Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Probing disorder in isometric pyrochlore and related complex oxides


There has been an increased focus on understanding the energetics of structures with unconventional ordering (for example, correlated disorder that is heterogeneous across different length scales1). In particular, compounds with the isometric pyrochlore structure2, A2B2O7, can adopt a disordered, isometric fluorite-type structure, (A, B)4O7, under extreme conditions3,4,5,6,7. Despite the importance of the disordering process there exists only a limited understanding of the role of local ordering on the energy landscape. We have used neutron total scattering to show that disordered fluorite (induced intrinsically by composition/stoichiometry or at far-from-equilibrium conditions produced by high-energy radiation) consists of a local orthorhombic structural unit that is repeated by a pseudo-translational symmetry, such that orthorhombic and isometric arrays coexist at different length scales. We also show that inversion in isometric spinel occurs by a similar process. This insight provides a new basis for understanding order-to-disorder transformations important for applications such as plutonium immobilization4, fast ion conduction8, and thermal barrier coatings9,10.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Neutron PDFs and structural models for ordered (Ho2Ti2O7) and disordered (Ho2Zr2O7) pyrochlore.
Figure 2: Neutron powder diffraction pattern (open circles) of Ho2Zr2O7 refined with the isometric disordered fluorite structure (solid red line).
Figure 3: Comparison of neutron PDFs (open circles) for intrinsically and extrinsically disordered pyrochlores.
Figure 4: Neutron PDFs and structural models for normal (MgAl2O4) and inverse (NiAl2O4) spinel.


  1. 1

    Keen, D. A. & Goodwin, A. L. The crystallography of correlated disorder. Nature 521, 303–309 (2015).

    CAS  Article  Google Scholar 

  2. 2

    Subramanian, M. A., Aravamudan, G. & Rao, G. V. S. Oxide pyrochlores—a review. Prog. Solid State Chem. 15, 55–143 (1983).

    CAS  Article  Google Scholar 

  3. 3

    Sickafus, K. E. et al. Radiation tolerance of complex oxides. Science 289, 748–751 (2000).

    CAS  Article  Google Scholar 

  4. 4

    Ewing, R. C., Weber, W. J. & Lian, J. Nuclear waste disposal-pyrochlore (A2B2O7): nuclear waste form for the immobilization of plutonium and “minor” actinides. J. Appl. Phys. 95, 5949–5971 (2004).

    CAS  Article  Google Scholar 

  5. 5

    Sickafus, K. E. et al. Radiation-induced amorphization resistance and radiation tolerance in structurally related oxides. Nature Mater. 6, 217–223 (2007).

    CAS  Article  Google Scholar 

  6. 6

    Zhang, F. X. et al. Phase stability and pressure dependence of defect formation in Gd2Ti2O7 and Gd2Zr2O7 pyrochlores. Phys. Rev. Lett. 100, 045503 (2008).

    CAS  Article  Google Scholar 

  7. 7

    Zhang, F. X., Lang, M., Liu, Z. & Ewing, R. C. Pressure-induced disordering and anomalous lattice expansion in La2Zr2O7 pyrochlore. Phys. Rev. Lett. 105, 015503 (2010).

    CAS  Article  Google Scholar 

  8. 8

    Wuensch, B. J. et al. Connection between oxygen-ion conductivity of pyrochlore fuel-cell materials and structural change with composition and temperature. Solid State Ion. 129, 111–133 (2000).

    CAS  Article  Google Scholar 

  9. 9

    Padture, N. P., Gell, M. & Jordan, E. H. Thermal barrier coatings for gas-turbine engine applications. Science 296, 280–284 (2002).

    CAS  Article  Google Scholar 

  10. 10

    Wu, J. et al. Low-thermal-conductivity rare-earth zirconates for potential thermal-barrier-coating applications. J. Am. Ceram. Soc. 85, 3031–3035 (2002).

    CAS  Article  Google Scholar 

  11. 11

    Castro Neto, A. H., Guinea, F., Peres, N. M. R., Novoselov, K. S. & Geim, A. K. The electronic properties of graphene. Rev. Mod. Phys. 81, 109–162 (2009).

    CAS  Article  Google Scholar 

  12. 12

    Hsieh, P. et al. Photon transport enhanced by transverse Anderson localization in disordered superlattices. Nature Phys. 11, 268–274 (2015).

    CAS  Article  Google Scholar 

  13. 13

    Civale, L. et al. Vortex confinement by columnar defects in YBa2Cu3O7 crystals—enhanced pinning at high fields and temperatures. Phys. Rev. Lett. 67, 648–651 (1991).

    CAS  Article  Google Scholar 

  14. 14

    Biswas, K. et al. High-performance bulk thermoelectrics with all-scale hierarchical architectures. Nature 489, 414–418 (2012).

    CAS  Article  Google Scholar 

  15. 15

    Oh, S. H., Black, R., Pomerantseva, E., Lee, J.-H. & Nazar, L. F. Synthesis of a metallic mesoporous pyrochlore as a catalyst for lithium-O2 batteries. Nature Chem. 4, 1004–1010 (2012).

    CAS  Article  Google Scholar 

  16. 16

    Rooksby, H. P. & White, E. A. D. Rare-earth niobates and tantalates of defect fluorite-type and weberite-type structures. J. Am. Ceram. Soc. 47, 94–96 (1964).

