Microstructure development and mechanical properties of Y2O3-doped tetragonal ZrO2 polycrystals and mullite composites

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I XI

Microstructure development and mechanical properties of Y2,Ocdoped tetragonal ZrO: polycrystals and mullite composites Shih-Cheng Chuang'',h, C'heng-Tzu Kuo" and Ai-Kang Li h "I.,~'lttZ~lc .l' Mechumcul I:,.gmce..g, NalloHol (.'hld¢~ 'Tilllg UHtvet.~tl3,, H,wltch. ~(10,'~(/('l-i.wa//) h /~lale.al,~," Research Lub~rolorre,~', I'T'RI (. lltllllllg, H,~'llli'htl .?1¢;I.~ ('Tan,t'an) ( R~'c~=vedAIJI.lU',I ,.)('), I m-~I, m rev=sed h ~rm

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Abstract (.'~)ITIp*~,lle~, ~.'~mlammg '~',(_), d, ~ped lel rag,real Zr(-)., D ~lycry,,lals ( Y 'TZ.F') and mulhle were prepared hy adding Y 'T"Z.P D~wder Io a ,:.d..'on ahJmmale ,.~1, wh=eh =,, Ihe precu=..,~n ~1 Ihe mulhle pha,,,e Atler hllral._m and drying, Ihe m=xed p~wder wa,,.,e~mpa¢led and smlered al I "41()"C m air h~r van~u,,., lenglhs ~1 lime The mulhle parltele,, were utah',truly di,'.,Ird~uled m a Y 'TZP malrix, energy dtsper,.,.ve ,~peelr~'.,e~pV mtcn~analv,,,=,~mdtcaled Ihal Ihe chemical ¢ornp~,.,Hl~m ol Ihe,.,e parl..'h~,,, ranged Ir~mi 1AI,(_)~-2Sff_), Io 2AI ,O~-,'.hO, Ir..'~nD~ralml~, mulhle parl,cle,., m a Y T'ZP rnalnx had Iw~ ,=v,denl eHecl!, ¢~n Ihe o,mD~,,He,, Iir~,l, Ihe Zr(.), gram ,,ize was ',uh,,,lanlially increased, se¢or.J, Ihe haelure h~ughne,,,,,ol Ihe c~)mp~,'.,lle',, ,,h~wed a ~()'V,,merease (from q h~ I ~,~ MPa m'~ '] 'T'hr. increased Ioughnes~ wa,, due I~ Ihe enhanced Iran,.,h~rmahdHy ~)1 Ihe lelrag~mal Zr(_), (I 7tO,), wh.ch re,.,ulled ma.nlv Ir~m Ihe enlarged gram '~ize and Ihe increased Iclrag~mahlv ~)1Ihe I Zr(_),

I. Introduction (."~m,,;~derable research w~)rk ha,'.; been dew_)led h~ lelrag~mal Z r O , (I-Z,r(_),) p~flycryslal ('TZP) ceramte,'.; because ol their excellenl mechameal properltes The enhanced I~ughness and strenglh ot 'T'ZPs are prtmardy altribuled t,~ the ,.;tres,.;-induced phase Iransh~rmalion lr~m Ihe lelragonal I,) m, moehmc phase [I ] 'Thus. m many mve,,.;ligaltons, 'T'ZP has been used as a I,~ughenmg agenl I¢~ h~ughen vart~u,,,, ceramtc matrices, such as AI,()~, spinel (Mg()-AI,O~), and mulhle [2] However, very hllle research ha,,., been omducled ulfltzmg a ceramic second phase Io Ioughen TZP, allh¢~ugh Ihe,~relteally Ihts sh,~uld als,) yteld posHwe resulls Fi~r m,'.;lance, Iw~ ,,.;ludte'.; rep~rled Ihal the addtlt,m ,~1 eilher SR." wht,'.;kers [,~1 or AI,(')~ parttcles 1,41 h~ Y,( )~-doped T Z P (Y-TZP) can increase =1,'.,ro, m~ lemperalure fraclure I~)ughness and slrenglh 'The Ioughenmg mechanism was believed h~ ,~rigmale tr~m crack deflecl.m and D~sstbly Irom mtcr~craekmg. Recently, Ishilsuka ~'I el. ISland Okada c/,H [h i have pubhshed research work ~n Y T Z P - m u l h l e cumD~stles showing a belier lraclure h)ughness lhan lhal ¢~I Y:T'ZP alone, bul lhe loughenm~ mechamsm has n~l been venhed In lhe presenl work Y T Z P - m u l h l e c,~mD~s=les were pnMuced lhr,)ugh a chem=cal coprecipilallon r~ule, m wh=ch a sdlcon alumlnale s(~l was used as lhe precurs¢~r ~I lhe mulhle phase 'T'he mm ~I lhts ql¢~ I "~q)q'~/q~/",", ll()

sludy IS to examine Ihe eflecl ~1 mulhle parhcles Iormed iH ,,,t/. on Ihe mtcr,~slruclure as well as Ihe mechanical properl He,',ol Y TZP.

2. Experimental procedure 2 I P.n'~h'r prep~m~/i.n am/,~m/c.ng Elhyl ,~rlhL~sdtcale ('T'E(.)S)(qX%, Janssen Chimica) and alummtum isopropox=de (more than ~H'Y,,, Janssen C'hlmica) were m.xed in ab,~lule elhan~)l and excess det,~ntzed waler accord,ng Io the sl~icluometric mulhle e,~mp~slll~n (alomic ralt~ ~1 AI/SI = 3) This elhanol s~lull~n was Ihen diluled using excess dei~mlzed water Alterwaxds, a 35 wl°/,, HN(_-)~ solul,on was slowly added h~ lhe ab~ve menti~med maced soluti~m wilh c, mlmu¢~us ~tirr,ng unlil the pH ,fl the s~luli~n was reduced h) aboul umly and a clear sol was h~rmed Fidh~wmg lhis, 'T'ZP D~wder d,~ped with ~ tool % Y,O~ Ipartlcle Mz.e, ab~ul ().'~ pm, 'T'oyo Soda) was lhen added to lhe s~l wilh vtgor~us a~,~lalion l'or I() nun h~ h~rm a hom¢~geneous slurry An aque~us solut,,m ~I NH.~C)H (2.~I w I % ) was added drop by droop h~ lhe c~nlmuouslv slirred slurry Io ra,se Hs pH I~ '7 5-PIll, aller which Ihe slurw was st=reed I',~r anolher 2 h. Al'ler aging lot 2(l h, the slurry was filtraled, washed wilh deum=zed waler, and Ihen oven dr=ed I'or 2 days al 12(t"C. The ground mixed D)wder was calcined al l~.>IOq2 - F'l,,evncr S,:quona All nghl~, re,,,erved

