Effect of Ta Substitution on the Dielectric and the Piezoelectric Properties of (Na 0.545 K 0.47 )(Nb 0.55 Ta 0.45 )O 3 Ceramics

Effect of Ta Substitution on the Dielectric and the Piezoelectric Properties of (Na _0.545 K _0.47 )(Nb _0.55 Ta _0.45 )O ₃ Ceramics

J. S. Kim ^∗ · S. Y. Lim · M. H. Kim

School of Advanced Materials Engineering, Changwon National University, Changwon 641-773, Korea

T. G. Park · J. Park

Department of Electronic & Mechanical Engineering, Changwon National University, Changwon 641-773, Korea

J. S. Song

Korea Electrotechnology Research Institute, Changwon 641-120, Korea (Received 5 October 2013 : revised 12 November 2013 : accepted 11 December 2013)

To improve the piezoelectric properties, we prepared Ta-substituted (Na

0.545

K

0.47

)(Nb

0.55

Ta

0.45

)O

3

(NKNT) ceramics by using a solid-state reaction method.

We studied the effect of Ta substitution on the dielectric and the piezoelectric properties of the NKNT ceramics. Phase transition temperatures, such as the T

O−T

(orthorhombic-tetragonal) and the T

c

(tetragonal-cubic) transition temperatures, decrease with increasing Ta substitution. In addition, the piezoelectric properties of NKNT were enhanced with increasing Ta substitution.

Especially, for the fabricated ceramic, a high piezoelectric coefficient d

33

= 284 pC/N was obtained at room temperature. We discuss the enhanced piezoelectric properties related to the formation of the orthorhombic-tetragonal phase and to polymorphic phase transition.

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

Keywords: (Na

0.5

K

0.5

)NbO

3

, NKN, Lead-free, Dielectric, Piezoelectric, Phase transition, Ta ion addition

Ta T  Y 8 Èc Ü R “ ¤Ž ì Å (Na 0.545 K _0.47 )(Nb _0.55 Ta _0.45 )O ₃ : g à k Ä8 ý Æ X Øy ¢; c   \ ¥ – ¥ ¹ Å õ m Í

° 

q ¹ Å — ¤V R Ë



™ » . > ¬ £ ^∗ ·  ™ »„ ç ¡* × < ·  ™ »' å ‡ Ú

‚

½ Ó" é ¶ @ /† < Ɠ §, ’  ™ èF / B N † < Æ Ò, ‚ ½ Ó" é ¶ 641-773

ƒ

‘

š? # Þ · ƒ ‘ š ø ¶ B¦ 

‚

½ Ó" é ¶ @ /† < Ɠ § „  l ·l >  / B N † < Æ Ò, ‚ ½ Ó" é ¶ 641-773

ö

¶ B< ) ç 

ô

 Dz D G„  l ƒ  ½ ¨" é ¶, ‚ ½ Ó" é ¶ 641-120

(2013¸   10 Z 4 5{ 9  ~ à Î6 £ §, 2013¸   11 Z 4 12{ 9  à º& ñ ‘ : r ~ à Î6 £ §, 2013¸   12 Z 4 11{ 9  > F  S X ‰& ñ )

6

£

x6   x: £ ¤$ í `  ¦ > h‚   l  0 AK  Ta`  ¦ u  ¨ 8 Š ô  Ç (Na

0.545

K

0.47

)(Nb

0.55

Ta

0.45

)O

3

(NKNT) [ j b ” `  ¦ ] j› ¸

% i “ ¦, Ta u  ¨ 8 Š \    É r Ä »„   x 9  · ú š„  : £ ¤$ í `  ¦ › ¸  % i  . ] j› ¸  ) a NKNT [ j b ” _   Œ ™~ ½ Ó& ñ > -& ñ ~ ½ Ó& ñ 1323

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Keywords: (Na

0.5

K

0.5

)NbO

3

, NKN, Á ºƒ  , Ä »„  , · ú š„  ,  © œ„  s , Ta s “ : r ' ‘ ´ òõ 

I. " e  ] Ø

Ä

ºÃ ºô  Ç y © œÄ »„   x 9  · ú š„  : £ ¤$ í `  ¦ ° ú   H PZT (PbZrTiO ₃ ) >  [ j b ” “ É r 6 £ x6   x ™ è  x 9  l œ íF « і Ð

