Influence of Dy on the dielectric aging and thermally stimulated depolarization current in Dy and Mn-codoped BaTiO 3 mul
- PDF / 261,785 Bytes
- 5 Pages / 584.957 x 782.986 pts Page_size
- 81 Downloads / 235 Views
Dielectric aging of Dy and Mn-codoped BaTiO3 multilayer ceramic capacitors was investigated. The increase of Dy concentration significantly decreased the aging rate and caused a disappearance of the thermally stimulated depolarization current peak associated with the defect dipole of Mn such as Mn99Ti VO or Mn9Ti VO , which was observed in low Dy-concentration specimens. These results experimentally demonstrate that the rare earth element, Dy, decreases the concentration of the defect dipoles and thereby controls dielectric aging.
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.347
depolarization field, which screen the spontaneous polarization and decrease the effective polarization response and dielectric constant with time. In the second model of the alignment of the defect dipoles (VO A00 or VO A0 ),5–7,10 which are formed by the association between oxygen vacancies (VO ) and ionized acceptors (A9, A0), the interaction between these dipoles and the spontaneous polarization causes their alignment in the direction of spontaneous polarization within a ferroelectric domain. Thus, it results in energy minimization and domain stabilization, and thereby a reduction of dielectric constant with time. Although there are a number reports on the dielectric aging-related phenomena that explained mostly using the above two models, those reports that directly showed the experimental evidence of the correlation between the dielectric aging and the defect dipole are very limited. Recently, the presence of the defect dipole and its correlation with dielectric aging was experimentally demonstrated by the thermally stimulated depolarization current (TSDC) in the variable-valence acceptor Mn and V-doped BaTiO3 MLCC.11 As the dielectrics of MLCC are exposed to progressively higher electric field conditions as the thickness of dielectric layer becomes thinner, the reliability problem is of increasing concern. The rare earth elements, such as Y, Dy, Ho, Er, etc., are well known to greatly improve reliability of acceptor-doped BaTiO3 dielectrics12–14 and thus widely used in BME MLCC. As these elements act as either donor or acceptor depending on their site occupancy, it is expected that they may influence ionic defect structure, defect dipole concentration, and thereby dielectric aging behavior. It has been reported that the increase of donor concentration reduced aging rate in donor–acceptor codoped system of K–F-codoped BaTiO3 single crystal and La–Mn-codoped BaTiO3 polycrystal.15 Although there are a number of reports that mentioned the
3252
Ó Materials Research Society 2013
I. INTRODUCTION
The base metal electrode (BME) multilayer ceramic capacitors (MLCC) are sintered in reducing atmospheres to prevent oxidation of nickel (Ni) inner electrodes. Thus, the dielectrics of MLCC are based on a defectchemically acceptor-doped BaTiO3 system, the composition of which includes amphoteric dopants of rare earth elements that can occupy the Ba or Ti site such as Y, Dy, Ho, and
Data Loading...
