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Title: Thermodynamics of radiation induced amorphization and thermal annealing of Dy 2Sn 2O 7 pyrochlore

Thermodynamics and annealing behavior of swift heavy ion amorphized Dy 2Sn 2O 7 pyrochlore were studied. Its amorphization enthalpy, defined as the total energetic difference between the irradiation amorphized and undamaged Dy 2Sn 2O 7 states, was determined to be 283.6 ± 6.5 kJ/mol by high temperature oxide melt drop solution calorimetry. It has been an enigma that stannate and some other pyrochlores do not follow the general r A/r B-radiation resistance relation seen in most pyrochlore systems. In this paper, we use the amorphization enthalpy, which reflects all the complex chemical and structural characteristics, as a more effective parameter to correlate the radiation damage resistance of pyrochlores with their compositions. It successfully explains the superior radiation damage resistance of the stannate pyrochlores compared with titanate pyrochlores. Differential scanning calorimetry (DSC) reveals a strong exothermic event starting at 978 K, which is attributed to long-range recrystallization based on X-ray diffraction (XRD) analysis, similar to the effect previously observed in Dy 2Ti 2O 7. A second pronounced heat event beginning at ~1148 K, which results from local structural rearrangement, is clearly decoupled from the first event for irradiated Dy 2Sn 2O 7. Both the heat releases measured by DSC on heatingmore » to 1023 and 1473 K, and the excess enthalpies of the annealed samples indicate that the recovery to the original, ordered state was not fully achieved up to even 1473 K, despite XRD showing the apparent restoration of crystalline pyrochlore structure. The remaining metastability may be attributed to local disorder in the form of weberite-like short-range domains in the recrystallized material. Intriguingly, the second event for different pyrochlores generally starts at similar temperatures while the onset of the long range recrystallization is compositionally dependent. Finally, the amorphization and thermal annealing behavior observed in irradiated Dy 2Sn 2O 7 may provide insights into the general mechanisms of radiation damage and recovery of pyrochlores relevant to their nuclear applications.« less
Authors:
 [1] ;  [2] ;  [3] ; ORCiD logo [4]
  1. Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab. Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Nuclear Engineering
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab. Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU)
Publication Date:
Report Number(s):
LA-UR-18-22912
Journal ID: ISSN 1359-6454
Grant/Contract Number:
AC52-06NA25396; SC0001089
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 155; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); LANL Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; pyrochlore; irradiation effect; amorphization; annealing; calorimetry
OSTI Identifier:
1457279

Chung, Cheng-Kai, Lang, Maik, Xu, Hongwu, and Navrotsky, Alexandra. Thermodynamics of radiation induced amorphization and thermal annealing of Dy2Sn2O7 pyrochlore. United States: N. p., Web. doi:10.1016/j.actamat.2018.06.003.
Chung, Cheng-Kai, Lang, Maik, Xu, Hongwu, & Navrotsky, Alexandra. Thermodynamics of radiation induced amorphization and thermal annealing of Dy2Sn2O7 pyrochlore. United States. doi:10.1016/j.actamat.2018.06.003.
Chung, Cheng-Kai, Lang, Maik, Xu, Hongwu, and Navrotsky, Alexandra. 2018. "Thermodynamics of radiation induced amorphization and thermal annealing of Dy2Sn2O7 pyrochlore". United States. doi:10.1016/j.actamat.2018.06.003.
@article{osti_1457279,
title = {Thermodynamics of radiation induced amorphization and thermal annealing of Dy2Sn2O7 pyrochlore},
author = {Chung, Cheng-Kai and Lang, Maik and Xu, Hongwu and Navrotsky, Alexandra},
abstractNote = {Thermodynamics and annealing behavior of swift heavy ion amorphized Dy2Sn2O7 pyrochlore were studied. Its amorphization enthalpy, defined as the total energetic difference between the irradiation amorphized and undamaged Dy2Sn2O7 states, was determined to be 283.6 ± 6.5 kJ/mol by high temperature oxide melt drop solution calorimetry. It has been an enigma that stannate and some other pyrochlores do not follow the general rA/rB-radiation resistance relation seen in most pyrochlore systems. In this paper, we use the amorphization enthalpy, which reflects all the complex chemical and structural characteristics, as a more effective parameter to correlate the radiation damage resistance of pyrochlores with their compositions. It successfully explains the superior radiation damage resistance of the stannate pyrochlores compared with titanate pyrochlores. Differential scanning calorimetry (DSC) reveals a strong exothermic event starting at 978 K, which is attributed to long-range recrystallization based on X-ray diffraction (XRD) analysis, similar to the effect previously observed in Dy2Ti2O7. A second pronounced heat event beginning at ~1148 K, which results from local structural rearrangement, is clearly decoupled from the first event for irradiated Dy2Sn2O7. Both the heat releases measured by DSC on heating to 1023 and 1473 K, and the excess enthalpies of the annealed samples indicate that the recovery to the original, ordered state was not fully achieved up to even 1473 K, despite XRD showing the apparent restoration of crystalline pyrochlore structure. The remaining metastability may be attributed to local disorder in the form of weberite-like short-range domains in the recrystallized material. Intriguingly, the second event for different pyrochlores generally starts at similar temperatures while the onset of the long range recrystallization is compositionally dependent. Finally, the amorphization and thermal annealing behavior observed in irradiated Dy2Sn2O7 may provide insights into the general mechanisms of radiation damage and recovery of pyrochlores relevant to their nuclear applications.},
doi = {10.1016/j.actamat.2018.06.003},
journal = {Acta Materialia},
number = ,
volume = 155,
place = {United States},
year = {2018},
month = {6}
}