Tunable ionic-conductivity of collapsed Sandia octahedral molecular sieves (SOMS).

Pless, Jason ; Nenoff, Tina Maria ; Garino, Terry J. ; Axness, Marlene

Sandia National Laboratories

关键词: Molecular Sieves;    Magnesium Oxides;    Dielectric Properties;    Perovskites;    Thermal Conductivity.;   

DOI  :  10.2172/899364
RP-ID  :  SAND2006-7116
RP-ID  :  AC04-94AL85000
RP-ID  :  899364

美国|英语

来源: UNT Digital Library

【 摘 要 】

This proposal focuses on the synthesis and characterization of ''tunable'' perovskite ceramics with resulting controlled strength and temperature of dielectric constants and/or with ionic conductivity. Traditional methods of synthesis involve high temperature oxide mixing and baking. We developed a new methodology of synthesis involving the (1) low temperature hydrothermal synthesis of metastable porous phases with ''tuned'' stoichiometry, and element types, and then (2) low temperature heat treatment to build exact stoichiometry perovskites, with the desired vacancy concentrations. This flexible pathway can lead to compositions and structures not attainable by conventional methods. During the course of this program, a series of Na-Nb perovskites were synthesized by calcining and collapsing microporous Sandia Octahedral Molecular Sieve (SOMS) phases. These materials were studied by various characterization techniques and conductivity measurements to better delineate stability and stoichiometry/bulk conductivity relationships. The conductivity can be altered by changing the concentration and type of the substituting framework cation(s) or by ion exchange of sodium. To date, the Na{sub 0.9}Mg{sub 0.1}Nb{sub 0.8}Ti{sub 0.2}O{sub 3-{delta}} shows the best conductivity.