Science o Sin e ing, 46 (2014) 283-290
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*) Co esponding au ho : [email p o ec ed]
_____________________________
doi: 10.2298/SOS1403283F
UDK 666.3.019; 622.785
Ad an ages o Combined Sin e ing Compa ed o Con en ional
Sin e ing o Mechanically Ac i a ed Magnesium Ti ana e
S. Filipo ić1*), N. Ob ado ić1, V. B. Pa lo ić1, D. Kosano ić1, M. Mi ić2,
N. Mi o ić3, V. Pouchly4, M. Kachlik4, K. Maca4
1 Ins i u e o Technical Sciences o SASA, 11000 Belg ade, Se bia,
2 “Vinča” Ins i u e o Nuclea Sciences, Uni e si y o Belg ade, 11001 Belg ade,
Se bia,
3 Facul y o Technical Sciences, Uni e si y o K aguje ac, 32000 Čačak, Se bia,
4 CEITEC BUT, B no Uni e si y o Technology, Technicka 10, 61600 B no,
Czech Republic
Abs ac :
In his a icle, he ad an ages o combined sin e ing in compa ison wi h he
con en ional one, o mechanically ac i a ed magnesium i ana e ce amic we e in es iga ed.
The s oichiome ic mix u es o MgO and TiO2 we e mechano-chemically ac i a ed o 0, 10,
40, 80 and 160 minu es by ball milling and hen isos a ically p essed (CIP) o o m g een
bodies. Con en ional sin e ing was ealized by hea ing up o 1400 oC and hold o 30 minu es
in ai a mosphe e. Resul ing ce amic samples wi h closed po osi y we e pos -sin e ed by
p essu e assis ed echnique Ho Isos a ic P essing (HIP) a 1280 oC/3h in a gon a mosphe e
wi h a p essu e o 200 MPa. The bes esul s we e obse ed in he case o samples pos -
sin e ed by HIP, when single-phase MgTiO3 samples wi h ela i e densi y o 96% we e
p epa ed.
Keywo ds: Sin e ing, Ce amics, Magnesium i ana e.
1. In oduc ion
In he ab ica ion o ce amic componen s, impo an achie emen is o each ull o
almos ull densi y o ce amics. In he las decades qui e la ge numbe o sin e ing echniques
besides con en ional sin e ing me hod was de eloped. Consolida ion o ce amic g een bodies
by hese echniques (e.g. spa k plasma sin e ing, mic owa e sin e ing, wo s ep sin e ing) a e
p e e ably used o ma e ials, which p ocessing is di icul because o he unsuiTab.
mic os uc u e, inal densi y o phase pu i y poin o iew.[1-5]
Magnesium i ana e is a ce amic ma e ial widely used as esona o s, il e s and
an ennas o communica ion sys ems ope a ing a mic owa e equencies and capaci o s.[6,7]
In he li e a u e, a ious me hods o MgTiO3 ab ica ion we e p esen ed, such as solid-s a e
eac ions, co-p ecipi a ion o sol–gel ou e.[6,8,9] Few seconda y phases we e o en de ec ed
along wi h MgTiO3 phase (MgTi2O5, Mg2TiO4).[10-12] P epa a ion o pu e MgTiO3 by solid
s a e eac ion was he aim o many pape s. Magnesium i ana e ob ained by sin e ing p ocess
wi hou addi i es eached densi y alues less han 95% o TD. [13]
In o de o imp o e p ope ies o ce amics, i is desi able o achie e mic os uc u es
wi h nea ly ull densi y and ine g ains wi h homogenous dis ibu ion. Along wi h powde
S. Filipo ić e al. /Science o Sin e ing, 46 (2014) 283-290
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284
syn hesis, consolida ion and shaping o he ce amic g een bodies, he op imiza ion o he
sin e ing p ocess has been in he ocus o a en ion du ing he las couple o decades. I is well
know ha densi y has e y impo an ole on dielec ic p ope ies o magnesium i ana e,
especially dielec ic cons an .[14,15]
In his pape , he au ho s compa ed p ope ies o magnesium i ana e ce amics
ob ained by con en ional and ad anced HIP sin e ing echnique, om mechanically ac i a ed
powde mix u es. Acco ding o au ho ’s bes knowledge, his is he i s s udy o he in luence
o mechano-chemical ac i a ion o p ecu so mix u e on he inal densi y and phase pu i y
(MgTiO3).
2. Expe imen al
Comme cial powde s MgO (99% Sigma–Ald ich) and TiO2, ana ase modi ica ion
(99.8% Sigma–Ald ich) we e mixed in mola a io 1:1 and milled in high ene gy plane a y
ball mill (F i sch Pul e ise e) o he ime in e al o 0, 10, 40, 80 and 160 minu es. Ball o
powde mass a io was 40:1 and ac i a ion was pe o med in ai a mosphe e. Balls and bowls
we e om Z O2. As MgO powde eac s easily wi h CO2 and H2O which a e always p esen ed
in ai , he p ecu so was calcined a 700oC o 2h igh be o e he milling p ocess. The
cylind ical g een bodies we e o med om mechanically ac i a ed powde s by cold isos a ic
p essu e a 300 MPa. The g een body samples we e consolida ed by con en ional sin e ing a
1400 oC wi h cons an hea ing a e o 10 oC/min, dwell o 30 min and cooling a e 5 oC/min.
This p essu eless sin e ing was pe o med in an ai a mosphe e. The samples we e hen cu in
hal and pos -sin e ed by p essu e assis ed echnique Ho Isos a ic P essing (HIP) a 1280 oC
o 3 hou s in a gon a mosphe e wi h applied p essu e o 200 MPa (ABRA Shi p,
Swi ze land). Densi ies o all samples we e es ablished by A chimedes me hod, (EN 623-2).
The mo phology o ob ained powde s has been in es iga ed by scanning elec on