~5(1%' h~r 2 h It~ expel lelamed water and amlmmlum mlrale 'The AI,(-)~ and SIO, e~)nlenl t~l' the calcined puwders was delermmed by wel chemical analysis, whde Ihe remaining, o~nlenl ~t Ihe p~wder wan analysed usm.g, mdueHvely c~upled pla~ma-ah~m=c emiss.m ,'.,peclr~l,,;c~pV The t~,T,ical ehenl~cal ct~mp~slti,~n ~1 '¥"TZP c, mtaming I() wfl'%, mulhle p~wdel ~s h'.;led tn ']-'able I. 'The rali,~ ot' conlents (wl % ) u l AI.,O ~/ (AI ,(_)~ + Sff:):)ts '71 ,4'Y,,,v,.h~ch ~s latrlv close I~ sl~)ich~ melric mulhle ('71.X'Y.,) 'The X lay d f l l r a c l , m (XELE)) pallern,~ ~1 Y:T'Z.P-31)wfl % mulhle c~mposile p~wder calcined al varlt~us lemperatures are sh,~wn tn F'=.g, I 'T'he existence ~1 munt~chme Z r O , (m 'Z,r(.),)in Ihe us dried p,~wder is due h~ Ihe as-recewed Y:T'ZP p,~wder The m Z r O , was Iransh~rmed ml¢ll Zr(_)., by heallng, al lemperalures ahuve I()()()"C The mulhle phase wa~ h~rmed al ar~mnd 12()()"C, wh=eh ts ctmsistent wilh Ihe resul! rep¢~rled hy Mazd=yasm and Br,~wn ]7] ']"he calcined p,~wdeI was uniaxmlly pressed al I() MPa I,~ h~rm plales (.~ ;,. 3~; x 52 ]nm ~), and Ihese plates were lurlher isoslalically pressed al 2()() MPa Samples ~fl pure Y . T Z P h~r c~mparts~m were pr~uJuced Iolh)w

TABLE I (_'h~m=calcomp~.,,H,m ol Y T'Z['- l()wfl.%mulhh' p,~wder allvr calcmm[:.al hhll "(.' Malcrlal

( ~ n l e n l (wl %)

AI ,(.)~ SiLl, Z.r(.), y,(_)~ Igml,m h~'.,

4 ff~ "1"() I() Iq'~--.() I() ~O.() _ (I ", "~(I A -I-() I() I }",;,.-I_ () I(i

,j~ •

rag, Ihe same pr~cedures. The I'~rmed phlles were smtered m air al I .~()()"(." lor ..~-2(I h wilt] a healing, rule ~1 .()(I (. h ~ and lhen furnace c~oled

2 2 'l't',Sllll,~tl/Itt ~'lltlltlt'lt'l t,:tltlt~ll 'T'he bulk densHy ol Ihe smlered h~dtes wan deter nrmed hv lhe Aiclumedes melh~d. T h e average ]..,.ram ,~iz.e ~I Zr(.), (ahm~rmal cuhic Zr(.): ((-ZrC).,) grams were n~l counled) wan measured on scarming electron mtcltL~2,raphs by Ihe hneal inleicepl lechnique [X]. More Ihan 2~() glares were counted h~l each mea.~uremenl ~1 Ihe mlcr~L/~,raph. T'he eryslalhne phase wa~ idenlflied using standald XRE) pioeedures will] (.'tl KII radtat,)n (.-I() kV and ?() mA). The relaltve e~)nlenl ~I lhe in~n~ chmc and cuhw phases t~l Zr(_), was delermmed by using, lhe peak inlen,~flies ~i lhe hdh~wm~, rel]eclitms t~hserved in lhe specimens I ( I I I ) , c ( l l l ) , m ( l l l ) , m( I I I). I(.-II)(I), t((l(14) and c(4(II))I'-~I. The m=crostruclure wan ~hserved ~n a thelmully etched (I,-I.S()"C, 3(I rain) suilace and Iraclure surface using a scannml2. electron mlcH~scl~pe. A .SCallrlln[2, Iranlnl.,4.SlOll eleclr, m m=cr~sc~pe (JE(_)L 2()(I()FX) wHh a Link ener~yd=spers=ve X ray speelr~meler altachmenl wa,~ emph~yed h~r further inici~slruvlure ~d_~serval,~n and m,.'r,~anulysts wilh lhe ~. lacl,~! cah.'ula[ed based ,)n the ChH-L,~=mler method I I(I]. 'The hendmL.,, slren.glh o~ was mea,~ured by lhe h~ur p~inl hendin1~, melhod acc~rdmlz , Io lhe .IIS lh()l slandurd 'The Iraclure It~u.glule,~s K h wan meusu=ed ustn1~, lhe single edge-nolched heam melh~d l l I l, H=g,hly p~flished plales were cut inlo .3 x 4 :,, ,-I() mm ~ bars and each hal was centre n~lched I,~ ~me-third t~l' ]Is lhick]Jess umng a dmm~md blade (). I .~ mm [hwk. B~lh lhe bendm.g slren~,th and Iraclure It~u~,Imess were measured al rt~,)m lemperalure utdizmg aJ] InstI~m leStlllg m a c h i n e t ) p e r a l e d al a ~.'~)llslanl er(~ss-head ,~peed ~II (I 5 mm ram-

