Accession Number ADA567120
Title Origin Of The Structural Phase Transition In Li7La3Zr2O12.
Publication Date Sep 2012
Media Count 6p
Personal Author K. Hoang M. D. Johannes N. Bernstein
Abstract Garnet-type Li7La3Zr2O12 (LLZO) is a solid electrolyte material with a low-conductivity tetragonal and a high-conductivity cubic phase. Using density-functional theory and variable cell shape molecular dynamics simulations, we show that the tetragonal phase stability is dependent on a simultaneous ordering of the Li ions on the Li sublattice and a volume- preserving tetragonal distortion that relieves internal structural strain. Supervalent doping introduces vacancies into the Li sublattice, increasing the overall entropy and reducing the free energy gain from ordering, eventually stabilizing the cubic phase. We show that the critical temperature for cubic phase stability is lowered as Li vacancy concentration (dopant level) is raised and that an activated hop of Li ions from one crystallographic site to another always accompanies the transition. By identifying the relevant mechanism and critical concentrations for achieving the high conductivity phase, this work shows how targeted synthesis could be used to improve electrolytic performance.
Keywords Conductivity
Critical temperature
Density functional theory
Phase transformations
Solid electrolytes
Structural properties
Transitions


 
Source Agency Non Paid ADAS
NTIS Subject Category 99F - Physical & Theoretical Chemistry
Corporate Author Naval Research Lab., Washington, DC. Center for Computational Materials Science.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1308
Contract Number N/A

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