Skip to main content
U.S. Department of Energy
Office of Scientific and Technical Information

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.

Sponsoring Organization:
USDOE
OSTI ID:
1619624
Alternate ID(s):
OSTI ID: 1542823
Journal Information:
npj Computational Materials, Journal Name: npj Computational Materials Journal Issue: 1 Vol. 5; ISSN 2057-3960
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United Kingdom
Language:
English

References (42)

Fast-Ion Conducting Y2(Zr Ti1-)2O7 Pyrochlores: Neutron Rietveld Analysis of Disorder Induced by Zr Substitution journal June 1995
Oxygen ion conduction and structural disorder in conductive oxides journal December 1994
Generalized cluster description of multicomponent systems journal November 1984
Cluster Approach to Order-Disorder Transformations in Alloys book January 1994
Interpreting oxygen vacancy migration mechanisms in oxides using the layered structure motif journal June 2015
MPInterfaces: A Materials Project based Python tool for high-throughput computational screening of interfacial systems journal September 2016
The effect of homovalent A-site substitutions on the ionic conductivity of pyrochlore-type Gd2Zr2O7 journal January 2009
The pyrochlore to ‘defect fluorite’ transition in the Y2(ZryTi1−y)2O7 system and its underlying crystal chemistry journal December 2004
Order in the disordered state: local structural entities in the fast ion conductor Ba2In2O5 journal January 2005
Linking the electronic structure of solids to their thermodynamic and kinetic properties journal March 2010
A2B′B″O6 perovskites: A review journal May 2015
Effect of Cation Ordering on Oxygen Vacancy Diffusion Pathways in Double Perovskites journal July 2015
Phase Composition and Disorder in La 2 (Sn,Ti) 2 O 7 Ceramics: New Insights from NMR Crystallography journal September 2016
Pyrochlore to Fluorite Transition: The Y 2 (Ti 1– x Zr x ) 2 O 7 (0.0 ≤ x ≤ 1.0) System journal November 2012
Spectroscopic Investigations of the Structural Phase Transition in Gd 2 (Ti 1 - y Zr y ) 2 O 7 Pyrochlores journal May 2002
Gradual Structural Evolution from Pyrochlore to Defect-Fluorite in Y 2 Sn 2– x Zr x O 7 : Average vs Local Structure journal December 2013
Cation Disorder in Pyrochlore Ceramics: 89 Y MAS NMR and First-Principles Calculations journal October 2009
Entropy-stabilized oxides journal September 2015
Cation ordering in perovskites journal January 2010
Large ferroelectric polarization in the new double perovskite NaLaMnWO6 induced by non-polar instabilities journal January 2011
The pyrochlore to defect fluorite phase transition in Y2Sn2−xZrxO7 journal January 2013
Atomic Radii in Crystals journal November 1964
Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl 6 journal March 2015
Electronic and ionic transport properties and other physical aspects of perovskites journal September 2004
Double perovskites with ferromagnetism above room temperature journal December 2006
Plane Nets in Crystal Chemistry journal February 1980
Special points for Brillouin-zone integrations journal June 1976
Effective cluster interactions from cluster-variation formalism. I journal September 1991
Projector augmented-wave method journal December 1994
Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set journal October 1996
From ultrasoft pseudopotentials to the projector augmented-wave method journal January 1999
Influence of thermally induced oxygen order on mobile ion dynamics in Gd 2 ( Ti 0.65 Zr 0.35 ) 2 O 7 journal May 2007
Cluster expansion and the configurational theory of alloys journal June 2010
Thermodynamics of the Zr-O system from first-principles calculations journal September 2013
Finite-temperature properties of strongly anharmonic and mechanically unstable crystal phases from first principles journal December 2013
Generalized Gradient Approximation Made Simple journal October 1996
Ordered double perovskites – a group-theoretical analysis journal July 2003
Thermodynamics of Ferroelectric Solid Solutions with Morphotropic Phase Boundaries journal May 2014
A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles journal October 2011
Radiation Tolerance of Complex Oxides journal August 2000
Crystal Chemistry of Complex Perovskites: New Cation-Ordered Dielectric Oxides journal August 2008
Structural modifications of Gd 2 Zr 2- x Ti x O 7 pyrochlore induced by swift heavy ions: Disordering and amorphization journal April 2009

Similar Records

The impact of chemical order on defect transport in mixed pyrochlores
Journal Article · Mon Feb 18 23:00:00 EST 2019 · Physical Chemistry Chemical Physics. PCCP · OSTI ID:1499367

Related Subjects