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F'q..,. I XRE) pallern,, h~l Y'TZ, P- ~()vol % mull,le p~wder heulc'd al vunou'., lemperalure!., I. lelrap,~rlul 'Z.r(_),, m. m~,noclllll~.' 'Z.r(.),, mu. mulhle

Resulls

3. I. [;elrs'ttv mr/ph.,s'~' ll.n,s'/~lrmtmt Iit The relullve ul]d bulk densilles qll lhe samples sinlered under varlL~US c~ndlllOns are sh~wn In Fig 2 'The hg,ure clearly sl]~ws Ihal Ihe YTZP-mLIIhle comptlSlleS ~.'an be sinIered Ill lull den,Slly, lUSt as is Ihe ease h~r pure Y-TZ.P smlered al temperatures ~1 1,4.() (_ uncl hl[2.hel 'The bulk den'.;Hy of Ihe L.'~n'tp~siles decreases will] increased volume c, mlent of Ihe mulhle phase 'Ttus seems reasonable, s.nee Ihe mulhle phase has a much h,wel the~,relwal densilV ( 3 1 7 . g e m - ' ) Ihun Y-'TZP (fl.()X g e m - ;) Allh~u~,h incorp~ruting mullnte purtncles d~es nol shrew any eflecl tm cemsohdallon ~1 Ihe ct~ml.~t~sfles, tl d,~e',; cause an ¢fl_'w._~us phase varml,_m m the ZrO.,

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T'ABLE, ? Pha,,e c, mh'nl in Ih~: 7,r(_), malrnx h~r Ihu ~i' T"Zf'-inullnl¢ L'(ffripq)Mle~, s m l e r e d ..il I ~()l)"( ' Mulhl('

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Mulllto Conlonl,Vol% F'iL.' ~ A x i a l rall~) , / . ,d I Z.r(.). a,., a h.incli,~rl ~1 m u l h l ¢ c~rllenl Irl Y T Z P - m u l h h ' c(imr)qlMir, h ,,nnlered al I "~()()"( ' h~l '~ h ,',1"11i nd li)li(~l

2 ,~In r~,~ln.'l.t~' dcl,elupmum FI~,Llle,~ 4(a)-,-l(l') shl~w Ihe ~,canlling eleelrl)n mierl~ graphs ~1 pure Y:T'ZP and Y'T'ZP-mulhle e~mp~.,,.lles ¢~mlaining I(t and t(I wfl'V., mulhle All ~t these sam pies were smtered at I ~(I(t"C hlr either ~ ~_ii I1) h 'The dalk .glare,,. m Fig,n 4(e)-.-l(I) ale mulhle pumele,,,. "[he m¢~rph~hLgy ~1 mulhte parliele,, wa,; u'quluxlal when lhe ~'~mp~slle was smtered h lr ', h, hut ii became r~d hke when the ,~mlermg lime was exlended I~ I(I h T'he i~d hke mullfle pameles are a tew mwr~melels hmg (les,~ Ihan 3 pro) and les,~ Ihan I ,,m wide. T'he aspeel rail() is e,~Hmaled h_1be n~ .p.realel Ihan 3 ~m avera.Rv The Z.r(_), grain size,, ~)1'Ihe c~mp(~niles are sh~wvn in F=g "~ I l l n m l e r e s t m g h l m q e t h a l l h e g l a m x = z e s ~ ) l l h e comp,~,.',,lles

malrt,x An .,.ih~)wn in Table 2, Ihe I Z.r(_), v~nlenl decreases an .,.,mlermg time and mulhle omlenl merea.se, the c-Z, rC), and m Z.lO, omlenln, ~m Ihe ~dher hand, in~.'leaSe us sinlering lime and mulhle c~mlenl are increased. Thi,s .',,uggesls Ihal lhe presence ol Ihe mulhle phase makes Ihe I 'Z,r(), phase suseepllhle h~ Iransh~rmuli~m This e~mjeclule can he lurlher nupporled hy lhe increase in lelrag~mahly ~1 lhe leliag~mal pha~e, ,' ~' increase in lallice paraineler r a l l ~ l ~'/d, as ,~hown m F'~.R

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smlered under the same e, mdH,mn The largesl Z,r(), grain s=ze =,,,;~l~lained when lhe mulhle c~mlenl leach~.'s Ill v~1% ']he Z.r(), grain .',;Ize ,,;larls I,~ deerea.,,,e ,~nce Ihe mulhle ¢,mlenl ~s grealer Ihan I(I wd'Y,,, mdwalmR Ihal lhe mhd'qlion ,~1 gram gr,~wlh Iw di.,;persed particle.,,; sllll h,_,hJ,~ II1 Ihln sWlei'n S~me al'm~.rmal .grams were tound h~ ~ceur lil s,)me sample~ 'l'h=s phem~memm I~ espeelallv d()minanl in samples e~n laming 'fi and I(I wfl'I/,, mulhle, as nh~wn m F'q:,, ~(d) T'hese large grains exluhll a charavlerlslic lweed ¢~mlra',;l ~1 e u h l c g r a m s w l l l l l i n e I ' Z . r ( ) , p r e e i p i l a l e s , an s h ~ w n In F'Ig t d a l T h i s c~HJhJ h e ~ e a d l l v c h a r a c l e i l z e d

