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1 Journal of the Korean Ceramic Society Vol. 46, No. 2, pp. 219~22, Capacitance Aging Behavior of Acceptor-Doped BaTiO uer DC Electrical Field Dong Woo Hahn a Young Ho Han Department of Materials Engineering, Sungkyunkwan University, Suwon , Korea (Received December 1, 2008; Revised March 20, 2009; Accepted March 2, 2009) w Acceptor ƒ BaTiO p y x w Áw y ³ w œw ( ; ; ) ABSTRACT Effects of MgO or R 2 O (R:Dy, Ho, Yb) on the capacitance aging behavior of multilayer ceramic capacitors (MLCCs) based on BaTiO dielectrics uer DC electrical fields has been udied. At a DC field of 1 V/µm, the capacitance of MLCC specimens dropped immediately in a very short period (<10 s, the fir age) a then decreased continuously with time (the seco age). Mn doping significantly increased the aging rate in the seco age. The addition of MgO or R 2 O notably decreased the seco age aging rate of Mn-doped specimens. Yb doping gives rise to the lowe aging rate in the seco age, which is due to the larger population of defect dipoles associated with oxygen vacancies. Key Words : DC bias, Capacitance aging, Reliability, BaTiO, Rare earth oxides 1. {»» dx f q l(mlcc) ƒ»» xy, y y š. x, š MLCC w d dy š, Ì d ƒ ƒw. w w 1,2) p y ƒ š MLCC ƒ ƒw š. -6) w w yx ƒ w, mechanism ³» y k. w yx (DC bias aging) ƒ ƒ š ù, w. 7,8) DC bias w p y ƒ z 10 ü ù» (1 age),» z w 2 age 2 š š. 7) Tsurumi» ƒ x w j Correspoing author : Young Ho Han yhhan@skku.ac.kr Tel : Fax : » w, 2 age w w y (aging) w wš. 7) w y(2 age) x w» w 2ƒ» ƒ. 5,7,8), trapped charge carrier w ü x» w w. 5,7) z w ƒ ƒ w w ù»œ ü w ü ƒ x. w ü» w w y x ù x w. 7) wù 90 o w y w y x. 7) Acceptor ƒ x w w w w(clamping)w. Mn, w ƒ š wš hopping mw Mn site w, +ƒ 4+ Mn, Mn Mn w w š ww. w c sww xkƒ. Tetragonal BaTiO c w a w w, w. 90 o w y 219

2 220 w Áw y» Mn 2 age y w. ù Mn w w yx w w w ƒ, š MLCC w. 9-12), Mn ƒ k w yx w syem š. BaTiO w w y jump v w B 4+ Ti w w y w j w, w ƒ 4+ƒ Ti w w w, wwš j z ƒ š š. 1-14) Nomura Y 2 O ƒƒ w p y w z š šw. ƒ y w y(aging) ƒ j Mn, ƒƒ š acceptor ƒ x w w w w z ùký w. 15) Mn ƒ BaTiO yx, Mg, m ƒƒ š acceptor ƒ ƒ e w w š w. 2. x x r MLCC xk. (100-x-y)BaTiO xmgo ymno (x+y)baco y (100-x-y)BaTiO (x/2) R 2 O ymno (x+y)baco w e w z, planetary mill w 2 yww. yw 120 C 24 k o z» m, p g yww w z, ha caing blade w Ì 20~25 µm p w. p Ni ü wš d, ƒ, ƒ w d green chip w. Green chip 100 C 2 o w. Ni ü y» w H 2 -H 2 O gas mixture w P(O 2 )~10 10 atm û w. y œ 1000 o C, N 2 gas» 2.5 w. r In-Ga w z» p d w. w yx d 1µm 1V ƒw k 10,000s y d w w. AC oscillation level 1 khz 0.2 mv/µm w. r j» yx w» w SEM w w. r 150 C 1µm 50V ƒw o k 24 d w.. š Mn ƒ BaTiO DC bias aging x Fig. 1 ùkü. Mn ƒ ƒw 2 age p y j ƒw 1 age y (aging rate) w w ùkû.» x š ew. 7,15) Mn ƒ ƒw ww w ( Mn' Ti ) ƒ ƒw, pinning w ƒ w. 1 age y (unclamped domain wall motion) w, Mn ƒ ƒ 1 age w ƒ w. ù Mn x w w Mn site w (electron hopping)w Mn 4ƒ(Mn )ƒ 4+. Hopping process w w y (relaxation process), ( Mn' Ti ) ƒ w 2 age yƒ w ƒ f. Mn ƒ w 1 age 2 age y ƒ ( Mn' Ti ) ƒ w. Fig. 2 Mg Mn wì ƒ r DC bias aging ùkü. 0.5 mol% Mn ƒ k Mg ƒ ƒ k 2 age aging Fig. 1. DC bias aging behavior of Mn-doped BaTiO. w wz

