306 Ionics 11 (2005) Nanoionics of Advanced Superionic Conductors A.L. Despotuli, A.V. Andreeva and B. Rambabu* Institute of Microelectronics Technology & High Purity Materials RAS, 142432 Chernogolovka, Moscow Region, Russia *Southern University and A&M College, Baton Rouge, Louisiana, 70813 USA ~E-mail:
[email protected] (A.L. Despotuli) Abstract. New scientific direction - nanoionics of advanced superionic conductors (ASICs) was proposed. Nanosystems of solid state ionics were divided onto two classes differing by an opposite influence of crystal structure defects on the ionic conductivity oi (energy activation E): 1) nanosystems on the base compounds with initial small o~ (large values of E); and II) nanosystems of ASICs (nano-ASICs) with E = 0.1 eV. The fundamental challenge of nanoionics as the conservation of fast ion transport (FIT) in nano-ASICs on the level of bulk crystal was first recognized and for the providing of FIT in nano- ASICs the conception of structure-ordered (coherent) ASIC//indifferent electrode (IE) hetero- boundaries was proposed. Nano-ASIC characteristic parameter P = d/Xo (d is the thickness of ASIC layer with the defect crystal structure at the heteroboundary, and Ao is the screening length of charge for mobile ions of the bulk of ASIC) was introduced. The criterion for a conservation of FIT in nano-ASIC is P = 1. It was shown that at the equilibrium conditions the contact potentials V at the ASIC//IE coherent heterojunctions in nano-ASICs are V << keT/e. Interface engineering approach "from advanced materials to advanced devices" was proposed as fundamentals for the development of applied nanoionics.