Microwave-Dielectric-Properties-of-(Ag0.5Bi0.5)(Mo

Structure,PhaseEvolution,andMicrowaveDielectricPropertiesof(Ag0.5Bi0.5)(Mo0.5W0.5)O4CeramicwithUltralowSinteringTemperatureDiZhou,*,†Wen-BoLi,†JingGuo,†Li-XiaPang,‡Ze-MingQi,§TaoShao,§Hui-DongXie,∥Zhen-XingYue,⊥andXiYao††ElectronicMaterialsResearchLaboratory,KeyLaboratoryoftheMinistryofEducation&InternationalCenterforDielectricResearch,Xi’anJiaotongUniversity,Xi’an710049,Shaanxi,People’sRepublicofChina‡Micro-optoelectronicSystemsLaboratories,Xi’anTechnologicalUniversity,Xi’an710032,Shaanxi,People’sRepublicofChina§NationalSynchrotronRadiationLaboratory,UniversityofScienceandTechnologyofChina,Anhui230029,Hefei,People’sRepublicofChina∥SchoolofScience,Xi’anUniversityofArchitecture&Technology,Xi’an710055,ShaanxiPeople’sRepublicofChina⊥StateKeyLaboratoryofNewCeramicsandFineProcessing,DepartmentofMaterialsScienceandEngineering,TsinghuaUniversity,Beijing100084,People’sRepublicofChinaABSTRACT:Inthepresentwork,themicrowavedielectricceramic(Ag0.5Bi0.5)-(Mo0.5W0.5)O4waspreparedbyusingthesolid-statereactionmethod.(Ag0.5Bi0.5)-(Mo0.5W0.5)O4wasfoundtocrystallizeinthescheelitestructure,inwhichAg+andBi3+occupytheAsiterandomlywith8-coordinationwhileMo6+andW6+occupytheBsitewith4-coordination,atasinteringtemperatureabove500°C,withlatticeparametersa=b=5.29469(2)Åandc=11.62114(0)Å,spacegroupI41/a(No.88),andacceptableRp=9.38,Rwp=11.2,andRexp=5.86.High-performancemicrowavedielectricproperties,withpermittivity∼26.3,Qfvalue∼10000GHz,andtemperaturecoefficient∼+20ppm/°C,wereobtainedinthesamplesinteredat580°C.ItschemicalcompatibilitywithaluminumatitssinteringtemperaturewasrevealedandconfirmedbybothX-rayandenergydispersivespectrometeranalysis.Thisceramiccouldbeagoodcandidateforultralow-temperaturecofiredceramics.■INTRODUCTIONLow-temperaturecofiredceramics(LTCC)technologyhasplayedamoreandmoreimportantroleinfabricatinghighlyintegratedmicrowavedevices.Inadditiontothetraditionalwayofloweringthesinteringtemperaturesofmicrowavedielectricceramicsbyaddingsinteringaids,thereisanincreasingneedtosearchfornewmicrowavedielectricceramicswithintrinsiclowsinteringtemperatures.1−3WiththeexplorationofTeO2-richandMoO3-richsystems,4−6LTCCtechnologyhasbeendevelopedintoanewlevel,ultralow-temperaturecofiredceramic(ULTCC)technology,inwhichtheceramicmatrixandintermetalelectrodecanbecofiredatatemperaturebelow700°C.Generally,asinteringtemperaturelowerthanthemeltingpointsofmetalelectrodes,chemicalcompatibility,highqualityfactor(Qf),andnear-zerotemperaturecoefficientofresonantfrequency(TCF)areallcriticalfactorsforULTCCtechnology.Itwasreportedinourpreviouswork7thatthescheelitestructure(Ag0.5Bi0.5)MoO4couldbesinteredat690°Cwithgoodmicrowavedielectricproperties,permittivity∼30.4,Qfvalue∼12600GHz,andTCFvalue+57ppm/°C.Althoughithasthesameelectrovalenceandsimilarionicradiusandpolarization,whenW6+fullyheldtheBsite,(Ag0.5Bi0.5)WO4wasfoundtocrystallizeinawolframitestructurewithmicrowavepermittivity∼35.9,Qf≈13000GHz,temperaturecoefficient∼−69ppm/°C,andsinteringtemperature580°C.8Itisnotedthatthescheelitestructure(Ag0.5Bi0.5)MoO4andwolframitestructure(Ag0.5Bi0.5)WO4ceramicspossessoppositeTCFvalues.Consideringthesuccessfulachievementoftemperature-stablemicrowavedielectricceramicsof(Li0.5Bi0.5)-(W0.6Mo0.4)O4bymixingthescheeliteandwolframitephases,((Li0.5Bi0.5)(W0.6Mo0.4)O4ceramicsinteredat620°Cwitharelativepermittivityof31.5,aQfvalueof8500GHz(at8.2GHz),andaTCFvalueof+20ppm/°C),9inthepresentworkW6+waschosentosubstituteforMo6+in(Ag0.5Bi0.5)MoO4.Thesinteringbehavior,microstructure,microwavedielectricproperties,andchemicalcompatibilitywithbothsilverandaluminumwereinvestigatedindetail.■EXPERIMENTALSECTIONProportionateamountsofreagent-gradestartingmaterials,Bi2O3(99%,Shu-DuPowdersCo.Ltd.,Chengdu,People’sRepublicofChina),Ag2CO3(99%,SinopharmChemicalReagentCo.,Ltd.,Shanghai,People’sRepublicofChina),WO3,andMoO3(99%,Received:February28,2014Published:May21,2014Articlepubs.acs.org/IC©2014AmericanChemicalSociety5712dx.doi.org/10.1021/ic5004808|Inorg.Chem.2014,53,5712−5716FuchenChemicalReagents,Tianjin,People’sRepublicofChina),weremeasuredaccordingtothestoichiometricformulation(Ag0.5Bi0.5)-(Mo0.5W0.5)O4.Powdersweremixedandmilledfor4hbyusingaplanetarymill(NanjingMachineFactory,Nanjing,People’sRepublicofChina)at150rpmwithzirconiaballs(2mmindiameter)asmillingmedia.Thepowdermixturewasthendriedandcalcinedat400and500°Cfor4h,respectively.Thecalcinedpowderswereball-milledfor5hat200rpmtoobtainfinepowders.Then,thepowderswerepressedintocylinders(10mmindiameterand4−5mminheight)inasteeldiewith5wt%PVAbinderatauniaxialpressureof150MPa.Samplesweresinteredinthetemperaturerangefrom520to600°Cfor2h.Room-temperatureX-raydiffraction(XRD)wasperformedbyusinganXRDinstrumentwithCuKαradiation(RigakuD/MAX-2400X-raydiffractometry,Tokyo,Japan).Priortoexamination,allsinteredpelletswerecrushedinamortarandpestletogiveapowder.Thediffractionpatternwasobtainedover10−80oatastepof0.02o.TheresultswereanalyzedbyusingtheRietveldprofilerefinementmethod,withtheFULLPROFprogram.Thespecimensfortrans-missionelectronmicroscopywerepreparedfromthesintered