Ion Irradiation of Ternary Pyrochlore Oxides

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• 作者：Gregory R. Lumpkin ; Katherine L. Smith ; Mark G. Blackford ; Karl R. Whittle ; Elizabeth J. Harvey ; Simon A. T. Redfern ; Nestor J. Zaluzec
• 刊名：Chemistry of Materials
• 出版年：2009
• 出版时间：July 14, 2009
• 年：2009
• 卷：21
• 期：13
• 页码：2746-2754
• 全文大小：887K
• 年卷期：v.21,no.13(July 14, 2009)
• ISSN：1520-5002

文摘

Polycrystalline synthetic samples of Y₂Ti_2−xSn_xO₇ with x = 0.4, 0.8, 1.2, and 1.6, together with Nd₂Zr₂O₇, Nd₂Zr_1.2Ti_0.8O₇, and La_1.6Y_0.4Hf₂O₇, were irradiated in situ in the intermediate voltage electron microscope (IVEM)-Tandem Facility at Argonne National Laboratory using 1.0 MeV Kr ions at temperatures of 50 to 650 K. Determination of the critical amorphization fluence (F_c) as a function of temperature has revealed a dramatic increase in radiation tolerance with increasing Sn content on the pyrochlore B site. Nonlinear least-squares analysis of the fluence-temperature curves gave critical temperatures (T_c) of 666 ± 4, 335 ± 12, and 251 ± 51 K for the Y₂Ti_2−xSn_xO₇ samples with x = 0.4, 0.8, and 1.2, respectively. The sample with x = 1.6 appears to disorder to a defect fluorite structure at a fluence below 1.25 × 10¹⁵ ions cm⁻² and remains crystalline to 5 × 10¹⁵ ions cm⁻² at 50 K. Additionally, the critical fluence-temperature response curves were determined for Nd₂Zr_1.2Ti_0.8O₇ and La_1.6Y_0.4Hf₂O₇, and we obtained T_c values of 685 ± 53 K and 473 ± 52 K, respectively, for these pyrochlores. Nd₂Zr₂O₇ did not become amorphous after a fluence of 2.5 × 10¹⁵ ions cm⁻² at 50 K, but there is evidence that it may amorphize at a higher fluence, with an estimated T_c of 135 K. The observed T_c results are discussed with respect to the predicted T_c values based upon a previously published empirical model (Lumpkin, G. R.; Pruneda, M.; Rios, S.; Smith, K. L.; Trachenko, K.; Whittle, K. R.; Zaluzec, N. J. J. Solid State Chem. 2007, 180, 1512). In the Y₂Ti_2−xSn_xO₇ pyrochlores, T_c appears to be linear with respect to composition, and is linear with respect to r_A/r_B and x(48f) for all samples investigated herein.