The synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanoparticles have a dominant SnO2 phase (as revealed by Wide Angle X-ray Scattering), with particles of the order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmed by SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-ray Scattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersed within the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sn content suggesting that the magnetization is not controlled solely by the amount of Fe dispersed within the nanoparticles

Ali, N.

Birjega, R.

Chipara, Mircea

Dumitrache, F.

George, T. A.

Georgescu, R.

Morjan, I.

Wei, X.

English

Scholarworks@UTRGV Univ. of Texas RioGrande Valley

University of Texas Rio Grande Valley ScholarWorks @ UTRGV Physics and Astronomy Faculty Publications and Presentations College of Sciences 2012 On the Synthesis and Physical Properties of Iron Doped SnO2 Nanoparticles X. Wei University of Nebraska - Lincoln R. Georgescu N. Ali I. Morjan T. A. George University of Nebraska - Lincoln See next page for additional authors Follow this and additional works at: https://scholarworks.utrgv.edu/pa_fac  Part of the Astrophysics and Astronomy Commons, and the Physics Commons Recommended Citation Wei, X.; Georgescu, R.; Ali, N.; Morjan, I.; George, T. A.; Dumitrache, F.; Birjega, R.; and Chipara, Mircea, "On the Synthesis and Physical Properties of Iron Doped SnO2 Nanoparticles" (2012). Physics and Astronomy Faculty Publications and Presentations. 305. https://scholarworks.utrgv.edu/pa_fac/305 This Article is brought to you for free and open access by the College of Sciences at ScholarWorks @ UTRGV. It has been accepted for inclusion in Physics and Astronomy Faculty Publications and Presentations by an authorized administrator of ScholarWorks @ UTRGV. For more information, please contact justin.white@utrgv.edu, william.flores01@utrgv.edu. Authors X. Wei, R. Georgescu, N. Ali, I. Morjan, T. A. George, F. Dumitrache, R. Birjega, and Mircea Chipara This article is available at ScholarWorks @ UTRGV: https://scholarworks.utrgv.edu/pa_fac/305 Copyright © 2012 American Scientific PublishersAll rights reservedPrinted in the United States of AmericaJournal ofNanoscience and NanotechnologyVol. 12,9299-9301, 2012On the Synthesis and Physical Properties ofIron Doped Sn02 NanoparticlesX. WeP, R. Georcescu", N. Ali3, I. Morjan2, T. A. Georqe', F. Durnitrachst,R. Birjega2, M. Chipara" *, R. Skomski', and D. J. Sellrnyer'1Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska, 68588, USA2National Institute for Lasers, Plasma and Radiation Physics, Laser Department,Bucharest, Atomisti/or 409, P.O. Box-MG-36, Romania3CNC Coatings, Rochdale, England4University of Texas Pan American, Department of Physics and Geology, Edinburg, Texas, 78541, USAThe synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanopar-ticles have a dominant Sn02 phase (as revealed by Wide Angle X-ray Scattering), with particles ofthe order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmedby SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-rayScattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersedwithin the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sncontent suggesting that the magnetization is not controlled solely by the amount of Fe dispersedwithin the nanoparticles.Keywords: Iron-Doped Tin Oxide, Laser Pyrolysis Synthesis, Magnetic Properties, BlockingTemperature, WAXS, TEM.1. INTRODUCTIONIn recent years, tin-oxide based