01846nas a2200229   4500008004100000022001400041245006000055210005900115260009500174300001200269490000600281520108900287653001501376653000901391653001201400653002501412100002101437700002001458700001701478700002701495856009401522       2008                        eng d  a1533-488000aSn-119 magic angle spinning NMR of nanocrystalline SnO20 aSn119 magic angle spinning NMR of nanocrystalline SnO2  a25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USAbAMER SCIENTIFIC PUBLISHERScJAN  a321-3280 v83 a<p>Nanocrystalline SnO2 samples of different grain sizes, prepared by inert gas condensation technique (IGCT) and chemical precipitation method and conforming to the tetragonal phase, have been studied by variable speed (3-10 kHz) Sn-119 MAS NMR at 11.74 Tesla field. Sn-119 solid-state NMR results show that the IGCT prepared samples have good crystallinity and phase purity compared to the samples prepared by the chemical method. The determination of Sn-119 chemical shielding parameters (delta(iso), Delta delta and eta) from slow MAS spectra shows that the Sn-119 isotropic chemical shift (delta(iso)) is strongly influenced at smaller grain sizes, attributable to the change in the O2- local symmetry for the surface Sn-119 ions at smaller grain sizes. The observed line widths in MAS spectra are significantly larger than the life-time broadening due to spin-lattice (T-1) and spin-spin (T,) relaxation. The Sn-119 MAS NMR spectra are thus inhomogeneously broadened by a distribution of isotropic chemical shifts, the line broadening increasing with decrease in grain size.</p>10aHydrolysis10aIGCT10aMAS NMR10ananocrystalline SnO21 aSabarinathan, V.1 aChandran, Vinod1 aRamasamy, S.1 aGanapathy, Subramanian  uhttps://library.ncl.res.in/content/sn-119-magic-angle-spinning-nmr-nanocrystalline-sno2-001993nas a2200265   4500008004100000022001400041245013600055210006900191260010600260300001200366490000800378520095700386653002001343653001001363653003101373653002401404100002101428700002301449700002001472700002301492700002901515700003201544700002501576856012601601       2010                        eng d  a0038-109800aEvidence for the co-existence of distorted tetrahedral and trigonal bipyramidal aluminium sites in SrAl12O19 from Al-27 NMR studies0 aEvidence for the coexistence of distorted tetrahedral and trigon  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJAN  a262-2660 v1503 a<p>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.</p>10aLocal structure10aMQMAS10aNuclear magnetic resonance10aStrontium aluminate1 aHarindranath, K.1 aViswanath, Anusree1 aChandran, Vinod1 aBraeuniger, Thomas1 aMadhu, Perunthiruthy, K.1 aAjithkumar, Thalasseril, G.1 aJoy, Pattayil, Alias  uhttps://library.ncl.res.in/content/evidence-co-existence-distorted-tetrahedral-and-trigonal-bipyramidal-aluminium-sites-0