简介:Duetotheremarkablemagnetoresistance(MR)effectonperovskite-typemanganite,magnetoelectronicsandspintronicshavebecomeattractivesubjectsofexperimentalandtheoreticalinvestigationsfortheapplicationpurpose.(La0.9Nd0.1)2/3Ca1/3Mn1-xFexO3(x=0,x=0.05)werepreparedsuccessfullybysol-gelmethod.Thestructure,magneticproperties,andtransportpropertiesofthecompoundswereinvestigated.Themagnetoresistanceeffectdependsonthecompositionandthetemperature.XRDpatternsshowthatthecompoundisasinglephasepolycrystalwithpseudocubicstructure.Alargenegativeisotropicmagnetoresistanceeffectinthesampleswereobservedatlowtemperatureregion.ThemaximumMRofthesampleswas77%and97%,respectively.Itwasmostlikelyduetothescatteringorthetunnelingtransportofspin-polarizedcarriersinlatticeunderstrongmagneticfield.
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简介:ThemeasurementsoftemperaturedependenceofthemagneticsusceptibilityofLa1-xSrxCoO3perovskiteoxidesatdifferentSrdoping(0≤x≤0.5)andannealingtemperaturewerepresented.Forthesamplewithx=0.1,ashoulderwasobservedaround150K,andapeakwhichisonefeatureofspinglassappearedaround50Kinthecurveofsusceptibilityversustemperature.Thehigh-temperature(250~420K)susceptibilityfitswellwithCurie-Weisslawforallsamples.WeissconstantandeffectivemagneticmomentweredeterminedandtheirvariationswithSrdopingandoxygenannealingconditionwereobtained.TheWeissconstantincreasesmonotonouslywithSrcontentforx>0.2.Thevaluesofeffectivemomentswereinterpretedwiththespinstateofcobaltions.Studiesonthesusceptibilitiesofthesampleswithx=0.2underdifferentpreparationtemperaturesandannealingtemperaturesshowthattherisingofsinteringtemperatureandannealingtemperaturewillincreasethepara-ferromagnetictransitiontemperature,andreducetheeffectivemomenttonormalvalue.OurresultshowsthatbothCo3+andCo4+ionsshouldbeinISstateafterannealingandtheoxygenannealingcausesthetransitionofCo3+spinstatefromHStoIS.
简介:采用自蔓延高温合成技术(SHS)制备固体氧化物燃料电池(SOFC)阴极材料La1-xSrxMnO3(LSM);研究成形压力、稀释剂添加量等参数对反应过程及合成产物性能的影响;采用XRD、ICP研究SHS法合成LSM的物相和晶型结构.结果表明:自蔓延高温合成产物为钙钛矿结构菱方晶系La1-xSrxMnO3,Sr含量的变化引起合成产物特征峰的位置和半峰宽变化;随着Sr含量的增加,合成的LSM粉末粒度变细,晶格常数a和c减小.
简介:NominalcompositionofCa1-xZnxTiO3:0.002Pr3+(x=0.000~0.200)phosphorswerepreparedbyconventionalsolidreactionroute.XRDandPLmeasurementswereusedtoinvestigatethesolid-solutionstructureandluminescencepropertiesofZn-dopedCa1-xZnxTiO3:0.002Pr3+phosphors.Theeffectofsolid-solutionstructureformedbysubstitutionbetweenCa2+andZn2+ionsontheluminescentpropertieswasanalyzed.Theresultsrevealthat,withtheincreaseofZnsubstitutioncontentbelow0.010,latticeparametersandtheintensityofexcitationpeakatboth260and330nmaswellasthecorresponding610nmemissionintensityaremonotonouslydecreasedquicklyinasimilartendency.Also,theevolutionofluminescenceintensityandcrystalcellparametersagainstZndopingconcentrationareingoodagreement.AboveresultsarecloselyrelatedwiththestructurechangewithinCa1-xZnxTiO3:0.002Pr3+solid-solutionphaseformedbytheZnionssubstitutionfortheCasites.Presentstudyrevealsthatthesolid-solutionstructureformedbysubstitutionbetweenCa2+andZn2+ionshassignificanteffectontheluminescencepropertiesofsinglephaseCa1-xZnxTiO3:0.002Pr3+phosphors.