    CAS  Article  Google Scholar 

  17. 17

    Li, Y. et al. Defect formation energies in A2B2O7 pyrochlores. Scr. Mater. 107, 18–21 (2015).

    CAS  Article  Google Scholar 

  18. 18

    Lian, J. et al. Effect of structure and thermodynamic stability on the response of lanthanide stannate-pyrochlores to ion beam irradiation. J. Phys. Chem. B 110, 2343–2350 (2006).

    CAS  Article  Google Scholar 

  19. 19

    Norberg, S. T. et al. Pyrochlore to fluorite transition: the Y2(Ti1−xZrx)2O7 (0.0 ≤ x ≤ 1.0) system. Chem. Mater. 24, 4294–4300 (2012).

    CAS  Article  Google Scholar 

  20. 20

    Blanchard, P. E. R. et al. Does local disorder occur in the pyrochlore zirconates? Inorg. Chem. 51, 13237–13244 (2012).

    CAS  Article  Google Scholar 

  21. 21

    Sanjuan, M. L. et al. Raman and X-ray absorption spectroscopy study of the phase evolution induced by mechanical milling and thermal treatments in R2Ti2O7 pyrochlores. Phys. Rev. B 84, 104207 (2011).

    Article  Google Scholar 

  22. 22

    King, G., Thompson, C. M., Greedan, J. E. & Llobet, A. Local structure of the vacancy disordered fluorite Yb3TaO7 from neutron total scattering. J. Mater. Chem. A 1, 10487–10494 (2013).

    CAS  Article  Google Scholar 

  23. 23

    Walker, J. D. S., Hayes, J. R., Gaultois, M. W., Aluri, E. R. & Grosvenor, A. P. A case for oxygen deficiency in Gd2Ti2−xZrxO7 pyrochlore-type oxides. J. Alloys Compd. 565, 44–49 (2013).

    CAS  Article  Google Scholar 

  24. 24

    Jiang, C., Stanek, C. R., Sickafus, K. E. & Uberuaga, B. P. First-principles prediction of disordering tendencies in pyrochlore oxides. Phys. Rev. B 79, 104203 (2009).

    Article  Google Scholar 

  25. 25

    Verwey, E. J. W. & Heilmann, E. L. Physical properties and cation arrangement of oxides with spinel structures I. Cation arrangement in spinels. J. Chem. Phys. 15, 174–180 (1947).

    CAS  Article  Google Scholar 

  26. 26

    Sickafus, K. E. et al. Cation disorder in high-dose, neutron-irradiated spinel. J. Nucl. Mater. 219, 128–134 (1995).

    CAS  Article  Google Scholar 

  27. 27

    Redfern, S. A. T., Harrison, R. J., O’Neill, H. S. C. & Wood, D. R. R. Thermodynamics and kinetics of cation ordering in MgAl2O4 spinel up to 1600 degrees C from in situ neutron diffraction. Am. Mineral. 84, 299–310 (1999).

    CAS  Article  Google Scholar 

  28. 28

    Asbrink, S., Waskowska, A., Olsen, J. S. & Gerward, L. High-pressure phase of the cubic spinel NiMn2O4 . Phys. Rev. B 57, 4972–4974 (1998).

    CAS  Article  Google Scholar 

  29. 29

    Ivanov, V. G. et al. Short-range B-site ordering in the inverse spinel ferrite NiFe2O4 . Phys. Rev. B 82, 024104 (2010).

    Article  Google Scholar 

  30. 30

    Jiang, C., Sickafus, K. E., Stanek, C. R., Rudin, S. P. & Uberuaga, B. P. Cation disorder in MgX2O4 (X = Al, Ga, In) spinels from first principles. Phys. Rev. B 86, 024203 (2012).

    Article  Google Scholar 

  31. 31

    Finkeldei, S. et al. Dissolution of ZrO2 based pyrochlores in the acid pH range: a macroscopic and electron microscopy study. Appl. Geochem. 49, 31–41 (2014).

    CAS  Article  Google Scholar 

  32. 32

    Ziegler, J. F., Ziegler, M. D. & Biersack, J. P. SRIM—The stopping and range of ions in matter (2010). Nucl. Instrum. Methods Phys. Res. B 268, 1818–1823 (2010).

    CAS  Article  Google Scholar 

  33. 33

    Farrow, C. L. et al. PDFfit2 and PDFgui: computer programs for studying nanostructure in crystals. J. Phys. Condens. Matter 19, 335219 (2007).

    CAS  Article  Google Scholar 

Download references


We thank T. Egami, A. Fuentes and B. Haberl for discussions. This work was supported as part of the Materials Science of Actinides, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0001089. This research at ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

Author information




J.S., C.L.T., R.C.E. and M.L. conceived and designed the experiments. M.L. and C.L.T. designed and coordinated the irradiation procedure. J.S., F.Z., S.F., D.B. and H.Z. synthesized the samples. J.S., M.F., C.L.T., J.N. and M.L. collected and interpreted the neutron scattering data. J.S., C.L.T., R.C.E. and M.L. prepared the manuscript.

Corresponding author

Correspondence to Maik Lang.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 5247 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Shamblin, J., Feygenson, M., Neuefeind, J. et al. Probing disorder in isometric pyrochlore and related complex oxides. Nature Mater 15, 507–511 (2016).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing