ª q4 (1–x)(Bi 0.5 K 0.5 )TiO 3 -xBiFeO 3 : g à k Ä8 ý – ¥ ¹ Å õ m Í ° q ¹ Å — ¤V R Ë

R

ª  q4  (1–x)(Bi ^0.5 K 0.5 )TiO 3 -xBiFeO 3 : g à k Ä8 ý – ¥ ¹ Å õ m Í °  q ¹ Å — ¤V R Ë



™ »+ ä  * > · ) ç a : @¬ £ ^∗ · ‚ Ð ø ¶ B‡ Ú · ö ¶ B? - ! H ·  ™ »' å ‡ Ú

‚

½ Ó" é ¶ @ /† < Ɠ §
” ¸·’  ™ èF  / B N † < Æ Ò, ‚ ½ Ó" é ¶ 614-773

+ ä

g ` @‡ Ú · ƒ ‘ š? # Þ

‚

½ Ó" é ¶ @ /† < Ɠ § „  l / B N † < Æõ , ‚ ½ Ó" é ¶ 614-773 (2009¸   2 Z 4 13{ 9  ~ à Î6 £ §)

q

± ú š>  (1–x)(Bi

^0.5

K

0.5

)TiO

3

-xBiFeO

3

[ j b ” \ " f BiFeO

³

_  € ª œ`  ¦ x = 0 mol% \ " f 10 mol%_  # 3  0

A– Ð    or v €  " f Õ ª\    É r Ä »„   x 9  · ú š„   : £ ¤$ í `  ¦ › ¸  % i  . XRD  r] X x ß ¼_  ì  r$ 3   õ   © œ“ : r \ " f 0

p x€  & ñ (rhombohedral)  © œ`  ¦ t   H BiFeO

3

 & ñ ~ ½ Ó& ñ (tetragonal)  © œ`  ¦ t   H (Bi

0.5

K

0.5

)TiO

3

\ 

“

¦6   x ÷ &# Q é ß –{ 9  & ñ ~ ½ Ó& ñ  © œ_  ` …– ÐÚ ÔÛ ¼ s à Ô ½ ¨› ¸\  ¦ Ä »t    H  כ `  ¦ S X ‰ “   % i  . · ú š„  > à º(d

33

)  H BiFeO

3

_  ' ‘ | ¾ Ó\    " f 7 £ x    x = 6 mol%\ " f 64 pC/N_  þ j“ ¦ ° ú כ`  ¦ & ’ Ü ¼ 9, Õ ª s  © œ '

‘  | ¨ c  â Ä º\   H y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i  . „  l l >    ½ + Ë> à º(K

^p

)  H & h & h  7 £ x  # Œ x = 10 mol%\ 

"

f 0.17`  ¦
 ? /% 3 Ü ¼ 9, l > & h  ¾ ¡ §| 9 > Ã º(Q

m

)  H & h  & h Ü ¼– Ð y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i  . » 1 Ïì  rF G “ : r

•

¸(depolarization temperature, T

^d

)  H BiFeO

3

_  ' ‘ | ¾ Ós  7 £ x † < Ê\     y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i “ ¦ x

= 10 mol% \ " f 245

^◦

C\  ¦
 Í Ç x  PACS numbers: 77.22.-d, 77.84.-s

Keywords: Lead-free, Bismuth potassium titanate, Bismuth ferrite, Depolarization temperature

I. " e  ] Ø

± ú

š(Pb)`  ¦ l ‘ : r F « і Ð  6   x ô  Ç Pb(Zr,Ti)O

₃

(PZT) > 

\ P

_  [ j b ”  F « Ñ[ þ t s  Õ ª Ä ºÃ ºô  Ç · ú š„   : £ ¤$ í Ü ¼– Ð · ú š„   [

j b ”  G ' p" f, " l oÆ Ó\ s ' ,   ¨ 8 Š l  1 p x õ  ° ú  “ É r · ú š„   ™ è  6

£

x6   x \  ´ ú §s  s 6   x ÷ &“ ¦ e ”   [1]. t ë ß – Õ ª ] j› ¸õ & ñ õ 

`

‚l Ó ü t % ƒo õ & ñ \ " f d ” y Œ •ô  Ç Ä »K Ó ü t| 9 `  ¦ µ 1 ÏÒ q tr &  ¨ 8 Š

 â

š ¸% i õ  “  ^ ‰\  d ” y Œ •ô  Ç ×  æ1 l q‰ & ³ © œ`  ¦  l r v   H ë  H ] j

&

h s  µ 1 ÏÒ q t÷ &“ ¦ e ”  . s  Qô  Ç ë  H ] j& h `  ¦ K    l  0 AK " f l

” > r _  PZT\  ¦ @ /^ ‰½ + É • 2 ;¨ 8 Š â & h “   q ± ú š> (Pb-free) · ú š„   [

j b ” \  @ /ô  Ç › ' a d ” s  Z  }  4 R Õ ª 1 l x î ß – ´ ú §“ É r ƒ  ½ ¨ ”   '

Ÿ ÷ &# Q M ® o  . s  Qô  Ç q ± ú š>  · ú š„   [ j b ”  F « Ñ ×  æ \ " f 1960¸  @ /\  % ƒ6 £ § µ 1 Ï|  ) a (Bi

0.5

K

0.5

)TiO

3

(BKT)  H A   o

\  Bi

³⁺

ü < K

⁺

 † < Êa  [ þ t # Q  H 4 Ÿ ¤ ½ + Ë ABO

3

` …– ÐÚ Ô Û

¼ s à Ô(perovskite) ½ ¨› ¸\  ¦ t   H Ó ü t| 9 – Ð" f  © œ“ : r \ " f

&

ñ ~ ½ Ó& ñ  © œ ½ ¨› ¸\  ¦ t  9, €  • 380

^◦

C _  Z  }“ É r T

c

(Curie temperature)\  ¦ t   H @ /³ ð& h “   y © œÄ »„  ^ ‰s   [2]. t  ë

ß – Õ ª › ¸$ í s  é ß –í  H † < Ê\ • ¸ Ô  ¦ ½ ¨ “ ¦   É r q ± ú š>  · ú š„   [ j



b ” \  q K  BKT\  @ /ô  Ç ƒ  ½ ¨ ´ ú §s   Ò7 á ¤ ô  Ç  כ “ É r ™ è  

∗

Corresponding author: [email protected]

õ & ñ \ " f Bi(Bismuth)_  6 fµ 1 Ï(volatile)\  _ ô  Ç í ß –™ è‘    o

 Ò q t$ í õ  K

2

CO

₃

_  f  ¨_ þ v$ í (hygroscopic)\  _ K " f Z  }“ É r x 9

• ¸_  Ò  re  ¦`  ¦ ] j Œ • l  # Q§ >    H X < e ”   [3–5]. s  Qô  Ç BKT _  é ß –& h `  ¦ > h‚  r v l  0 AK  †  Ò á ÔY UÛ ¼ (Hot-Press), a

% ¦- 0 q (Sol-Gel) 1 p x _  / B N& ñ õ  › ¸$ í _     o\  ¦ : Ÿ x # Œ ] jì ø Í :

£ ¤$ í `  ¦ > h‚  r v  9  H ƒ  ½ ¨ ”  ' Ÿ ÷ &“ ¦ e ”   [6–12].



 " f ‘ : r ƒ  ½ ¨\ " f  H  © œ“ : r \ " f & ñ ~ ½ Ó& ñ ½ ¨› ¸\  ¦ t   H BKT\  ¦ l ‘ : rÓ ü t| 9 – Ð # Œ  © œ“ : r \ " f 0 p x€  & ñ  © œ ½ ¨› ¸\  ¦  t

 9,  © œ@ /& h Ü ¼– Ð Z  }“ É r T

c

( €  • 830

^◦

C)\  ¦ t   H BiFeO

3

(BF)\  ¦ ' ‘  # Œ BKT_   © œ„  s  “ : r • ¸    oü < & ñ ~ ½ Ó& ñ  © œ õ

 0 p x€  & ñ  © œ  s _   © œ â >  % ò % i (morphotropic phase boundary, MPB) _  + þ A$ í Ä »Á º\  ¦ S X ‰ “   % i “ ¦, BF_  ' ‘ 

\

   É r BKT _  · ú š„  , Ä »„  : £ ¤$ í `  ¦ › ¸  % i   [13,14].

II. ÷ m Ç] M öU ê s0 n É

Ø

 ¦ µ 1 Ï " é ¶ « і Ð" f Bi

²

O

3

(Aldrich 99.9 %), K

2

CO

3

(Aldrich 99.995 %), TiO

2

(Aldrich 99.9+ %), Fe

2

O

3

(Alfa Aesar 99.945 %)\  ¦  6   x # Œ { 9 ì ø Í& h “   [ j b ”  ] j

›

¸~ ½ ÓZ O “   “ ¦ © œì ø Í6 £ xZ O (Solid-State Reaction Method)Ü ¼– Ð

-586-

Fig. 1. Scanning Electron Microscope images of (1–x)(Bi

0.5

K

0.5

)TiO

3

-xBiFeO

3

ceramics sintered at 1060

^◦

C for 6 h in air : (a) x = 0 (b) x = 0.02 (c) x = 0.04 (d) x = 0.05 (e) x = 0.06 (f) x = 0.07 (g) x = 0.08 (h) x = 0.1.

(1–x)(Bi

_0.5

K

_0.5

)TiO

₃

-xBiFeO

₃

r ¼ # `  ¦ ] j Œ • % i  . r ¼ #  [

þ

t _  › ¸$ í “ É r x = 0, 2, 4, 5, 6, 7, 8, 10 mol% (BKT, BKT-2BF, BKT-4BF, BKT-5BF, BKT-6BF, BKT-7BF, BKT-8BF, BKT-10BF) – Ð › ¸] X  # Œ z  ´+ « > % i  . s [ þ t ì  r

´ ú

˜_  ™ D ¥ ½ + ˓ É r 0 A_   o† < Æd ” \  ´ ú >  g A| ¾ Ó % i Ü ¼ 9, : £ ¤ y 

@

/l  ×  æ \ " f f  ¨_ þ v$ í s  e ”   H K

2

CO

₃

ì  r ´ ú ˜“ É r | › ¸š ¸‘ É r \ 

"

f Ø  æì  r y  | › ¸r †   Ê ê g A| ¾ Ó % i  . g A| ¾ Ó  ) a ì  r ´ ú ˜`  ¦ s  à

Ôo   î ß –& ñ  o t Ø Ô ïm  (YSZ) ^  ¦(ball)[ þ t õ  † < Êa  Á º Ã

º(anhydrous) \ ò ø Í`  ¦`  ¦  6   x # Œ 2r ç ß – 1 l x î ß – _ þ vd ”  x 9  a A(milling) % i  . x 9 a Aô  Ç ì  r ´ ú ˜`  ¦ 80

^◦

C | › ¸š ¸‘ É r \ " f

|

› ¸r †   Ê ê, 750

^◦

C \ " f 1  ™ è(calcination) % i  .

ì

 r ´ ú ˜_  ç  H| 9 $ í `  ¦ Z  } s “ ¦ u x 9 ô  Ç ™ è  ^ ‰\  ¦ % 3 l  0 AK  x 9  a A, | › ¸_  õ & ñ `  ¦ 2  r ì ø Í4 Ÿ ¤ ô  Ç Ê ê 800

^◦

C \ " f 2r ç ß – 1 l x î

ß – 2  ™ è % i  . þ j7 á x ™ è  ) a ì  r ´ ú ˜`  ¦  r  _ þ vd ”  x 9  a A # Œ | › ¸r †   Ê ê $ í + þ A`  ¦ 0 A # Œ PVA(Polyvinyl Al- cohol) 5 wt% à º6   xÓ  o`  ¦   ½ + Ë] j– Ð" f ' ‘  # Œ } Œ •    µ