mic oscopy (JEOL JSM-6390 LV). The pelle s we e c acked and co e ed by gold laye in
o de o inc ease he con as du ing obse a ion by SEM. Phase composi ion o sin e ed
samples we e de e mined by X- ay di ac ion pa e ns using a Philips PW-1050
di ac ome e wi h λCu-Kα adia ion and a s ep/ ime scan mode o 0.05 ο/s.
3. Resul s and discussion
Fo calcula ion o ela i e densi y he au ho s used he heo e ical alue o densi y
(TD) ρ heo = 4.00 g/cm3.[16] Ob ained densi ies as well as con en o open and closed po osi y
a e gi en in Tab. I.
Tab. I Rela i e and absolu e densi ies as well as ela i e con en o open and closed po osi y
o samples sin e ed by con en ional sin e ing.
Sample
Absolu e
densi y
[g⋅cm-3]
Rela i e
densi y
[%]
Rel. open
po osi y
[%]
Rel. closed po osi y
[%]
MT-0 2.97 74 3 . 20 7 . 5. 0
MT 10 -
3.70 92 6 .
0 .1
7. 3
MT 40 -
3.68 92 1 .
0 .1
7. 9
MT 80
-
3.71 92 8 .
0 .1
7. 1
MT-160
3.76
94.0
0.0
6.0
S. Filipo ić e al./Science o Sin e ing, 46 (2014) 283-290
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285
Tab. II Rela i e and absolu e densi ies o samples sin e ed by HIP.
Sample
Absolu e
densi y
[g⋅cm-3]
Rela i e
densi y
[%]
MT0-HIP 3.00 75.0
MT10-HIP 3.78 94.6
MT40-HIP 3.74 93.6
MT80-HIP 3.84 96.0
MT160-HIP 3.84 96.0
As i can be seen om Tab. I non-ac i a ed samples sin e ed a 1400 oC has he
smalles densi y alues, only 74.3 % o TD. In case o ac i a ed samples, alues a e
signi ican ly highe , in he ange 92-94 % o TD. The e a e p obably ew easons o such
beha io : non-ac i a ed powde has dominan ly la ge agglome a es o calcina ed magnesium
oxide, a ound 7 μm [17], inhomogenei y o s a ing powde which was mixed only manually
in mo a and chemical eac ion ha has jus begun. This sample is in medium sin e ing s age,
(Fig. 2. a)), and ela i e open po osi y is mo e han 20 %. As i is well known, mechanical
ac i a ion could simpli y o accele a e solid-s a e eac ion, educing empe a u es o chemical
eac ion o sin e ing empe a u e.[18] In ac i a ed powde s a mechanically induced ene gies
can inc ease sin e abili y and acili a e densi ica ion. I is no iceable om Tab. I ha samples
MT-10 - MT-160 has negligible open po osi y. Densi ies ob ained a e HIP sin e ing a e
p esen ed in Tab. II. The abo e alues show ha samples ac i a ed o 80 and 160 minu es
eached maximum o densi ies 96% o TD. Non-ac i a ed sample has low ela i e densi y
a e HIP sin e ing because i has g ea open po osi y, and in ha case HIP was no
e ec i e.[19] Also, i can be obse ed ha sample MT-160 has highe alues o densi ies
be o e HIP han samples MT-80, bu he same one a e second sin e ing p ocess. The main
eason o such beha io could be apping o po es in he g ain in e io owing o sudden g ain
g ow h du ing sin e ing a 1400 oC. Po es c ea ed his way s ay e en a e he HIP.[19]
Densi ies be o e and a e HIP a e g aphically p esen ed a Fig. 1, whe e he in luence o
mechano-chemical ac i a ion is clea ly shown.
0 20 40 60 80 100 120 140 160 180
3.0
3.2
3.4
3.6
3.8
4.0
4.
2
Absolu e densi ies, (g/cm3)
Ac i a ion ime, (min)
 1400oC 30min ai
 1400oC 30min ai , HIP 1280oC 3h a gon
TD
Fig. 1. E ec o Ho Isos a ic P essing on he sample densi ies.
S. Filipo ić e al. /Science o Sin e ing, 46 (2014) 283-290
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286
Mic os uc u e o sample MT-0 indica es a medium sin e ing s age wi h high amoun
o open po osi y and p esence o ew di e en phases, which is p ecisely ob ained by XRD.
Ac i a ed samples a e cha ac e ized, Fig. 2.b)-c), wi h closed po es which a e no comple ely
sphe ical in shape because s a ing powde consis agglome a es. Samples MT-80 and MT-
160 indica e a inal sin e ing s age wi h dominan ly sphe ical po es.
b)
a)
c) d)
e)
Fig. 2. Mic og aphs o samples sin e ed a 1400 oC 30 minu es: a) MT-0,
b) MT-10, c) MT-40, d) MT-80 and e) MT-160.
S. Filipo ić e al./Science o Sin e ing, 46 (2014) 283-290
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287
a) b)
c) d)
e)
Fig. 3. Mic og aphs o samples sin e ed a 1400 oC o 30 minu es and pos -sin e ed by HIP a
1280 oC o 3 hou s in a gon: a) MT0-HIP, b) MT10-HIP,
c) MT40-HIP, d) MT80-HIP and e) MT160-HIP.
SEM pic u e o non-ac i a ed samples shows la ge open po osi y. In addi ion, i can
be no iced p esence o small sphe ical po es due o sin e ing inside agglome a es ha exis ed
in he ini ial powde . Mic og aphs o samples ac i a ed o 10 and 40 minu es ha e
dominan ly closed po es bu hey a e no comple ely sphe e in shape, mos p obably due o
he exis ence o agglome a es in s a ing powde s. A he si es o he ac u e, i is no iceable
p esence o he second phase. Fo he samples ac i a ed 80 and 160 minu es domina e
compac s uc u e along wi h closed sphe ical po es, indica ing a inal sin e ing s age.
F ac u e h ough g ains can be seen.
I we compa e SEM mic og aphs o samples sin e ed by con en ional and HIP