简介:ThephaseandmorphologytransformationduringthehydrothermaltreatingprocessofY2O3wasevaluatedwithX-raydiffcrcnce(XRD),scanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM),particlesizeandspecificsurfaceareadetermination.TheresultsshowedthatthecubicY2O3didnottransferintohexagonalY(OH)3inpurewater.Therefore,purehexagonalY(OH)3withnanotubeandmicrorodmorphologieswereobtainedbyhydrothermaltreatingY2O3at150℃for12hin15mlof2mol/LNaOHsolutionwithandwith-outPVAorPEGItwassuggestedthatthecharacteristicpreferentialgrowthofY(OH)3wasattributedtothestructureanisotropyofhexahedronY(OH)3.TheadditionofPVAorPEGcouldpromotetheformingprocessofnanotubesbyselectiveadsorptionondifferentcrystalplanes,whichalteredthegrowthratealongdifferentdirectionsandresultedinthediffusionlimitofconstructingionsinthecentertopofrods.Finally,Y(OH)3:EuandY2O3:Eunanotubeswerealsosynthesizedbyusingthismethod,andtheirphotoluminescencepropertieswereevaluated.
简介:Whitelight-emittingYVO_4:1mol.%Dy~(3+),xmol.%Eu~(3+)phosphorpowderswithordermorphologyandwellcrystallizationwerehydrothermallysynthesizedat180°C.Themicrostructure,white-lightemission,andlight-emittingmechanismofthepowderswerecarefullystudiedusingX-raydiffractometry,scanningelectronmicroscopyandphotoluminescencespectra.TheexcitationandemissionspectraofthephosphorpowdersindicatedthecoexistenceofefficientenergytransferfromEu~(3+)toDy~(3+)andinefficientenergytransferfromDy~(3+)toEu~(3+)besidestheenergytransferfromVO_4~(3–)toEu~(3+).IncreasingtheEu~(~(3+))concentrationinitiallyenhancedandthenweakenedtheluminescentintensityofDy~(3+).Thewhite-lightemissionsofYVO_4:1mol.%Dy~(3+),xmol.%Eu~(3+)phosphorpowderswerebothrelatedtotheenergytransferbetweenVO_4~(3–)andDy~(3+)/Eu~(3+),aswellasbetweenEu~(3+)andDy~(3+).TheinefficientenergytransferfromDy~(3+)toEu~(3+)wasfirstfound.
简介:Thesolutionreactionmechanisms,composition,donoratoms,propertiesofcoordinatelinkandstabilityofthecomplexesonthesystemsofadrenalinewithNa3+,Gd3+andTm3+havebeenstudiedbypH-potentiometrictitrationandelectronicspectroscopy.Adrenalineperturbsthef-felectronictransitionofNd3+andTm3+sothattheabsorptionspectraoftheircomplexesareshiftedtowardlongerwavelengths.Theabsorptionspectraofthecomplexesformedbythethreef-blockelementionswithadrenalineareshiftedtowardshorterwavelengthswiththeincreaseofPHinΔγ=350~650nm
简介:ThetransportpropertieswerestudiedforrareearthmanganeseoxideLa0.67Cao.33Mn1-xFexO3(x=0-O.3)systems.ItisfoundthatwithincreasingFe^3+-dopingcontentx,theresistanceincreasesandtheinsulator-metaltransitiontemperature(T1M)shiftstolowertemperature.Ifthedopingcontentissmall,thetransportpropertiesmanifestmetalliccharacteristicsinthetemperaturerangeofT<T1M,whiletheywillobeyathermalactivationmodelinthetemperaturerangeofT>T1M.SuchabehaviormaybeattributedtotheFe^3+-dopingandpossibleMnionsscatteringtoelectrons.TheFe^3+dopingmayleadtotheformationofFe^3+-O^2--Mn^4+channels,whichcouldterminatethedoubleexchangeMn^3+-O^2--Mn^4+channels.TheantiferromagneticclustersofFeionsmayinducetheMnionstoscettertotheelectrons.
