Details
| Original language | English |
|---|---|
| Pages (from-to) | 23784-23789 |
| Number of pages | 6 |
| Journal | Journal of Physical Chemistry C |
| Volume | 115 |
| Issue number | 48 |
| Publication status | Published - 8 Dec 2011 |
Abstract
Fast ion conductors are urgently needed in many research areas of materials science. Advanced preparation strategies take advantage of an interplay of structural disorder, nanosize effects, and metastability. Getting access to detailed insights into the microstructure of such solids is crucial to identify the origins of fast ion conduction. High-resolution and high-sensitive spectroscopic techniques are well-suited to meet this challenge. Here, ion transport properties of a highly conducting, metastable fluoride with two isovalent cations were interrelated with the microscopic, atomic-scale structure probed by ultrafast 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR). Nanocrystalline samples of Ba1-xCaxF 2 (0 ≤ x ≤ 1) were prepared according to a mechanochemical route from BaF2 and CaF2. The resulting DC ion conductivity, when plotted as a function of x, passes through a well-developed maximum, which is located at xm = 0.5, while the associated activation energy Ea shows a minimum at xm. As revealed by 19F MAS NMR, five magnetically inequivalent F sites are present in the cation-mixed fluorides. These sites are characterized by a distinct number of Ba and Ca cations in the first coordination shell: [Ba]n[Ca] 4-n (0 ≤ n ≤ 4). The mixed sites with n = 1,2,3 dominate the NMR spectra at intermediate values of x. Presumably, the mixed cation sublattice, causing the metastability of the compounds, influences both the formation energy of, for example, F interstitials, as well as the migration energy leading to the fast ion conduction observed.
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Energy(all)
- General Energy
- Chemistry(all)
- Physical and Theoretical Chemistry
- Materials Science(all)
- Surfaces, Coatings and Films
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In: Journal of Physical Chemistry C, Vol. 115, No. 48, 08.12.2011, p. 23784-23789.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Mixed alkaline-earth effect in the metastable anion conductor Ba 1-xCaxF2 (0 ≤ x ≤ 1)
T2 - Correlating long-range ion transport with local structures revealed by ultrafast 19F MAS NMR
AU - Düvel, A.
AU - Ruprecht, B.
AU - Heitjans, P.
AU - Wilkening, M.
PY - 2011/12/8
Y1 - 2011/12/8
N2 - Fast ion conductors are urgently needed in many research areas of materials science. Advanced preparation strategies take advantage of an interplay of structural disorder, nanosize effects, and metastability. Getting access to detailed insights into the microstructure of such solids is crucial to identify the origins of fast ion conduction. High-resolution and high-sensitive spectroscopic techniques are well-suited to meet this challenge. Here, ion transport properties of a highly conducting, metastable fluoride with two isovalent cations were interrelated with the microscopic, atomic-scale structure probed by ultrafast 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR). Nanocrystalline samples of Ba1-xCaxF 2 (0 ≤ x ≤ 1) were prepared according to a mechanochemical route from BaF2 and CaF2. The resulting DC ion conductivity, when plotted as a function of x, passes through a well-developed maximum, which is located at xm = 0.5, while the associated activation energy Ea shows a minimum at xm. As revealed by 19F MAS NMR, five magnetically inequivalent F sites are present in the cation-mixed fluorides. These sites are characterized by a distinct number of Ba and Ca cations in the first coordination shell: [Ba]n[Ca] 4-n (0 ≤ n ≤ 4). The mixed sites with n = 1,2,3 dominate the NMR spectra at intermediate values of x. Presumably, the mixed cation sublattice, causing the metastability of the compounds, influences both the formation energy of, for example, F interstitials, as well as the migration energy leading to the fast ion conduction observed.
AB - Fast ion conductors are urgently needed in many research areas of materials science. Advanced preparation strategies take advantage of an interplay of structural disorder, nanosize effects, and metastability. Getting access to detailed insights into the microstructure of such solids is crucial to identify the origins of fast ion conduction. High-resolution and high-sensitive spectroscopic techniques are well-suited to meet this challenge. Here, ion transport properties of a highly conducting, metastable fluoride with two isovalent cations were interrelated with the microscopic, atomic-scale structure probed by ultrafast 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR). Nanocrystalline samples of Ba1-xCaxF 2 (0 ≤ x ≤ 1) were prepared according to a mechanochemical route from BaF2 and CaF2. The resulting DC ion conductivity, when plotted as a function of x, passes through a well-developed maximum, which is located at xm = 0.5, while the associated activation energy Ea shows a minimum at xm. As revealed by 19F MAS NMR, five magnetically inequivalent F sites are present in the cation-mixed fluorides. These sites are characterized by a distinct number of Ba and Ca cations in the first coordination shell: [Ba]n[Ca] 4-n (0 ≤ n ≤ 4). The mixed sites with n = 1,2,3 dominate the NMR spectra at intermediate values of x. Presumably, the mixed cation sublattice, causing the metastability of the compounds, influences both the formation energy of, for example, F interstitials, as well as the migration energy leading to the fast ion conduction observed.
UR - http://www.scopus.com/inward/record.url?scp=82555177333&partnerID=8YFLogxK
U2 - 10.1021/jp208472f
DO - 10.1021/jp208472f
M3 - Article
AN - SCOPUS:82555177333
VL - 115
SP - 23784
EP - 23789
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 48
ER -