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Received April 16, 2004
Accepted July 7, 2004
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Formation of La2Ti2O7 Crystals from Amorphous La2O3-Tio2 Powders Synthexized by the Polymerized Complex Method
Department of Chemical Engineering/Institute of Environmental and Energy Technology, Pohang University of Science and Technology (POSTECH), San 31 Hyoja-dong, Pohang 790-784, Korea
jlee@postech.ac.kr
Korean Journal of Chemical Engineering, September 2004, 21(5), 970-975(6), 10.1007/BF02705579
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Abstract
Amorphous La2O-TiO2 powders were synthesized by the polymerized complex (PC) method. The activa-tion energies for crystallization and grain growth of La2Ti2O7 from these precursors were determined from results of XRD and DTA and compared with those for La2Ti2O7 precursors by the conventional solid-state reaction (SSR). Activation energy of grain growth of La2Ti2O7 in PC-sample was determined to be 7.1 kJ/mol while that of SSR sample was 14.8 kJ/mol. The energy required for the phase transformation from amorphous PC sample to layered perovskite was 432 kJ/mol. while the SSR sample did not show this transition below 900℃. It was clearly demonstrated that the La2Ti2O7 crystals were formed at a lower temperature and they grew in size faster in the sample prepared by the PC method relative to the sample prepared by the SSR method. Mixing of elements in molecular level in PC preparation appeared responsible for these differences.
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References
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Ikeda S, Hara M, Kondo JN, Domen K, Chem. Mater., 10, 72 (1998)
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Inoue Y, Kubokawa T, Sato K, J. Phys. Chem., 95, 4059 (1994)
Ismagilov ZR, Kerzhentsev MA, Sazonov VA, Tsykoza LT, Shikina NV, Kuznetsov VV, Ushakov VA, Mishanin SV, Kozhukhar NG, Russo G, Deutschmann O, Korean J. Chem. Eng., 20(3), 461 (2003)
Jarcho M, Bolen Ch, Doremus RH, J. Mater. Sci., 11, 2027 (1976)
Kakihana M, Yoshimura M, Ball Chem. Soc. Jpn., 72(7), 1427 (1999)
Kim HG, Hwang DW, Kim J, Kim YG, Lee JS, Chem. Commun., 1077 (1999)
Kim HG, Hwang DW, Bae SW, Jung JH, Lee JS, Catal. Lett., 91, 193 (2003)
Kissinger HE, J. Res. Natl. Bur: Stand. (US), 57, 217 (1956)
Kudo A, Kato H, Chem. Lett., 867 (1997)
Moon DJ, Ryu JW, Lee SD, Ahn BS, Korean J. Chem. Eng., 19(6), 921 (2002)
Reddy VR, Hwang DW, Lee JS, Korean J. Chem. Eng., 20(6), 1026 (2003)
Redhead PA, Vacuum, 12, 203 (1962)
Yang TH, Park GG, Pugazhendhi P, Lee WY, Kim CS, Korean J. Chem. Eng., 19(3), 417 (2002)
