Structural and optical studies of high dielectric constant (Na 0.5A0.5)Cu3Ti4O12 (A = la and Bi)

K. C. Liang, Hsiang Lin Liu, H. D. Yang, W. N. Mei, D. C. Ling

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Abstract

We report x-ray powder diffraction and temperature-dependent infrared reflectivity measurements of (Na0.5La0.5)Cu 3Ti4O12 and (Na0.5Bi 0.5)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.

Original languageEnglish
Article number275238
JournalJournal of Physics Condensed Matter
Volume20
Issue number27
DOIs
Publication statusPublished - 2008 Jul 9

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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