MIRANDA, Laura, FETEIRA, Antonio, SINCLAIR, Derek C, BOULAHYA, Khalid, HERNANDO, Maria, RAMÍREZ, Julio, VARELA, Aurea, GONZÁLEZ-CALBET, Jose M. and PARRAS, Marina (2009). Composition−structure−property relationships of 6H- and 12R-Type Hexagonal Ba(Mn,Ti)O3−δPerovskites. Chemistry of Materials, 21 (8), 1731-1742.Full text not available from this repository.
The crystal structures of 6H-type BaMn0.15Ti0.85O3, BaMn1/4Ti3/4O2.95, and BaMn1/2Ti1/2O2.84 and 12R-type BaMn2/3Ti1/3O3 have been established by a combination of X-ray, neutron, and electron diffraction, and high-resolution electron microscopy. The 6H-type structure (space group P63/mmc) can be described by a stacking sequence (hcc)2 along the c-axis with any anion deficiency located exclusively in the h-BaO3 layers. Ti atoms display a strong preference for the corner-shared octahedral site, whereas both Mn and Ti are distributed over the octahedral sites in the face sharing dimers. The 12R-type structure (space group R3̅m) can be described by a stacking sequence (hhcc)3. Ti atoms again display a strong preference for the isolated corner-sharing octahedral site, whereas Mn atoms occupy the central site of the face-sharing trimers. The electrical properties have been characterized by impedance spectroscopy and reveal the fully oxidized compounds to be electrical insulators with relative permittivity values of 45−55 at 300 K. The oxygen-deficient compounds are semiconductors, which is attributed to the presence of mixed Mn3+ and Mn4+ ions on the B-site sublattice. Antiferromagnetic (AFM) interactions occur within the face-sharing units of the respective structures. The AFM interactions inside the dimers (6H-type) and trimers (12R-type) become stronger with increasing Mn content and result in an increase in the magnitude of the Curie−Weiss constant.
|Research Institute, Centre or Group:||Materials and Engineering Research Institute > Structural Materials and Integrity Research Centre > Centre for Corrosion Technology|
|Depositing User:||Hilary Ridgway|
|Date Deposited:||06 Jun 2012 11:01|
|Last Modified:||06 Jun 2012 11:01|
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