Relationship between Dielectric Properties and Microphonics of Mulutilayer Ceramic Capacitors

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Gd-and Mg-substituted barium titanate crystals (Ba 1%x Gd x )(Ti 1%x/2 Mg x/2 )O 3 with the Gd composition range of x > 0.1 show no ferroelectric phase transition. To discuss atomic thermal fluctuations in such unusual barium titanate crystals with cubic symmetry, accurate crystal structure analyses were performed by the maximum entropy method (MEM)/Rietveld method with the split-atom model and anharmonic temperature factor model using high-energy synchrotron radiation X-ray diffraction data. The off-centered positions of Gd ions at the Ba site in the probability density function were clearly observed at a low temperature but smeared in the high-temperature region by the over-barrier motion of Gd ions.

Section: Introductionmentioning

confidence: 99%

Structure fluctuation in Gd- and Mg-substituted BaTiO₃with cubic structure

Takeda

Zhang

Moriyoshi

et al. 2017

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“…To satisfy the requirements for such use such as the lower dielectric loss, lower microphonics, and longer lifetime for the application of BaTiO 3 ceramics as MLCC, the atomic substitution effects of rare-earth R and Mg ions on BaTiO 3 ceramics have been investigated. [1][2][3][4][5][6][7] When the trivalent R and divalent Mg ions are substituted simultaneously for the Ba and Ti ions, respectively, solid solutions of the chemical formula (Ba 1−x R x )(Ti 1−x=2 Mg x=2 )O 3 are formed from the viewpoint of charge compensation. This atomic co-substitution improves the dielectric properties and stability of BaTiO 3 ceramics, 8) and at the same time reduces the ferroelectric phase transition temperature T C of BaTiO 3 with increasing Gd and Mg contents.…”

Section: Introductionmentioning

confidence: 99%

Off-centering of rare-earth ion in (Ba,R)(Ti,Mg)O₃ (R = Gd, Dy)

Takeda

Yasuda

Moriyoshi

et al. 2016

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To investigate the off-centering behavior of rare-earth ions that were partially substituted for A site ions in ABO3-type crystals, accurate crystal structure analyses of (Ba,R)(Ti,Mg)O3 (R = Gd, Dy) were performed by high-energy synchrotron radiation X-ray powder diffraction analysis and the maximum entropy method (MEM)/Rietveld method. The R ions were observed at the six equivalent off-center sites in the 〈100〉 directions from the corner of a unit cell in the cubic phase. In the tetragonal phase, the R ions occupied one off-center site along the [001] direction. The R off-centering can be attributed to the covalent nature of the bond between the R and O ions in (Ba,R)(Ti,Mg)O3 crystals.

“…Thus far, BaTiO 3 has generally been used as a dielectric for MLCCs owing to its low dielectric loss and high permittivity. To satisfy requirements the lower dielectric loss and lower microphonics, Gd-and Mg-doped BaTiO 3 are proposed as candidates for the dielectric materials, [3][4][5] which enable us to suppress various problems involved in applying the ferroelectric properties of pure BaTiO 3 to MLCCs. 6) The temperature dependence of permittivity can be improved by increasing the Gd and Mg contents, although the Curie temperature (T C ) is significantly decreased.…”

Section: Introductionmentioning

confidence: 99%

Structural Characteristics of (Ba_0.94Gd_0.06)(Ti_0.97Mg_0.03)O₃in Cubic Structure Determined by High-Energy Synchrotron-Radiation Powder Diffraction

Inoue

Okamatsu

Andõ

et al. 2009

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Structural study by high-energy synchrotron-radiation powder diffraction has been performed for (Ba 0:94 Gd 0:06 )(Ti 0:97 Mg 0:03 )O 3 (BGTM) at 473 K to investigate the substitution effects of Gd and Mg on the cubic structure of BaTiO 3 . Our precise electron-density analysis using the maximum entropy method (MEM)/Rietveld method demonstrates that the bonding electron density between the Ti and O atoms in BGTM decreases with the substitution of Gd and Mg elements, which provides a significant contrast to the fact that the Ti-O bond length is shortened in BGTM. No obvious change is observed on the Ba-O ionic bonding. It is considered that the lowering of the cubic-tetragonal phase transition temperature in BGTM is attributed to the decrease in covalency on the Ti-O bond in BGTM. The features of thermal motions of the constituent atoms are discussed on the basis of the mean square thermal displacement parameters by taking account of the chemical bonding nature and tolerance factor of the BaTiO 3 system. #