@article { ISI:000274459600009, title = {Evidence for the co-existence of distorted tetrahedral and trigonal bipyramidal aluminium sites in SrAl12O19 from Al-27 NMR studies}, journal = {Solid State Communications}, volume = {150}, number = {5-6}, year = {2010}, month = {JAN}, pages = {262-266}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Strontium aluminate, SrAl12O19, is a ceramic material having the hexagonal magnetoplumbite-type structure, with multiple Al coordination environments. An earlier low-field Al-27 solid-state NMR study reported five different Al sites in this system: one AlO4, one AlO5, and three AlO6 sites; whereas a later high-field study showed that the AlO5 site is a distorted AlO4 site with a very large quadrupolar coupling constant (similar to 20 MHz). Our magic angle spinning (MAS) and 3-quantum magic angle spinning (3QMAS) NMR studies at 7.05 T unambiguously show evidence for an AlO5 site. However, evidence for the presence of a distorted AlO4 site is obtained from studies at high fields (16.4 and 17.6 T), in addition to the AlO5 site. Thus the present solid-state NMR studies give evidence for the simultaneous presence of both the five-coordinated and distorted four-coordinated sites in this system. (C) 2009 Elsevier Ltd. All rights reserved.

}, keywords = {Local structure, MQMAS, Nuclear magnetic resonance, Strontium aluminate}, issn = {0038-1098}, doi = {10.1016/j.ssc.2009.11.008}, author = {Harindranath, K. and Viswanath, K. Anusree and Chandran, C. Vinod and Braeuniger, Thomas and Madhu, Perunthiruthy K. and Ajithkumar, Thalasseril G. and Joy, Pattayil Alias} }