Jurnal f the Krean Ceramic Sciety Vl. 44, N. 12, pp. 710~714, 2007. Effect f the LDC Buffer Layer in LSGM-based Ande-supprted SOFCs Eun Hwa Sng* S **, Tai-J Chung**, Hae-Ryung Kim*, Ji-Wn Sn*, Byung Kk Kim*, Jng-H Lee*, and Hae-Wen Lee* *Materials Science & Technlgy Research Divisin, Krea Institute f Science and Technlgy, Seul 136-791, Krea **Schl f Materials Science & Engineering, Andng Natinal University, Andng 760-749, Krea (Received Nvember 7, 2007; Accepted Nvember 56, 2007) LSGM x š y LDC d z y*, **Á k **Á½x * Á *Á½ *Á y*á w * *w w»» ** w œw (2007 11 7 ; 2007 11 26 ) ABSTRACT LSGM(La 0.8 O 3-δ) is the very prmising electrlyte material fr lwer-temperature peratin f SOFCs, especially when realized in ande-supprted cells. But it is ntrius fr reacting with ther cell cmpnents and resulting in the highly resistive reactin phases detrimental t cell perfrmance. LDC(La 0.4 ), which is knwn t keep the interfacial stability between LSGM electrlyte and ande, was adpted in the ande-supprted cell, and its effect n the interfacial reactivity and electrchemical perfrmance f the cell was investigated. N severe interfacial reactin and crrespnding resistive secndary phase was fund in the cell with LDC buffer layer, and this is due t its ability t sustain the La chemical ptential in LSGM. The cell exhibited the pen circuit vltage f 0.64 V, the maximum pwer density f 223 mw/cm 2, and the hmic resistance f 0.17 Ωcm 2 at 700 C. These values were much imprved cmpared with thse frm the cell withut any buffer layer, which implies that frmatin f the resistive reactin phases in LSGM and then deteriratin f the cell perfrmance is resulted mainly frm the La diffusin frm LSGM electrlyte t ande. KeyG wrds : SOFC, LSGM electrlyte, Buffer layer, Interfacial reactin, Cell perfrmance 1. š y (slid xide fuel cell; SOFC) xk yz š p w w j» l w, w ƒÿ š. û š (500 ~ 800 C) SOFC w y w š, w w y 6-7) w. 1-3) š y w» w 1,4), w, w w., (10 18 P O2 /atm 1) ù (inic transference number)ƒ 1 w., ƒ Crrespnding authr : Hae-Ryung Kim E-mail : hrkim@kist.re.kr Tel : +82-2-958-6674 Fax : +82-2-958-5529 f w w yw w., š» w., wš, q w w w w w. e w(dense) x w yw ù w w. w l x š w š g (ZrO 2 )ù (CeO 2 ) x (flurite) y LaGaO 3 r e p(pervskite) y. g y ƒ š yw /» w YSZ(Y 2 O 3 -stabilized ZrO 2 )ƒ t, YSZ 1000 C ƒ 0.1 S/cm ƒ 800 C 0.04 S/cm w û p e. 5) y 800 C w g ƒ ù, y» ƒ f e w 710