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Mulllte Content,Vol% FI[,, "~ ,,S,w.~rage/.,rain sizx' ~I 'Z.l(_), a,, a lun~.'l~m ~I mulhlc ~ ~.'~mk.'nl h~l 'Y T'ZP-rruJlhh ~ ~.'~mpo'sllt"., ',,inlered al I "dill"(.' h~r ~ h ' ' l a n d lllh(Al

by a I I 12}, type ~)1 rellect._m in selecled-area diLl'racII()n (SAD) patterns Ir()m Z = ( I I I ) , and Z = ( I I()), I I 21, as sh~wn in Fig. h(b) A l~¢pical Iransmnssn~m eleclr~m mier~graph ~)t Y:TZP-I(Iw_fl'Y,~ mulhle ~s shown m F'ng 7. Energy dnspersnve speclr~metrv (EDS) mncr~analvsns ol Ihe mulhle grams sh~)wed Ihal Ihe chemical c(~mposfl,~n (fl' Ihe mulhle (AI/Sn at~mnc rallo) ranged tram 3 I to 4.(I, mdncalmg Ihal lhe comp~)sfl.~n ol Ihe mulhle parlneles was n~l very h~m~)gene()us, although Ihe comp(~sfl,~n ~)1 all Ihe samples tell inh) Ihe mulhle sohd s~lulnon re~on (Ir(,m ,3AI.O~-2Sff), I~)2AI,(.)~-Sn(.),). 'T'hns nmphes Ihal a small amounl o1' Sfl-), lel'l in the mple lUnCln~ms and gram buundaries ~fl' Ihe ZrO, h)rmed a glassy phase, since Ihe p~wder was originally prepared according I~) an AI/Si ral,_~ ~fl' 3 Figure .~ sh()ws Ihe Inansmissn~n electrum m n c r o graph ~fl' Y TZP-.%(~I "/.. mullile smlered al I S()(I "(." for I(I h An SAD patlern ~)1 a mulhle grain wn/h zone axis ]1 I11] us als() presented in F~g. ~ The resulls ~t EE)S mncroanalvsns .m Ihe p~)snl,ms marked a-d m Fng. showed the exnslence ol s~lnd s~luhflily ~1 AI,(.)~ and St(_), m Z r O , and ZrO, m mulhle, as flluslraled m Fig ~. 'T'hns phem~menon unamhgu~uslv .nphes Ihal a strong c~herence exnsls belween mullile and Z,r(-), grams Ihrough Ihe s~)lnd solut,m tormali~m I I ,3]. Using lnansmnss,~n eleclron micr(.scopy, glassy phases h)caled al gram b~undarnes and Iriple lunct,ms were ~fl~served (Fngs I()(a) and I()(b)) Sngmhcanl

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Fig h (a) T'ran,,mi;,,s.m ele¢lr~m rniLr~)grapl'l ot Y ' T Z P - I ( ) w f l "A. iTiiJIhl,: ,dnl~red al I'~(l(t"(' h~r I~) h. ~.hl)wlrl~2, L Z r(_), wllh I Z r O . pr,:¢tptlale,J ( m a r k e d (.')arid ii.veallrl[., Iweed c~,|lra~l. (h) an %A [) p a l l e r n ~)1L' Z r(.I. w l l h zq~rle a_~.t,, I I I I1, ',h~wlnl., all Ihree I Z,u(_), vartarll,,, 1me ~pl Ih~' II I 2}, sp~,ls ~,,, mdnealcd h~' an azr~,w

um~)unls ()I' Sff-), and AI:O~ were dnss4~Ived in lhe glassy phase, while .,,mall amounts ~I Zr(-),, Y.,()~ and Irate ,npuntnes such as (Ca(.) and K:(.) ~.'~)uld '.;fill be tdentihed I'W E[)S n]ter(~analvsis al the triple lUneltL)ns (see F'tg I()(c)) The tmpurflies may haw' L.'~)me Ir~m lh,~ slarlmg malertals, suL.'h as lhe TEOS or aluminum

Fip, 7 E'.DS p~,nl mt~.'r~anulys,',, ~n mulhle parliele,., ir= "t' 'T'Z P- I(I,,,,~1'%, mullile '.,irilered al I ",()ll "C h)r Ill h, given a.'.,lhe ,Jt~mi~.' rali~ ,,'~1/_"51.indi~.'alinL.,, ;In AI/S= ah~mne ralll~ rangtr=/.,,Ir~m

t.,,,~pr~p~lxide R~unded edge grain e(.~rnets al Ihe Ir,ple luneln~_m.',, are als~'~ revealed, mdtealmg Ihal Ihe am~unl ~1 ~,la.,.,,,,~'phase t,,,, m~l small. t ~' .,1h'~'ham~'al pt'~ ~p¢'~'t~¢'.~ T'he dependem.'e ~1' Ihe bendnn~, stren~,lh ~a (.~1'Ihe L'(_~mp,~.',,tte.~ ,)n mulhle e~nlenl is sh¢~wn m F'n.g 1 I. Fbr Ihe pune Y'TZP, lhe ~~a value ns ab¢~ul ~()() MPa, however, when mulhle t.s added, Ihe hendmg .~trenglh deehnes pn_)pc~rltLmally t~ the mulhle e(~nlenl There i,s alm(~sl n~, dtH'etence belween Ihe a~ ,~1 the .,,;ample.',, .,.;irileted I,Lt,r ~ h and Ihe ~ ,,ll Ih,~,.se .,.;mlered I'(~,r ll) h II seems,,; thai .smlerm.~, Inme ham,,;m),~bvtc)u.s mlluenee ~n I~endinl:..,, slrenglh, mdiealmg Ihal gram ~,rowlh n.',,n,~,l an imp,~rtanl laelc~r in degradin.~, lhe rnalerial. ['he relalt~!,nshnps helween traclure Iou~,hne.ss E l , , ttan.'.,hlrmed m~m(~,ellme phase Iraeln,t)n and mullile c~_mlenl are .,,,h~)wn m F'ngs. 1 2(a) and 1 2(1"~) T h e resUlts,.; .,,,hl.'~w Ihal, when Ihe am,L~unl ol mulhle added I(_~ the Y'T'ZP malrnx n.'.,les.,., Ihan II) w~l.'~,,, an merea.'.,e nn K~, t,., i~bserved T'he httt,he.sl I,L)ui:.~,hne.,;,.sh~r lhe t'omp~.stles wa.,., I~ 5 MPa m " ' and 12 ~ MPa m " ' t'~r .'.;ample'., ,.,mlered h~r I(I h and ~ h respeelively Allh~_~u,~,h Ihe Kn, value .slarl.'., I,,~, dechne when Ihe mulhte c()nlenl is .grealer Ihun I() ~.o1.'%,, tl t.'., .,.,ttll hLu,her than Ihul ~_11pure Y:TZP even h~t e~mp~sile.~ wtlh a rnulhte L'~mlent a.s h~t:..,h a'., ?,l) w~1% A semnquanlHalive measuremenl ~1 Ihe m~m~ehnic pha~e ~bserved on Iraelure sudaee,',, al.,.,~ ,,,h~w~ Ihe same varnali(~n pallern c~rrelaled I~ mulhle ~.'~nlenl Figure I ~ .,,,h~ws Ihe .,,,canning ele~.'lr~n rnter~,raph.', ~1 Ihe IraclLiUe .sudaees ~1 pure Y ' T Z P and Ivv~ ¢~m-

