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Updated: Aug 6, 2026
06:49
Radio Frequency Magnetron Sputtering of GdBa2Cu3O7−δ/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates
Published on: April 12, 2019
The phase transitions and crystal structures of Ba3RM2O7.5 complex oxides (R = rare-earth elements, M = Al, Ga)
Abakumov1, Shpanchenko, Lebedev
1Department of Chemistry, Moscow State University, Moscow 119899, Russia, and EMAT, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Summary
The study reveals two crystal structures, alpha and beta, in complex oxides. An order-disorder phase transition between these forms is driven by oxygen ordering within tetrahedral Al(2)O(7) slabs.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Complex oxides with perovskite-related structures are crucial in various applications.
- Understanding the structural variations and phase transitions in these materials is key to controlling their properties.
Purpose of the Study:
- To elucidate the crystal structures of alpha-Ba(3)RAl(2)O(7.5) and beta-Ba(3)RM(2)O(7.5) complex oxides.
- To investigate the order-disorder phase transition between the alpha and beta forms.
Main Methods:
- X-ray diffraction (XRD)
- Electron diffraction (ED)
- High-resolution electron microscopy (HREM)
- High-temperature XRD
- Differential thermal analysis (DTA)
Main Results:
- Two distinct crystal structures, alpha (orthorhombic) and beta (monoclinic), were identified.
- The structures feature slabs with vertex-sharing tetrahedral Al(2)O(7) pairs.
- An order-disorder phase transition occurs due to oxygen ordering within these tetrahedral units.
- Defects such as twins and antiphase boundaries were observed during the transition.
Conclusions:
- The alpha and beta phases represent different ordering states of oxygen within the complex oxide structure.
- The identified phase transition is critical for understanding the material's behavior at varying temperatures.
- The study provides insights into defect formation during structural transformations in complex oxides.
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