nanomaterials have beeninvestigated for potential applications in the harvestingof the energy of sun (actually indium tin-oxide"), newlithium-ion batteries.? and hydrogen photo-production orsensor applications.' Due to finite size effects, nanoma-terials display properties that are distinct from the cor-responding bulk alloys. Nanoparticles of tin-iron oxideswith different stoichiometry have been obtained either bymechanical alloying (such as milling) of tin oxide withiron oxides"), chemical synthesis (precipitation exchangemethod"], or more recently by pulsed laser deposition,"sol-gel techniques," or pulsed laser pyrolysis.", Tin (IV)oxide, tin dioxide, or stannic oxide (Sn02) is an oxygendeficient n-type semiconductor with a forbidden gap of3.6 eV, and a tetragonal (rutile like) crystalline structure.Cassiterite is the mineral form of Sn02• Tin (II) oxide orstannous oxide (SnO) is a semiconductor with a forbiddengap ranging between 2.5 eV and 3.0 eV characterized bya tetragonal crystalline structure analogous to PbO. Tin-iron oxide or tin ferrite nanoparticles are combining the tinoxide semiconducting features with the magnetic charac-teristics of iron and iron oxides. SnFe02 is a typical diluted*Author to whom correspondence should be addressed.J. Nanosci. Nanotechnol. 2012, Vol. 12, No. 12magnetic semiconductor. At the other extreme, thin filmsof SnFe204 are semiconducting ferromagnetic materialswith a band gap of about 2.6 eV at room ternperature.?Mossbauer studies revealed three different sites of Fe ionswithin the Sn02 lattice? and reported a complex behaviorof the magnetization. From the magnetic point of view,tin-iron oxides belong to the class of diluted magneticsemiconductors; in this case, the Sn4+ ion is replaced bythe smaller Fe3+ ion simultaneously with a weak shrink-age of the Sn02 lattice.f Even more, the magnetic proper-ties of oxides and in particular the magnetic properties ofdefected magnetic oxides is under investigation.P'!"2. EXPERIMENTAL METHODSSnl_xFex02 nanoparticles with various ratios between Feand Sn were synthesized by pulsed laser pyrolysis." Thelaser was operating at 1060 nrn at a nominal power of400 W. Gas phase precursors were Sn(CH3)4 and Fe(CO)s.Air has been used as an oxidizing agent and C2H4 as laserlight absorber. The temperature within the reaction cham-ber was ranging between 600 and 650°C. Nanoparticles oftin oxide containing various amounts of iron or iron oxidehave been synthesized by pulsed laser pyrolysis by adjust-ing the flow of Fe(CO)s' The samples have been labeled1533-4880/2012112/92991003 doi: 10.1 166/jnn.20 12.6784 9299bOn the Synthesis and Physical Properties of Iron Doped SnOz NanoparticlesTable I. Atomic composition of tin oxide-Fe nanoparticles.EDX measurements [at%] 800Sample label C ° Sn Fe Sn/O C/(Sn +Fe) Fe/SnSnO 0 50 50 0 1.0 0 600Sn02 0 66 33 0 0.50 0 0 '§'SnOFe-2 12.18 55.54 31.12 1.16 0.56 0.37 0.04 'c::JSnOFe-6 11.77 58.14 27.62 2.46 0.47 0.42 0.08 .e 400SnOFe-8 15.10 57.09 21.39 6.41 0.11 0.37 0.39 ~SnOFe-1O 14.65 57.91 21.20 6.24 0.10 0.36 0.29200aWei et al.as SnOFe-2, SnOFe-4, SnOFe-6, SnOFe-8, and SnOFe-lOand contain various amounts of iron.The crystalline structure of pristine and Fe-doped tinoxide nanoparticles has been characterized by Wide AngleX-ray diffraction by using a Bruker Discovery 8 spec-trometer. The atomic composition of the as obtained sam-ples was determined by X-rays energy dispersive analysis(EDX). Additional information about the morphology,size, and particle