Exploring the Role of Phosphate Structural Distortions on the Sodium Jump Dynamics in NASICON Phases

Abstract

ABSTRACTHigh temperature solid state sodium (23Na) magic angle spinning (MAS) NMR spin lattice relaxation times (T1) were evaluated for a series of NASICON (Na3Zr2PSi2O12) materials to directly determine Na jump rates. Simulations of the T1 temperature variations that incorporated distributions in Na jump activation energies, or distribution of jump rates, improved the agreement with experiment. The 23Na NMR T1 relaxation results revealed that distributions in the Na dynamics were present for all of the NASICON materials investigated here. The 23Na relaxation experiments also showed that small differences in material composition and/or changes in the processing conditions impacted the distributions in the Na dynamics. The extent of the distribution was related to the presence of a disordered or glassy phosphate phase present in these different sol-gel processed materials. The 23Na NMR T1 relaxation experiments are a powerful tool to directly probing Na jump dynamics and provide additional molecular level details that could impact transport phenomena.