02064nas a2200181   4500008004100000022001400041245011400055210006900169260000800238300001400246490000700260520139700267100001701664700002101681700003201702700002201734856012601756       2014                        eng d  a0002-782000aIdentification of the Zn substitution sites in La-Zn substituted SrAl12O19 from Al-27 solid-state NMR studies0 aIdentification of the Zn substitution sites in LaZn substituted   cSEP  a2990-29950 v973 a<p>The La-Zn substituted hexagonal strontium aluminate, Sr1-xLaxAl12-xZnxO19, with the magnetoplumbite structure and having five different coordination environments for Al with different symmetries, is investigated using Al-27 solid-state NMR to get detailed information on the sites of substitution of Zn and the associated changes in the local coordination environments of Al. The objective of the study was to get information on the local structural variations in the isostructural La-Co substituted strontium ferrite, Sr1-xLaxFe12-xCoxO19, showing enhanced magnetic performance on substitution. The NMR studies on the aluminate give direct evidence for the sites of substitution and the changes in the local coordination environments. It is found that Zn is substituted at the 2a and 4f(2) AlO6 octahedral sites. However, an interesting observation from the NMR studies is the stabilization of the Al site occupancy at the penta-coordinated 2b site over the distorted tetrahedral 4eAl site, without any substitution at these sites. Large changes in the quadrupolar coupling constant of the 2a and 4e sites are observed between x=0.2 and 0.3, corresponding to the compositional region showing higher performance in the case of Sr1-xLaxFe12-xCoxO19, indicating the role of distortion of local coordination environments on suitable substitution in controlling the performance parameters.</p>1 aBaby, Bindhu1 aDey, Krishna, K.1 aAjithkumar, Thalasseril, G.1 aJoy, Pattayil, A.  uhttps://library.ncl.res.in/content/identification-zn-substitution-sites-la-zn-substituted-sral12o19-al-27-solid-state-nmr01758nas a2200229   4500008004100000022001400041245011200055210006900167260011000236300001400346490000700360520082900367100002901196700002401225700003201249700002801281700002301309700002101332700002601353700001801379856013101397       2014                        eng d  a1477-922600aInvestigations into variations in local cationic environment in layered oxide series InGaO3(ZnO)(m) (m=1-4)0 aInvestigations into variations in local cationic environment in   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcNOV  a2120-21260 v433 a<p>Layered oxides of the series InGaO3(ZnO)(m) (m = 1-4) are interesting due to their structural anisotropy. Here, we report a comprehensive study of their structural details, focusing on the local cationic environment in bulk powder samples by MASNMR and EXAFS, which is hitherto not attempted. It is found that the Ga geometry varies gradually from pure pentacoordinated to a mixture of penta and tetracoordinated with increasing amounts of tetracoordination as we move across the series, contrary to previous reports suggesting exclusively trigonal bipyramidal coordination in all the compounds. A similar observation is also made in the case of Zn and structural evolution involving the dissolution of Ga in a ZnO4 tetrahedral network in a sandwich layer can be discerned, as the insulating ZnO layer size increases.</p>1 aNarendranath, Soumya, B.1 aYadav, Ashok, Kumar1 aAjithkumar, Thalasseril, G.1 aBhattacharyya, Dibyendu1 aJha, Shambhu, Nath1 aDey, Krishna, K.1 aRaja, Thirumalaiswamy1 aDevi, Nandini  uhttps://library.ncl.res.in/content/investigations-variations-local-cationic-environment-layered-oxide-series-ingao3znom-m1-4-002137nas a2200229   4500008004100000022001400041245003500055210003500090260006700125300001000192490000700202520145200209100002201661700002101683700001701704700003201721700001901753700002201772700002401794700002001818856006901838       2015                        eng d  a0002-782000aVanadium in borosilicate glass0 aVanadium in borosilicate glass  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcJAN  a88-960 v983 a<p>Understanding the role of V2O5 within borosilicate glass matrices is important for the development of novel matrices toward immobilization of sulfate containing high-level nuclear wastes. Present investigation shows, within sodium barium borosilicate glass matrix V2O5 can be homogeneously added up to 5mol% and beyond which it separates out into three phases, for example, (i) silica (ii) Barium (Ba) - Vanadium (V) oxide, and (iii) glass matrix. Si-29 MAS NMR (Nuclear Magnetic Resonance) studies of the samples show that below 5mol% V2O5 addition, silicate network is dominantly constituted of Q(2) and Q(3) structural units, whereas above this, the network gets more polymerized through formation of Q(3) and Q(4) units. In case of borate network, B-11 MAS NMR investigations revealed that the concentration of BO4 [(0B, 4Si)] unit increases gradually up to 5mol% and then it decreases at the cost of BO4 [(1B, 3Si)], BO3 (symmetric) and BO3 (asymmetric) units. Micro-Raman analyses of the samples showed that with additions of V2O5 in diluted concentrations, amorphous silicate network remained unaltered, whereas some amplification in signals corresponding to ring-type metaborate and VO5 units exists. It is therefore apparent from both MAS-NMR and micro-Raman studies that with V2O5 additions within the solubility limit (5mol%), borate network gets depolymerized leading to decrease in hardness from an average value of 5.0-4.2GPa.</p>1 aSengupta, Pranesh1 aDey, Krishna, K.1 aHalder, Rumu1 aAjithkumar, Thalasseril, G.1 aAbraham, Geogy1 aMishra, Raman, K.1 aKaushik, Chetan, P.1 aDey, Goutam, K.  uhttps://library.ncl.res.in/content/vanadium-borosilicate-glass-0