(Na Super Ionic Conductors, discovered by Hong and Goodenough 1975) are
a very useful family of solid electrolytes with potential technological
applications in high energy density batteries, fuels cells, etc. The
prototypical NaZr2P3O12 consists of a rigid oxide framework of corner
shared ZrO6 octahedra and PO4 tetrahedra. The large number of alkali
ion sites that populate the framework in high density are well
connected by channels of low energy barriers allowing fastion
transport. The NASICON structure permits a wide range of ion
substitution at the Zr and P sites making them a versatile family of
solids. Among other useful properties of these materials are the high
thermal and chemical stability, and low/negative thermal
studies on these solids began with the development of a high quality
inter-atomic potential that reproduces several known experimental data
in excellent agreement. Faithful reproduction of the structural
parameters and ionic conductivity as functions of both temperature and
alkali ion content, and the site occupancy of alkali ions are
particularly note worthy. The simulation studies employing the model
provides valuable atomic level picture of a variety of phenomena, such
as, the nature of the fast ion transport, phase transitions and low
thermal expansivity of these solids. The study also resolved some of
the long debated issues related to the preferred conduction channel in these solids. The enhanced
diffusion of optimally-sized ions in NASICON framework predicted in our study forms a very useful insight
in the tailor making of superionic solids.
- J. Phys. Chem. B, 106, 7081-7089 (2002), "Structure, Conductivity and Ionic Motion in Na1+xZr2SixP3-xO12: A Simulation Study", Padma Kumar, P. and Yashonath, S.
- J. Am. Chem. Soc. (Communication), 124, 3828-3829 (2002), "A Full Interionic Potential for Na1+xZr2SixP3-xO12 Superionic Conductors", Padma Kumar, P. and Yashonath, S.
J. Phys. Chem. B, 106, 3443-3448 (2002), "Ion Mobility and Levitation
Effect: Anomalous Diffusion in NASICON-type Structures", Padma Kumar,
P. and Yashonath, S.
- J. Phys. Chem. B, 105, 6785-6791 (2001), "Lithium Ion Motion in LiZr2P3O12", Padma Kumar, P. and Yashonath, S.
- J. Chem. Sci., 118, 135-154 (2006), "Ionic Conduction in the Solid State", Padma Kumar, P. and Yashonath, S.