„

  í ß –\ O _  # Œ Qì  r  \   6   x ÷ &t ë ß – [1] 60% s  © œ Ÿ í† < Ê

 )

a ± ú š (Pb)s  ¨ 8 Š â `  ¦ š ¸% i r v   H ë  H ] j µ 1 ÏÒ q tô  Ç . ¨ 8 Š

 â

˜ Р ñ ×  æ כ ¹ô  Ç ë  H ] j– Ð “  d ” H † d \     ‚  ”  ² D G`  ¦ ×  æd ”  Ü

¼– Ð ± ú š1 p x ×  æF K5 Å q s  Ÿ í† < ʝ ) a F « Ñ_   6   x s  % 3    >  ½ © ]

j÷ &“ ¦ e ”  .   " f ± ú šs  † < ÊÄ »  ) a PZT F « Ñ\  ¦ @ /^ ‰½ + É

’

 l 0 p x$ í F « Ñ > hµ 1 Ïs  € 9 כ ¹  9 [2], s  ƒ  ½ ¨ ×  æ Á ºƒ   (Na 0.5 K 0.5 )NbO 3 (NKN)`  ¦ l œ íF « і Ð · ú š„   6 £ x6   x: £ ¤$ í

`

 ¦ > h‚    9  H ƒ  ½ ¨  Ö ¸ µ 1 Ï >  ”  ' Ÿ ÷ &“ ¦ e ”   [3–14].

Õ

ª Q
 NKN l ‘ : r › ¸$ í \  Ÿ í† < ʝ ) a Ÿ í ¸ o u (K) õ  ™ è´ o u (Na)“ É r _ þ v l \  ¦ f  ¨ à º # Œ 0 l q  H › ¸K $ í s  y © œ # Œ › ¸$ í $ í ì

 r _  " é ¶ « Ñì  r ´ ú ˜`  ¦ & ñ S X ‰ >  › ¸] X  l  # Q§ >  .   " f NKN`  ¦ l œ íF « і Ð î ß –& ñ  ) a Ó ü t$ í `  ¦ ° ú   H € ª œ| 9 _  [ j b ”  ]

j› ¸  H # Œ„  y  # Q 9î  r  כ Ü ¼– Ð · ú ˜ 94 R e ”   [3,5,7,8]. ] j› ¸ /

B N& ñ \ " f
 
  H é ß –& h `  ¦ ˜ Ð ¢ - a l  0 AK  hot pressing, spark plasma sintering ~ ½ ÓZ O 1 p x`  ¦  6   x  
 BaTiO ³ , SrTiO 3 , LiNbO 3 , LiTaO 3 1 p x`  ¦ ' ‘  # Œ NKN`  ¦ l œ í F

« і Ð € ª œ| 9 _  [ j b ” `  ¦ ½ + Ë$ í % i   [2–10].

s

„  ƒ  ½ ¨\   Ø Ô€  , (1-x)(Na _0.5 K _0.5 )NbO ₃ -xLiNbO ₃ (NKN-LN) › ¸$ í “ É r  Œ ™~ ½ Ó& ñ >  (orthorhombic)õ  & ñ ~ ½ Ó& ñ

>

 (tetragonal)  © œs  / B N” > r   H  © œ â >  % ò % i  (MPB, mor- photropic phase boundary) \ " f · ú š„  : £ ¤$ í s  ß ¼>  † ¾ Ó © œ

÷

& 9, s  M :, · ú š„  > à º (d ³³ ) x 9  „  l l >   ½ + Ë> à º (k ^p )  y

Œ

•y Œ • 200 - 235 pC/N x 9  0.44 - 0.48– Ð
 z Œ ¤  [4]. ‘ : r

ƒ

 ½ ¨\ " f  H NKN >  [ j b ” `  ¦ l œ íF « і Ð Nb @ /’   Ta\  ¦ 45 mol% u  ¨ 8 Š ô  Ç (Na _0.545 K 0.47 )(Nb 0.55 Ta 0.45 )O 3 [ j b ” 

`

 ¦ ] j› ¸ % i Ü ¼ 9, “ : r • ¸\    É r Ä »„   x 9  · ú š„  : £ ¤$ í `  ¦ ƒ  ½ ¨

% i  .

