2007/09/07 by Ch. Kant, T. Rudolf, F. Mayr +5 · 3 citations
Materials Science · Physics and Astronomy · #Dielectric properties of ceramics #Ferroelectric and Piezoelectric Materials #Multiferroics and related materials #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.77.045131
published as Phys. Rev B 77, 045131 (2008) · 7 pages, 8 figures
arxiv created 2007/09/07 · openalex publication_date 2008/01/25 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We report on phonon properties and electronic transitions in CaCu3Ti4O12, a material which reveals a colossal dielectric constant at room temperature without any ferroelectric transition. The results of far- and midinfrared measurements are compared to those obtained by broadband dielectric and millimeter-wave spectroscopy on the same single crystal. The unusual temperature dependence of phonon eigenfrequencies, dampings, and ionic plasma frequencies of low-lying phonon modes is analyzed and discussed in detail. Electronic excitations below 4\phantom\rule0.3em0exeV are identified as transitions between full and empty hybridized oxygen-copper bands and between oxygen-copper and unoccupied Ti\phantom\rule0.2em0ex3d bands. The unusually small band gap determined from the dc conductivity (\ensuremath∼200\phantom\rule0.3em0exmeV) compares well with the optical results.