TY - JOUR

T1 - Structural control of ionic conductivity in LiAlSi2O6 and LiAlSi4O10 glasses and single crystals

AU - Welsch, Anna Maria

AU - Behrens, Harald

AU - Ross, Sebastian

AU - Murawski, Dawid

N1 - Funding Information: The authors are grateful for the financial support by DFG via project FOR 1277. We thank O. Diedrich for preparation of excellent sample sections used for experimental study and P. E. Wolff for assistance with the EMPA measurements.

PY - 2012/6/1

Y1 - 2012/6/1

N2 - In order to better understand the mechanisms of lithium dynamics and to elucidate the influence of defects in lithium mobility, we have studied the Li-ion propagation through natural single crystals of a-spodumene, LiAlSi 2O6 and petalite, LiAlSi4O10 using impedance spectroscopy. Electrical conductivity in petalite and α-spodumene is 4-5 orders of magnitude lower than in glasses of the same composition, and three orders of magnitude lower than in synthetic β-spodumene. Conductivity in α-spodumene is anisotropic with conductivity along the c-axis being 0.3-0.4 log units higher than perpendicular to the c-axis. Contrary to α-spodumene, isotropic conductivity was observed for petalite single crystals. Despite the large difference in conductivity values, the activation energies for ionic conduction of α-spodumene along the c-axis (74 to 86 kJ/mol) are only slightly higher than for LiAlSi2O6 and LiAlSi4O10 glasses (∼ 67 kJ/mol). On the other hand, much higher activation energies of 112-134 kJ/mol were determined for petalite. Based on our investigation, a vacancy-controlled transport mechanism is indicated for the densely packed α-spodumene structure, while in the open framework structure of petalite formation and movement of Li interstitials is proposed to be dominant mechanism for charge transfer.

AB - In order to better understand the mechanisms of lithium dynamics and to elucidate the influence of defects in lithium mobility, we have studied the Li-ion propagation through natural single crystals of a-spodumene, LiAlSi 2O6 and petalite, LiAlSi4O10 using impedance spectroscopy. Electrical conductivity in petalite and α-spodumene is 4-5 orders of magnitude lower than in glasses of the same composition, and three orders of magnitude lower than in synthetic β-spodumene. Conductivity in α-spodumene is anisotropic with conductivity along the c-axis being 0.3-0.4 log units higher than perpendicular to the c-axis. Contrary to α-spodumene, isotropic conductivity was observed for petalite single crystals. Despite the large difference in conductivity values, the activation energies for ionic conduction of α-spodumene along the c-axis (74 to 86 kJ/mol) are only slightly higher than for LiAlSi2O6 and LiAlSi4O10 glasses (∼ 67 kJ/mol). On the other hand, much higher activation energies of 112-134 kJ/mol were determined for petalite. Based on our investigation, a vacancy-controlled transport mechanism is indicated for the densely packed α-spodumene structure, while in the open framework structure of petalite formation and movement of Li interstitials is proposed to be dominant mechanism for charge transfer.

KW - Defects

KW - Lithium

KW - Petalite

KW - Spodumene

KW - Transport mechanism

UR - http://www.scopus.com/inward/record.url?scp=84862838403&partnerID=8YFLogxK

U2 - 10.1524/zpch.2012.0230

DO - 10.1524/zpch.2012.0230

M3 - Article

AN - SCOPUS:84862838403

VL - 226

SP - 491

EP - 511

JO - Zeitschrift fur Physikalische Chemie

JF - Zeitschrift fur Physikalische Chemie

SN - 0942-9352

IS - 5-6

ER -