m

Q

FII.~, X la) Hn[~hl field Iran.smi.'.,.,.,,m ¢lcclrqm micr,~p,raph ~1 a Y 'T'Z.P-",w)l '%, mulhle ,.,ample ,.,irilured al I :',,()(I"(_' Iq~r I() h. and (h) an _~AD pallern ,~t mulhle wilh zlm¢ a~=,.,I I I()l, mi~.'r~.'ra~.'ks are iridtrafed hy arrq=w,,, and Ih¢ pu',,tli, m (a-d)h~r EDS mi~.'r~) unalv,,i,, :lrt' ,.,ll,~wn acr,~,,,., Ihl.' I~ralrl hq~unda~' helween m Z.r(), and Ih¢ mulhle grair=

p~snfe.s e,)nlamin~. I1) w)l.'/,, mullile and 3() w)l.'/,, mulhte re._,,peclively The Z r O , matrix Io15_)w.,, a mixed mq~de (~1'mlergranular and trans+,ranulal l'raelure, whtle Ihe niulhte parlit'les are q_)nly Iraelured transgranularly An indenlatnem lesl sh~wed Ihat Ihe craek pr~.~pa~,ale,',, m41sllv Ihr~.~u~,h Ihe mulhle parlieles, as .,.,h~wn un F'=~, I-I.

8

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k~'. I) c'.l', 15~;

5.5

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=.i.~

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FII,' L~ F'.D~ ',peclfu I;Jkerl a~'[,~,, Ihe Zr(_),-mulhle I-,~undary al Ihe p,~,,lll~_~rl~,ma[kcd iri F'q,. ~. ~,h~winl..,,~,~m~'amolJnl ~,1 ,,l~lld ,,,~luhilll~v i~l AI ,(_), and ..%1(_),irl 7[(), ,]rid ,,~rrle 'Z.r(.), in mulhh'

4.

Discu,~ion

'The relatwe dens~l~es ~11'all ,.;ample.,., were mdepen denl (_~1'.'.,mlerm.~, t~me and mullite e~ntent, mdiealm~, Ihal mc(_~rporat~)n ol mulhle parlieles has nu adverse eH'eel ~n Ihe smlerm~, t~ehav~ir ~1' Y'T'ZP T h e r~_lunded-ed~,e ~,,ram ¢~_~rners ~)h~erved ~n the tran~mis.'.,~n eleclr~)n m~.'r~,raphs (F'ig. I ( ) ) m d w a l e that a tairly larg, e um~_~unl ~1 hquld phase ex~.',,led ahmt:.,, Ihe g,ram b~_~undar~e.,,, (11 Z.r(.), durin.R .~mlerm.~, The re arranging, eapahlhly ~t the liqu,J phase cwershad~)w,., the pmnLng eHeet ~1 the mulhle p~.lJ'licles. 'T'hu'., Iiqu,d phase sinlerimg, hehavlclur ,,qmdar I~ Ihal (_)1 a ~)~le c(lmp~.menl material i,,, {)bserved in Ihi.~ 'Z.r(.),-mullile ,~y,~tem

T h e liquid phase is h_)rmed bused ~in ,~l(_),. v,,hwh ~rl~,tnales Ir()m the nlm-slcll(.'hl,_~melrtc mulhle, and AI.,O~. As idenllhed by E.[)S IntL.'r(lanalvst~ (F'I~J, I()(c)). Ihe ~,la.'.,sy phase wan enriched vdlh SI(-),, AI ,(.)~, .,.,mull am(tunis ill Zr(_), and Y,(~)~, and Iraee amllunl,., ~1 impurHw.'., such a,~ (.'a(_) and K ,(-) F'lgUle I I ,.,h~lws Ihal Ihe mullile partl~.'le~ have AI,(_)L e~_mlenl,., ran~,mp, Irc)m '72 hl '7'7 .'~ wl % (equivalent I(_~ an AI/SI ahmHe rali~) tr(_)m t I(i ,-I), whwh are hi.~,her Ihan lhat (~1 Ihe sl~,etll~melnL.' mulhle ('71X wl'Y,, AI.,(_)~) prepared al Ihe he[_,pnnm~ ~1 lhe pilwder preparal,~n T h e exee'.,'., Sl(_). IhaI ~,alher;~ al Ille I...,,raln I'~,lundarle~, bee,~me,., Ihe ha,.,e h~r lhe liquid phase, 'T'hr., .~,la.~sy phase ~.'.,Ih~_lu..u,hl I¢~ he ;I I~w ws~.'c~slly liquid phase in Itle ~IO,-AI,(~)~-Y.,(_)~ ,.,yslein thai .~l;.,irl~ h~ s~llen between I ~llil and I.-I()(I "(.' l 14 L 'T'hi~, re'.,ull is ~n a~?,leemenl wllh K~fl'~;iyu.'.,hr,., w'~rk