简介:Theeffectofanexternalelectricfieldonthecrystallizationbehaviorofamorphous(Nd0.1Fe0.9)3Balloywasinvestigated.ThecrystallizationproductofNd2Fe23B3phasewasobtainedforthisamorphousalloyannealedat923Kfor300sinthepresenceofanexternalelectricfieldof300kV·m-1(50Hz);whilethecrystallizationproductsareNd1.1Fe4B4,α-Fe,andFe3Bphasesunderthesameannealingconditionexceptforfree-electricfield.Ontheotherhand,thesampleswereannealedat1023K,whichishigherthanthedecompositiontemperatureofmetastableNd2Fe23B3phase,for600s.Inthecaseofthepresenceofanexternalelectricfield,themetastableNd2Fe23B3phase,asamainphase,isstillstayedinthesample.ThisfactsuggeststhattheexternalelectricfieldenhancesthestabilizationofthemetastableNd2Fe23B3phase.Theeffectoftheexternalelectricfieldonthephaseselectionandstabilizationwasexplainedintermsofthespecificconductancedifferencebetweenthecrystallizationproducts.
简介:YbAl3(BO3)4crystalofgoodopticalqualitywasgrownbythefluxmethod.ThestructureofYbAl3(BO3)4crystalwasdeterminedbysingle-crystalX-raydiffraction.TheexperimentshowsthatYbAl3(BO3)4belongstothedoubleborateswithatrigonalstructure.ThespacegroupisR32anditsunitcellconstantsweremeasuredtobea=0.92965nm,c=0.72129nm,V=0.53673nm3,Z=3.Thetransmittancespectraweremeasured.Thecut-offofYbAl3(BO3)4crystalis216nm,andtherearetwoabsorptionpeakslocatedat940and975nmfrom190nmto2600nm.ThethermalpropertiesofYbAl3(BO3)4crystalwerestudiedforthefirsttime.Theaveragethermalexpansioncoefficientsweredeterminedtobe2×10-6/℃,9.5×10-6/℃alonga-andc-direction.ThespecificheatofYbAl3(BO3)4crystalwasmeasuredtobe0.6695J·(g·℃)-1atroomtemperature.AllresultsindicatethattheYbAl3(BO3)4crystalisanexcellentstoichioimetriclasermaterial.
简介:Er3+-Tm3+-Yb3+tri-dopedBaMoO4phosphorsweresynthesizedbyco-precipitationtechniqueandcharacterizedbyX-raydiffractionanalysis,absorptionstudyandfieldemissionscanningelectronmicroscopyanalysis.Upconversionaswellasdownconversionluminescencestudieswereperformedbyusingnearinfrared(980nm)andultraviolet(380nm)excitations.Energyleveldiagram,pumppowerdependenceandcolourcoordinatestudywereutilizedtodescribethemulticolorupconversionemissionproperties.Undersingle980nmdiodelaserexcitationthedualmodesensingbehaviourisrealizedviaStarksublevelsandthermallycoupledenergylevelsoftheTm3+andEr3+ionsinthepreparedtri-dopedphosphors.AcomparativefluorescenceintensityratioanalysisforintegratedemissionintensitiesarisingfromtheStarksublevels{1G4(a)and1G4(b)}andthermallycoupledenergylevels{2H11/2and4S3/2}oftheTm3+andEr3+ions,respectivelywascarriedoutinthepreparedtri-dopedBaMoO4phosphors.ThemaximumsensitivityforthermallycoupledenergylevelsoftheEr3+andStarksublevelsoftheTm3+ionwasreported.Thedevelopedphosphorscouldbeusefulinthedisplaydevicesandopticalthermometricapplications.