II. ÷ m Ç ] M ö

‘

: r z  ´+ « >\ " f  H ’ < Hz  ´`  ¦ ˜ Ð © œ l  0 AK  Na 1.5 mol%\  ¦

œ

íõ ô  Ç › ¸$ í \  Nb @ /’   Ta`  ¦ 45 mol% u  ¨ 8 Š ô  Ç

∗

E-mail: [email protected]

(Na 0.545 K 0.47 )(Nb 0.55 Ta 0.45 )O 3 (NKNT) [ j b ” `  ¦ í ß – o Ó

ü

t ™ D ¥ ½ + ËZ O Ü ¼– Ð ] j› ¸ % i  . s  NKNT [ j b ” _  Ä »„   x 9 

· ú

š„  : £ ¤$ í `  ¦ l ‘ : r › ¸$ í “   (Na _0.50 K _0.50 )NbO ₃ (NKN) [ j  b ”

õ  q “ § % i  .

_ þ

v l _  % ò † ¾ Ó`  ¦ þ j™ è o l  0 AK  Na ² CO 3 õ  K ² CO 3

ì

 r ´ ú ˜`  ¦ 200 <sup>◦</sup> C \ " f 10 r ç ß –1 l x î ß – \ P  % i  . s  Ê ê Na 2 CO 3 , K 2 CO 3 , Nb 2 O 5 ü < Ta 2 O 5 ì  r ´ ú ˜`  ¦ › ¸$ í q \   



 ™ D ¥ ½ + Ë # Œ (Na ^0.545 K 0.47 )(Nb 0.55 Ta 0.45 )O 3 ì  r ´ ú ˜`  ¦ ] j

›

¸ % i  . · ú ˜c + t`  ¦  6   x ô  Ç _ þ vd ”  ~ ½ Ód ” Ü ¼– Ð NKNT ì  r ´ ú ˜`  ¦ 2 r ç ß –1 l x î ß – ™ D ¥ ½ + Ë % i “ ¦, 100 ∼ 120 ^◦ C \ " f 6 r ç ß – s  © œ Ä

»t r &  ¢ - a„  y  | › ¸ % i  . s  NKNT ì  r ´ ú ˜`  ¦ • ¸m 

\

 V , # Q 1  800 ^◦ C ü < 2  850 ^◦ C \ " f 5 r ç ß –1 l x î ß – ™ è

% i “ ¦, 1500 kg×  æ/cm ² _  · ú š§ 4 `  ¦  # Œ f ”  â 10 mm_  [

j b ”  ò Á ša Å @`  ¦ ë ß –[ þ t% 3  . s  Ê ê 1180 ^◦ C \ " f 4 r ç ß – 1 l x î

ß – þ j7 á x ™ è  `  ¦ % i  .

X-ray  r] X ì  r$ 3  (XRD)`  ¦ : Ÿ x K  s  NKNT [ j b ” _    

&

ñ  © œõ    & ñ ½ ¨› ¸\  ¦ ¨ î  % i  . Ä »„   x 9  · ú š„  : £ ¤$ í ¨ î 

\

 ¦ 0 AK  ¿ ºa  0.5 mm_  n Û ¼ß ¼ + þ A [ j b ” `  ¦ ë ß –[ þ t% 3 “ ¦,

€

ª œ€  \  “ É r (Ag) „  F G`  ¦  ïh A % i  . 120 <sup>◦</sup> C _  z  ´o – B H (Si) š ¸{ 9 \ " f 40 kV/cm_  „  l  © œ`  ¦ [ j b ” \  “   # Œ 30ì  r ç ß – ì  rF G % ƒo  (poling)\  ¦ % i Ü ¼ 9, piezo-d 33 meter (IACAS, ZJ-6B)\  ¦ s 6   x # Œ · ú š„  > à º (d ³³ )\  ¦ 8 £ ¤& ñ % i 



. ¢ ¸ e ” x ~  Û ¼ / B N”   x 9  Ä »„  : £ ¤$ í `  ¦ ¨ î  l  0 AK  e ” x 

~

 Û ¼ ì  r$ 3 l  (impedance analyzer, SI1260ü < HP4194A)

\

 ¦ s 6   x K  „  l 6   x | ¾ Ó x 9  Ä »„  ’ < Hz  ´`  ¦ 8 £ ¤& ñ % i  .

