Origin(s) of the apparent high permittivity in CaCu3Ti4O12 ceramics: clarification on the contributions from internal barrier layer capacitor and sample-electrode contact effects

Li, Ming; Shen, Zhifu; Nygren, Mats; Feteira, Antônio; Sinclair, Derek C.; West, Anthony R.

doi:10.1063/1.3253743

Cited by 192 publications

(140 citation statements)

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“…This is caused by a nonhomogeneous conductivity of the sample in the ceramic grains and grain boundaries, which is responsible for the creation of internal barrier layer capacitors on the grain boundaries. This mechanism is responsible for a "giant" effective permittivity in many dielectric or multiferroic materials [25][26][27].…”

Section: Dielectric and Conductivity Studiesmentioning

confidence: 99%

Strong spin-phonon coupling in infrared and Raman spectra ofSrMnO3

et al. 2014

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Infrared reflectivity spectra of cubic SrMnO 3 ceramics reveal 18% stiffening of the lowest-frequency phonon below the antiferromagnetic phase transition occurring at T N = 233 K. Such a large temperature change of the polar phonon frequency is extraordinary and we attribute it to an exceptionally strong spin-phonon coupling in this material. This is consistent with our prediction from first-principles calculations. Moreover, polar phonons become Raman active below T N , although their activation is forbidden by symmetry in the P m3m space group. This gives evidence that the cubic P m3m symmetry is locally broken below T N due to a strong magnetoelectric coupling. Multiphonon and multimagnon scattering is also observed in Raman spectra. Microwave and THz permittivity is strongly influenced by hopping electronic conductivity, which is caused by small nonstoichiometry of the sample. Thermoelectric measurements show room-temperature concentration of free carriers n e = 3.6 × 10 20 cm −3 and the sample composition Sr 2+ Mn 4+ 0.98 Mn 3+ 0.02 O 2− 2.99 . The conductivity exhibits very unusual temperature behavior: THz conductivity increases on cooling, while the static conductivity markedly decreases on cooling. We attribute this to different conductivity of the ceramic grains and grain boundaries.

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Section: Dielectric and Conductivity Studiesmentioning

confidence: 99%

Strong spin-phonon coupling in infrared and Raman spectra ofSrMnO3

et al. 2014

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Section: Introductionmentioning

confidence: 99%

“…6,7,20 The plateau in C9 spectroscopic plots observed for dense CCTO ceramics sintered at y1100 uC is dominated by a grain boundary or an electrode response, depending on the relative magnitude of the resistance for each response. 6,7 The ceramic processing conditions have a significant influence on the electrical properties, especially regarding the grain boundary resistivity (R gb ). 6 In most reports, CCTO ceramics have been sintered at 1000-1100 uC for 2-10 h with R gb at RT typically exceeding 1 MV cm; R gb is therefore much larger than the electrode responses (R e ) and the grain resistivity (R b ) which is typically ,100 V cm at RT.…”

Section: Introductionmentioning

confidence: 99%

“…6,7 The ceramic processing conditions have a significant influence on the electrical properties, especially regarding the grain boundary resistivity (R gb ). 6 In most reports, CCTO ceramics have been sintered at 1000-1100 uC for 2-10 h with R gb at RT typically exceeding 1 MV cm; R gb is therefore much larger than the electrode responses (R e ) and the grain resistivity (R b ) which is typically ,100 V cm at RT. In this case, the high effective permittivity (y10 [3][4] ) observed at radio-frequencies is dominated by the grain boundary response and can be described as an Internal Barrier Layer Capacitance (IBLC) or MaxwellWagner mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] For CCTO ceramics, spectroscopic plots of the real component of the capacitance (C9) near room temperature (RT) exhibit a frequency-independent plateau over the range y10-10 5 Hz.…”

Section: Introductionmentioning

confidence: 99%

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Modulus spectroscopy of CaCu3Ti4O12 ceramics: clues to the internal barrier layer capacitance mechanism

Costa

Frade

et al. 2013

RSC Adv.

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aTo date, all existing literature on the so called 'high permittivity' perovskite oxide CaCu 3 Ti 4 O 12 (CCTO) in the form of ceramics, single crystals and thin films show the grains (bulk) to exhibit semiconductivity with room temperature, RT, resistivity of y10 100 V cm. Here we show that CCTO grains can be highly resistive with RT resistivity >1 GV cm when CCTO ceramics are processed at lower temperature (700 uC). With increasing processing temperature, the semiconducting CCTO phase commonly reported in the literature emerges from grain cores and grows at the expense of the insulating phase. For sintering temperatures of y1000 1100 uC, the grains are dominated by the semiconducting phase and the insulating phase exists only as a thin layer grain shell/grain boundary region. This electrical microstructure results in the formation of the so called Internal Barrier Layer Capacitance (IBLC) or Maxwell Wagner mechanism that produces the commonly reported high effective permittivity at radio frequencies in dense ceramics. The relationship between Cu loss at elevated processing temperatures and the transformation of the grain resistivity from an insulating to semiconducting state with increasing processing temperature is also discussed.

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