Comment on “Origin of Giant Dielectric Response in Nonferroelectric CaCu3Ti4O12: Inhomogeneous Conduction Nature Probed by Atomic Force Microscopy”

Fu, Desheng; Taniguchi, Hiroki; Taniyama, Tomoyasu; Itoh, Makoto; Koshihara, Shin‐ya

doi:10.1021/cm801275k

Cited by 13 publications

(12 citation statements)

References 26 publications

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“…On the other hand, Desheng Fu and his colleagues propose an alternative model on the basis of the measurement of current‐sensing atomic force microscopy (AFM), which suggests that the grain is a mixture of semiconducting and insulating regions and the grain boundary is percolation conducting network . This interpretation is contradictory to previous results and has been challenged by other researchers . In addition, in a more recent study, Fiorenza et al .…”

Section: Resultsmentioning

confidence: 89%

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

et al. 2013

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The effects of La concentration on the electrical conductivity and electric modulus of Y2/3−xLaxCu3Ti4O12 ceramics (0.00 ≦ x ≦ 0.20) were investigated in detail. Proper amount of La substitution in Y2/3−xLaxCu3Ti4O12 ceramics made the dielectric loss decreased. When x = 0.10, Y2/3−0.10La0.10Cu3Ti4O12 ceramics exhibited the highest grain‐boundary resistance (0.893 MΩ) and the lowest dielectric loss (about 0.025 at 1 kHz), meanwhile the samples exhibited a relatively high dielectric constant above 6000 over a wide frequency range from 40 Hz to 1 MHz. The decreased dielectric loss was attributed to the enhanced grain‐boundary resistance. With the increase in La concentration, the dielectric relaxation behaviors correlated with the grain‐boundary effects were significantly enhanced. By La doping, the activation energies for the conduction in grain boundaries were slightly depressed, and the activation energies for the relaxation process in grain boundaries were slightly changed. Based on the activation values, it can be concluded that the doubly ionized oxygen vacancies VO∙∙ had substantial contribution to the conduction and relaxation behaviors in grain boundaries.

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Section: Resultsmentioning

confidence: 89%

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

et al. 2013

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“…Among so called giant permittivity compounds with room temperature permittivity ε′~10 5 the most important are ACu 3 Ti 4 O 12 [1,2] and complex perovskites AFe 1/2 B 1/2 O 3 [3]. It is widely proposed in the literature that the unusual dielectric behavior of the materials is related to the electrically inhomogeneous microstructure (grainboundary structure) of the ceramics that enhances the dielectric permittivity by the barrier layer mechanism [4][5][6][7][8][9][10]. Malone and Subramanian point out to the contribution of electric conductivity originating from the multivalent Cu and Fe ions and oxygen vacancies [11].…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

et al. 2011

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Dielectric behaviour of BiFeO 3 ceramics, obtained by hot-pressing of nanopowders produced by mechanochemical synthesis from Bi 2 O 3 and Fe 2 O 3 oxides (weight ratio 2:1), was studied in the temperature range 125-575 K. The ceramics was found to exhibit step-like dielectric response ε*(T) with high permittivity values, similar to the behaviour of materials with giant dielectric permittivity. Three overlapping relaxation processes contribute to the dielectric response: i) relaxation in the lowtemperature range (220-420 K), characterized by activation energy of 0.4 eV, ii) relaxation in the temperature range 320-520 K with activation energy of 1.0 eV and iii) broad dielectric anomaly in the vicinity of 420 K, which disappears after 1 h annealing at 775 K. The lowtemperature relaxation is ascribed to the carrier hopping process between Fe 2+ and Fe 3+ ions. The presence of mixed valence of the Fe ions was proved by X-ray photoelectron spectroscopy. Dielectric relaxation in the middle-temperature range is considered as a result of grain boundary effect and internal barrier layers related to Bi 25 FeO 40 phase as verified by X-ray diffraction. The high-temperature dielectric anomaly we relate to short-range hopping of ordered oxygen vacancies.

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“…In particular, we compare our results to earlier SPM investigations and provide insights towards the controversial interpretation of existing literature data, [16][17][18][19] merging all of the reported conclusions on the physical nature of the grain boundaries and finally providing the ultimate C-AFM resolution and sensitivity for these heterogeneous materials.…”

Section: Introductionmentioning

confidence: 53%

“…16 On the other hand, a paper commenting on that C-AFM study claimed that the C-AFM technique is a deficient method to probe $nm grain boundaries because of its poor resolution. 17 On the basis of these arguments, two main issues now need to be addressed: View Online -the criteria for reliable nano-electrical characterization, and -the resolution limit for nano-electrical characterization. Both issues, in turn, will now be discussed.…”

Section: C-afm Analysis Of Cacu 3 Ti 4 O 12 (Ccto) Ceramicsmentioning

confidence: 99%

Nanoscale electrical probing of heterogeneous ceramics: the case of giant permittivity calcium copper titanate (CaCu3Ti4O12)

et al. 2011

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Scanning Probe Microscopy with conductive tips has been used to image and study the dielectric properties of giant permittivity CaCu3Ti4O12 ceramics at the nanoscale. Since measurements are generally carried out on sections of a sample, particular attention has been devoted to possible artefacts due to surface imperfections, such as substantial surface roughness and/or contamination that can result in controversial interpretation, particularly at nanometric spatial dimensions. A reliable surface investigation has been carried out after the definition of both the physical and geometrical unbiased criteria to avoid any artefacts due to surface roughness and/or anomalous tip-sample contact variations. The presence of insulating grain boundaries and the measurement of a depletion layer at the grain-grain boundary interfaces unambiguously demonstrate the relevance of the Internal Barrier Layer Capacitor effect, among all the proposed physical mechanisms, to explain the giant dielectric behaviour. Such imaging provided a clear correlation between the macroscopic dielectric properties and the nanometric structure at the interfaces. Moreover, the "general criteria" for reliable nanoelectrical characterization as well as the related measurement resolution have been defined.

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Comment on “Origin of Giant Dielectric Response in Nonferroelectric CaCu₃Ti₄O₁₂: Inhomogeneous Conduction Nature Probed by Atomic Force Microscopy”

Cited by 13 publications

References 26 publications

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

Nanoscale electrical probing of heterogeneous ceramics: the case of giant permittivity calcium copper titanate (CaCu3Ti4O12)

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Comment on “Origin of Giant Dielectric Response in Nonferroelectric CaCu3Ti4O12: Inhomogeneous Conduction Nature Probed by Atomic Force Microscopy”

Cited by 13 publications

References 26 publications

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y2/3Cu3Ti4O12 Ceramics

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y2/3Cu3Ti4O12 Ceramics

Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

Nanoscale electrical probing of heterogeneous ceramics: the case of giant permittivity calcium copper titanate (CaCu3Ti4O12)

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Comment on “Origin of Giant Dielectric Response in Nonferroelectric CaCu₃Ti₄O₁₂: Inhomogeneous Conduction Nature Probed by Atomic Force Microscopy”

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics