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STUDIAUNIVERSITATISBABEŞ-BOLYAIPHYSICASPECIALISSUE2001D.__NIUT.ILIESCUI.ARDELEANI.BRATUC.DEMSTU___SOFBORATEVANADATEGLASSESUSINGRA__NANDIRSPECTROSCOPYSTU___SOFBORATEVANADATEGLASSESUSINGRA__NANDIRSPECTROSCOPYD.__NIU*1T.ILIESCU1I.ARDELEAN1I.BRATU2C.DEM31BabesBolyaiUniversityFacultyofPhysicsKog¾lni__anu13400Cluj-NapocaRo__nia2InstituteforIsotopicMolecularTechnologyP.O.Box7003400Cluj-Napoca5Ro__nia3InstitutfürPhysicalicheChemieUniversitatWürzburgAmHublandD-97074WürzburgGer__nyABSTRACT.Ra__nandIRspectraofxV2O
5.1-xB2O3glasseswith
0.05x
0.8h__ebeenmeasuredand____ysed.Thebandcharacteristictoboroxolgroups806cm-1ispresentonlyatverylowV2O5content.Thisbandhas__allintensityanddisappearswhenV2O5contentincreaseswhiletheRa__nbandsassignedtodiborategroupsandisolatedBO4unitsarepresentinallspectra.Thepresen__ofV2O5inB2O3glassesdeterminestheappearan__offour-foldcoordinatedboronatomindiborategroupsandisolatedBO4units.Inthisglasseschaintypemetaborategroupsarealsoidentified.ForhighV2O5contenttheintensityoftheband__nteredat993cm-1doesnotdecreaseasthatfrom1022cm-1bothassignedtodiborategroups.Thereforewepresumethatat993cm-1areoverlaptwobands:oneischaracteristictodiborategroupsandtheotheronetovanadatestructure.IRspectrarevealsamechangesasinRa__nspectra.Forsamplesh__ingx
0.6apeakcharacteristictoV2O5appears.Thisisanindicationthatvanadatestructurewasforming.Thereforeweconcludethatthevanadiumoxideactsasnetworkmodifierintheseglassesfor
0.05x
0.
5.For
0.6x
0.8vanadiumoxideactsasglassforming.Keywords:Ra__nIRborateglassesvanadiumoxide.
1.IntroductionRa__nandIRspectroscopybecomeeffectivetoolsforresolvingthestructureoflocalarrangementinglasses.ThetransitionmetalTMoxideglassesh__ebeenextensivelystu___dbyseveralauthorsduringthelasttwentyyears.Theseglassesareofimportan__duetotheirsemiconductingpropertiesandtheelectricalconductionisduetoelectronhopping[1-3]onaccountofthe__ailableredu__dstatesoftheTMions.Someauthorsh__estu___dtheeffectofsingle
[4]andmultiple
[5]TMionsasdopantsinalkalioralkalineearthoxideglasses.Ontheotherhandsomeh__ereportedtheeffectofglassformersontheseTMoxidesasregardstheglassfor__tionandh__eexaminedtheelectricalbeh__ior
[6]andperformedspectroscopicstu___s
[7].InthispaperwereportthestructurestudyofboratevanadateglassesusingRa__nandIRspectroscopy.
2.ExperimentalGlassesofxV2O51-xB2O3systemwith
0.05x
0.8werepreparedbymixingH__O3andV2O5h__ingreagentgradepurityinsuitableproportionsandmeltingthisadmixturesinsinteredcorundumcruciblesatT=1523Kfor
0.5hour.Vitrificationwasachievedbyrapidcoolingofthemeltsonstainlesssteelplatesatroomtemperatureandatmosphericpressure.TheRa__nspectrawereobtainedusingthemicro-Ra__ntechnique.ASpectraPhysics166Ar+laser
514.4__wascoupledwithanopticalmicroscopeOlympusU-C__D-2withtwoo__ectivesDPLAN20160/
0.17andULWDMSPLAN80/
0.
75.Thelaserpowerwas350mWatthesample.A180geometrywasusedaswellasaSpexmodel1404doublemonochro__torwithaspectralslitwidthof2cm-
1.Thespectrawererecordedwithoutapolarizerinthecollectionoptics.TheIRspectrawererecordedin4000-400cm-1spectralrangewithaBruckerIFS120spectrometerusingtheKBrpellettechnique.AMIRGlowbarsour__andaMCTdetectorcooledwithliquidnitrogenwereused.Themeasurementswerecarriedoutforapressurelessthan1mbarattheroomtemperature.Foreachspectrum100scanswere__deandthespectralresolutionwas1cm-
1.
3.ResultsanddiscussionRa__nspectraRa__nspectraofxV2O51-xB2O3glasseswithvariouscontentsofcopperoxide
0.05x
0.7areshowninFig.
1.Thefollowingbandsarepresentinthesespectra:407cm-1471cm-1526cm-1694cm-1806cm-1993cm-1and1022cm-
1.Fig.
