NMR and conductivity studies of the mixed glass former effect in lithium borophosphate glasses

Abstract

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.

Structural and topological aspects of borophosphate glasses and their relation to physical properties

“…8(a) are fitted using Eq. (3) where N c,crit is fixed to be 2.5, while dH V /dN c is a free variable and found to be 9.4 GPa/constraint at a load of 0.49 N. These values are in excellent agreement with both our calcium borophosphate data presented here and with results from soda-lime-borate glasses. 44 We found similar values by multiple linear regression, where N c,crit = 2.4 and dH V /dN c = 8.3 GPa/constraint, which yields an almost indistinguishable trend.…”

“…3,8,14,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]65,[83][84][85][86][87] In the following, we derive analytical expressions for the amount of B and P NFUs in borophosphate glasses spanning 0 ≤ x ≤ 0.67, which is well beyond the conventional glass forming region. The structural description is simplified by separating the compositional diagram into three regions, in which different NFUs exist.…”

“…16 The MNFE in borophosphate glasses is believed to be due to a non-linear variation of the structural units with composition, which is caused by the high affinity between boron and phosphorous oxide. [17][18][19] Although numerous studies of the structure of borophosphate glasses have been reported, 3,8,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] a quantitative structure-property relation has not been fully established and understood.…”

Lithium motion in the anode material LiC6as seen via time-domain7Li NMR

“…2 which were recorded at different temperatures T . Let us first discuss the central line of the spectrum which is also determined by a distinct powder pattern because of electric 094304-2 32,33 At high temperatures the central line reveals a slight anisotropic broadening which reflects the Li ions exposed to the layer structure of LiC 6 . Furthermore, in this high-T range, the NMR linewidths of the two-pulse spectra are presumably affected by internal inhomogeneous magnetic fields 29 that arise from the nonzero susceptibility of the LiC 6 particles (see also below, Sec.…”

Structure and lithium‐ion mobility in Li1.5M0.5Ge1.5(PO4)3 (M = Ga, Sc, Y) NASICON glass‐ceramics

“…It was not possible to estimate the activation energy for sample LGGP‐C‐606 since T onset could not be determined for this sample, as the low‐temperature plateau could not be reached due to hardware limitations (Figure ). As frequently reported, the activation energies deduced from NMR lineshape analysis are significantly lower than those determined by electrical conductivity measurements, even though the compositional trends are the same . The discrepancy most likely arises because the two techniques probe into ionic motion on different length scales .…”