Oxygen adsorption properties ofYBaCo4O7-type compounds

YBaC0407一工的透氧性研究

SolidStateIonics177(2006)631–

Oxygen adsorption properties ofYBaCo4O7-type compounds

Oxygen adsorption properties ofYBaCo4O7-type compounds

637

http://www.51wendang.com/locate/ssi

OxygenadsorptionpropertiesofYBaCo4O7-typecompounds

HaoshanHaoa,JinghuaCuib,ChangqingChena,LijunPana,JieHua,XingHua,

a

SchoolofPhysicalEngineeringandMaterialPhysicsLaboratory,ZhengzhouUniversity,Zhengzhou450052,China

b

DepartentofPhysics,LuoyangNormalCollege,Luoyang471002,China

Received13October2005;receivedinrevisedform17January2006;accepted21January2006

Abstract

TheoxygenadsorptionanddesorptionofnewlyfoundcompoundsRBaCo4O7(R=Y,Dy–Lu,In)wereinvestigatedbythermogravimetry(TG)inthetemperaturerangefromroomtemperatureto1100°C.TheinfluenceofCoreplacedbyZnandFeontheoxygendiffusionpropertiesofYBaCo4O7wasalsostudied.TGresultsshowedclearlythatallRBaCo4O7compoundsbasicallyexperiencetwooxygenadsorptionanddesorptionprocessesinthetemperaturerange20~1100°Cinoxygenflow.Onehappensatabout200~450°Candtheanotherhappensatabout660~1050°C.ThedifferencesbetweentheresultingstatesbyadsorbingoxygenatlowerandhightemperaturewerediscussedbasedontheX-raydiffraction(XRD)patternsandTGdata.Weshowedevidencethattheoxygenadsorptionatthelowertemperaturehasasmallactivationenergy,whiletheoxygenadsorptionatthehighertemperaturehasalargeactivationenergy.TheoxygenadsorbedathightemperaturewilldestroytheRBaCo4O7structure.ZnsubstitutingintheYBaCo4 xZnxO7influencestheoxygendiffusionbehaviorprominently,theamountofoxygenadsorbedbecomesincreasinglyweakwiththeincreaseofZncontentanddisappearscompletelyforthesampleswithx≥2.0.However,replacementofCobyFehaslittleeffectontheoxygenabsorptionprocess.©2006ElsevierB.V.Allrightsreserved.

Keywords:Oxygenadsorption;RBaCo4O7;Thermogravimetry

1.Introduction

Theoxygendiffusionpropertyofperovskite-likecompoundsisimportantforthemtohavewidelyapplicationsinfieldssuchasoxygensensors[1,2],oxygenpermeationmembranes[3,4]andsolidoxidefuelcell[5,6].Therefore,studyingoftheiroxygendiffusionpropertyissignificantfortheirapplications.Itiswellknownthattheoxygendiffusionpropertiesofpero-vskite-likecompoundsareaffectednotonlybythetemperatureandsurroundingoxygenpartialpressurebutalsobytheircrystalstructures.Differentcrystalstructurewillresultindifferentoxygendiffusionproperties.

Recently,anewclassofperovskite-likecompoundsRBa(Co,M)4O7(R=Y,In,Dy–Lu,M=Zn,Fe,Al),thesocalled114phase,havebeensynthesizedbyMartinValldor[7,8].ThecrystalstructureissimilartothatofhexagonalLuBaZn3.09-Al0.91O7[9]andBaIn2Zn3O7[10],andthespacegroupwasreportedasP63mc.Inthisstructure,thepackingoftheoxygenis

Correspondingauthor.Tel.:+8637167767671.E-mailaddress:xhu@http://www.51wendang.com(X.Hu).

0167-2738/$-seefrontmatter©2006ElsevierB.V.Allrightsreserved.doi:10.1016/j.ssi.2006.01.030

amixtureofcubicandhexagonalalongcaxisandeveryeighthoxygenisreplacedbyBa,leavingBainananticuboctahedroncoordinating12oxygenatoms.Inturn,theBa–OstructurecanbedescribedasanhcpofcornersharingBaO12-polyhedra.InthetetrahedralholeinthepackingofBaO12-polyhedra,anoctahedronisformedwheretheYatomcanbefound,andintheoctahedralvolumeintheBaO12packingfourcorner-sharingCoO4tetrahedronsaresituated(fordetailofthestructure,seeFig.8,Ref.[7]andFig.1,Ref.[8]).These114phaseoxidesexhibitinterestingmagneticbehavior,whichresemblesaspin-glassandhasauniquemagneticsubstructure[7,11,12].

Karppinenetal.haveshownthatYBaCo4O7hasinterestingoxygendiffusionproperties,itexperiencestwooxygenadsorp-tionanddesorptionprocesseswhenheatedfromroomtempera-tureto1100°Cinoxygenflow[13].TheoxygendiffusionpropertiesofYBaCo4O7areverydifferentfrommostotherperovskite-likestructureoxides.Forexample,whenheatedtohightemperaturethetypicalperovskitestructurecompoundSrFeO3andfamousperovskite-likecompoundYBa2Cu3O7willreleaseoxygengraduallyandthereleasedoxygencanbeabsorbedbackintothesamplewhentemperatureis

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