On the nanostructure of radiation-amorphized zircon and pyrochlores: a small-angle x-ray scattering study
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Susana Ríos
Abstract
Nanoscale structural features of amorphous zircon and pyrochlore produced by self-irradiation induced amorphization have been characterized by small-angle X-ray scattering (SAXS). Electron density fluctuations were observed in the untreated samples and studied as a function of annealing temperature (up to 1300 °C). In untreated zircon, density fluctuations were found to have a characteristic length-scale of approximately 1 nanometer diameter. A clear scattering maximum develops at ∼3 nm–1 as a function of the degree of damage, but only for amorphous fractions higher than 70%. For the untreated pyrochlore sample such a strong signal was not observed in the scattering function. As annealing temperature increases, phase segregation is observed in zircon with a clear nucleation at 850 °C of zirconia grains. The SAXS contribution, however, points towards a lower nucleation temperature, ca. 700 °C. In the pyrochlore structure, at temperatures as low as 300 °C the appearance of a first crystalline phase, Ca2Nb2O7, is observed, with the subsequent crystallization of TiO2 at 800 °C. Observed electron density variations are compared between the two structures and discussed in terms of nanoscale phase segregation phenomena.
© by Oldenbourg Wissenschaftsverlag, München
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Articles in the same Issue
- Phase Transitions
- Structural phase transitions in two-dimensional systems: Pb/Ge(111) and Sn/Ge(111)
- Theoretical approach to reconstructive and morphotropic phase transitions
- Surface relaxations at mineral surfaces
- Methods for pseudosymmetry evaluation: a comparison between the atomic displacements and electron density approaches
- Revised prediction of B1 to B2 phase transition pressures in YbN, YbP and YbAs
- Crossover from classical to 3d-Ising critical behaviour near the antiferrodistortive phase transition of lawsonite
- CaZrGeO5 and the triclinic instability of the titanite structure type
- The high-pressure structural phase transitions of sodium bismuth titanate
- Ferroelastic phase transitions and domain structures in powders
- Phase transitions in BaTiO3: a high-pressure neutron diffraction study
- Nanoscale phase transformations in relaxor-ferroelectric lead scandium tantalate and lead scandium niobate
- On the nanostructure of radiation-amorphized zircon and pyrochlores: a small-angle x-ray scattering study