III. + s ÇÊ Ý õ m Í À X Ø8 ý

1. : g à k Ä ¶  ¥V R Ë õ m Í  Œ º — ¤V R Ë

&

h

] X ô  Ç ™ è   “ : r • ¸\  ¦   & ñ   H  כ “ É r € ª œ| 9 _  [ j b ” `  ¦

%

3 l  0 AK  B Ä º ×  æ כ ¹  . ™ è  “ : r • ¸ ± ú Ü ¼€  , $ í  © œ÷ &



 H   & ñ { 9    Œ •Ü ¼ 9,   & ñ { 9   ç ß –_    ½ + Ës  €  •K  x 9 • ¸

 Z  }“ É r r « Ñ ë ß –[ þ t # Qt t  · ú §  H  . ¢ ¸ ™ è  “ : r • ¸  -Á º Z

 } Ü ¼€  ,   & ñ { 9  _  ß ¼l   -Á º & t “ ¦,   & ñ { 9    s 

\

 l / B N s  Ò q t  x 9 • ¸ ± ú  ”   .   " f þ j& h _  \ P % ƒ o

 “ : r • ¸\  ¦ % 3 l  0 AK  1080 ∼ 1210 ^◦ C “ : r • ¸\ " f \ P % ƒo 

Fig. 1. (Color online) X-ray diffraction (XRD) patterns of NKNT and NKN ceramics.

Fig. 2. (Color online) Temperature dependence of the dielectric constant of NKN ceramics at various frequen- cies.

\

 ¦ r • ¸ % i “ ¦, þ j7 á x ™ è  “ : r • ¸ 1180 ^◦ C \ " f x 9 • ¸ Z  }

“

É r NKNT [ j b ” `  ¦ ] j› ¸ % i  . Fig. 1“ É r ™ è   ) a NKNT ü

< NKN [ j b ” _  X-ray  r] X J ‡  s  . NKN [ j b ” “ É r (202) x 9  (020)  r] X x ß ¼– Ð Â Ò'   Œ ™~ ½ Ó& ñ >    & ñ ½ ¨› ¸\  ¦
 

? /% 3 Ü ¼ 9, s    õ   H NKN _  s „   ƒ  ½ ¨  õ  [3]ü < ¸ ú ˜ { 9

u  % i  . ô  Ǽ #  (002) x 9  (200)_  ì  r o   ) a X-‚    r] X x  ß

¼– Ð Â Ò'  NKNT [ j b ” “ É r  Œ ™~ ½ Ó& ñ > ü < & ñ ~ ½ Ó& ñ > – Ð ½ ¨

$ í

 ) a ™ D ¥ ½ + Ë © œ`  ¦ S X ‰ “  ½ + É Ã º e ”   [4,5,8,9].

2. Æ X Øy ¢ õ m Í — ¤ • ¤; c   \ ¥ – ¥ ¹ Å — ¤V R Ë

Figure 2 ü < Fig. 3“ É r “ : r • ¸ 7 £ x ½ + É M : 100 Hz, 1 kHz, 10 kHz, 100 kHz x 9  1 MHz Å Ò à º\ " f 8 £ ¤& ñ  ) a NKN õ 

Fig. 3. (Color online) Temperature dependence of the dielectric constant of NKNT ceramics at various frequen- cies.

NKNT [ j b ” _  Ä »„   © œÃ º\  ¦
  · p  כ s  . NKN [ j  b ”

“ É r 183 ^◦ C x 9  406 ^◦ C \ " f Ä »„  x ß ¼ (dielectric peak)\  ¦

° ú

  H  . s  M :, 183 ^◦ C _  Ä »„  x ß ¼  H  Œ ™~ ½ Ó& ñ > -& ñ ~ ½ Ó& ñ > 



© œ„  s  (T ^O−T ) s  . ¢ ¸ 406 ^◦ C _  Ä »„  x ß ¼  H & ñ ~ ½ Ó& ñ

>

-{ 9 ~ ½ Ó& ñ >  ½ ¨› ¸ © œ„  s  7 £ ¤, y © œÄ »„  - © œÄ »„   © œ_  Ç ©o “ : r

•

¸ (T c)s  . s  NKN [ j b ” _  Ä »„  : £ ¤$ í “ É r s p  ¸ ú ˜ · ú ˜



94 R e ” “ ¦, ‘ : r z  ´+ « >_    õ • ¸ s „   NKN ƒ  ½ ¨  õ ü < Ä »



 > 
 z Œ ¤  [2,8,9].

