

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Using deuteron nuclear magnetic resonance, the molecular motions of specifically isotope-labeled ibuprofen were probed at the carboxylic group and at the methin group next to it. Spin relaxometry revealed slight differences between the molecular motions of the two isotopomers that are rationalized with reference to the hydrogen bonding of the COOH moiety. In the glassy state, a small-angle jump process among about four sites, related to the so-called γ-process, was identified using stimulated-echo spectroscopy. Indications for a Debye-like process, previously found to leave a weak signature in the dielectric loss, could not unambiguously be detected in magnetic resonance or shear mechanical experiments carried out for supercooled liquid ibuprofen.