1.Ra__nspectraofofxV2O51-xB2O3glasseswith
0.05x
0.7InthespectrumobtainedforlowestV2O5contentthe__inpeaksappearat993694526and407cm-
1.TheintensitiesofthesepeaksdecreaseastheV2O5contentincreases.Somebandsdisappearathighcontentofvanadiumoxide.Theband__nteredat806cm-1ispresentonlyatverylowV2O5content.Thebands__nteredat527cm-1and471cm-1disappearforx
0.
5.ForhighestcontentofV2O5x=
0.7thebands__nteredat993cm-1694cm-1and407cm-1arestillobservedandnonewbandsappearwhenV2O5contentfurtherincreases.TheRa__nspectrumofvitreousB2O3isdominatedbyastrongband__nteredat~806cm-
1.The806cm-1bandwasassignedtotheboroxolringoxygenbreathinginvolvingaverylittleboronmotionboronatomcoordinateis3
[8].AlistofborategroupsfoundinboratecompoundsisgivenbyMeeraetal.
[9].ThisbandcharacteristictoboroxolringsappearsonlyforlowV2O5content.Thereforetheraisingofvanadiumoxidecontentdeterminesadisruptionoftheboroxolnetwork.Allrecordedspectraexhibitpeaksat:407cm-1526cm-1694cm-1993cm-1and1022cm-
1.Inordertoassignthesebandswetookintoaccountcrystallineboroncompounds.CrystallineZnO-2B2O3andLi2O-2B2O3whichconsistonlyofdiborategroupsh__eRa__npeaksat1050cm-1and980cm-1
[10].Onthisbasisweconsiderthatthebandat993cm-1andtheshoulderat1022cm-1observedinourspectraindicatethepresen__ofdiborategroupsinstu___dglasses.DiborategroupsconsistofsixmemberedringscontainingtwoBO4tetrahedra.Thelineoccurringat993cm-1couldarisebothfromdiborategroups
[10]andfromvanadatestructures
[11].BecauseforhighV2O5contenttheintensityiftheRa__nband__nteredat993cm-1doesnotdecreaseastheotherbandassignedtodiborategroups1022cm-1wepresumethatat993cm-1areoverlaptwobands:onetypicaltodiborategroupsandtheotheronecharacteristictovanadatestructure.Thebandsbetween400and550cm-1wereassignedbyKamitsosetall
[12]tothesymmetricstretchingvibrationoftheisolatedBO4unitstetrahedraconnectingvarioussegmentswithoutparticipatinginthespecificboratearrangementsandanti-symmetricstretchingvibrationofsuchBO4tetrahedrarespectively.Thereforethebandat407cm-1and526cm-1canbeassignedtothesymmetricstretchingvibrationsofisolatedBO4units.The471cm-1bandisassignedtoaringanglebendingB-O-B
[13]thatisobservedat470cm-1forpureB2O3
[14].Ra__nspectraoflithiumandcalciumborateglasseswhichconsistofchaintypemetaborategroups
[13]exhibitastrongpeakat710cm-
1.Inourspectrafig.1thisbandappearsat694cm-1andindicatesthepresen__ofthechaintypemetaborategroups.EvenfortheRa__nspectraobtainedforlowestV2O5contentthe806cm-1arenotdominant.Thereareanotherbandswithhigherintensities.Thesebandsarecharacteristicin__joritytoborategroupscontainingBO4unitsaswejustshown.Thereforetheadditionofavery__allamountofV2O5x=
0.5leadstothefor__tionoffourcoordinationboronatoms.TheincorporationofBO4unitsintheringstructureresultsinaweakeningoftheB-Obondandasconsequen__theringopening.DiborategroupschaintypemetaborategroupsandisolatedBO4unitsarealleviden__dbeginningwiththelowestvanadiumoxidecontent.ThedecreaseofallRa__nbandsintensitiesdeterminedbytheincreaseoftheV2O5contentindicatesthediminutionofthenumberofthesegroups.AtveryhighcontentofV2O5Ra__nspectraindicatethefor__tionofvanadatestructure.ThesefactsdenotethatvanadiumoxideinthebinarysystemV2O5-B2O3actslikeaglassmodifierandonlyforveryhighcontentofV2O5actasaglassformer.Thepresen__ofboronoxideaverystrongglassformerpermitstovanadiumoxidetoactasaglassformeronlyathighcon__ntrations.IRspectraIRspectraofxV2O51-xB2O3glasseswithvariouscontentsofcopperoxide
0.05x
0.8areshowninFig.
2.Thefollowingbandsarepresentinthesespectra:642cm-1796cm-1883cm-11023cm-11195cm-11384cm-11465cm-11630cm-12260cm-12360cm-12520cm-13220cm-1and3443cm-
1.Fig.
2.IRspectraofxV2O51-xB2O3glasseswith
0.05x
0.8Samplesh__ingupto
0.5V2O5showawaterbandat3220cm-1and-OHstretchingpeaksat2520cm-12360cm-1and2260cm-
1.TheseareintenseforlowV2O5contentasshowninfig
2.AccordingtoBorrellieetal.
[15]thesebandsandpeaksareduetothehygroscopiccharacterofthepowderedglasssamples.Hen__itcanbesafelyconcludedthatthesamplesarequitehygroscopicinnatureatlowxcontent.Anabsorptionpeakwasobservedat1630cm-
1.TheoriginofthispeakisnotobviousbuttheH-O-Hbendingmodegivesrisetoanabsorptioninthisregion
[16]andthepossibilityofsomeadsorbedwatergivingrisetothispeakcannotberuledout.Abroadbandataround1450cm-1asobservedincrystallineB2O3ispresentinlowcompositionV2O5glassesbutitscharacterchangesinsamplesabove
0.5V2O
5.AsalreadyreportedinNa2O-B2O3glasses
[17]thecharacteristicB-O-stretchingbandintheB2O3glassnetworkisassignedtoabroadbandfrom1428cm-1to1333cm-
1.ThisbandappearsinourIRspectraconfirmingtheamorphousnatureofstu___dglasses.ThelowV2O5contentglassesshowaverysharpabsorptionpeakat1195cm-
1.Thispeak__ybeattributedtotriangularB-Ostretchingvibrations
[16].ThispeakdisappearswhenV2O5contentincreases.Thespectracorrespondingtox
0.6presentabandat1250cm-1anddonotexhibitthe1195cm-1peak.Thedisappearan__ofthe1195cm-1peakandtheprogressivelyappearan__oftheband__nteredat1250cm-1correspondstoachangefromtriangulartotetrahedralboronstructurewhenthesystemgoestohigherV2O5content
[16].Anabsorptionbandat1023cm-1wasobservedinallthesamplesalsoathighestV2O5content.ThispeakinattributedtoV=Ostretchingvibrations
[18].Thepeakat883cm-1whichisobservedforlowV2O5contentdisappearforx
0.
5.ThisdisappearmightbeduetotheruptureofboronringstructurewhentheV2O5contentincreases
[16].Abroadabsorptionpeakbetween740cm-1and800cm-1incrystallineB2O3andat825cm-1incrystallineV2O5isobserved
[16].Forhighercompositionsthisbanddisappearscompletely.Theabsen__ofthisbandindicatesthateitherthestructuralunitsofV2O5inV2O5-B2O3glassesisnotthesameasthatincrystallineV2O5ortheintensityofthepeakbecomesveryweakandcouldnotbedetected.Below800cm-1thereareseveralabsorptionpeaksincrystallineB2O3aswellinV2O5
[16].Thereforewecannotassumethesebandstoparticulargroupsborateorvanadate.ForlowV2O5contentIRspectrarevealthepresen__oftriangularandtetrahedralborateunits.AthighV2O5contentonlyIRbandscorrespondingtothetetrahedralborateunitsappearinagreementwithRa__nconclusions.Thisindicatesamodificationofthestructureofstu___dglassesdeterminedbythechangesofthevanadiumoxidecontent.BothRa__nandIR____ysesshowthepresen__ofvanadategroupsathighcon__ntrationofvanadiumoxide.ThusathighV2O5contentvanadiumoxidestartstoactasaglassformer.
4.ConclusionsThevanadiumoxideactsintheinvestigatedxV2O51-xB2O3glasssystemasamodifierandonlyatveryhighcontentasaglassformer.Avery__allV2O5contentdeterminesthebreakoftheregularstructureofboroxolgroupsinB2O3glassandthefor__tionofdiborategroupschaintypemetaborategroupsandisolatedBO4units.Theappearan__ofdiborategroupsandisolatedBO4unitsisanindicationforthefour-foldcoordinatedboronatomspresen__intheglassesstu___d.Atveryhighcontentvanadiumoxideactsasglassformer.TheIRspectraofstu___dglassesh__ebeenqualitativelyinterpretedintherangeof4000cm-1to500cm-
1.The__incharacteristicisthedisappearan__ofsomebandswhenV2O5contentincreases.ForlowvanadiumoxidecontentspecificallyborateunitswithtriangularandtetrahedralconfigurationarepresentwhileforhighV2O5contentarepresentonlyborateunitswithtetrahedralconfiguration.InthesametimethefeatureofIRspectrarevealbandscharacteristictovanadatestructure.Thereforeweconcludethatvanadiumoxideactsasnetworkmodifierintheseglassesfor
0.05x
0.
5.Forhighercon__ntrationvanadiumoxidestartstoactasglassformer.InthestructureofxV2O51-xB2O3glassesboroxolringsatlowV2O5contentchaintypemetaborategroupsdiborategroupsandisolatedBO4unitsarepresent.ForhighV2O5contentvanadategroupsappearbothborateandvanadateglassnetworkbeenpresentintheglassesstructure.REFEREN__S
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