1 Ï\ " f “ ¦À Ò [ O # Q 150 µm ß ¼l _  ^ ‰– Ð ^ ‰2 £ §`  ¦ % i 



. r ¼ # _  $ í + þ A“ É r { 9 » ¡ ¤ · ú š$ í + þ A Z O Ü ¼– Ð 150 MPa_  · ú š

§ 4

`  ¦ Å Ò# Q f ”  â 10 mm, ¿ ºa  1 mm_  " é ¶ ó ø Í+ þ AÜ ¼– Ð ] j



Œ

• % i  . $ í + þ A ) a r ¼ # “ É r 1060

^◦

C \ " f 6r ç ß – 1 l x î ß – ™ è

 

(sintering) % i Ü ¼ 9, ™ è   ) a r ¼ # _    ˜ Ðl  x 9 • ¸  H   Ø

Ôv B jX <Û ¼(Archimedes) " é ¶ o \  ¦ s 6   x # Œ > í ß – % i  .

r

¼ # _  ƒ     H 400, 800, 1200 ƒ   t (emery paper)– Ð € ª œ

€

 `  ¦ ƒ    # Œ 0.5 mm ¿ ºa  ÷ &• ¸2 Ÿ ¤ % i  . BF ' ‘ 

|

¾ Ó\    É r y Œ • r ¼ # _   © œ ì  r$ 3 õ      © œÃ º ì  r$ 3 “ É r XRD (X’Pert APD System, Philips) J ‡  _  ì  r$ 3 `  ¦ : Ÿ x # Œ S X ‰

“

  % i Ü ¼ 9, SEM (Scanning Electron Microscope, Hi- tachi, S-2400)`  ¦  6   x # Œ p [ j½ ¨› ¸_     o\  ¦ › ' a ¹ 1 Ï % i 



. s [ þ t r ¼ # _  · ú š„   x 9  Ä »„   : £ ¤$ í 8 £ ¤& ñ `  ¦ 0 AK  € ª œ€  \ 

silver paste\  ¦ • ¸Ÿ íô  Ç Ê ê 650

^◦

C \ " f 30ì  r ç ß – \ P % ƒo \  ¦ 

%

i Ü ¼ 9, · ú š„   : £ ¤$ í 8 £ ¤& ñ `  ¦ 0 AK  100

^◦

C z  ´o – B H š ¸{ 9  5 Å q \ 

"

f 4 kV/mm_  f ” À Ó „  · ú š`  ¦ 30ì  r ç ß – “   # Œ ì  rF G % ƒo 

% i  . ì  rF G % ƒo  f ” Ê ê  H  â r    o ß ¼Ù ¼– Ð 24r ç ß – r 

´

ò(aging) % ƒo \  ¦ % i  . s X O >  ì  rF G % ƒo ô  Ç r ¼ # [ þ t“ É r e ”

x ~  Û ¼ ì  r$ 3 l (Impedance Analyzer HP4192A)– Ð “ : r

•

¸   o\    É r Ä »„   © œÃ º(ε)ü < Ä »„  ’ < Hz  ´(tan δ)`  ¦ 8 £ ¤& ñ 

%

i  . „  l l >   ½ + Ë> à º(planar electromechanical cou- pling factor, K

p

) ü < l > & h  ¾ ¡ §| 9 > Ã º(mechanical qual- ity factor, Q

_m

)  H e ” x ~  Û ¼ ì  r$ 3 l (Impedance Analyzer HP4194A)\  ¦ s 6   x # Œ  © œ“ : r \ " f / B N”  Å Ò à º(resonance frequency) x 9  ì ø Í/ B N”  Å Ò à º(antiresonance frequency)ü <

1 kHz \ " f_  & ñ „  6   x | ¾ Ó(capacitance)`  ¦ y Œ •y Œ • 8 £ ¤& ñ # Œ >  í

ß – % i Ü ¼ 9, Piezo d

33

-meter (IACAS, ZJ-6B)\  ¦  6   x 

#

Œ · ú š„   > à º(piezoelectric coefficient, d

³³

)\  ¦ 8 £ ¤& ñ % i 



.

