在压敏电阻氧化锌-氧化铜内中添加氧化铬, 氧化铋, 氧化镍对显微结构与电流-电压特性的改变

ResearchArticle研究報告MicrostructureandCurrent-voltageCharacteristicsof(ZnO-CuO)VaristorSysteminthePresenceofAdditiveOxides,Cr2O3,Bi2O3andNiO在壓敏電阻氧化鋅-氧化銅內中添加氧化鉻,氧化鉍,氧化鎳對顯微結構與電流-電壓特性的改變S.E.Mansour,O.A.Desouky,S.M.NegimandW.A.Kamil作者：馬來西亞聖英大學(UniversitySainsMalaysia)翻譯：晟銘電子技術長&達安企業科學顧問-邱耀弘博士，國立台灣科技大學機械所材料科學組畢業ABSTRACT摘要Themicrostructure,electricalpropertiesanddensityofZnO-basedvaristorceramicswithdifferentCuOcontentpreparedbyballmillingandsinteredat(900~1200°C)wereinvestigated.Thenonlinearcoefficient(α)anddensityincreasewithincreasingCuOcontent.Thepresenceofaliquidphasefacilitatedthesinteringprocessanddevelopedatomicallyinterfaces,uniformintergranularphaserequiredfornon-linearconduction.ThepresenceofCr2O3ingroup(II)absentofgraingrowth(inhibitionofgraingrowth)andenterinsolidsolutionwithZnO.X-raydiffractionanalysisofsinteredsamplesrevealsnoformationofnewphases,butlatticeconstantsofthephaseswerechangedaftersintering.利用球磨法添加不同重量的氧化銅到現有的氧化鋅為基礎的壓敏電阻陶瓷系統中，然後燒結(900~1200°C)後觀察其顯微結構,電子特性以及密度。氧化銅的量增加造成非線性係數(α)與陶瓷體密度的值增加。由於燒結過程液相出現在晶界，其提供原子進出的便利通道、均勻的晶界相，這是非線性傳導的要求。實驗發現添加氧化鉻該第2組(II)的晶粒不成長(被抑制了)同時與氧化鋅發生固溶反應。以X光繞射分析燒結後的試片沒有發現新的相，但在燒結後的相其晶格常數改變。Howtocitethisarticle如何引用本文章S.E.Mansour,O.A.Desouky,S.M.NegimandW.A.Kamil,2011.MicrostructureandCurrent-voltageCharacteristicsof(ZnO-CuO)VaristorSysteminthePresenceofAdditiveOxides,Cr2O3,Bi2O3andNiO.CurrentResearchinChemistry,3:29-48.DOI:10.3923/crc.2011.29.48URL:=crc.2011.29.48Received:November10,2010;Accepted:November14,2010;Published:April22,2011INTRODUCTION簡介Varistorsarematerialswithnonlinearcurrent-voltagecharacteristics.Theyareusedbothasprotectingdevicesagainstovervoltagesinelectronicandindustrialequipmentsandassurgearrestors(Souzaetal.,2003).CommercialvaristorsusedinprotectionsystemsarebasedonSiC(siliconcarbide)orZnO(zincoxide).SiC-basedvaristorshavelownonlinearitycoefficients(α=5)whereαisthenonlinearityconstantdefinedbytherelation:I=KVα,whereIiscurrent,VisvoltageandKisaproportionalityconstant(Skuratovskyetal.,2004).TheZnO-basedvaristorshaveveryhighnonlinearitycoefficients(α=50)andtheirmajorphasecontains(besidesZnO)smallamountsofBi2O3,Sb2O3,CoO,MnO2andCr2O3(Tongetal.,2009;Wuetal.,2010).ThereactionbetweentheZnOandtheadditivesathightemperaturesleadstotheformationofseveralphasesattheZnOgrainboundaries(Peiteadoetal.,2005).Thus,despitetheirchemicalcompositionandphases,theprocessingmethodaswellasthesinteringtemperature,heatingandcoolingratesinfluencetheelectricalpropertiesoftheseceramicsfundamentally(Linetal.,2007).Inviewofthisfact,theliteraturecontainsextensivereportsdescribingtheinfluenceofprocessingvariablesonthepropertiesandmechanismsthatgovernthesesystemproperties(BernikandDaneu,2007;Ottetal.,2001;Congetal.,2007;SoandPark,2002;Nahm,2004,2007).