S. Filipo ić e al. /Science o Sin e ing, 46 (2014) 283-290
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288
sin e ing p ocess, i can be concluded ha combined sin e ing induced much mo e compac
ce amics ma ix han single s age sin e ing esul ing in highe densi ies, along wi h smalle
sha e o po es.
Fig. 4. XRD pa e ns o samples: a) single s age sin e ed (1400 oC 30 minu es),
b) HIP sin e ed (1400 oC 30 minu es and HIP a 1280 oC o 3 hou s in a gon).
Fig. 4. p esen s XRD analysis o non ac i a ed and all ac i a ed samples sin e ed by
wo di e en echniques. All de ec ed peaks we e iden i ied using JCPDS ca ds: 79-0831 o
MgTiO3, 73-1723 o Mg2TiO4, 76-2373 o MgTi2O5, 89-4920 o TiO2 u ile, 87-0651 o
MgO, 85-1060 o Ti8O16 and 52-0622 o Mg1.05Ti1.95O5.
Di ac ion pa e ns showed sha p and in ensi e e lec ion indica ing ha
ec ys alliza ion p ocess occu s du ing he sin e ing. I we obse e a phase composi ion o
samples sin e ed by con en ional me hod, we can iden i y a ew di e en phases. In non-
ac i a ed sample, MgTiO3, Mg2TiO4, MgTi2O5, TiO2 u ile, MgO and Ti8O16 a e p esen
indica ing ha chemical eac ion is s ill no inished. Ac i a ed samples a e combina ion o
MgTiO3 as he dominan phase wi h p esence o MgTi2O5 as a mino phase.
In he pa e ns o HIP sin e ed samples a MgTiO3 as a dominan phase is de ec ed
along wi h small amoun o esidual phases, MgTi2O5, Mg1.05Ti1.95O5, MgO, sugges ing ha
chemical eac ion is nea comple ion. Fu he mo e, X- ay analyses o MT-HIP40 and MT-
HIP80 indica e he p esence o pu e MgTiO3 phase, which was one o he main goals o his
in es iga ion.
4. Conclusion
The aim o his pape was o highligh bene i s o combined sin e ing compa ed o
con en ional sin e ing o magnesium i ana e ce amic. Calcula ion o densi ies, by
A chimedes me hod, showed ha samples ob ained om HIP sin e ing achie e highe alues,
96% o TD o MT-HIP80 and MT-HIP160, ill samples con en ionally sin e ed has he mos
20 30 40 50 60 70 80 90
0
200
400
600