III. + s ÇÊ Ý õ m Í w Š²  o

Figure 1“ É r BF _  ' ‘ | ¾ Ó\    É r (1–x)BKT-xBF [ j  b ”

_  p [ j½ ¨› ¸  ”  Ü ¼– Ð" f „  ^ ‰& h Ü ¼– Ð z Œ —· ú ˜(grain)_  — ¸

€

ª œ“ É r ½ ¨+ þ As % 3  . BF_  ' ‘ | ¾ Ó\    É r z Œ —· ú ˜ ß ¼l _   H



  o  H › ' a ¹ 1 Ͻ + É Ã º \ O % 3 Ü ¼ 9, s  z  ´+ « >› ¸$ í ? /\ " f  H BF

 BKT_  z Œ —· ú ˜ ß ¼l     o\   H % ò † ¾ Ó`  ¦ p u t  · ú §“ É r  כ Ü

¼– Ð S X ‰ “  ÷ &% 3  .

Figure 2“ É r BF _  ' ‘ | ¾ Ó\    É r (1–x)BKT-xBF [ j  b ”

_  XRD  r] X x ß ¼\  ¦ ì  r$ 3 ô  Ç   õ \  ¦
  · p  כ s  . 8 £ ¤

&

ñ õ & ñ \ " f µ 1 ÏÒ q t   H š ¸ \  ¦ þ j™ è– Ð l  0 AK  silicon ì  r

Fig. 2. X-ray diffraction patterns of (1–x)(Bi

_0.5

K

_0.5

)TiO

₃

- xBiFeO

₃

ceramics sintered at 1060

^◦

C for 6 h in air.

´ ú

˜`  ¦ ³ ðï  rÓ ü t| 9 – Ð  6   x # Œ ˜ Ð& ñ % i  . „   › ¸$ í \    5 g

"

f BKT  © œ“   & ñ ~ ½ Ó& ñ ` …– ÐÚ ÔÛ ¼ s à Ô ½ ¨› ¸\  ¦ Ä »t  % i  Ü

¼ 9, Ô  ¦í  HÓ ü t  © œ_  x ß ¼  H › ' a ¹ 1 Ï÷ &t  · ú §€ Œ ¤ . s   H BF  s

 z  ´+ « >› ¸$ í ? /\ " f  H BKT \  ¢ - a„   “ ¦6   xH † d`  ¦ _ p ô  Ç .

BF _  ' ‘ | ¾ Ós  7 £ x ½ + Éà º2 Ÿ ¤ {h00}  r] X  x ß ¼_  0 Au 

low angle A á ¤ Ü ¼– Ð s 1 l x “ ¦, {00l}  r] X x ß ¼_  s 1 l x s  \ O 



 H  כ Ü ¼– Ð ˜ Ð  BF BKT\  “ ¦6   x ÷ &# Q a-» ¡ ¤     © œÃ º

 7 £ x    H ì ø ̀  \  c-» ¡ ¤     © œÃ º  H   † < Ês  \ O 6 £ § Ü ¼– Ð Tetragonality, 7 £ ¤ c/a  H y Œ ™™ è # Œ BKT_  & ñ ~ ½ Ó& ñ  © œ\ " f BF _  0 p x€  & ñ  © œÜ ¼– Ð & h & h  „  s  H † d`  ¦ · ú ˜ à º e ” % 3  . s  z  ´ +

« >› ¸$ í ? /\ " f  H & ñ ~ ½ Ó& ñ  © œõ  0 p x€  & ñ  © œs  / B N” > r   H  © œ

 â

>  % ò % i (MPB)“ É r › ' a ¹ 1 Ï÷ &t  · ú §€ Œ ¤t ë ß –, BF_  ' ‘ | ¾ Ós  s

   z  ´+ « >› ¸$ í “   x = 0 ∼ 10 mol%˜ Ð   8 ' ‘  | ¨ c  â Ä º

\

  H MPB  ˜ Ð# Œ| 9  à º e ” `  ¦  כ Ü ¼– Ð \ V © œ  ) a  .