壓敏電阻是一種具有非線性的電流-電壓的特性之功能陶瓷，被用來作為電器裝置的過電壓保護電路以及工業上的避雷器的兩種應用。商業化的壓敏電阻有兩大系列材料-以碳化矽(SiC)和氧化鋅(ZnO)，因為碳化矽的低非線性係數(α=5)，α這個非線性係數決定於I=KVα,I為電流(單位為安培),V為電壓,K為比例常數。氧化鋅的比例常數就非常高(α=50)，其中以氧化鋅為主並添加有微量的氧化鉍，氧化銻，氧化鈷，氧化錳和氧化鉻的材料系統為主。複雜的添加物造成高溫燒結過程會在氧化鋅晶粒邊界析出形成複雜的相。如此，利用這些化學成份和相，可以影響壓敏電阻的燒結溫度、加熱過程與冷卻速率，使整個功能陶瓷的電子特性改變。鑑於這一事實，文獻中描述的處理變量、屬性和管理機制，這些影響壓敏電阻系統特性已經有廣泛的研究和報告。OthervaristorsystemsbasedonSrTiO3(Skuratovskyetal.,2006)orTiO2(GlotandSkuratovsky,2006;Antunesetal.,2002;Leach,2005)havebeendescribedintheliterature,butthenonlinearityofthesesystemsisaround(2α12),whichislowercomparedtothatofthemulticomponentZnOvaristors.RareearthelementscanimproveEbofZnObasedvaristorceramics(Berniketal.,2004)andotherpropertiesofvariousvaristors(Santosetal.,2001;Wangetal.,2005).TheZnOvaristorceramicswithY203addedexhibitedimprovedEb(Glot,2006a;Wangetal.,2000)reportedthatadditionofrareearthoxidesRE,O,(RE=Er,Y,Dy)toZnO-Pr6OI1-basedvaristorsimprovedbothEbandnonlinearity.However,theyallusedtraditionalballmillingorlow-energyballmillingandhigh-temperaturesinteringmethods,whichborenoadvantageinbothtechnologyandeconomy.其他壓敏電阻材料還有如鈦酸鍶或是氧化鈦也被發表過一些研究、但它們的非線性係數較低(2α12)，同時沒有辦法與多重添加物之氧化鋅系統相比。當然還有利用稀土元素來改善氧化鋅的Eb值(擊穿電場強度)。例如加入氧化釔可以提升Eb,還有添加一些稀土元素氧化物(稀土RE=鉺,釔,鏑)到氧化鋅-氧化鐠的壓敏電阻材料中同時改善擊穿電場和非線性係數。無論如何，這些添加物都是透過傳統的球磨或是低壓撞擊球磨後加入材料系統，再經過高溫燒結方法，在經濟價值和技術性並沒有太多改善。(譯者：意思就是以氧化鋅系統為主流，添加賤金屬氧化就好不要用稀土，貴且沒有提升性能太多)MATERIALSANDMETHODS材料準備與研究方法Experimentalprocedures實驗程序ReagentgradeZnOandoneormoreadditiveoxidesoftypeCuO,Bi2O3,Cr2O3andNiOweremixedinthedesiredproportionandballMilledfor2h.FiveseriesofmixesweresuggestedtostudytheeffectofcopperoxidealoneinabinarysystemZnOplusCuOandinthepresenceofadditiveoxides,Cr2O3,Bi2O3andNiOaccordingtoTable1.Themixturewasthenpressedintodiscsandsinteredattemperaturesof900to1200°Cinair.Thefinaldimensionsofthesampleswere1.2cmdiameterand0.2cmthickness.Thesinteredsampleswerelappedtoremovesurfaceflawsandanohmiccontactwasprovidedonbothsurfacesbycoatingwithsilverpaint.ThesamplesthuspreparedcouldbeusedformeasurementofelectricalpropertiessuchasV-Icharacteristics.TheV-Imeasurementsofthesamplesweremadebyusingadcpowersupplyincurrentrangeupto2mAandpulsetechniqueforhighercurrentranges.TheelectriccircuitofthevaristorsampleisshowninFig.1.所有的添加物如氧化銅,氧化鉍,氧化鉻和氧化鎳等與氧化鋅的混合都是使用球磨