Complex oxides such as A₂B₂O₇ exhibit a variety of properties that find application in a number of different technologies, from electrolytes in solid oxide fuel cells to actinide-bearing phases. Ion beams in the GeV energy range have been used to systematically study the irradiation effects of pure electronic excitation and ionization in Gd₂Zr_2-xTi_xO₇. Synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) revealed radiation-induced phase transitions that include the crystalline-to-amorphous and the order-disorder structural transformations, as well as the generation of high-temperature and high-pressure phases. The extreme conditions prevailing in a single ion track trigger the formation of equilibrium- and non-equilibrium phases, and entire phase diagrams are accessible at the nanoscale. The specific type of material modification can be manipulated by changing the target composition (e.g., Ti-content), beam parameters (e.g., energy loss), and external irradiation condition (e.g., pressure and temperature). As an important application, we show that the combination of energetic heavy ions and high pressure can result in the formation and stabilization of a new metastable Gd₂Zr₂O₇ phase that cannot be obtained by irradiation or pressure applied separately. TEM and quantum-mechanical calculations suggest that these novel structural modifications are caused by the formation of nanocrystals that change the energetics of the phase transformations. This result highlights the importance of the combined use of high pressure and high-energy ion irradiation as a new means for manipulating and stabilizing novel materials to ambient conditions that otherwise could not be recovered.

Maik Lang*, Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States
Fuxiang Zhang, Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States
Jiaming Zhang, Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States
Jianwei Wang, Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States
Ram Devanathan, Pacific Northwest National Laboratory, Richland, Washington, United States
Marcel Toulemonde, Centre interdisciplinaire de recherche sur les Ions, les Matériaux et la Photonique (CIMAP), CEA-CNRS-ENSICAEN-University of Caen, Caen, France
Beatrice Schuster, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
Christina Trautmann, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
William J. Weber, Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee, United States
Rodney C. Ewing, Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States

*presenting author