Jurnal f the Krean Ceramic Sciety Vl. 44, N. 3, pp. 182~187, 2007. Micrwave Sintering f Gd-Dped CeO 2 Pwder Yung Gun Kim and Seuk-Bum Kim Department f Materials Science and Engineering, Gyenggi University, Suwn 443-760, Krea (Received February 14, 2007; Accepted March 13, 2007) Gd-Dped CeO 2 j q ½ ³Á½» w œw (2007 2 14 ; 2007 3 13 ) ABSTRACT 10 ml% Gd 2 -CeO 2 pwder was sintered by micrwave in a 2.45 GHz multimde cavity t develp a dense electrlyte layer fr intermediate temperature slid xide fuel cells (IT-SOFCs). Samples were sintered frm 1100 C upt 1500 C by 50 C difference and kept fr 10 min and 30 min at the maximum temperature respectively. Theretical density f the sample sintered at 1200 C fr 10 min was 95.4% and increased gradually upt 99% in the sample sintered at 1500 C fr 30 min. All f sintered samples shwed very fine micrstructures and the maximum average grain size f the sintered sample at 1500 C fr 30 min was (0.87 ±0.42) µm. Inic cnductivity f the samples were measured by DC 4 prbe methd. Key wrds : SOFC, Gd-dped, CeO 2, Micrwave prcess, Ceramic electrlyte, Sintering SOFC, Gd-dped, CeO 2, Micrwave prcess, Ceramic electrlyte, Sintering 1. 3 š y (SOFC : slid xide fuel cell) w š w w z 50~ 60%. ƒ w wù š w» ƒ, kƒ w xk ƒ w. 1,2) ù x ¾ š y 800 C š. w, w, q w g SOFC y j. 3,4) ƒ 800 C w x (Intermediate Temperature-SOFC) w ƒ y w š. w 5,6) š w w k s œ rw š ƒ». ù š y û ü Crrespnding authr : Seuk-Bum Kim E-mail : sbkim@kynggi.ac.kr Tel : +82-31-249-9761 Fax : +82-31-244-6300 w ƒ w. w w» w ZrO 2 w ƒ Bi 2, CeO 2, LaGa w ƒ w. 7,8) x SOFC w wù Ce y e, 9) œe, 10) w 11), Ce y Gd ù Sm y ƒw j ƒ. w 12,13) w w Gd š Ce (GDC) 14)ù C Mn 15) y (transitin metal xides) ƒ w ù ù j» 16) w û ƒ w, ƒ r s³ j» w š š. wr œ» w»¾ v w ù t v w w w» w š ƒ. ù ƒ œ k ù ƒ w ùš j q û y y e yƒ w 182
ƒ š d p j ƒ š. w mw ³ w ùkü j q r j q w ü v w r ü ù kù. w p w jš w r š ³ w w g ³ w. 17-19) p ƒ j q w ƒ w š 10 ml% Gd 2 - CeO 2 w j q w œ ƒ w w. 2. x ƒƒ 99.9% ƒ CeO 2 Gd 2 (Kjund Chemical Lab. C. Ltd., Japan) yw Ce 0.90 Gd 0.10 O 1.95 (GDC10, 0.5~1 µm) w ³ w yw w k ü Al 2 w 24 z w. 18 mm w 70 MPa 1 xw z 140 MPa x w x r. j q r Fig. 1 ùkù j q e w w r ƒ w» w e š insulatin bx w z SiC susceptr w 2.45 GHz multimde j q ƒ (3 kw) 30 C/min w w. 1100 C 1500 C¾ 50 C d w t ƒƒ 10 30 w š œ» ww. Fig. 2 w insulatin bx ü j q pwer level r ƒ xk š ùkü. j q Fig. 1. A schematic diagram f the micrwave furnace. Gd-Dped CeO 2 j q 183 Fig. 2. Temperature prfile and the pwer level f the micrwave during the sintering prcess. Eurtherm Cntrller(Eurtherm- 2404) w r d insulatin bx mw R-type w d w. z r Archimedes w» w, y yƒ w» w X- z»(x-ray diffractmeter, SIEMENS D5005) w w r w y w. r x (SEM, JEOL, JSM-6300, Japan) w w š, r j» line intercept w SEM l d w. d w w r diamnd cutter 2 3 13 mm š sand paper w w z ƒ w r z 600~1000 C DC 4 100 C 3C þ ƒw d w. 3. š 10 Fig. 3 j q 1100 C w r 1500 C 30 w r XRD w GDC r 2 sw w š. r s³ y Fig. 4 x j q w 1100 C 10 30 w r 90% ùkù x x w š q. 1100 C 10 w w r 91.6% ùkü 1200 C 10 w 95.4% ùkù 1200 C e yƒ 44«3y(2007)
184 ½ ³Á½ Fig. 3. XRD diffractin patterns f the samples sintered by micrwave; (a) 1500 C fr 30 min and (b) 1100 C fr 10 min. Fig. 5. Average grain size f samples sintered by micrwave as a functin f temperature. Fig. 4. Relative density f sintered samples by micrwave as a functin f temperature. w. z 50 C ƒ w w 1500 C 10 w 98.5% ùkü. 30 w w 1350 C l 10 w w ƒw ù w 30 w ƒ w ƒ f 1500 C 30 w 99% 1350 C ƒ j ùkû. s³ j» ùkü Fig. 5 1200 C 10 w s³ (0.17 ±0.42) µm ù j» w x ƒ 1500 C 10 w s³ (0.57 ±0.42) µm ƒ j ùkû. r ƒ j ùkù 1500 C 30 w w r s³ (0.87 ±0.42) µm ùkù j q w œ r s ³ j» 1µm w j». Zhang œe 20) GDC10» 1550 C 5 w j» ~14 µm ~97%, Han 21) w w GDC20 1300 C 4 w r 97.8%, s³ 0.73 µm šwš, x j q 1300 C 10 w r 97.2% s³ (0.24 ± 0.08) µm ùkù w š ù j». y yw ~0.55 µm (CeO 2 ) ~0.5 µm (Gd 2 O 2 ) w GDC20 r 1500 C 5 w Ma ~92% 22) ~4 µm, Park x 15) w GDC10 w 1600 C 12 w s³ (4.2 ±1.1) µm 99% ùkü šwš. j q w 99% ùkü 1500 C 30 w w Park 15) w 100 C ûš j» ~1/5 1/24, j q ¾ 1 sww œ w w j. w wz
Gd-Dped CeO 2 Fig. 6. 분말의 마이크로파 소결 185 SEM micrgraphs f sintered samples by micrwave at (a) 1200 C, (b) 1250 C, (c) 1450 C, (d) 1500 C fr 10 min, and (e) 1500 C fr 30 min hlding time. Fig. 6은 마이크로파로 1200~1500 C의 온도 범위에서 유지시간에 따른 시편의 파단면의 미세구조 사진을 나타 내었다. Fig. 6(a)는 1200 C에서 10분간 소결한 미세조직으 로서 밀도가 95.4%이며 기공이 불균일하게 입계에 존재하 는 것을 볼 수 있으나, 1250 C에서 소결한 시편인 Fig. 6(b) 의 경우부터는 1200 C 보다는 기공이 많이 줄어든 것으 로 관찰되었고, 밀도가 98%인 1450 C에서 10분 유지한 경우인 Fig. 6(c)에서는 기공이 거의 보이지 않으며 치밀 하며 균일한 형태의 결정립을 가진 미세구조를 관찰할 수 있었다. 각각 1450 C와 1500 C에서 10분 유지한 경우인 Fig. 6(d)와 6(c)의 두 경우 사이에는 밀도 값은 약간 증 가하였으나 입자의 성장이 별로 크지 않아 비슷한 크기의 입경을 나타내고 있는 것을 볼 수 있다. 그러나 Fig. 6(d) 와 1500 C에서 30분 유지한 경우인 Fig. 6(e)에서는 밀도 가 각각 98.5%와 99%로써 치밀화된 미세구조를 보이고 있으며 Fig. 6(e)의 경우에는 입성장이 빨라져 Fig. 6(d)의 경우보다 평균입경이 커진 모습을 볼 수 있다. Fig. 7에는 마이크로파로 1200 C에서 10분 유지하여 소 결한 시편과 1500 C에서 30분 유지한 시편의 온도에 따른 이온전도도를 DC 4단자법으로 측정한 값을 아래 Arrhenius 식을 이용하여 나타내었다. σ ------α- σin Scm 1 = -----0 exp E T (1) kt 고온인 1000 C 근처에서는 1500 C에서 30분을 유지하 Fig. 7. Electrical cnductivity f the 10 ml% Gd O -CeO samples sintered by micrwave. 2 3 2 여 소결한 경우가 1200 C에서 10분간 유지한 시편의 이 온전도도 값보다 약간 높은 값을 나타내지만 온도가 낮 아질수록 차이가 커져서 600 C 근처에서는 그 차이가 더 크게 나타나고 있다. Table 1에 있는 이 시편들의 이온전도도와 활성화에너 지 값(Ea)을 비교하여 보면 1500 C의 경우가 1200 C 경 우에 비하여 더 낮은 활성화에너지 값을 가지고 있기 때 문이며, 그 이유는 온도가 높은 1000 C 근처에서는 grain bundary effect가 크게 영향을 나타내지 않으나 온도가 낮아지면서는 그 영향이 크게 나타나는 것으로 판단되며, 제 44 권 제 3호(2007)
186 ½ ³Á½ Table 1. Inic Cnductivity and Activatin Energy Data f the Samples by Micrwave Sintering Micrwave sintering 1200 C-10 min 1500 C-30 min Ea 0.70±0.1 ev 0.59±0.04 ev σ 1.4 ±0.2 10 5 5.51 ±0.2 10 4 1200 C 10 w w s³ (0.17 ±0.04) µm 1500 C w 1/5 j» d ƒw û ùküù 1500 C ƒ w r f w d w û ùkü. 23-25) 4. w ƒ 10 ml% Gd 2 -CeO 2 2.45 GHz j q w 30 C ƒ w 1100~1500 C t ¾ k z ƒƒ 10 30 w w 1.5 ü j w, r w w w ù s³ ùkû. r 90% s³ 1 µm w, 1200 C 10 w r 95.4% (0.17 ±0.42) µm s³ 1500 C 30 w ƒ ƒ 99% (0.87 ±0.42) µm ³ e w ùkü. 1500 C 30 w r ƒ 1200 C 10 w r w w ùkü d, r j» d ƒ ù w. w j q w 1500 C¾ 50 t 10 30 w ƒ ƒ 98.5% 99% ùkü š e» w w». l j q w w ƒ w w wì œ w z SOFC w Gd š Ce (GDC) w ƒ ƒ q. Acknwledgment 2004w» w w ( ) w w. REFERENCES 1. O. Yamamt, Slid Oxide Fuel Cell: Fundamental Aspects and Prspects, Electrchimica Acta., 45 2423-35 (2000). 2. E. I. Tiffee, A. Weber, and D. Herbstritt, Materials and Technlgies fr SOFC-Cmpnents, J. Eur. Ceram. Sc., 21 1805-11 (2001). 3. N. Q. Minh and T. Takahashi, Science and Technlgy f Ceramic Fuel Cell, pp. 1-14, Elsevier Science, Amsterdam, 1995. 4. B. C. H. Steele, Science and Technlgy f Zircnia:, vl, V, pp. 713, J. Am. Ceram. Sc., Clumbus (1993). 5. T. Tsai, E. Perry, and S. Barnett, Lw-Temperature Slid Oxide Fuel Cells Utilizing Thin Bilayer Electrlyte, J. Electrchem. Sc., 144 130-32 (1997). 6. P. K. Srivastava, T. Quach, Y. Y. Duan, R. Dnelsn, S. P. Jiang, F. T. Ciacch, and S. P. S. Badwal, Electrde Supprted Slid Oxide Fuel Cells: Electrlyte Films Prepared by DC Magnetrn Sputtering, Slid State Inics, 99 311-19 (1997). 7. K. Huang, M. Feng, and J. B. Gdenugh, Synthesis and Electrical Prperties f Dense Ce 0.9 Gd 0.1 O 1.95 Ceramics, J. Am. Ceram. Sc., 81 357-62 (1998). 8. T. T. Sai and S. A. Barnett, Bias Sputter Depsitin f Dense Yttria-Stabilized Zircnia Films n Prus Substrates, J. Electrchem. Sc., 142 3084-87 (1995). 9. T. S. Zhang, J. Ma, L. B. Kng, P. Hing, and J. A. Kilner, Reparatin and Mechanical Prperties f Dense Ce 0.8 Gd 0.2 O 2-δ Ceramics, Slid State Inics, 167 191-96 (2004). 10. K. Higashi, K. Snda, H. On, S. Sameshima, and Y. Hrata, Synthesis and Sintering f Rare-Earth-Dped Ceria Pwder by Oxalate Cprecipitatin Methd, J. Mater. Res., 14 957-67 (1999). 11. K. Yamashita, K. V. Ramanujachary, and M. Greenblatt, Hydrthermal Synthesis and Lw Temperature Cnductin Prperties f Substituted Ceria Ceramics, Slid State Inics, 81 53-60 (1995). 12. C. Keinlgel and L. J. Gauckler, Sintering and Prperties f Nansized Ceria Slid Slutins, Slid State Inics, 135 567-73 (2000). 13. C. Keinlgel and L. J. Gauckler, Sintering f Nancrystalline CeO 2 Ceramics, Adv. Mater., 13 1081-85 (2001). 14. D. P. Fagg, J. C. C. Abrantes, D. Pérez-Cll, P. Núñez, V. V. Khartn, and J. R. Frade, The Effect f Cbalt Oxide Sintering Aid n Electrnic Transprt in Ce 0.8 Gd 0.2 O 2-δ Elec- w wz
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