TY - JOUR
T1 - Ion dynamics in Al-Stabilized Li7La3Zr2O12 single crystals - Macroscopic transport and the elementary steps of ion hopping
AU - Posch, Patrick
AU - Lunghammer, Sarah
AU - Berendts, Stefan
AU - Ganschow, Steffen
AU - Redhammer, Günther J.
AU - Wilkening, Alexandra
AU - Lerch, Martin
AU - Gadermaier, Bernhard
AU - Rettenwander, Daniel
AU - Wilkening, H. Martin R.
PY - 2020/1
Y1 - 2020/1
N2 - Li
7La
3Zr
2O
12 (LLZO) garnet-type ceramics are considered as very promising candidates for solid electrolytes and have been extensively studied in the past few years. Several studies report on an increase in ionic conductivity by doping with ions, such as Al
3+ and Ga
3+, to stabilize the cubic modification of LLZO. Unfortunately, so far ion dynamics have mainly been studied using powdered samples. Such studies may suffer from chemical heterogeneities concerning Al distribution. Here, we took advantage of Al-stabilized LLZO single crystals to throw light on the elementary steps of ion hopping. We used
7Li nuclear magnetic resonance (NMR) spin-lattice relaxation measurements and conductivity spectroscopy to probe dynamic parameters from both a microscopic and macroscopic point of view. At 293 K the total conductivity turned out to be 0.082 mS cm
−1, which is remarkably good for LLZO exhibiting an Al-content of only 0.37 wt%. Most importantly,
7Li NMR spin-lock transients revealed two overlapping diffusion-induced processes. Overall, activation energies from spin-lock NMR excellently agree with that from conductivity measurements; both techniques yield values around 0.36 eV. The corresponding diffusion coefficients deduced from NMR and conductivity measurements almost coincide. The magnetic spin fluctuations sensed by NMR provide an in-depth look at the elementary jump processes, which can barely be revealed by macroscopic impedance spectroscopy providing average values. In particular, we were able to precisely measure the local hopping barrier (0.20 eV) characterizing forward-backward jumps between the sites 24d and 96h.
AB - Li
7La
3Zr
2O
12 (LLZO) garnet-type ceramics are considered as very promising candidates for solid electrolytes and have been extensively studied in the past few years. Several studies report on an increase in ionic conductivity by doping with ions, such as Al
3+ and Ga
3+, to stabilize the cubic modification of LLZO. Unfortunately, so far ion dynamics have mainly been studied using powdered samples. Such studies may suffer from chemical heterogeneities concerning Al distribution. Here, we took advantage of Al-stabilized LLZO single crystals to throw light on the elementary steps of ion hopping. We used
7Li nuclear magnetic resonance (NMR) spin-lattice relaxation measurements and conductivity spectroscopy to probe dynamic parameters from both a microscopic and macroscopic point of view. At 293 K the total conductivity turned out to be 0.082 mS cm
−1, which is remarkably good for LLZO exhibiting an Al-content of only 0.37 wt%. Most importantly,
7Li NMR spin-lock transients revealed two overlapping diffusion-induced processes. Overall, activation energies from spin-lock NMR excellently agree with that from conductivity measurements; both techniques yield values around 0.36 eV. The corresponding diffusion coefficients deduced from NMR and conductivity measurements almost coincide. The magnetic spin fluctuations sensed by NMR provide an in-depth look at the elementary jump processes, which can barely be revealed by macroscopic impedance spectroscopy providing average values. In particular, we were able to precisely measure the local hopping barrier (0.20 eV) characterizing forward-backward jumps between the sites 24d and 96h.
KW - Garnets
KW - Single crystal
KW - NMR
KW - Dynamics
KW - Conductivity
UR - http://www.scopus.com/inward/record.url?scp=85071845795&partnerID=8YFLogxK
U2 - 10.1016/j.ensm.2019.08.017
DO - 10.1016/j.ensm.2019.08.017
M3 - Article
SN - 2405-8297
VL - 24
SP - 220
EP - 228
JO - Energy Storage Materials
JF - Energy Storage Materials
ER -