Dielectric properties of high permittivity ceramics based on Dy2/3CuTa4O12

Szwagierczak, D.; Kulawik, J.

doi:10.1016/j.jallcom.2009.10.229

Cited by 12 publications

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References 30 publications

(72 reference statements)

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“…The formation of such an electrically heterogeneous system during the one step fabrication process in air leads to spontaneous internal barrier layer capacitance effects responsible for a high and relatively stable dielectric permittivity of the developed material. [10]. Strong tilting of TiO 6 octahedra and fourfold coordination of small Cu ions in A sites of the ABO 3 perovskite structure are characteristic of these compounds [1].…”

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Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Szwagierczak

2012

Acta Phys. Pol. A

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A new perovskite material Nd 2/3 CuTa 4 O 12 was applied as a naturally formed internal barrier layer capacitor. The powder prepared by solid state synthesis and ball milling was pressed into pellets and sintered at 1180-1220• C. Dielectric properties of ceramic samples were characterized by impedance spectroscopic studies carried out in the temperature range from −55 to 700• C at frequencies 10 Hz ÷ 2 MHz. Two types of the dielectric response were revealed -a high frequency response attributed to grains which occurred at low temperatures, and a low frequency one related to grain boundaries which dominated at higher temperatures. Resistances and capacitances of grains were found to be two orders lower than those of grain boundaries. Two plateaus were observed in the dielectric permittivity versus frequency plots -a low frequency step corresponding to a high value of 10 4 and a high frequency step at a level of 40. Scanning electron microscopy observations and energy dispersive spectroscopy analysis confirmed that Nd 2/3 CuTa 4 O 12 ceramics were composed of semiconducting grains and insulating oxygen-enriched grain boundaries. The formation of such an electrically heterogeneous system during the one step fabrication process in air leads to spontaneous internal barrier layer capacitance effects responsible for a high and relatively stable dielectric permittivity of the developed material.

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Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Szwagierczak

2012

Acta Phys. Pol. A

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“…Scanning electron microscopy (SEM) studies revealed dense microstructure with grains 1-5 m in diameter. The energy-dispersive X-ray spectroscopy (EDS) microanalysis showed that grain boundaries are enriched with oxygen and tantalum, while grain interiors in copper (Szwagierczak and Kulawik, 2010, Szwagierczak, 2012. Such phenomena as evaporation of copper oxide, partial reduction of Cu 2ϩ to Cu ϩ ions (above 1,030°C in air) and small oxygen loss are known to occur during the sintering process.…”

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confidence: 99%

Dielectric properties of high-permittivity A_2/3CuTa₄O₁₂ ceramics

Szwagierczak

2014

Microelectronics International

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Purpose -This paper aims to present the comparative study on the composition, microstructure and dielectric behavior of a group of new nonferroelectric high-permittivity A 2/3 CuTa 4 O 12 (A ϭ Y, Nd, Sm, Gd, Dy or Bi) ceramics. Design/methodology/approach -The materials under investigation were synthesized by solid-state reaction method and sintered at 1,120-1,230°C. Dielectric properties were investigated in the temperature range from Ϫ55 to 740°C at frequencies 10 Hz to 2 MHz. Microstructure, elemental composition and phase composition of the ceramics were examined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) methods. DC conductivity was studied in the temperature range 20-740°C. Findings -XRD analysis revealed peaks corresponding to Cu 2 Ta 4 O 12 along with small amounts of secondary phases based on tantalum oxides. Impedance spectroscopic data and the results of SEM and EDS studies imply the spontaneous formation of internal barrier layer capacitors in the investigated materials. Two steps can be distinguished in the dielectric permittivity versus frequency plots. The low-frequency step of 1,000-100,000 is assigned to grain boundary barrier layer effect, while the high-frequency one of 34-46 is related to intrinsic properties of grains. Originality/value -Search for new high-permittivity capacitor materials is important for the progress in miniaturization and integration scale of electronic passive components. The paper reports on processing, microstructure, microanalysis studies and dielectric properties of a group of novel nonferroelectric materials with the perovskite structure of CaCu 3 Ti 4 O 12 and the general formula A 2/3 CuTa 4 O 12 , being spontaneously formed internal barrier layer capacitors.

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“…Perovskite-type material CaCu 3 Ti 4 O 12 (CCTO) has attracted much attention because of its extraordinarily high dielectric constant (up to 10 4 for bulk ceramic or single crystal) over a broad temperature range [1][2][3][4][5][6][7][8][9]. With the help of neutron powder diffraction [2] and high-resolution X-ray diffraction (XRD) [3], there is no evidence of any lattice distortion in CCTO from 100 K to 600 K, which is very desirable for practical application in capacitors. In order to apply CCTO in microelectronic devices and give a more fundamental understanding of its physical properties, some groups have grown high-quality epitaxial CCTO films on oxide substrates [10,11].…”

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Rietveld analysis of CaCu3Ti4O12 thin films obtained by RF-sputtering

Foschini

Tararam

Simões

et al. 2015

J Mater Sci: Mater Electron

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Calcium copper titanate, CaCu 3 Ti 4 O 12 , CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO 2 /Si (100) substrates at a room temperature followed by annealing at 600°C for 2 h in a conventional furnace. The crystalline structure and the surface morphology of the films were markedly affected by the growth conditions. Rietveld analysis reveal a CCTO film with 100 % pure perovskite belonging to a space group Im3 and pseudo-cubic structure. The XPS spectroscopy reveal that the in a reducing N 2 atmosphere a lower Cu/Ca and Ti/Ca ratio were detected, while the O 2 treatment led to an excess of Cu, due to Cu segregation of the surface forming copper oxide crystals. The film present frequency-independent dielectric properties in the temperature range evaluated, which is similar to those properties obtained in single-crystal or epitaxial thin films. The room temperature dielectric constant of the 600-nm-thick CCTO films annealed at 600°C at 1 kHz was found to be 70. The leakage current of the MFS capacitor structure was governed by the Schottky barrier conduction mechanism and the leakage current density was lower than 10-7 A/cm 2 at a 1.0 V. The current-voltage measurements on MFS capacitors established good switching characteristics.

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Dielectric properties of high permittivity ceramics based on Dy2/3CuTa4O12

Cited by 12 publications

References 30 publications

Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Dielectric properties of high-permittivity A_2/3CuTa₄O₁₂ ceramics

Rietveld analysis of CaCu3Ti4O12 thin films obtained by RF-sputtering

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Dielectric properties of high permittivity ceramics based on Dy2/3CuTa4O12

Cited by 12 publications

References 30 publications

Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

Dielectric properties of high-permittivity A2/3CuTa4O12 ceramics

Rietveld analysis of CaCu3Ti4O12 thin films obtained by RF-sputtering

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Dielectric properties of high-permittivity A_2/3CuTa₄O₁₂ ceramics