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Neutron diffraction study of phi-Bi(8)Pb(5)O(17): structure refinement and analysis of cationic ordering
L Righi1, G Calestani, M Gemmi
1Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica and CNR-CSSD, Università di Parma, Viale delle Scienze, 43100 Parma, Italy. borchi06@nemo.cce.unipr.it
Summary
The triclinic crystal structure of the Bi(2)O(3)-PbO phase diagram
Area of Science:
- Materials Science
- Crystallography
- Solid-state Chemistry
Background:
- The Bi(2)O(3)-PbO phase diagram is crucial for understanding oxide materials.
- The triclinic varphi phase's structure was previously determined using electron and X-ray diffraction.
Purpose of the Study:
- To re-examine and refine the crystal structure of the varphi phase using powder neutron diffraction.
- To investigate cationic ordering and charge distribution within the varphi phase structure.
Main Methods:
- Powder neutron diffraction data collection.
- Rietveld refinement for structural analysis.
- Bond-valence calculations and charge distribution analysis.
Main Results:
- The triclinic crystal structure of the varphi phase was confirmed and refined.
- Accurate oxygen atom positions were determined, enabling detailed analysis.
- Significant cationic ordering was observed, with Bi and Pb atoms occupying distinct lattice sites.
Conclusions:
- The varphi phase exhibits a high degree of cationic ordering.
- This ordered structure suggests it is the thermodynamically stable low-temperature polymorph in the Bi(2)O(3)-PbO system.