Crystal structure stability of simulated Sr_1–1.5xY _xTiO₃ (x = 0–0.12) waste forms

Abstract

A series of Sr_1–1.5xY _xTiO₃ (x = 0–12) solid solutions were synthesized by a solid state reaction process. The effects of reaction temperature and dopant on the crystallinity, microstructure and morphology of Sr_1–1.5xY _xTiO₃ (x=0–0.12) were investigated. Pure and single-phase perovskite-type Sr_1–1.5xY _xTiO₃ (x<0.08) solid solutions were obtained at 1 400 °C for 6 h. The perovskite-type SrTiO₃ and pyrochlore-phase Y₂Ti₂O₇ coexisted for x = 0.08–0.12, leading to an unstable and unfavourable solid solution structure for long-term immobilization of the ⁹⁰Sr. The X-ray diffraction patterns for Rietveld refinement analysis confirmed the formation of a Sr_1–1.5xY _xTiO₃ (x = 0–0.12) continuous solid solution. Stretching and bending vibrations were assigned in the infrared region. The SrTiO₃ grain size increased with Y content. The leaching behavior of Y³⁺ from the waste forms of Sr_1–1.5xY _xTiO₃ was controlled by its structural change.

Keywords

perovskite-type / SrTiO₃ / phase transition / temperature / leaching behavior

References

[1] Donald LW, Metcalfe B L, J Taylor R N. The Immobilization of High Level Radioactive Wastes Using Ceramics and Glasses[J]. J. Mater. Sci., 1997, 32: 5851-5887.

[2] Nakayama S, Takahashi N, Itoh K. Leaching Property of Cesium Immobilized by Zirconium Phosphate under High Temperature[J]. J. Mater. Sci.Lett., 2001, 20: 513-518.

[3] Itoh K, Nakayama S. Immobilization of Cesium by Crystalline Zirconium Phosphate[J]. J. Mater. Sci., 37: 1701–1709

[4] Itoh K, Nakayama S. Immobilization of Stronium by Crystalline Zirconium Phosphate[J]. J. Euro. Ceram. Soc., 2003, 23: 1047-1053.

[5] Yamasaki N, Yanagiswa K, Kanahara S, et al. Production of Hydroxyapatite-glass Compacts by Hydrothermal Hot-pressing Technique[J]. J.Nucl. Sci. Technol., 1984, 21: 71-78.

[6] Tsunoda N. Immobilization of Barium, Cadmium and Antimony over Titania[J]. Ceram. Jpn, 1977, 12: 913-918.

[7] Fujiki Y, Komatsu Y U, Yogyo KS. Immonilization of Divalent Transition Metals from Aqueous Solutions Using Crystalline Hydrated Titania fibers[J]. J. Mater. Sci., 1985, 93: 225-231.

[8] Bhattacharyya D K, Dutta N C. A Study of the Immobilization of Strontium over Crystalline Titania[J]. J. Mater. Sci., 1995, 27: 5948-5952.

[9] Bhattacharyya D K, Dutta N C. Immobilization of Barium, Cadmium and Antimony Cations over Zirconia[J]. J. Nucl. Sci. Technol., 1991, 28: 1014-1020.

[10] Hungría T, Castro A. Grain Growth Control in NaNbO₃-SrTiO₃ Ceramics by Mechanosynthesis and Spark Plasma Sintering[J]. J. Mater. Synth. Proc., 2000 8

[11] Xu H W, Navrotsky A, Su Y L, et al. Perovskite Solid Solutions along the NaNbO₃-SrTiO₃ John: Phase Transitions, Formation Enthapies and Implications for General Perovskite Energetics[J]. J. Mater. Sci.Lett., 2005, 17: 1880-1886.

[12] Sasaki T, Komatsu U Y, Fujiki Y. Strontium Immobilization by Fibrous Cerium(IV) Bis(monohydrogenphosphate) Under Hydrothermal Conditions[J]. Bulletin of the Chemical Society of Japan, 1997, 70: 1701-1708.

[13] Hungra T, Alguero M, Hungra A B. Fine-Grained Ba_1-xSr_xTiO₃ Ceramics Prepared by the Combination of Mechanosynthesized Nnanopowders and Spark Plasma Sintering[J]. Chem. Mater., 2005, 17(24): 6205-6212.

[14] Boldyrev V V, Tkacova K. Mechanochemistry of Solids: Past, Present, and Prospects[J]. J. Mater. Synth. Proc., 2000, 8: 121-132.

[15] Ewing R C, Weber W J, Lian J. Nuclear Waste Disposal-Pyrochlore (A2B₂O₇): Nuclear Waste Form for the Immobilization of Plutonium and “Minor” Actinides[J]. J. Appl. Phys., 2004, 95: 5949-5971.

[16] Wang S X, Begg B D, Wang L M, et al. Radiation Stability of Gadolinium Zirconate: A Waste Form for Plutonium Disposal[J]. J. Mater. Res., 1999, 14: 4470-4473.

[17] Weber WJ, Ewing RC, Catlow CRA, et al. Radiation Efects in Crystalline Ceramics for the Immobilization of High-level Nuclear Waste and Plutonium Disposal[J]. J. Mater. Res., 1998, 13: 1434-1484.

[18] Weber W J, Ewing R C. Plutonium Immobilization and Radiation Effects[J]. Science, 2000, 289: 2051-2052.

[19] Donald IW, Metcalfe BL, Taylor RNJ. The Immobilization of High-Level Wastes Using Ceramics and Glasses[J]. J. Mater. Sci., 1997, 32: 5851-5887.

[20] Terra O, Clavier N, Dacheux N, et al. Preparation of Optimized Uranium and Thorium Bearing Brabantite or Monazite/Brabantite Solid Solutions[J]. J. Am. Ceram. Soc., 2008, 91(11): 3673-3682.

[21] Clarke DR. Ceramic Materials for Immobilization of Nuclear Waste[J]. Ann. Rev. Mater. Sci., 1983, 13: 191-218.