Browse > Article

Study on Phase Relation and Synthesis of Pyrochlore in the System of Ca-Ce-Zr-Ti-O  

Chae Soo-Chun (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Bae In-Kook (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Jang Young-Nam (Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources)
Yudintsev S.V. (Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry)
Publication Information
Economic and Environmental Geology / v.37, no.6, 2004 , pp. 603-612 More about this Journal
Abstract
Pyrochlore is known as one of the most promising materials for the immobilization of radionuclide in high level waste. This study included the synthesis, phase relation and characteristics of $pyrochlore(CaCeZr_xTi_{2-x}O_{7,\;x=0.2\~2.0)$ in the system of Ca-Ce-Zr-Ti-O. Using the CPS(Cold pressing and sintering) method, the mixtures of $CaCO3_,\;CeO_2,\;ZrO_2\;and\;TiO_2$ oxides were pressed, and sintered at $1100\~1600^{\circ}C$ for 20 hours. The optimal synthetic conditions at various compositions were differed from 1300 to $1600^{\circ}C$ Even in the optimal temperatures, pyrochlore or fluorite coexisted with minor amount of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$. It was confirmed that pyrochlore and fluorite structures were stable at $x\leq0.6\;and\;x\geq1.0$, respectively. Especially, the compositions of pyrochlore or fluorite showed non-stoichiometric compositions in that contents of Ca and Ti were more deficient and those of Zr and Ce were more excess than batch compositions with the increase of x value. These characteristics stemmed from the behavior of elements occupied at eight- and six-coordinated site, and then caused the coexistence of perovskite, $CeO_2\;or\;Ce_{0.75}Zr_{0.25}O_2$ along with pyrochlore or fluorite.
Keywords
pyrochlore; perovskite; immobilization; sintering; Synroc;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Begg, B.D., Hess, N.J" McCready, D.E., Thevuthasan, S.,and Weber, w.J, (2001a) Heavy-ion irradiation effectsin Gdz(Tiz.xZrJ07 pryochlore. J, Nuc!. Mat., v. 289, p.188-193.
2 Ringwood AE. (1985) Disposal of high-level nuclearwaste: a geological perspective. Mineralogical Magazine,v. 49, Pt. 2, p. 159-176.
3 Yamamura, H., Nishino, H., Kakinuma, K, and Nomura,K (2003) Electrical conductivity anomaly around fluorite-pyrochlore phase boundary. Solid State Ionics, v.158, p. 359-365.
4 Begg, B.D., Hess, N.J" Weber, WJ., Devanathan, R., Icenhower,J.P., Thevuthasan, S., and McGrail, B.P.(2001b) Heavy-ion irradiation effects on structuresand acid dissolution of pyrochlore. J. Nucl. Mat., v.228, p. 208-216.
5 Weber, w.j. and Ewing, RC. (2000) Plutonium immobilizationand radiation effects. Science, v. 289, p.2051-2052.
6 Vance E.R., Begg B.D., Day RA, and Ball C.J, (1995) Zirconolite-rich ceramics for actinide wastes. In: ScientificBasis for Nuclear Waste Management-XVIII.MRS Symposia Proceedings, v. 353, Pt. 2, p. 767-774.
7 Ringwood, A.E., Kesson, S.E., Reeve, KD., Woolfrey,J,L., and Ramm, E.J. (1988) Radioactive waste formsfor the future. Edited by W. Lutze and Ewing, RC.,Elsev., Arnst., 233p.
8 Teterin, Yu. A., Stefanovskii, sv. Yudintsev, S.v., BekUzarov,G.N., Tetrerin, A.Yu., Maslakov, KL, andUtkin, 1.0. (2004) X-ray photoelectron study of calciumcerium titanate ceramics. Russian [orunal ofInorganic Chemistry, v. 49, p. 87-94.
9 Laverov, N.P., Yudintsev, S.v., Stefanovsky, S.v., and jang,Y.N., Lapina, M.L, Sivtsov, AV., and Ewing, RC.(2002) Phase transformations during synthesis ofactinide matrices, Doklady of the Russian Academy ofSciences, 385A, v. 6, p. 671-675.
10 Wang, J" Nakamura, A., and Takeda, M. (2003) Structuralproperties of the fluorite- and pyrochlore-type compoundsin the Gdz03-ZrOz system xGd01.5_(1_xlZrOZwith 0.18~~0.62. Solid State Ionies, v. 164, p. 185191.
11 Kulkarni, N.K., Sampath, S. and Venugopal, V. (2000)Preparation and characterisation of Pu-pyrochlore:[Lal_xPuxjzZrZ07 (x=O-I). J. Nuc!. Mat., v. 281, p. 248250.
12 Laverov, N.P., Yudintsev, S.v., Stefanovsky, S.v., and jang,Y.N. (2001) New actinide matrix with pyrochlorestructure. Doklady of the Russian Academy of Sciences,381A, v. 9, p. 1053-1056.
13 Luo S., Zhu X., and Tang B. (1998) Actinides containmentby using zirconolite-rich Synroc. In: Proceedings ofInternational Meeting on Nuclear and HazardousWaste Management (Spectrum 98), ArnericanNuclear Society, La Grange Park, IL, p. 829-833.
14 Sobolev, LA, Stefanovsky, S.v. and Lifanov, EA (1995)Synthetic melted rock-type wasteforms. MRS Sympo,Proc. v. 353, p. 833-840.
15 채수천, 배인국, 장영남, Yudintsev, S.V. (2004) Gd-Ti-O계 및 Gd-Zr-O계에서의 파이로클로어 합성연구. 자원환경지질, 37권, p. 303-309.
16 Feighery, A.J" Irvine, J.T.S., and Zheng, S. (2001) Phaserelation at 1500°C in the ternary system ZrOz-Gdz03'no, J, Solid State Chern., v. 160, p. 302-306.