Insights into low electronic and ultrahigh ionic conductivities of sodium tantalum oxychlorides NaTaOxCl6-2x in crystalline and amorphous phases

TI Ri and JG Pak and SH Choe and KC Ri and CJ Yu, APPLIED PHYSICS LETTERS, 127, 054101 (2025).

DOI: 10.1063/5.0280992

Anion mixing and amorphization are recognized as an effective strategy to develop solid-state electrolytes with low electronic but high ionic conductivities. Here, we present atomistic insights into ultrahigh ionic conductivities with very low electronic conductivities of oxychlorides NaTaOxCl6-2x ( 0 <= x <= 1 ) using ab initio calculations and molecular dynamics simulations. We observe a flat feature in the conduction bands, which leads to low electronic conductivities on the order of 10 - 9 S/cm. Furthermore, our calculations reveal that oxygen mixing increases Na ionic conductivity to a higher degree than amorphization, which is attributed to the shrinkage of Ta-centered polyhedra by oxygen substitution.

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