3 직류 전계에 의한 Acceptor 첨가 BaTiO 의 유전특성 열화 현상 221 rate는 크게 감소하였다. Mg은 Mn과 달리 원자가가 고정 된 이온(Mg )이므로, 결함 쌍극자의 소멸에 의한 분역 벽의 이동이 발생할 가능성이 낮다. 따라서 Mg가 형성한 결함 쌍극자 ( Mn Ti VO )는 1 age에서 분역 벽의 자유 로운 이동을 제한하는 동시에 2 age에서 시간에 따른 분역 벽의 이동도 억제 함으로서 aging rate를 감소시키는 효과를 나타내는 것으로 보인다. Mg 단독첨가 혹은 Mg, Mn이 복합 첨가된 BaTiO 의 미 세구조를 Fig. 에 나타내었다. 0.1 mol%의 Mg이 첨가된 시편의 경우 단독 첨가시 약 1~ m, 0.5 mol%의 Mn과 함께 첨가된 경우 ~ m의 큰 결정립과 낮은 기공률을 µ µ 갖는 미세구조가 관찰되었다. Mg 첨가량을 1.0 mol%로 증가시킨 경우 결정립 크기는 크게 감소하였으며, Mn 첨 가 여부에 관계없이 매우 기공률이 높고 엉성한 미세구 조가 관찰되었다. 하소 과정을 거치지 않았으므로 불균일 한 core-shell 구조가 형성되어 있음을 예상할 수 있으며, 이 경우 MgO가 BaTiO 의 소결시 결정립 성장을 방해하 는 역할을 함으로서 이와 같이 엉성한 미세구조가 나타 난 것으로 보인다. 결정립의 평균 크기가 감소할 경우 유 전율도 감소하게 되며, 이는 1 age와 연관이 있는 것으 로 보고되고 있다. 따라서 MgO에 의한 결정립 크기 의 감소는 Fig. 2에 나타난 1 age의 감소에 어느 정도 기여했다고 볼 수 있다. Fig. 4는 희토류 원소와 Mn이 복합 첨가된 BaTiO 의 DC bias aging 거동을 나타낸다. Mg 와 동일한 양의 R 를 첨가할 경우 절반 농도의 산소빈자리를 생성할 것이 예상되므로, 동일한 조건에서의 비교를 위하여 R 를 Mg 7,15) + + Fig. 2. Fig.. Effects of MgO on DC bias aging behavior of Moped BaTiO. Microructures of BaTiO co-doped with Mg a Mn. (a) Mg 0.1 mol%, (b) Mg 0.1 mol%, Mn 0.5 mol%, (c) Mg 1.0 mol%, (d) Mg 1.0 mol%, Mn 0.5 mol%. Fig. 4. Effects of rare earth oxides or MgO on DC bias aging behavior of Mn-doped BaTiO. (Rare earth: Dy, Ho, Yb) (a) 0.1 mol% Mg or 0.2 mol% rare earths, (b) 1.0 mol% Mg or 2.0 mol% rare earths. 제 46 권 제 2호(2009)

4 222 w Áw y 2 ƒw. 0.5 mol% Mn ƒ BaTiO m ƒw 1 age 2 age aging rateƒ j w ƒ. m ƒ Yb ƒ r y ƒ ùkû. Yb Å x m Dy(0.912Å) Ho(0.90Å) w r, w r e p B site eyw. w ey p w Dyù 16) Ho ƒ r w x w 1 age y jš 2 age ww w ƒ r w. ƒƒ š acceptor w x w ƒ aging rate j w w ƒ ww w. y m ƒ 0.2 mol% 2.0 mol% ƒ k w. Mn site ƒ DC bias w (hopping)w 2 age aging rate ƒ j š, core-shell core ù x. m ƒ ƒ 7,15) w shell ƒƒ DC bias aging rate» w. w Fig. ù kû Mg ƒ r ƒ, m ƒ 2.0 mol% ƒ r 0.2 mol% ƒ r w ûš j» y, g 1 age y j» w. Fig. 4(b) ù kù m 2.0 mol% ƒ r y Fig. 4(a) ùkù 0.2 mol% ƒ r w shell y ù w ƒ w, w w eš y w. m y Mn wì ƒw BaTiO y Fig. 5 ùkü. r d 1µm 50V ƒw 150 C 24 o d w. ƒ mw œ acceptor w w ³ x w» w DC field w w, w yx j. 9-12) Mg, Ho, Yb acceptor ƒ ƒ r 24 ü q j y. Dy ƒ r DC field ƒw q ƒ û, r e p A B eyw (amphoteric) j Fig. 5. Insulation resiance degradation of acceptor doped BaTiO uer DC electrical field. (a) specimens without Mn doping, (b) specimens doped with 0.5 mol% Mn. ƒ Dyƒ ƒ A site yw donor w š, mw, û w ƒ». ù Fig. 5(b) ùkù 0.5 mol% Mn wì ƒ acceptor w w yx j y w. Mn ƒ ƒ w y ƒ j w w ù, w y w z ƒ w» MLCC w y. y yx w» w y r w e ü acceptor MnO co- w wz

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