Ceramics and Thick Films : Fabrication and Characterization (original) (raw)
Related papers
2010
ABSTRACT The influence of sintering temperature and dwell time on the microstructure formation and dielectric properties of CaCu3Ti4O12 ceramics was investigated. For sintering temperatures of 1050 and 1100 °C significant differences in the CaCu3Ti4O12 ceramic microstructure and the segregation of a CuOx-rich phase towards the grain boundary (GB) areas were observed with increasing dwell time. In addition to the formation of a semiconducting bulk and insulating grain boundary phase the segregated CuOx forms an intergranular phase, and the effects of this phase on the dielectric properties are rather intriguing. At sintering temperature below 1050 °C only small amounts of CuOx segregate, whereas sintering above 1050 °C (e.g., 1100 °C) leads to increased evaporation of the CuOx. Therefore, the effects of the CuOx-rich intergranular phase upon the dielectric properties are felt strongest in samples sintered at 1050 °C. Such effects are discussed in terms of microstructural variations due to liquid phase sintering behavior facilitated by the TiO2-CuOx-eutectic, which appears to be melted at high sintering temperature prior to evaporation of CuOx at prolonged dwell times at the highest sintering temperatures (1100 °C).
Applied Physics A, 2020
CaCu 3 Ti 4 O 12 (CCTO) electro ceramic was prepared by a solid-state reaction technique. The formation of CCTO was confirmed by X-ray diffraction (XRD). Pellets of calcined powder were sintered at different temperatures for two different durations, i.e., 2 and 10 h (h). The morphology and grain size of the samples were observed using scanning electron microscopy (SEM). SEM images showed that the minor phase (CuO) plays an important role in the growth of grain size. It seems that higher sintering temperatures led to change in the oxidation states of Cu and Ti, which increase the volume fraction of the CuO minor phase. Dielectric studies show that the dielectric constant is increasing with increasing sintering temperature, holding time, and presence of the CuO phase. The highest dielectric constant of ~ 41,000 was observed for CCTO samples sintered at 1100 °C for 10 h. The present samples find application in the energy storage devices.
Journal of Alloys and Compounds, 2017
The CaCu 3 Ti 4 O 12 ceramic, CCTO, remains as the best material due to its high dielectric constant. In this context, Sr-doped CCTO, Ni-doped CCTO and Sr,Ni co-doped CCTO ceramics were prepared by the solid-state reaction method and were sintered at 1100°C for 24 h in order to enhance the geometric microstructure and dielectric properties. X-ray diffraction data refined via rietveld method for CaCu 3 Ti 4 O 12 confirms the formation of single phase. SEM micrographs revealed that the substitution of Sr 2+ and/or Ni 2+ on Ca and Cu sites respectively increase the grain size of CaCu 3 Ti 4 O 12 ceramics. Raman scattering measurements shows the presence of TiO 2 phase at grain boundaries, which is an important parameter to reduce the dielectric loss of samples. It is found that Sr,Ni co-substitution in CCTO leads to the best dielectric measurements at low frequency. The highest grain boundary resistance value is also obtained for co-doped CCTO sample in the order of 1.84 10 6 Ω. This value is 10 times higher than pure CCTO. Meanwhile, the nonlinear coefficient values were improved, whereas, the breakdown electric field and leakage current decreased for all ceramic samples and co-doped CCTO is considered as the best conductive grain and insulating grain boundary.
Microstructure and dielectric properties of CaCu 3Ti 4O 12 ceramic
Mater Lett, 2007
CaCu3Ti4O12 (CCTO) was prepared by the solid state technique. The sample was calcined at 900 °C/12 h and sintered at 1050 °C/24 h, then subjected to XRD to ensure CCTO formation. The microstructure was observed by SEM. XRD results identified both samples as single phase CCTO, whereas the microstructure shows abnormal grain growth and large pores. Sintering was studied in the temperature range of 950–1050 °C for 3–12 h. Increasing sintering temperature enhances the density and secondary formation of Cu2O. A clear grain boundary and dense microstructure were observed. The results show that the sample sintered at 1040 °C/10 h yields a clearly uniform grain size with the highest εr (33,210).
Copper–cobalt oxide ceramic thin films from single source precursors:
Two heterobimetallic coordination complexes [Co(acac)Cu 2 (bdmap) 2 Cl 3 ]ÁC 7 H 8 (1) and [Co(acac)Cu 2 (bdmap) 2 Cl 3 ]Á3CH 2 Cl 2 (2) [bdmap = 1,3-Bis(dimethylamino)-2-propanol and acac = 2,4-pentanedionate], have been synthesized by simple chemical technique and characterized by their melting points, elemental composition, FT-IR spectroscopy, mass spectrometry and single crystal X-ray analysis. Thermograms of both the precursors indicated their facile decomposition at relatively low temperature of 454°C to give stable residual mixture of Cu and CoO. Both the precursors are utilized for the deposition of Cu-CoO thin films by aerosol-assisted chemical vapor deposition (AACVD) equipment at 450°C on glass substrates that were subsequently characterized for their morphology and composition of the ceramic material. The scanning electron microscopy of copper-cobalt oxide films grown from both the precursors describe highly compact and smooth morphology with homogenously dispersed spherical particles with excellent adhesion properties to the substrates. The EDX analysis shows homogeneous distribution of metallic elements with Cu:Co ratio close to 2:1. Powder X-ray diffraction analysis of the films shows that they are composed of Cu/CoO composite and are crystalline in nature having particle size in the range of 0.3-0.8 lm.
