Document Type

Article

Publication Date

7-2-2018

Publication Title

Inorganic Chemistry

Volume

57

Issue

24

First page number:

15051

Last page number:

15061

Abstract

Natural specimens of the pyrochlore (A2B2O7) compounds have been found to retain foreign actinide impurities within their parent framework, undergoing metamictization to a fully amorphous state. The response to radionuclide decay identifies pyrochlore systems with having high radiation tolerance and tailored use in radioactive waste applications and radionuclide sequestration. High pressure is a powerful pathway to high density states and amorphization with parallels to radiation-induced processes. Here, La2Sn2O7 is evaluated under extreme conditions via the combination of laser heating in a diamond anvil cell with X-ray diffraction and Raman spectroscopy. The measurements are supported by ab initio random structure searching and molecular dynamics calculations. A new ground state at 70 GPa is revealed, and high temperature annealing is fundamental to access its crystalline ground state and fully determine the structure. This crystalline phase (P21/c) retains its structural integrity during decompression and is fully recoverable to ambient conditions. The final state of the system is shown to be highly pathway dependent due to the covalent nature of the Sn–O bonding. The Tc pyrochlore, La2Tc2O7, is analyzed for similarities in the bonding to determine the likelihood of an analogous pathway dependency to a final state.

Disciplines

Inorganic Chemistry

File Format

PDF

File Size

641 KB

Language

English

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Download

UNLV article access

Search your library

Share

COinS