LSGM x š y LDC d z 711 x w. r e p 9) LaGaO 3 (La 0.8 O 3-δ; LSGM) y 800 C w e w ƒ, w w ƒ. w 10) LSGM w yw w ƒ. ù g w 11-15) LaSrGa 3, LaSrGaO 4, La 2 Zr 2, Sr 2 ZrO 4» ƒ û j j š. 11,14,15) NiO LaNiO 3 LSGM r e p w w e š. y w 8) w x x wù, x w / œ ƒ w e. LSGM x w / w d š w š, d w CeO 2 La š LDC(La 2 O 3 -dped CeO 2 ) w. LDC d LSGM w e w k, p z w š w. 2. x LSGM w d LDC(La 0.4 ) š (slid state reactin) w. La 2 O 3 ( 99.99%, by Strem Chemicals, USA) CeO 2 ( 99.99%, by Strem Chemicals, USA) w. La 2 O 3 CeO 2 yw 40 : 60 vl% y d wš g wì 24 ball-millingw z, yww wš, w ³ w, 1350 C 5 w w. w w /»(thermgravimetry/differential thermal analysis; TG/DTA, STA409PC by Netzsch, Germany) d š x14,16) ü k w w. w X- z»(x-ray diffractin; XRD, D/max2000 by Rigaku, Japan) w w ww, d 40 kv, 30 ma, 4 /min scanning speed. x (ande-supprted unit cell) w GDC(Gd 0.1 Ce 0.9 O 1.95, by Rhdia, USA) NiO(by Sumitm, Japan) 40 : 60 vl% yww z, (liquid cncentratin prcess; LCP) mw ³ w j» NiO-GDC w. 10 MP ƒ xw z 1100 C 2 ƒ w 1mm Ì»q w. w w. LSGM(La 0.8 O 3-δ, by Seimi Chemical, Japan) w LSCF(La 0.6 Sr 0.4 C 0.8 Fe 0.2 O 3-δ, by Seimi Chemical, Japan) LDC(La 0.4 ) d Planetary Milling(Pulverisette5 by Fritsch, Germany) w r p w š, w j d z w. LDC d 1400 C 5, LSGM w 1400 C 6, LSCF 1100 C 2 w. y w» w x (scanning electrn micrscpy; SEM, XL-30 by Philips/ FEI, Netherlands) (secndary electrn; SE) z (back-scattered electrn; BSE) w š, ƒ y» w x» (energy dispersive spectrscpy; EDS) / (line/pint mapping) ww.»yw d e w šw. 21) w ƒƒ Pt mesh Ni spnge w Pt w»» w. ƒ 200 sccm, yƒ 400 sccm œ» w, ƒ yƒ yw» w w ƒ fx w. 600 ~ 700 C 50 C - š v rp d w (1260A & 1287A by Slartrn Analytical, England) p w. 3. š 3.1. LDC w d ƒ y / yw w, w w. LDC» ƒ, La 40% LSGM w ü La yw sl g w La y w š š. 16) š w LDC w w z, sƒ mw w y w. Fig. 1 LDC TG/DTA, 300 ~ 800 C w ƒ, y s ùkû. Y y (%) / w ƒ 100» 44«12y(2007)
712 yá k Á½x Á Á½ Á yá w w ƒ. w 1300 C w y w. sƒ š x14,16) ü k LDC w 1350 C w. Fig. 2 1350 C 5 w w LDC X- z, k 1350 Cƒ (cubic) x w ww. 3.2. LDC d e z LDC d e w wš, Fig. 3 d EDS ùkü. d, w d (Fig. 3(a)). Fig. 3(b) EDS, w La, Ni w w w š, w y x d x w. Fig. 3(c) EDS mw, d w ƒ¾ z d (A) La, Sr, Ga, O LaSrGa 3, ƒ¾ d(b) Ni, O NiO y w. Ni LSGM w LaNiO 3 ƒ j, mw w. Fig. 4 LDC d w w EDS. w / w š(fig. 4(a)), Ni, O y. LDC d y y wš, EDS / ww (Fig. 4(b-c)). LDC d ü La yw sl w w La š, LSGM/LDC La y La, Sr, Ga, O w ƒ d. LDC/ LDC d La ƒ y w, LDC w» d. ù w ü Ni, LDC d w w Ni y y w., w / y, p w La ùƒ w j La-Sr-Ga-O d x w e. La š LDC d w w w y w š, w w w. ù w Ni LDC d w w. 3.3. LDC d»yw e z»yw - š l z (pen circuit vltage; OCV) (maximum pwer density), v rp l w w d w sƒw. Fig. 5 LDC d w w d. 700 C OCV 0.64 V, 223 mw/cm 2. 650 C OCV 0.65 V 174 mw/cm 2, 600 C ƒƒ 0.66 V 2 108 mw/cm d. Fig. 6 w v rp. ƒ w rp, š q r w ù kü, l q r¾ ¼ ƒ w w w. w w j» w v d z (effective area) š w w (area specific resistance; ASR) w. 700 C ASR 0.17 Ω cm 2 š, 650 C 600 C ASR ƒƒ 0.26 Ω 2 cm 0.46 Ω cm 2 d. w š x9,16-20) š, LDC d x w û r, w z w w. Fig. 7 700 C LDC d d w v. sƒw 0.7 V w, OCV j k 700 C w. d 2 700 C OCV 0.42 V š, 0.40 mw/cm û. w û OCV d k LSGM w w w j La-Sr-Ga-O w q. LDC d 700 C OCV 0.64 V, 223 mw/cm 2 d, d w 400. 3.2., LDC d LSGM La š g w w š» w» š. LDC d w Ni», Ni y w La y w d x w e w wz