Figure 3“ É r ì  rF G % ƒo ô  Ç r ¼ # [ þ t`  ¦ “ : r • ¸   o\    

"

f Ä »„   © œÃ ºü < Ä »„  ’ < Hz  ´`  ¦ 8 £ ¤& ñ # Œ
  · p Õ ªA á Ôs 



. Ä »„   © œÃ º_  þ j@ /° ú כ`  ¦
 ? /  H “ : r • ¸  H BKT (x = 0 mol%) \ " f €  • 350

^◦

C – Ð s    z  ´+ « > › ¸$ í ? /\ " f  © œ Z  }

“ É

r ° ú כ`  ¦
 ? /% 3 Ü ¼ 9, BF_  ' ‘ | ¾ Ós  7 £ x ½ + Éà º2 Ÿ ¤ & h  

&

h Ü ¼– Ð y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i “ ¦ x = 10 mol%\ " f  © œ

± ú

“ É r 336

^◦

C \  ¦
 Í Ç x . Ä »„  ’ < Hz  ´_   â Ä º “ : r • ¸ 7 £ x 

†

< Ê\     y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ðs   BKT_   â Ä º €  • 300

◦

C Â Ò   H \ " f & ñ & h `  ¦ ˜ Ðs “ ¦ y Œ ™™ è   H X < s   H s  “ : r • ¸ s 

\ " f  H & ñ ~ ½ Ó& ñ (tetragonal)  © œs  › ' a ¹ 1 Ï÷ &“ ¦, 300

^◦

C s 



© œ\ " f  H _   { 9 ~ ½ Ó& ñ (pseudo cubic)  © œs  › ' a ¹ 1 Ï÷ &  H % ò

%

i s l  M :ë  H s  . ¢ ¸ô  Ç “ : r • ¸  8  © œ5 p x † < Ê\     Ä »„   ’ < H z 

´s  y Œ ™™ è   €  • 350

^◦

C Â Ò   H \ " f / å L  y  7 £ x ÷ &  H X <

s

 Â Ò   H \ " f _   { 9 ~ ½ Ó& ñ  © œ\ " f { 9 ~ ½ Ó& ñ (cubic)  © œÜ ¼– Ð _

    o e ” 6 £ §`  ¦
  · p  [3,5,6,15].

Figure 4  H (1–x)BKT-xBF [ j b ” _  · ú š„   > à º(d

33

)\  ¦ z 

´“ : r \ " f 8 £ ¤& ñ # Œ
  · p Õ ªA á Ôs  . BKT\ " f  H 31

Fig. 3. Temperature dependence of dielectric constants (a) and losses (b) of (1–x)(Bi

0.5

K

0.5

)TiO

3

-xBiFeO

3

ce- ramics poled at 4 kV for 0.5 h with various x at 10 kHz.

Fig. 4. Piezoelectric coefficient (d

33

) and depolarization temperature (T

d

) of (1–x)(Bi

0.5

K

0.5

)TiO

3

-xBiFeO

3

ce- ramics sintered at 1060

^◦

C for 6 h in air.

pC/N _  ° ú כ`  ¦ ˜ Ð% i “ ¦ BF_  ' ‘ | ¾ Ós  7 £ x ½ + Éà º2 Ÿ ¤ · ú š„  

>

à º• ¸ & h & h  7 £ x    6 mol%\ " f 64 pC/N_  þ j“ ¦

° ú

כ`  ¦
 Í Ç xÜ ¼ 9 ' ‘ | ¾ Ós   8 7 £ x ½ + Éà º2 Ÿ ¤ · ú š„   > à º  H y

Œ

™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i  . BKT (x = 0 mol%)_   â Ä º, t

F K  t   7 Hë  H \  ˜ Г ¦  ) a · ú š„   > à º_  ° ú כ“ É r [ j b ” _  ] j

›

¸õ & ñ õ  K(Potassium)_  € ª œ, Õ ªo “ ¦ ™ è  “ : r • ¸\    

"

f €  • ∼103 pC/NÜ ¼– Ð ˜ Г ¦÷ &# Q e ”   [6, 11, 12]. s  Q

Fig. 5. Planar electromechanical coupling factor(K

_p

) and mechanical quality factor (Q

_m

) of (1–x)(Bi

_0.5

K

_0.5

)TiO

₃

- xBiFeO

₃

ceramics sintered at 1060

^◦

C for 6 h in air.