l

li

l

x

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z

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iL Fig I(I. (a). (t~) Brll~h! held Iran,,mr~,l~n eleetn~n micr~pl.~,raph~, i~l Y 'T'ZP- I()vqd.'Y,, mull,le ,.,infered at I SIJI)"C' h~r I() h, ,~h~w,nl~, Ihe ,~la,,,~,v pha,.,e in Inple luril.'llq~n ,, and I~,rain hcpundune,~ q~l 'Z,r(), ~:,,rain',,,, Ihe dd-hJsed hah~ q~t Ihe i:la,.,',;y pha,.;e ts als~ revealed (c) F,,E)S Sl',.'~:lra laken in Ihe Inple lUm.'lil~n ,` n'iarked X and Y, !,h~_~wiril.:Ihe elemenl.~ in Ihe I?,la.'.,.'.,ypha,,e T'he ~.'<~pper mlg,nal I,¢ due I<~ eonlamlna lion hy Ihe ~.'~pp~-'r I:,fld

1000 1500 "C/bh

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Mulllte Content,Vol% 35

50

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Mulll'l'e Contenf,Vol%

(hi

F'q}, I I D e p e n d e n c e ,~1 huridln~.; slrerll~,lh ,~n m u l h l e c,)rlleril I,~, Y'T'Z.P-mulhle c ~ r r l l ~ , , l l e s .slnlcrcd al I '~()()"C I ~ r '~ h (l:l} arid (th(A)

1500 "C x I Oh

14 40

t

o I0 i

151, in which Ihe .glassy phase ~11 a lerl')aly svslem including Sff_),-AI,(_)~-(.-'a(~), Zr(-), and Y,(_)~ was studied and it wan sh~lwn Ihal Ihe ~-.:,lassy phase aided hquld-phase staler m.~, ~1 'T'Z.P 'The presence ~1 a glassy phase can markedly enhance Ihe ~,,raln .gr¢~wlh ~)1'Z r O : , as sh~)wn m Fig, '~ In ~iher w~rds, Ihe Sl(-),-rlch glassy phase can pr,~m~le mass transport1 thr~)ugh grain h,~undar~es during slnter ing, 'The average Z r O , g,raln size in the samples increases w~tl) increasing mulhle c~mlenl in the beginning, and Ihen declines, illuslratmg that inculpc~ratl~n ul' mulllle parllcles has tw~ ellecls ¢~n grain gr~)wlh in ~_)ne dlrecil, m, iI enhances grain gr~wlh because ~1 c~)nt[ibules h_)Ihe h~rmmg ~1 liquid phase, but in Ihe c~lher dlrecl~,)n iI mhlhlls glaln gr,_lwlh because ~1 lhe pinning, eHecl ~1 Ihe mulhle parllcles l-.r~m Ihe kmellcs ~l'Zr(_),graingr~_~wthlllustraled in F.ig IS, weseelhal the increase ,~1 dispersed mullile phase d,_~es have a pinning, el-I'ecl ~n glaln gruwlh. 'T'hls is why the Zr(.), grain size in Y'T'ZP-3()vuI'V,, mulllte in smaller Ihan that c~l Y-'TZP- l()v~1% mulhle In all samples, c-Z, rL), was present regardless ~II the presence ~ff' mulhle When Ihe mullite wan preserll, huwever, it procreated Ihe h~rmatl~m ~)1 c-Zr(_),. 'T'ahle 2 shuws Ileal Ihe quanlily ,~1 c 7,rO, in each sample increased wllh increases in mulht¢ omlenl and slnler ing time Meanwhde, the c/,~ rail,_)(telrag,_malllvl ~1 I-'Z.r(_), als,~ increased as mulhle c~mlenl and slnlerlng lime were increased (see Fig, 3) 'These phem~mena

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Mulllte Conlent,Vol~,, F'nI.,, 12 Relaln~m,,hnp h e l w e c n lh¢' Iru~.'liJn,' hHJi..,.lIrl~',,,,, llle m Z . r ( ) . pha,;e I r a c l l q m q)rl Ibm' I r a c l u r c ',lJrl;Jl'l' ;Jlld IhL' IrllJlhle ~.',~rllL'rll h,r u¢~rnp~,,ll~. ~,, ,,,nnlurcd al I hll(l"(_' h~r (a) "~ h arid {h',,

I(Ih

result Ir,~m lhe depleli, m ,)I ytlllurn m lhe ll'lrag~mal phase, whJch causes an increase in lellagqmahl~ 11~,I and enrlchmenl ~_~Iyllrlum ,n the cuhc phase hy mean,, ~I' hquld film mlgratlun I 1 7-I'~I .4 J ~ Ic'r'htmlr'~H prr ~p,.'lm.'.,,' L.~wer bending slrength cau,.,ed hy me~rp,~ratmg dmpersed mulhle may resull Ir,~m the hdh~wml.,, Iw,~ taclq~r,., (I) Ihe inherenl h~wer strenglh ~1 mulhte, and (2) tensile residual slress .~,eneraled =n Ihe vicmilV ,,I mulhle parlleles m Ihe Z.r(_), malr,x du¢' 1,, Ihe Ihermal

I,-I()

A' ¢ (_'hmmy el,d

/

)',~'/~ ~t~I~'~1Z~ ~, ,m,I m.lhle ~'~lllp~,ll,',~,

Fig 14. Crack prl~pagalior= tr,~rn Vicker~ mdenlalt~m wflh url mdenlal,m h~ad ~1 ,.Iq() N h~r (a) YTZP- I()vol% mulhle and (h) Y'T'ZP- ~l(Iv~d.v..mulhle B~lh were sinlered ul 1%()()"(" h~r I() h

Fig I ~,. SLannmg ch.'Cl[~m mlcrograph,~ i~1 Ih~' t'raclure ,~uflacc hH Ihrce scls OI K h ,,pecimen,, ,~lnlc'r~d al 1%()11"("h~r I() h (a) pure YTZ.P, (h) Y'T'ZP-II)voI",./. mulhh =, (~') Y'TZP-h)vqd.°,l, mulhh'

expans,m mismalch helween Zr(-), and Ihe mulhle. A stmtlar case was rep,~rled in an Al,(_)~-mulhle syslem

12q~l ['he Iraelure loug, hness ~d' the Y-TZP-mulhle e~rn postles increases remarkably for samples c~mlaming

I() w)l'Y,, mulhle and Ihen e x h i b , s a steady decline as mulhle c~mlenl mcleases, as shuwn .n Fig. 12. T h e same pr~pensity is revealed h~r lhe lranslormed mona ¢hnw phase Iraclion delecled ~n the Iraclure surface. "['his mdicales lhal lhe Iraclure loughness is greally al:lecled by lhe stress-reduced tetragunal-m~mt~ehnic phase Iransl'~rmal,m. (-)n the ~ther hand, lhe gram size varial,m pallerns (F'i[..,, S) ch~sely hdh~w lhe patlerns oI' lhe Iransh~rmed mqm~chme phase Irm.'tt~m and K~, vx mulhte conlenl (in F'tg. 1 2) 'T'l'us dem~mslrates unam

.~ (.' ~ 'lma,g ct al

/

)'.t ~r doped ZtC ~. m M rmdhte~ ,,,p~,stle.',

and Zr(_), grains and the similar Y,~ung's moduh (about 2111GPa) ~1 mulhte and Zr(.),

2.S 0

Y-T'ZP

I-I

30 vol~ mulllte

I 0 vol'~ mulllte

Slnterlng hemper~ur~: 1500 "C

2,0

5.

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15

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F'll.. I'~ Average !:,ruin size ,~1 'Z.r(), h~r sample,, ~,lrllcred al I'~(l()"(.' t'~ '~irilenng lim~.... , pure Y'T'Z.P. A, YTZF' wHh I1) v~fl 'Y,,mulhle' I-I, Y T'Z.F'wllh '1()v~l "/,, mulhle

blguously that grain size has a dt~minanl eLlecl ~n the Iranslormahihly lr~m lelragonal phase h~ monochmc phase under applied slress [ 14, 2 I] Besides Ihe grain size eft'eel, Ihe Iransmlss,m ~1 yllrium I~ns m Z r O , grams als~ plays an imp~)rlanl r~le m enhancemenl ol lhe transh~rmabdfv ol t-ZrO, As Ihe grain h~undarws are Idled with glassy phase, Ihev lorm a c~mvenienl d=ftus=on path I'~r Y,(.)~ I~ leach Ir~)m I Z r O , and enrich Ihe stahilized c Zr(.), grains The depleliun ol Y,C)~ conlenl in I - Z r O , grams causes Ihe increase in lelragonahtv ~1'1 Zr(_), (Fig 3), and Ihus makes lhe I Zr(.), grains m~re suscepllble I~ Iranslormall~)n This iseonsistent wllh I h e w ~ r k ed'Ruhleand c,~workers sh~wmg Ihal lhe lelragonal-m,m~)chnlc lransh.)rmatl(~n ()ccurs easily in areas where the e~m cenlraln~m ,d' Y,(.) ~us hel,~w average I 1,4,221 The residual hoop tensile micr~slress caused hy thermal mismatch belween lhe mulhle phase and the I Zr(_), malrtx may als~ have an eHecl ~n h~ughenmg the c()mposHe (Ihe o~eHioenl ol thermal expans,m for Ihe l-Zr(_)., is ab,~ul I ( i x I i ) - " " ( . "-I, while Ihal h)r mullile phase is ahoul '~ .3 .x:l()-" "("-~) 'T'h~s residual tensile stress will make cracks tend I,~ propagale I~wards Ihe mulhle parlleles 'T'h~s causes Ihe Irans granular traclure ,~t mulhlc parl~cles (F~g. I.-1) and induces Ihe adlaeenl I-Zr(_), I~ Iransh~rm when cracks penelrate Inl¢~ Ihe I-Zr(_), phase (.'rack detleclion ar~und mulhle parlieles d=d m~l ~ccur. lhJs is pr~hahly because ~1 the slr~mg coherence belween mulhle phase

Conclusions

'This research leads LIS tO h~rm Ihe lullowlng concluSl()ns. (1) Free mulhle parllcles pr¢~dueed Ihr**ugh chemical copreopflal.m can be h,~mogeneously d~spersed in a Y:T'ZP malr=x wllhoul influencing Ihe sinlermg behav.~ur ol Zr(-),. The chemical compos=l=un ,~1' ~he mulhte parucles ~s n~l very umh~rm bul lalls within a dlslrlhull~n langmg Ir,)m 3Ale() ~- 2S1(): I~ 2AI .(-)~-SIO,,. (2) The addition ,~1 mulhle phase has a dual eft'eel on Z,r(.), gram gr~wlh: gram gn~wth is enhanced, resulting I'r~,m Ihe Iormat.m ,~1 hqu~d phase, bul als,~ Intuhiled, heeause td' Ihe pinning eHecl ol mulhle palllcles This ilthibillng eft eel is ~mlv nollceable, h~w,'evel, when Ihe mulhle c~mtenl exceeds I() vtd.'Y.. (3) The presence ~1 dispersed mullile phase in a Y-'TZ, P matrix leads h~ an increase in Iraclure U)ughness ~1 tr~m q - I l l MPa m ' " (l'~r pure Y : T Z P ) h ~ 12-13.5 MPa m"" (h~r Y:T'ZP-I()v~l.'~,, mullile); bendIng slrenglh remains alxwe ~.t(1 MPa as Ihe mullile omlenl increases I~ II) vol 'I/,, (.4) The h~ughenlng eflecl ~I incorp~ratlng mulhle parlleles in Y ' T Z P is due l~) lhe enhanced slressinduced lelrag~mal-mom~chnlc Iransh_)rmali~m ~)I 7.r(_), ,)~i~,~nallng mainly Ir~m an increase in I Zr(_), grain size as well as from an increase in lhe lelrag~malitv ~I I Z r O ,.