LSGM x š y LDC d z 713. LDC d w La y w š š w. Fig. 8 LDC d ƒƒ w 700 C v mw ASR w. d ASR 10.99 Ω cm 2, LDC d 0.17 Ω cm 2 d. y w l, La y La-Sr-Ga-O d w w ƒ w. LDC d ASR š 5/10/10 µm LDC/LSGM/LDC d ƒ x ASR 16) w (Fig. 9). š x ASR 10 µm LSGM ƒ x ASR 17) w 3 j, LDC/LSGM/LDC d ̃ 25 µm w k w. LSGM w LDC d ̃ ƒƒ 20 µm, Ì ASR 10 µm LSGM» ASR 4 j ù, 10. w ƒ š w. Fig. 10 w w ü ³, LSGM w LSCF q w ü (interfacial thermal stress) w, 20) mw. w La y w Ni y w j w w, OCV ù w ƒ w w w ƒ v w. l, LSGM x w d w w, LDC d w w ü La š g w j d w ü w ywš w w y w. wr y w / w, w Ni y ƒ w w. 4. LSGM w w x SOFC w w w» w LDC d w, w ƒw. SEM EDS LSGM La y w x, ü w ƒ wƒ. LDC d w LSGM w ü La yw sl w w y w. ù y w / w, w Ni y ƒ w w. Acknwledgment ƒ y w. REFERENCES 1. N. Q. Minh and T. Takahashi, Science and Technlgy f Ceramic Full Cells, pp. 69-116, Elsevier, Amsterdam, 1995. 2. N.Q. Minh, Ceramic Fuel Cells, J. Am. Ceram. Sc., 76 [3] 563-88 (1993). 3. T. Ishihara, N. M. Sammes, and O. Yamamt, Electrlytes, pp. 83-118, in <High Temperature Slid Oxide Fuel Cell: Fundamentals, Design and Applicatins>, Ed. by S.C. Singhal and K. Kendall, Elsevier, New Yrk, 2003. 4. B.C.H. Steele, Ceramic In Cnducting Membranes, Current Opinin in Slid State & Materials Science, 1 [5] 684-91 (1996). 5. Y. Arachi, H. Sakai, O. Yamamt, Y. Takeda, and N. Imanishai, Electrical Cnductivity f the ZrO 2 -Ln 2 O 3 System, Slid State Inics, 121 [1-4] 133-39 (1999). 6. T. Fukui, S. Ohara, K. Murata, H. Yshida, K. Miura, and T. Inagaki, Perfrmance f Intermediate Temperature Slid Oxide Fuel Cells with La(Sr)Ga(Mg)O 3 Electrlyte Film, J. Pwer Surces, 106 [1-2] 142-45 (2002). 7. N.P. Brandn, S. Skinner, and B.C.H. Steele, Recent Advances in Materials fr Fuel Cells, Annu. Rev. Mater. Res., 33 183-213 (2003). 8. P.Huang, A. Hrky, and A. Petric, Interfacial Reactin between Nickel Oxide and Lanthanum Gallate during Sintering and Its Effect n Cnductivity, J. Am. Ceram. Sc., 82 [9] 2402-406 (1999). 9. Z.H. Bi, B.L. Yi, Z.W. Wang, Y.L. Dng, H.J. Wu, Y.C. She, and M.J. Cheng, A High-perfrmance Ande-supprted SOFC with LDC-LSGM Bilayer Electrlytes, Electrchem. Slid St., 7 [5] A105-07 (2004). 10. T. Ishihara, H. Matsuda, and Y. Takita, Dped LaGaO 3 Pervskite Type Oxide as a New Oxide Inic Cnductr, J. Am. Chem. Sc., 116 [9] 3801-803 (1994). 11. M. Hrvat, A. Ahmad-Khanln, Z. Samardzija, and J. Hlc, 44«12y(2007)
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