Table 1. Dielectric and piezoelectric properties of the (1–x)(Bi

_0.5

K

_0.5

)TiO

₃

-xBiFeO

₃

ceramics.

x (mol%) 0 2 4 5 6 7 8 10

Density (g/cm

³

) 5.57 5.68 5.83 5.88 5.88 5.89 5.87 5.89 K

p

(%) 15.5 15.8 16.3 16.7 17.3 17.1 17.4 17.5 Q

m

47.9 44.4 44.3 43.2 45 42.1 40.5 37.7 T

d

(

^◦

C) 302 312 263 275 272 287 272 245 T

m

(

^◦

C) 353 365 348 353 351 341 344 336 d

33

(pC/N) 31 31 39 43 64 54 53 43

ô

 Ç ‰ & ³ © œ“ É r BF _  ' ‘ | ¾ Ós  7 £ x ½ + Éà º2 Ÿ ¤ BKT _  & ñ ~ ½ Ó& ñ



© œ\ " f BF_  0 p x€  & ñ  © œÜ ¼– Ð_   © œ „  s \  _  # Œ    



 + þ A(lattice distortion)s   Œ • 4 R" f domains  ì  rF G % ƒo  õ & ñ \ " f K t   H „  l  © œ\  _ K  ô  ÇA á ¤ ~ ½ ӆ ¾ ÓÜ ¼– Ð_  F  C

\ P s  ~ 1 >  s À Ò# Qt l  M :ë  H \  · ú š„   > à º 7 £ x ô  Ç  כ Ü

¼– Ð ˜ Ð# Œ”   . ì ø ̀  \  » 1 Ïì  rF G “ : r • ¸  H BKT \ " f 302

^◦

C

\

 ¦ ˜ Ð% i “ ¦ BF_  ' ‘ | ¾ Ós  7 £ x ½ + Éà º2 Ÿ ¤ & h  & h Ü ¼– Ð y Œ ™™ è

  10 mol%\ " f 245

^◦

C\  ¦
 Í Ç x . 7 £ ¤, · ú š„   > à º

 7 £ x † < Ê\     » 1 Ïì  rF G “ : r • ¸  H y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ðs 



 H X <, s   H l ” > r _   7 Hë  H \  ˜ Г ¦  ) a   õ ü < Ä » ô  Ç  ⠆ ¾ Ó`  ¦

˜

Ð% i   [15,16].

Figure 5“ É r BF _  ' ‘ | ¾ Ó\    É r (1–x)BKT-xBF [ j  b ”

_  „  l l >    ½ + Ë> à º(K

^p

) ü < l > & h  ¾ ¡ §| 9 > Ã º(Q

^m

)\  ¦ 8

£ ¤& ñ ô  Ç ° ú כ`  ¦
  · p Õ ªA á Ôs  . „  l l >    ½ + Ë> à º  H '

‘ | ¾ Ó\     & h  & h Ü ¼– Ð 7 £ x    H  ⠆ ¾ Ó`  ¦ ˜ Ð% i Ü ¼ 9 þ j@ /° ú כ“ É r 10 mol% \ " f 0.18`  ¦
 ? /% 3 “ ¦, l > & h  ¾ ¡ §| 9 

>

à º  H y Œ ™™ è   H  ⠆ ¾ Ó`  ¦ ˜ Ð% i  . ‘ : r ƒ  ½ ¨\ " f 8 £ ¤& ñ ô  Ç (1–

x)BKT-xBF [ j b ” _  Ä »„   x 9  · ú š„   : £ ¤$ í [ þ t`  ¦ & ñ o  # Œ Table 1 \ 
 ? /% 3  .

