A Multinuclear MAS NMR Investigation of Environmentally Relevant Materials: Lanthanum Strontium Gallium Magnesium Oxide and Magnesium Aluminum Layered Double Hydroxides
EMSL Project ID
16112
Abstract
The desire to find alternate sources of energy and new methods for preserving the environment has prompted the synthesis and testing of numerous materials, among them, Lanthanum Strontium Gallium Magnesium Oxide (LSGM) and Magnesium Aluminum layered double hydroxides (LDHs). The former exhibits moderate to high oxygen conductivity, making it a suitable candidate for the electrolyte used in solid oxide fuel cells. The latter is an anion exchanger which has potential uses in separation technology. The properties of these two classes of materials are, in large part, due to their local structure. A thorough understanding of the changes in local structure where crystallographic substitutions occur will aid in the tailoring of these materials for specific applications. In this proposal, we are primarily interested in the changes to local structure as a function of strontium and magnesium doping in LSGM and aluminum doping in Magnesium Aluminum LDHs. 25Mg, 71Ga and 17O spectra will provide insight into the types of vacancies that exist in LSGM, which are directly related to the oxygen conductivity. Our studies have indicated the possible existence of different Ga sites, which imply the presence of nearby vacancies. 25Mg and 27Al spectra will provide insight into cation ordering in the LDHs, which plays a role in the anion exchange capacity of the material and the exchange mechanism. Initial experiments have indicated the presences of multiple environments for specific cases of aluminum doping. 2H NMR would provide information on the mobility and orientation of the anions, water and hydroxides present in the LDHs.
Project Details
Project type
Capability Research
Start Date
2006-02-06
End Date
2006-04-06
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Sideris PJ, UG Nielsen, Z Gan, and CP Grey. 2008. "Mg/Al Ordering in Layered Double Hydroxides Revealed by Multinuclear NMR Spectroscopy." Science 321(5885):113-117. doi:10.1126/science.1157581