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Raman and x-ray absorption spectroscopy study of the phase evolution induced by mechanical milling and thermal treatments in R(2)Ti(2)O(7) pyrochlores

DOI: 10.1103/PhysRevB.84.104207 DOI Help

Authors: M. L. Sanjuan (Universidad de Zaragoza) , C. Guglieri (Universidad de Zaragoza) , S. Diaz-moreno (Diamond Light Source) , G. Aquilanti (Sincrotrone Trieste, ELETTRA) , A. F. Fuentes (CINVESTAV-Unidad Saltillo) , L. Olivi (Sincrotrone Trieste, ELETTRA) , J. Chaboy (Universidad de Zaragoza)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 84 (10)

State: Published (Approved)
Published: September 2011

Abstract: We report here a study of the local order in R 2 Ti 2 O 7 , (R = Y, Gd, and Dy) pyrochlores obtained by mechanical milling (MM) performed by combining both Raman and x-ray absorption (XAS) spectroscopies. In addition to both as-milled and annealed MM samples, measurements have been also recorded by performing an in situ thermal treatment of the MM pyrochlores in the range from ambient to 1300 ? C. The analysis of both Raman and XAS data yields a disentangled view of the evolution of the different degree of structural disorder at the Ti and rare-earth sites of the MM samples with the thermal treatment. Moreover, this study allowed us to follow the structural transformation of the MM samples through the region where exothermic processes have been previously observed. Our experiments show that an average fluorite-like structure is never formed in these pyrochlores. As milled-samples are better described as if formed by nanometer-sized pyrochlore domains embedded in a fluorite-like matrix. Thermal annealing induces domain growth, so that the event observed by differential thermal analysis can be attributed to an evolution from medium to long-range pyrochlore ordering, typically from tens to hundreds of nanometers.

Subject Areas: Physics

Facility: Elettra