Acknowledl~menls Funding supp~rt hy Ihe MInlslrv ~1 Ecom~mic AHmrs ~1' T'alwan is gralelullv ackm~wledged We are als~ gralefiJI I,~ Dr Li (.-'hang Ior his assislanee m trans mission eleclr~m micr~scope observal~cms

References I 'T K (Jupla, F F L,an~.:eand J H Beeh.fld, ,I /llm('t .~_'cl, I t(Iq7X) 14¢t,.I-147() 2 N. L'laussen. in N Claussen. M Ruhle and A Heuer (eds). .~','wrlte artd

[echr,~h~D' ~f Zlrt'orlltl II. irl ,~dvllrl~t'~ Itl

t. etmmc.~. Vol 12. Amcncan Ceramic _~l~,'lely, Culumhus. OH, IqN,4,pp ~,2'~-tSl *, N Clau,~sen, K L Welssk~pe and M Ruhle, I ,-Ira t't'tam ,4 K Tsukuma, K Ueda and M Slnmada, I ,,4m t emm ,_~,~l , t~8(I)(IqNS)c .4-e '~ ~, M Ish,suka. 'T' Sala. T' Endl~ and M Shimada, I ,4m t. emrn ._~f,, /'#(ll)(IqX7)c ~,42-c "~..It~

I,~2

~_' ~_' ~ tmmtgetal

/

Y,O~ doped Z~t_~,andmollm'rlmipo,~m'~

¢~ K. (.)kada. N Ol,,uka, R J Bnlok arid A .l M~uls, m,.I A m (_'emm .~_'o~ , 72(I 2)( I q,~q) 2 ~lt#~-2 ~'72 7 K ..% Mazdlyaxnl and L.. M. B[(iwn, .I A m ('elm~l ,%'o~ , ~'~ (I I ) ( I q ' 7 2 ) ~,-IX-'~,2 H J (.' Wursl and l A N e l ~ ) n . . I ,4m I",'ram ._~'o,', '~ (2) (Iq'72) I()q q 'T' Ma,,akl and K Shnnl~l. in ..% ..%,)rnnya, N Yamanl~h~ and H Yanu~,~da (ed,~), ,.~c~t'oce m M 1-'erlmologv o / Z m ' m l l a III, Irl ,4dv, mt'es m ¢.t'mmi, s, V~I 24, American Ceramic S~lclel~', We.~lervllle, {.)H, I q,~,X, pp 7(lq-'72() I() (.; ChH and (.3 W L.onmer, I ,~hrm.w (~i~,~1), I0~(Iq'7'~) 2(I~-2()7 I I R F Pabsl, irl R (.' B~adl, E) F' H. Hasselman and F' F' L,ange (eds J, Mlt'ro~'trllt ~lilt', t~tl,tlenal% mid ,,~ppht,m, ms, in Fra; l/lit' /t.le,'ha/tl~ ~, o/ (. ~,'rtt,'llrt '~, V~_,I 2, Plenum, New 'tq~rk, NY, I q"7q, pp '~'~'~- '~t~'~ 12 V L.anlen, A H. Heuer and T' El Milchell, in N (.'lau,~,~en, M Ruhlc and A Heuer (~d,,), ,.~cten~e uml 'r~','l.,*hlg~, ,'I Z~rcoma II, ,n ,4dv-m'e~ m ¢.'eralmrs, Vol 12, American Cerunuc Slle,ely, ( ',dumbus, (.)H, I qN,4, pp I I H- I 3(L I 3 'T' R DInger, K M. Kn.~hnan, C; 'T'h,~ma,,, M I (-).~end, and J S'. rVl~ya, Aria Me/a~/, ¢2(IqN,.I) I t d l l - lid)'7

I,-I M Ruhle. N C'lau~,,~en and A H. Heuer, in N Clau,~,,en. M Ruhle arid A Heuer (eds), .Ycrt'llce m i d fi', Imo/o/._D, o / Zm',mul II, m ..4dl,m,e.~ m (.'e~am.'.~, V~I 12, American Ceramic S~clely. Columbus, O H . I qX.-I, pp ~2'~- ~,'71) I ~ S k~haya,~hl, .I ,~latt'r .~'~I L.ell, 4 (IqX'~) 2t~X- 2 711 It~ D .J Knm, I ,.ira ~.'eram ..~'o, , 7¢(I )(I~q()) I I ~- 1 2() 17 R.('hanm, A H Hcuer arid I-) (3 Brand, m, I ,.ira c e r a m ._~',,', rl~ ( I qXt~) 2,.I ~ - ?,-IX IX R. Chanm, D (3 Brund~mand A H Hcuer, A,m.,%h'la//, ~4 (l~Xt~) I~ ~A- I ~ , q Iq R CI-lanrrl, M Ruhlc and A H Heu~r .I ,qm ( 'clam .%,p~',r~' (X)( I~X~).-I 2 7-,-I 3 I 2() A H k u m a r and I. B Niklew.~kl, ,.-tin ('t'lm~l .~'or fin/l, ~,~' '~Iq'7q) II 7'~-IIXI 21 I W Chen, Y H C'hla,~ arid K 'T,,uzukl, ,4r/a .,~h'/all, ~l (I qX'~)I X..I 7- I X'~q 22 M Ruhle. A Slreeke~, D Waldeheh and B K[au~ in N (_'lau~en, M Ruhle arid A H Heue¢ (eds.), .%'~'tenre ,rod f,'rlm, dogv ,~i Zm mini II. in ,4dvml,'e~ m ¢.'elam. ~. V~I I 2, American (.'etamlc S~clely, C',dumhu.~, t-)H. IqX4. pp 2 ~ - 2 7.4