ô

 Ǽ #  NKNT [ j b ” _   Œ ™~ ½ Ó& ñ > -& ñ ~ ½ Ó& ñ >   © œ„  s  T O−T x 9  & ñ ~ ½ Ó& ñ > -{ 9 ~ ½ Ó& ñ >   © œ„  s  T c  H y Œ •y Œ • 40 ^◦ C ü <

156 ^◦ C – Ð
 z Œ ¤ . 7 £ ¤, NKN l ‘ : r [ j b ” õ  q “ § €   NKNT [ j b ” _  ¿ º > h_   © œ„  s  “ : r • ¸ $ “ : r A á ¤ Ü ¼– Ð s  1

l

x % i   [4, 5, 8, 9]. ô  Ǽ #  1 kHz\ " f 8 £ ¤& ñ  ) a z  ´“ : r   H % ƒ _

 NKN [ j b ” _  Ä »„   © œÃ º  H 500“   ì ø ̀  , NKNT_  Ä »

„

  © œÃ º  H 1200 Ü ¼– Ð 8 £ ¤& ñ ÷ &# Q NKN [ j b ” _  Ä »„   © œÃ º

\

 q K  ß ¼>  7 £ x  % i  . ¢ ¸ô  Ç 1 kHz\ " f 8 £ ¤& ñ  ) a z  ´“ : r



 H % ƒ_  NKN [ j b ” _  Ä »„  ’ < Hz  ´“ É r 0.5“   ì ø ̀  , NKNT_  Ä

»„  ’ < Hz  ´“ É r 0.02 – Ð 8 £ ¤& ñ ÷ &# Q NKN [ j b ” \  q K  y Œ ™™ è

% i   [8]. ô  Ǽ #  ± ú  ”   Ä »„  ’ < Hz  ´`  ¦ : Ÿ x K  [ j b ” _  € ª œ€  

„

 F G \  Z  }“ É r „  l  © œ`  ¦ “  ½ + É Ã º e ” # Q Ø  æì  r ô  Ç ì  rF G % ƒo 

 0 p x  .

3. Æ X Øy ¢; c   \ ¥ °  q ¹ Å — ¤V R Ë õ m Í Æ k ÈY þ Ÿ Å­ Ž Œ Ÿ «à à Š— ¤V R Ë

· ú

š„  : £ ¤$ í `  ¦ ¨ î  l  0 AK  · ú š„  > à º d ³³ \  ¦ 8 £ ¤& ñ % i 

“

¦ Fig. 4  H T O−T \  ¦ Ÿ í† < Êô  Ç “ : r • ¸ ½ ¨ç ß –\ " f 8 £ ¤& ñ ô  Ç NKNT

Fig. 4. Temperature dependences of piezoelectric coeffi- cient d 33 .

[

j b ” _  · ú š„  > à º\  ¦
 ? /% 3  . z  ´“ : r \ " f NKNT [ j  b ”

_  · ú š„  > à º  H 284 pC/N Ü ¼– Ð NKN_  · ú š„  > à º  H 100 pC/N Ü ¼– Ð
 z Œ ¤ . NKN_  · ú š„  > à º  H 80 - 120 pC/N Ü

¼– Ð · ú ˜ 9”   s „  _  ƒ  ½ ¨  õ ü < [3] Ä » ô  Ç ô  Ǽ #  NKNT [

j b ” _  · ú š„  > à º  H NKN [ j b ” _  · ú š„  > à º\  q K  ß

¼>  7 £ x Ù þ ¡6 £ §`  ¦ · ú ˜ à º e ”  .

“

: r • ¸ 7 £ x † < Ê\     · ú š„  > à º  H " f" fy  7 £ x  # Œ €  • 40 ^◦ C   H % ƒ\ " f þ j@ /° ú כ 320 pC/N\  ¦
 ? /% 3 “ ¦  8 s  © œ _

 “ : r • ¸ 7 £ x \ " f · ú š„  > à º  H y Œ ™™ è % i  . : £ ¤ y  s  · ú š„  

>

à º þ j@ /° ú כ`  ¦ ° ú   H “ : r • ¸ 40 ^◦ C Â Ò   H“ É r  Œ ™~ ½ Ó& ñ > -& ñ

~

½ Ó& ñ >   © œ„  s  (T O−T ) \  K { © œ   H “ : r • ¸s  9, T O−T  © œ

„

 s  “ : r • ¸ Â Ò   H \ " f · ú š„  > à º_     o ß ¼> 
 z Œ ¤  [13,14].

z 

´“ : r  Ò'  150 ^◦ C  t  e ” x ~  Û ¼ (Z)ü < e ” x ~  Û ¼ 0 A



© œ (Θ)`  ¦ 8 £ ¤& ñ # Œ / B N”   x 9  ì ø Í/ B N”   : £ ¤$ í `  ¦ › ¸  % i  .

