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Title: Distortion-stabilized ordered structures in A2BB’O7 mixed pyrochlores

Journal Article · · npj Computational Materials

Abstract Pyrochlore oxides (A 2 B 2 O 7 ) are interesting for a number of technological applications, including radiation damage tolerance and as ionic conductors. Mixed pyrochlores—containing two A and/or two B site cations—provide even more flexibility for tailoring properties owing to the diverse chemical and configurational degrees of freedom accessible within this chemical space. Here, we examine relative stability of different cation orderings in one model double pyrochlore Gd 2 (Zr x Ti 1− x ) 2 O 7 , as a function of Zr content x . Our results show that, in the presence of some very specific local cation arrangements, certain cation-ordered compositions in this system are highly stabilized as a result of large oxygen relaxation displacements, leading to the formation of an ordered ‘double’ pyrochlore structure. The origins of these anomalous oxygen relaxations are traced back to both the local cation symmetry and a strong chemical preference of Zr atoms towards adopting a 7-fold coordination environment, as opposed to a 6-fold coordination available in a regular pyrochlore structure. Subsequently, we examine the stability of this type of ordering in 131 other pyrochlore compositions. Implications of our findings are discussed in relation to the observed composition-dependent ionic conductivity in these systems and connections with previously reported experimental findings are made.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
89233218CNA000001
OSTI ID:
1619624
Alternate ID(s):
OSTI ID: 1542823
Report Number(s):
LA-UR-18-26270; 7; PII: 144
Journal Information:
npj Computational Materials, Journal Name: npj Computational Materials Vol. 5 Journal Issue: 1; ISSN 2057-3960
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United Kingdom
Language:
English
Citation Metrics:
Cited by: 15 works
Citation information provided by
Web of Science

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Figures / Tables (7)