IV. + s Ç Â ] Ø

“

¦ © œì ø Í6 £ xZ O Ü ¼– Ð ] j› ¸ô  Ç BKT [ j b ” \  BF_  € ª œ`  ¦ 0

∼ 10 mol% – Ð    or &  s \    É r p [ j½ ¨› ¸, · ú š„   x 9  Ä »

„

  : £ ¤$ í `  ¦ › ¸  % i  . XRD  r] X x ß ¼_  ì  r$ 3   õ  „   › ¸

$ í

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˜

Ð% i Ü ¼ 9, BF BKT\  ¢ - a„   “ ¦6   xH † d`  ¦ S X ‰ “   % i  . · ú š

„

  > à º  H BKT \ " f 31 pC/N_  ° ú כ`  ¦ ˜ Ð% i “ ¦, BF_  ' ‘ 

| ¾ Ós  7 £ x † < Ê\     & h & h  7 £ x  # Œ x = 6 mol%\ " f 64 pC/N _  þ j“ ¦u \  ¦
 Í Ç xÜ ¼ 9 Õ ª s Ê ê– Ð  H y Œ ™™ è % i 



. BF_  ' ‘ | ¾ Ós  7 £ x † < Ê\     · ú š„   > à º 7 £ x    H

 כ

“ É r BF _  ' ‘ \  _ K " f      + þ As   Œ • 4 R domain[ þ t s

 ì  rF G % ƒo õ & ñ \ " f K t   H „  l  © œ\  _ K " f ô  ÇA á ¤

~

½ ӆ ¾ ÓÜ ¼– Ð_  F C \ P s  ~ 1 >  s À Ò# Q4 R · ú š„   > à º 7 £ x  ô

 Ç  כ Ü ¼– Ð Ò q ty Œ •÷ & 9, ì ø ̀  \  » 1 Ïì  rF G “ : r • ¸  H BF _  ' ‘ 

|

¾ Ós  7 £ x † < Ê\     & h  & h Ü ¼– Ð y Œ ™™ è % i  . „  l l > 

 

½ + Ë> à º  H & h  & h Ü ¼– Ð 7 £ x    x = 10 mol%\ " f 0.18`  ¦
 ? /% 3 Ü ¼ 9, l > & h  ¾ ¡ §| 9 > à º  H y Œ ™™ è   H  ⠆ ¾ Ó

`

 ¦ ˜ Ð% i  .

P

c p 8 ý ò k >

‘

: r  7 Hë  H“ É r ô  Dz D G † < ÆÕ ü t”  < É ª F é ß –_  t " é ¶(KRF-2006-005- D02702) õ  “ §¹ ¢ ¤ õ † < Æl Õ ü t  Òü < ô  Dz D G í ß –\ O l Õ ü t F é ß –_  t % i  +

À :’  “  § 4 € ª œ$ í  \ O \  _  # Œ à º' Ÿ  ) a ƒ  ½ ¨  õ – Ð" f, s \  y

Œ

™  × ¼w n m  

Y

c p w Š à U Ø ”  ô

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25, 809 (1954).

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Dielectric and Piezoelectric Properties of Lead-free (1–x)(Bi _0.5 K _0.5 )TiO ₃ -xBiFeO ₃ Ceramics

J. M. Kim, Y. S. Sung,

^∗

J. H. Cho, T. K. Song and M. H. Kim School of Nano & Advanced Materials Engineering,

Changwon National University, Changwon 641-773

H. H. Chong and T. G. Park

Department of Electrical Engineering, Changwon National University, Changwon 641-773 (Received 13 February 2009)

Dielectric and piezoelectric properties of lead-free (1–x)(Bi

0.5

K

0.5

)TiO

3

-xBiFeO

3

ceramics pre- pared by using a conventional solid-state reaction method were investigated in the range of x = 0 ∼ 10 mol%. With increasing x, the piezoelectric coefficient increased from 31 pC/N at x = 0 mol% to 64 pC/N at x = 6 mol% and then decreased. The electromechanical coupling factor (K

p

) increased up to 0.18 at x = 10 mol%. On the other hand, the mechanical quality factor (Q

m

) decreased.

The grain size did not change much with variations in x, and a single perovskite with tetragonal symmetry was maintained at all compositions, forming a solid solution between (Bi

0.5

K

0.5

)TiO

3

and BiFeO

3

. The depolarization temperature (T

d

) gradually decreased with increasing x from 302

◦

C at x = 0 to 245

^◦

C at x = 10 mol%.

PACS numbers: 77.22.-d, 77.84.-s

Keywords: Lead-free, Bismuth potassium titanate, Bismuth ferrite, Depolarization temperature

∗

Corresponding author: [email protected]