Complex dielectric dispersion in Ba(Zr,Ti)O3 ceramics; dynamics of relaxors and diffuse ferroelectrics (Comunicazione a convegno)

Type
Label
  • Complex dielectric dispersion in Ba(Zr,Ti)O3 ceramics; dynamics of relaxors and diffuse ferroelectrics (Comunicazione a convegno) (literal)
Anno
  • 2013-01-01T00:00:00+01:00 (literal)
Alternative label
  • M. Savinov (1), J. Petzelt (1), D. Nuzhnyy (1), V. Bovtun (1), G. Canu (2), V. Buscaglia (2) (2013)
    Complex dielectric dispersion in Ba(Zr,Ti)O3 ceramics; dynamics of relaxors and diffuse ferroelectrics
    in 13th International Meeting on Ferroelectricity (IMF-13), Krakow, Poland, September, 2013
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • M. Savinov (1), J. Petzelt (1), D. Nuzhnyy (1), V. Bovtun (1), G. Canu (2), V. Buscaglia (2) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • 1. Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague 8, Czech Republic; 2. Institute for Energetics and Interphases, National Research Council, I-16149 Genoa, Italy (literal)
Titolo
  • Complex dielectric dispersion in Ba(Zr,Ti)O3 ceramics; dynamics of relaxors and diffuse ferroelectrics (literal)
Abstract
  • Ba(ZrxTi1-x)O3 (BZT-x) solid solution is a very attractive and intensively studied system because it is lead free, isovalent, and passes from standard ferroelectric behaviour of neat BaTiO3 (BTO, x = 0) over diffuse ferroelectric behaviour (0.15 < x < 0.25), relaxor ferroelectric (0.25 < x < 0.75), dipolar glass (0.75 < x < 1), and weak incipient ferroelectric of neat BaZrO3 (BZO, x = 1). Dielectric responses of ceramics with x=0, 0.2, 0.4, 0.6, 0.7, 0.8, 1 were investigated from Hz frequencies up to the infrared using several techniques in a broad temperature range (10 - 700 K). In neat BZO the dielectric response is fully determined by polar phonons, the lowest-frequency one being of the Last type, unlike in BTO, where it is of the Slater type. On the other hand, response in BTO in a broad range around the ferroelectric transition near ~400 K is dominated by an overdamped central mode (CM) in the THz range in addition to the soft phonon mode [1]. In all the studied BZT samples the lowest frequency phonon mode in the 100 cm-1 range is almost not softening and the response below room temperature is dominated by two additional CM relaxations: The higher-frequency one in the 1010 - 1011 Hz range, which is not very temperature dependent, and the lower-frequency one which is slowing down from the GHz range and below room temperature it is thermally activated and broadening. At low temperatures it merges into a near-constant loss background, which decreases with increasing x. In the case of diffuse transition in BZT-0.2, the CM softens only to the GHz range near the transition temperature and below it only the near-constant loss background dominates the response below ~1 GHz. The picture of polar nanoregions in BZT differs from that in heterovalent relaxors, because they are pinned to the nanoregions of the BTO clusters (frozen in our temperature range), where from first-principle theories it follows that the Ti4+ ions are off-centered as in the neat BTO whereas the Zr4+ ions remain centered as in the neat BZO. Therefore we assign the soft CM to the hopping of the off-centered Ti4+ ions. The origin of the higher-frequency CM might be connected with the polar nanoregion dynamics (e.g. fluctuations of their boundaries inside the BTO nanoclusters). Unlike BTO, the dynamic instability, which is responsible for the diffuse ferroelectric and relaxor behavior in BZT, is mainly due to the hopping dynamics of the offcentered Ti4+ ions rather than due to the soft phonons and therefore the diffuse transition in BZT is essentially of the order-disorder type. 1. D. Nuzhnyy, J. Petzelt, M. Savinov, T. Ostapchuk, V. Bovtun, M. Kempa, J. Hlinka, V. Buscaglia, M. T. Buscaglia and P. Nanni, \"Broadband dielectric response of Ba(Zr,Ti)O3 ceramics: From incipient via relaxor and diffuse up to classical ferroelectric behavior\", Phys. Rev. B 86, 014106 (2012). (literal)
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