Structural and optical studies of high dielectric constant (Na0.5A0.5)Cu3Ti4O12 (A=La and Bi)

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Title:	Structural and optical studies of high dielectric constant (Na0.5A0.5)Cu3Ti4O12 (A=La and Bi)
Authors:	Liang, K. C.;Liu, H. L.;Yang, H. D.;Mei, W. N.;林大欽;Ling, D. C.
Contributors:	淡江大學物理學系
Date:	2008-07-01
Issue Date:	2010-08-09 15:45:44 (UTC+8)
Publisher:	Institute of Physics (IOP)
Abstract:	We report x-ray powder diffraction and temperature-dependent infrared reflectivity measurements of (Na0.5La0.5)Cu3Ti4O12 and (Na0.5Bi0.5)Cu3Ti4O12 in order to investigate the origin of their lower room-temperature dielectric constants in comparison with the giant value of CaCu3Ti4O12. Substituting Ca with Na/La or Na/Bi is found to decrease all Ti–O–Ti angles by the TiO6 octahedra tilts, resulting in an increase of the local structural disorder on the Na/La and Na/Bi compounds. Further, several infrared-active phonon modes show a broadening in their linewidths, reflecting that the coherency in these vibrational modes is degraded by disorder. Additionally, the lowest-frequency mode of the Ca material is observed to strengthen dramatically at low temperatures, but to a lesser extent in the Na/La and Na/Bi compounds. These results suggest the important role of the local structural disorder on the anomalous low-frequency dielectric response in these materials.
Relation:	Journal of Physics: Condensed Matter 20(27), pp.275238(8 pages)
DOI:	10.1088/0953-8984/20/27/275238
Appears in Collections:	[Graduate Institute & Department of Physics] Journal Article

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