 TiO2 u ile













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







In ensi y, (a. u.)
2θ, (o)
MT0
 MgO
 MgTiO3  Mg2TiO4
 MgTi2O5  Ti8O15
0
150
300
450























0
150
300
450
MT10
















MT40
0
150
300
450


















MT80
0
150
300
450






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











MT160
a)
20 30 40 50 60 70 80 90
0
100
200
300
400
500
2θ, (o)




0
200
400
600
800
MT-HIP40
MT-HIP10
MT-HIP0
0
100
200
300
400
500
0
200
400
600
800










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
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






















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















 MgO  MgTiO3
 MgTi2O5  Mg1.05Ti1.95O5
MT-HIP160
MT-HIP80
0
200
400
600
In ensi y, (a. u.)
b)
S. Filipo ić e al./Science o Sin e ing, 46 (2014) 283-290
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289
94% o TD. I was de e mined ha sample MT-160 had highe alues o densi ies be o e HIP
han samples MT-80, bu he same one a he end o p ocess, because apping o po es in he
g ain in e io . SEM mic og aphs showed ha HIP sin e ing induced much mo e compac
ce amics ma ix han single s age sin e ing. XRD analyses con i med ha samples MT-HIP40
and MT-HIP80 a e pu e MgTiO3 ce amic. Based on all p esen ed ac s i can be concluded
ha HIP sin e ing has be e achie emen s con a y con en ional sin e ing. Sample ac i a ed
o 80 minu es and HIP sin e ed eaches almos ull densi y and pu e MgTiO3, along wi h
inal sin e ing s age wi h closed and sphe ical po es.
Acknowledgemen
The esul s p esen ed in his pape a e a pa o P ojec OI 172057 inanced by
Minis y o Educa ion, Science and Technology De elopmen o Republic o Se bia and
P ojec F/198, unded by he Se bian Academy o Science and A s. The au ho s g a e ully
acknowledge he unding p o ided by he Eu opean Regional De elopmen Fund h ough a
p ojec CEITEC (CZ.1.05/1.1.00/02.0068).
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Садржај: У овом раду су испитане предности комбинованог процеса синтеровања,
механички активиране магнеѕијум титанатне керамике, у поређењу са
S. Filipo ić e al. /Science o Sin e ing, 46 (2014) 283-290
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290
конвенционалним. Стехиометријска смеша прахова MgO и TiO2 је механички
активирана у трајању од 0, 10, 40, 80 и 160 минута а потом изостатички пресована
да се формирају таблете. Конвенционално синтеровање је реализовано загревањем до
1400 o
C и задржавањем од 30 минута у атмосфери ваздуха. Узорци код којих је
постигнута затворена порозност су подвргнути додатном ступњу топлог
синтеровања под притиском на 1280 o
C/3h у атмосфери аргона и под притиском од
200 MPa. Најбољи резултати су постигнути за узорке који су синтеровани под
притиском, где је добијен чист MgTiO3 релативне густине 96% oд теоријске
вредности.
Kључне речи: синтеровање, керамика, магнезијум титанат.