Fig. 5  H “ : r • ¸\    É r 1 kHz \ " f Ä »„   © œÃ º, / B N”   x 9  ì ø Í /

B N”   Å Ò à ºü < „  l l >   ½ + Ë> à º_     o\  ¦
 ? /% 3  .

s

 M : Fig. 5(b)_  ¶ ú š{ 9 Õ ªa Ë >“ É r 30 ^◦ C \ " f 8 £ ¤& ñ  ) a / B N”   x 9  ì

ø Í/ B N”   e ” x ~  Û ¼ : £ ¤$ í `  ¦
  · p  כ s  . Fig. 5(b)\ " f

˜

Ð1 p w s  “ : r • ¸ 7 £ x † < Ê\     / B N”   x 9  ì ø Í/ B N”   Å Ò à º  H y

Œ

™™ è # Œ €  • 40 ^◦ C \ " f þ j$ ° ú כ`  ¦ ˜ Ð% i  . s Ê ê “ : r • ¸

7

£

x † < Ê\     / B N”   x 9  ì ø Í/ B N”   Å Ò à º  H  r  7 £ x  % i 

“

¦, s  / B N”   : £ ¤$ í “ É r €  • 150 ^◦ C s  © œ_  “ : r • ¸\ " f   & ’ 



.

s

 M :, / B N”   x 9  ì ø Í/ B N”   Å Ò à º þ j$ ° ú כ`  ¦
  · p 40

◦ C  H  © œ„  s  “ : r • ¸ T ^O−T ü < { 9 u  % i  .   " f s  “ : r • ¸



 H  © œ„  s  “ : r • ¸ T ^O−T \  K { © œ  9, e ” x ~  Û ¼ / B N”  : £ ¤$ í _ 



  o  © œ„  s  “ : r • ¸ T O−T Â Ò   H \ " f Ò q tl   H  כ e ” `  ¦ · ú ˜ Ã

º e ”  . ¢ ¸ô  Ç / B N”   x 9  ì ø Í/ B N”   : £ ¤$ í s    t   H 150 ^◦ C s

 © œ_  “ : r • ¸  H y © œÄ »„   © œ- © œÄ »„   © œ_  Ç ©o “ : r • ¸ 156 ^◦ C \ 

Fig. 5. (Color online) (a) Dielectric constant, (b) Impedance resonance (f _r ) and anti-resonance frequency (f _a ) and (c) electromechanical coupling coefficient (k _p ).

 Ä º 9, s  M :,   & ñ † < Æ& h  @ /g A“   { 9 ~ ½ Ó& ñ > – Ð ½ ¨› ¸  © œ

„

 s † < Ê\     / B N”  : £ ¤$ í s    f ” `  ¦ · ú ˜ à º e ”  .

Figure 5(c) _  „  l l >   ½ + Ë> à º (k p )  H / B N”   f _r x 9  ì ø Í /

B N”   f _a Å Ò à º\  ¦ s 6   x # Œ  6 £ § õ  ° ú  “ É r d ” Ü ¼– Ð > í ß – 

%

i   [13,14].

1 k p

= s

0.395 f _r f a − f r

+ 0.574

z 

´“ : r   H % ƒ\ " f NKNT_  „  l l >   ½ + Ë> à º  H 0.36 Ü ¼

–

Ð
 z Œ ¤Ü ¼ 9,  © œ„  s  “ : r • ¸ T ^O−T \  s \  ¦ M :  t  €  • ç ß

– 7 £ x  % i “ ¦, s  Ê ê “ : r • ¸ 7 £ x † < Ê\     y Œ ™™ è % i   [13,14]. s  „  l l >   ½ + Ë> à º_  y Œ ™™ è  H / B N”   x 9  ì ø Í/ B N”   s

   t   H Ç ©o “ : r • ¸ T c\  s Ø Ôl   t  t 5 Å q ÷ &% 3  .

PZT › ¸$ í “ É r  © œ â >  (MPB, morphotropic phase boundary) \ " f · ú š„  : £ ¤$ í s  ß ¼>  † ¾ Ó © œ÷ &  H  כ Ü ¼– Ð · ú ˜ 9 4

R e ”   [1]. s ü < Ä »  >  NKN › ¸$ í “ É r  Œ ™~ ½ Ó& ñ > -& ñ

~

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This work was supported by a National Research Foundation of Korea Grant funded by the Korean Gov- ernment (2010-0023129). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (2011- 0030058).

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