Inorganic Chemistry Communications, 2008
Thin films of halide free Cu-Co mixed metal oxide have been prepared at 390°C from the heterobimetallic complex Co 4 (THF) 4 (TFA) 8 (l-OH) 2 Cu 2 (dmae) 2 Á 0.5C 7 H 8 (1) [dmae = N,N-dimethylaminoethanol ((CH 3 ) 2 NCH 2 CH 2 O À ), TFA = triflouroacetate (CF 3 COO À ), THF = tetrahydrofurane (C 4 H 8 O)] which was prepared by the reaction of [Cu(dmae)Cl] 4 and Co(TFA) 2 Á 4H 2 O. The precursor was characterized for its melting point, elemental composition, FTIR and X-ray single crystal structure determination. Thin films grown on glass substrate by using AACVD out of complex 1 were characterized by XRD and SEM. TGA and AACVD experiments reveal it to be a suitable precursor for the deposition of halide free Cu-Co mixedmetal oxide thin films at relatively low temperatures.
Materials
NSCTO (Na0.5Sm0.5Cu3Ti4O12) ceramics have been prepared by reactive sintering solid-state reaction where the powder was prepared from the elemental oxides by mechanochemical milling followed by conventional sintering in the temperature range 1000–1100 °C. The influence of sintering temperature on the structural and dielectric properties was thoroughly studied. X-ray diffraction analysis (XRD) revealed the formation of the cubic NSCTO phase. By using the Williamson–Hall approach, the crystallite size and lattice strain were calculated. Scanning electron microscope (SEM) observations revealed that the grain size of NSCTO ceramics is slightly dependent on the sintering temperature where the average grain size increased from 1.91 ± 0.36 μm to 2.58 ± 0.89 μm with increasing sintering temperature from 1000 °C to 1100 °C. The ceramic sample sintered at 1025 °C showed the best compromise between colossal relative permittivity (ε′ = 1.34 × 103) and low dielectric loss (tanδ = 0.043) values a...
Dielectric properties of CaCu3Ti4O12 ceramics: effect of high purity nanometric powders
Journal of Materials Science: Materials in Electronics, 2014
In this letter, the dielectric properties of CaCu 3 Ti 4 O 12 ceramics modified by SrTiO 3 have been investigated. These ceramics were prepared successfully by conventional ceramic processing. X-ray diffraction results show that the ceramics with SrTiO 3 sintered at 1060°C for 3 h are mixed phase and consist of CaCu 3 Ti 4 O 12 and SrTiO 3 . The change of dielectric constant is explained well by Lichtenecker's logarithmic law of composite. And the reduction in dielectric loss is attributed to the increase of grain boundary resistance according to internal boundary layer capacitor model, with the increase of SrTiO 3 . When CaCu 3 Ti 4 O 12 /SrTiO 3 = 6/4 (volume ratio), an optimum component was obtained, exhibiting a high dielectric constant of about 2000 and a low dielectric loss (b0.03) with a good temperature stability from −55°C to 150°C at 1 kHz.
Synthesis of nanocrystalline giant dielectric constant Gd2CuO4 ceramic by Pechini process
International Conference on Advanced Nanomaterials & Emerging Engineering Technologies, 2013
Phase pure (T'-type, sp. gpo I4/mmm), category of materials to be explored fully for their dielectric nanocrystalline Gd2Cu04 powders were synthesized by a wet properties. However, the observed high £/ was contested to be chemical citrate gel complexation process known as "Pechini process". The T'-type phase was realized at much lower (_ 1073 mostly intrinsic in nature and extrinsic factors affecting £/ K) temperature than those reported for conventional ceramic were not studied. Further, these few select compounds studied powder mixing and solid state reaction process (_ 1223 K). The so far were synthesized using standard ceramic powder average particle size of the solid state reacted particles from HR-mixing and solid state reaction process, which requires high TEM was found to be-50 nm. The dielectric studies on the synthesis temperatures and often encountered with Gd2Cu04 pellets revealed extremely high values of E/ (�10 4) inhomogeneity of constituent ions. In contrast, wet chemical over the measure frequencies (1 <5. f <5. 1 MHz) and temperature synthesis process facilitates the molecular level mixing of (173 K <5. T<5. 423 K) ranges. Being non-ferroelectric, we propose constituent elements, which in turn contribute towards such high values of E/ arise due to an Internal barrier layer maintaining better stoichiometry and lower synthesis capacitance effect, formed by insulating grain boundaries and semiconducting grains in the ceramics. temperatures [7]. However, there have been a very few reports Keywords-Pechni process, T'-cuprate, giant dielectric on wet chemical synthesis of T'-type cuprates, including constant. GdzCu04 [8]. Hence, alternate method of synthesis of T'-type cuprate, viz. wet chemical process seems an interesting