Review

∫∑§«“¡
«“√ “√«‘∑¬“»“ µ√å ¡¢. ªï∑’Ë 39 ©∫—∫∑’Ë 1 73
N d
+
+
Potential barrier
+
+
+
+ +
+ +
+ +
+ + + + + + +
d
N S
-
- -
Grain boundary
Acceptor state
Conduction band
Fermi level
√Ÿª∑’Ë 2 —Èπªî¥ (blocking layer) ∑’Ë¢Õ∫‡°√π (grain boundary) µ“¡·∫∫®”≈ÕߢÕß Heywang (1961, 1964)
1) µ”Àπ‘Õ‘‡≈Á°∑√Õπ‘° å (electronic defect)
La
1
2 2 2 6
e
2
x x
2O3
TiO2
LaBa
Ti
Ti
OO
O2
2
2) µ”Àπ‘‰∑µ“‡π’¬¡‰ÕÕÕπ (Titanium ion defect)
La O
2
3
/ x
2TiO2
2LaBa
2TiTi
6OO
O2
3) µ”Àπ‘àÕß«à“ß·∫‡√’¬¡ (Barium vacancy defect)
La 9O
// x
2O3
3TiO2
2LaBa
VBa
3TiTi
1
2
x
O
/
Daniels (1976, 1978/1979) ∫Õ°«à“¢≥–∑’Ë
‡º“ºπ÷° (sinter) „π∫√√¬“°“»·∫∫ÕÕ°´‘‡¥—π BaTiO 3
∑’ˇ®◊ե⫬‰ÕÕÕπµ—«„Àâ®–¡’µ”Àπ‘À≈—°‡ªìπµ”Àπ‘
Õ‘‡≈Á°∑√Õπ‘° å (electronic defect) ´÷Ëß∑”„À⇰‘¥
Õ‘‡≈Á°µ√Õπ®”π«π¡“°‡ªìπæ“À–ª√–®ÿ (Hill, 1991)
µàÕ¡“‡¡◊ËÕ≈¥Õÿ≥À¿Ÿ¡‘≈ß¡“µ”Àπ‘À≈—°¢Õß BaTiO 3
∑’Ë
‡®◊ե⫬‰ÕÕÕπµ—«„Àâ®–‡ªìπàÕß«à“ß·∫‡√’¬¡ (Barium
//
vacancy defect; V Ba ) ·≈–µ”Àπ‘¥—ß°≈à“«®–¡’®”π«π
¡“°¢÷Èπ‡¡◊ËÕ≈¥Õÿ≥À¿Ÿ¡‘≈߉ª‡√◊ËÕ¬Ê µàÕ¡“àÕß«à“ß
·∫‡√’¬¡ (Barium vacancy defect) ´÷Ë߇°‘¥∑’Ë¢Õ∫‡°√π
®–·æ√ஓ°¢Õ∫‡°√π‡¢â“‰ª„π‡°√π ·µà‡π◊ËÕß®“°µ”Àπ‘
π‘¥π’È·æ√à (diffuse) ‰¥ââ“¡“°®÷ß¡—°®–‰¡à “¡“√∂·æ√à
‡¢â“‰ª„π‡°√π‰¥âÀ¡¥ à«π„À≠à®÷߬—ߧ߇°“–°—πÕ¬Ÿà
µ“¡¢Õ∫‡°√π Õ“®®–¡Õß—Èπ¢Õßµ”Àπ‘π‘¥π’È«à“‡ªìπ
—Èπ¢Õß©π«πÀÿâ¡√Õ∫Ê ‡°√π ¥—ß√Ÿª∑’Ë 3a Daniels
(1976, 1991) Õ∏‘∫“¬µàÕ‰ª«à“—Èπ¢Õß©π«ππ’È¡’
惵‘°√√¡‡ªìπµ—«√—∫ (acceptor) ∑”Àπâ“∑’Ë®—∫Õ‘‡≈Á°µ√Õπ
®“°‡π◊ÈÕ “√ (bulk) ·≈–∑”„À⇰‘¥°”·æß»—°¬å¢«“ß°—Èπ
°“√‡§≈◊ËÕπ∑’Ë¢Õßæ“À–ª√–®ÿ¥—ß√Ÿª∑’Ë 3b