distribution of these samples has beenobtained by transmission electron microscopy (TEM),high-resolution electron microscopy (HREM), and selectedarea electron diffraction (SAED). The magnetic propertiesof iron doped tin oxide nanocomposites were measuredby Squid measurements performed at various temperaturesranging from 10K to room temperature.3. EXPERIMENTAL RESULTS ANDDISCUSSIONSEDX measurements were performed in order to assess theconcentration of Fe in the SnOz. Table I collects detailsabout the atomic composition of the samples investigated,including the Fe/Sn ratio. As noticed from Table I, Fe ionshave been successfully incorporated within the tin oxide.Fig. 1. Transmission Electron Microscopy photos of SnOFe6 sample,characterized by a Fe/Sn ratio of about 0.08 (Figs. I(A and B» and ofSnOFe2 sample characterized by a Fe/Sn ratio of about 0.04 (Fig. I (C».Figure I(D) shows the SAED spectrum of SnOFe2 sample.9300SnOFe-l05' 34.0926.7252.1620 40 50 602 theta [0)70 8030Fig. 2. Wide Angle X-Ray Scattering of SnOFelO nanoparticles show-ing the coexistence of three Sn related phases; metallic Sn (JCPDS04-0673). SnO or romarchite (JCPDS 06-0395) and Sn02 or cassiterite(JCPDS 41-1445). Indexed reflections indicate the Sn02 phase, which isdominant.The table reveals that some C has been incorporated alsowithin the nanoparticles and suggests the possibility ofoxygen vacancies in the as prepared samples.The as obtained iron doped tin oxide particles havean average size of the order of 10 nm. Figure I shows,for example, the Transmission Electron Microscopy pho-tos of SnOFe-6 sample, characterized by a Fe/Sn ratio ofabout 0.08 (Figs. leA) and (B)) and of SnOFe-2 samplecharacterized by a Fe/Sn ratio of about 0.04 (Fig. I (C)).Figure leD) shows the SAED spectrum of SnOFe-2 sam-ple. It is noticed that the nanoparticles are well crystallizedand almost randomly oriented. The presence of metallictin and tin-oxide (both SnO and SnOz) is inferred fromFigure leD).Wide Angle X-ray Scattering (WAXS) of iron dopedtin-oxide nanoparticles confirms the coexistence of threeSn related phases; metallic Sn (JCPDS 04-0673), SnO0.31.0x10-2-0.3-5.0x10-30.2 •••••SnOFe-4 ---.-* •• 5.0x10-3_SnOFe-6SnOFe-2 * •S'E~ 0.1co~ 0.0N'a;§, -0.1C1l~0.0-0.2l-'/'--r-~~""'~~""'-~~~""~~---r-' -1.0x1 0.2iooo-iooo -500 0 500Magnetic Field fOe)Fig. 3. The magnetization curves (magnetic moment versus the appliedmagnetic field for various Sn1_xFex02 nanoparticles.J. Nanosci. Nanotechnol. 12, 9299-9301,20123 A~W de II' .!'IUIOn the Synthesis and Physical Properties of Iron Doped SnOz NanoparticlesWei et al.o•30 ~ alal ~03~<Il"0 ID20 ~ Eu, alall-~E'(3 010 ~ ~U@••o ,.J...T._~-r-.-'.--r-+';'--,---.-...----,_--.-----e_-T-' 00.0 0.2 0.4 ~Fe/Sn [at 'Yo]00~c'"Fig. 4. The dependence of the coercitive field on the Fe/Sn ratio (leftpanel) or on composition of iron doped tin oxide (right panel) as shownin Table I.S'E~§ 0.10~N~Cg> 0.05~.-~0.15 .....o 100 200 300Temperature [K]400Fig. 5. The temperature dependence of the magnetization in Zero FieldCooling experiments for two iron doped tin-oxides.or romarchite (JCPDS 06-0395) and SnOz or cassiterite(JCPDS 41-1445). The ratio between these three phasesdepends on the synthesis' details. Typically, the Sn02phase is dominant, as it is shown in Figure 2 for the sam-ple SnOFe-lO.The average lattice parameters for a and c (for Sn02)are ranging between 0.47 and 0.474 nm (for a) and respec-tively between 0.315 and 0.321 nm (for c). The dopingby iron affects weakly the parameters of the crystallinelattice.While the elemental analysis confirmed the presence ofiron, WAXD data failed to notice an iron or iron-oxidephase. This suggested that the iron embedded within tin-oxide is very well dispersed. The. presence of iron oriron oxides is supported by Squid measurements. Figure 3shows the hysteresis loops for various iron doped tinoxide at room temperature. Excepting sample SnOFe-4,all other samples show weak magnetic features. The coer-cive field is expected to depend on the composition ofJ. Nanosci. NanotechnoJ. 12,9299-9301,2012the sample (iron content). However, the coercivity of thesenanoparticles does not increase proportional to the con-centration of Fe (or with the Fe/Sn ratio) as noticed fromFigure 4. This suggests that other parameters such asthe size of the crystalline lattice or the oxygen vacanciesare competing to the overall magnetic properties of thesenanocomposites.The large differences between the magnetic propertiesof these samples are illustrated by Figure 5, where theZFC dependencies have been represented for two samples .A large difference in the blocking temperature between thesamples SnOFe-4 and SnOFe-6, with sample SnOFe-4 stillmagnetic at room temperature.4. CONCLUSIONSThe synthesis of iron doped tin oxides by pulsed laserpyrolysis is reported. Both elemental and magnetic mea-surements investigations confirmed the presence of ironor iron oxide. WAXS and SAED measurements confirmedthat the iron component is well dispersed within, the tinoxide crystals. The complex dependence of magnetic prop-erties on the Fe/Sn ratio may reveal the role of oxy-gen vacancies or of combined iron/iron oxides dispersedphases on the magnetic properties of the as obtainednanocomposites.Acknowledgments: This research has been supportedby the CONTACT grant (Air Force Research Laboratoryunder agreement number FA8650-07-2-5061), by NSF-MRSEC (Grant No. DMR-0820521), and by NCMN.References and Notes1. H. Schmidt, H. Fluegge, TWinkler, T. Buelow, T. Riedl, andW. Kowalsky. Applied Physics Letters 94, 243302 (2009).2. F. Belliard, P. A. Connor, and J. T. S. Irvine, Solid State Ionics135, 163 (2000).3. S. Shukla, S. Patil, S. C. Kuiry, Z. Rahman, T. Du, L. Ludwig,C. Parish, and S. Seal. Sensors and Actuators B-Chemical 96, 343(2003).4, O. N. C. Uwakweh, R. P. Moyet, R. Mas, C. Morales, P. Vargas,J. Silva, A. Rossa, and N. L6pez, Journal of Physics: ConferenceSeries 217, I (2010).5. L. Yanwu, O. Yiyu, and L. Fangxin, Rare Metals 25, 493 (2006).6. R. K. Gupta and F. Yakuphanoglu. Journal of Alloys and Compounds509, 9523 (2011).7. K. Nomura, C. A. Barrero, J. Sakuma, and M. Takeda. Phys. Rev. B75, 184411 (2007).8. R. Alexandrescu, I. Morjan, F. Dumitrache, R. Birjega, C. Fleaca,I. Soara, L. Gavrila, C. Luculescu, G. Prodan, V. Kuncser, and G.Filoti, Applied Surface Science 257, 5460 (2011).9. R. Skomski, X. H. Wei, B. Balamurugan, M. Chipara, and D. 1.Sellmyer, IEEE Transactions on Magnetics 46, 2427 (2010).10. M. Scarisoreanu, I. Morjan, R. Alexandrescu, R. Birjega, I. Voicu,C. F1eaca, E. Popovici, I. Soare, L. Gavrila-F1orescu, O. Cretu,V. Ciupina, and E. Figgemeier, Appl. Surf. Sci. 253, 7908 (2007).Received: 1 January 2012. Accepted: 15 June 2012.9301menm»JJo:I:»JJ:::!or-

On the Synthesis and Physical Properties of Iron Doped SnO2 Nanoparticles

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On the Synthesis and Physical Properties of Iron Doped SnO2 Nanoparticles

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