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Leakage current density (J)-electric field (E) curves with a typical nonlinear behaviors and b linear fitting with logarithmic plot for CCTO samples modified by different TiO2 content
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The fabrication of TiO2 modified CaCu3Ti4O12 (w = 0, 0.01, 0.1, 2%) ceramics were obtained by a sol–gel process. The influence of TiO2 amount on the microstructures and dielectric properties was studied. The results indicate that TiO2 modified CaCu3Ti4O12 ceramics exhibits higher density, more obvious grain boundaries, and larger grains, and show i...
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Citations
... The development of capacitors with a giant dielectric constant is of great significance given devices' functionalization, miniaturization, and the actual industrial application requirement [1][2][3][4][5][6][7]. The perovskitelike materials Copper Calcium Titanate (CaCu 3 Ti 4 O 12 , CCTO) with body-centered cubic Im 3 structure has been widely investigated owing to their permittivity (e 0 ) in the order of 10 3 -10 5 with excellent temperature stability over a wide temperature range from 100 to 500°C [8][9][10][11][12][13][14][15][16]. ...
... Because of their giant permittivity, CCTO materials have potential microelectronics applications such as intelligent distributed grid systems, distributed energy storage systems, Super-capacitor, and memory (DRAM) devices [17][18][19][20][21][22]. However, the high low-frequency dielectric loss (tan d) hinders its many commercial applications [6,21,23]. Thus, investigating the cause of high tan d value and giant dielectric constant value is a substantial issue that should be intensively performed for its practical application in the industrial field [2,[22][23][24][25]. ...
CaCu3Ti4O12/CaTiO3/TiO2 (CCTO/CTO/TiO2) composite ceramics were fabricated by an in situ route and sintered at 1040 °C for 8 h. The micrographs of FESEM show that the ceramics are dense and delicate, with an average particle size of about 0.9–1.4 μm. XPS found the existence of Cu⁺ and Ti³⁺, which was caused by the charge compensation reaction derived from part of Ti⁴⁺ ions entering the V″Cu to form the donor Ti··Cu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm {Ti}}^{\cdot\cdot}}_{\rm {Cu}}$$\end{document}. The impedance analysis shows that excessive CTO and TiO2 significantly reduce the grain boundary resistance of CCTO/CTO/TiO2 ceramics. Furthermore, it can be found that due to excessive CTO, TiO2 reacts with segregated CuO to form CCTO again and reduce the CuO concentration at the grain boundaries. Therefore, this significantly reduces the grain boundary width, resulting in a colossal dielectric constant of 9.0 × 10⁵ at 30 Hz.
... The giant dielectric properties (GDPs) of dielectric materials with a high dielectric constant () have been extensively studied for use in electronics applications, such as capacitive devices used in high-energy storage devices [1][2][3][4][5][6][7][8][9][10][11][12][13]. Most recently, giant dielectric materials have been proposed as potential epsilon-negative or mu-negative materials [14][15][16]. ...
... Most recently, giant dielectric materials have been proposed as potential epsilon-negative or mu-negative materials [14][15][16]. High values of 10 3 10 5 in the low-frequency range without detectable phase transitions have been reported for a wide range of functional electroceramics, such as doped TiO 2 [4,17], doped SnO 2 [18], doped NiO [19], CaCu 3 Ti 4 O 12 (CCTO) and its related structures [3,5,[20][21][22][23], and La 2−x Sr x NiO 4 [24]. These ceramic oxides can be used in electronic devices, such as capacitors, sensors, and varistors. ...
The giant dielectric behavior of CaCu3Ti4O12 (CCTO) has been widely investigated owing to its potential applications in electronics; however, the loss tangent (tanδ) of this material is too large for many applications. A partial substitution of CCTO ceramics with either Al³⁺ or Ta⁵⁺ ions generally results in poorer nonlinear properties and an associated increase in tanδ (to ~0.29-1.15). However, first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Ti⁴⁺ sites, which can improve the electrical properties of the grain boundary (GB). Surprisingly, in this study, a greatly enhanced breakdown electric field (~200-6588 V/cm) and nonlinear coefficient (~4.8-15.2) with a significantly reduced tanδ (~0.010-0.036) were obtained by simultaneous partial substitution of CCTO with acceptor-donor (Al³⁺, Ta⁵⁺) dopants to produce (Al³⁺, Ta⁵⁺)-CCTO ceramics. The reduced tanδ and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure. The significant reduction in the mean grain size of the (Al³⁺, Ta⁵⁺)-CCTO ceramics compared to pure CCTO was mainly because of the Ta⁵⁺ ions. Accordingly, the increased GB density due to the reduced grain size and the larger Schottky barrier height (Φb) at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance, improved nonlinear properties, and reduced tanδ values compared to pure and single-doped CCTO. In addition, high dielectric constant values (ε′ ≈ (0.52-2.7) × 10⁴) were obtained. A fine-grained microstructure with highly insulating GBs was obtained by Ta⁵⁺ doping, while co-doping with Ta⁵⁺ and Al³⁺ resulted in a high Φb. The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.
... Compared with the BNT-BT and BNKT materials, Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 has excellent piezoelectric, dielectric, and ferroelectric properties, and its composition locates near the morphotropic phase boundary (MPB), near which it is easy for dielectrics to obtain excellent electrical properties. The compound has been intensively investigated, and its piezoelectric coefficient could reach to 620 pC/N [3,14,15]. Bai and co-workers synthesized lead-free (Ba 0.85 Ca 0.15 ) (Zr x Ti 1−x )O 3 (BCZT, 0.03 ≤ x ≤ 0.25) ceramics in a wide compositional range, and they claimed the composition of x = 0.1 located near MPB region is close to tetragonal phases, leading to the outstanding electrical behavior at room temperature [16]. Additionally, Liu and Ren synthesized the lead-free Ba(Ti 0.8 Zr 0.2 )O 3 − (Ba 0.7 Ca 0.3 )TiO 3 (Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 ; BCZT) ceramics by conventional solid-state reaction (SSR) method. ...
... Worse still, the inhomogeneous microstructure and impurity phases are easily formed in powders prepared using SSR routes [20]. Fortunately, the homogeneous microstructure, chemical purity, and fine particle sizes can be achieved at low calcining temperature and sintering temperatures through the wet chemical synthesis techniques [14,15]. Subsequently, a series of BCZT works have been conducted through wet chemical synthesis [21][22][23]. ...
... In this study, a sol-gel process was applied to prepare Ba 0.85 Ca 0. 15 2 and Ca(NO 3 ) 2 ·4H 2 O were mixed with distilled water and subsequently stirred at 80 °C for around 3 h until all salts were absolutely solved. In solution B, the C 16 H 36 TiO 4 was mixed with ethanol and citric acid while stirring at 80 °C for 1 h, and the molar ratio of citric acid to metal cations was 1.25:1. ...
The Ba0.85Ca0.15Zr0.1Ti0.9O3 (referred to as BCZT) ceramic powders were synthesized by the sol–gel method followed by calcining, and then the ceramics were obtained by sintering at different temperatures varied from 1200 to 1350 °C. The effects of sintering temperature on the microstructure, impedance spectroscopy, dielectric, and ferroelectric properties for BCZT ceramics have been thoroughly investigated. The pure perovskite structure and homogenous microstructure with high relative density (> 90%) for all BCZT ceramics are identified by XRD analysis and SEM measurement, and the stability is identified by the variable-temperature dielectric characterization. The impedance spectroscopy and well-defined polarization–electric field hysteresis loops for BCZT samples were detected at room temperature. In particular, the BCZT ceramic sintered at 1300 °C resulted the highest dielectric constant (εr ~ 2170), the lowest dielectric loss (tan δ ~ 0.027), and the highest grain boundary resistance (Rgb ~ 8.9 × 107 Ω cm).
... Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gfer. has a high dielectric loss which is not desirable for electrical applications [12][13][14]. To decrease the dielectric loss, many researchers have substituted Mn 2þ [15], Eu 3þ [16], Zr 4þ [17], Al 3þ [18], Ag 3þ [19], Te 4þ [20], Yb 3þ [21], Fe 3þ [22], and Nb 5þ and Fe 3þ together [23], into CCTO ceramics. ...
CaCu3Ti4-xAxO12 (CCTAO) ceramics, where A is one of the following: no ion, Nd³⁺, Gd³⁺, Sb³⁺ or Sn⁴⁺ were synthesized by the solid-state reaction method. The effects of ion substitution into CCTAO ceramics on the structure, microstructure and dielectric properties were studied. The structure of the CCTAO ceramics was characterized by X-ray diffraction with the patterns fit by the Rietveld refinement technique using the FullProf program. The results indicated that all the samples were mono-phased and had a cubic structure. Gd³⁺, Nd³⁺, Sb³⁺ and Sn⁴⁺ ions strongly inhibited grain growth in CCTAO ceramics. The densification increased and porosity decreased with the addition of Gd³⁺, Nd³⁺ and Sb³⁺ ions. The dielectric loss of CCTAO ceramics substituted with a very small amount of Sb³⁺ greatly reduced, while maintaining a high dielectric constant. The dielectric loss of CCTAO ceramics substituted with a very small amount of Sb³⁺ greatly reduced, while maintaining a high dielectric constant. The substitution of Gd³⁺ increased the dielectric constant and dielectric loss. The substitution of Nd³⁺ and Sn⁴⁺ caused a drop of the dielectric constant at low temperatures and increased the dielectric constant at high temperatures by >90 °C for Nd³⁺ and >130 °C for Sn⁴⁺.
... One of the most important electronic components is the ceramic capacitor. The development of a smaller capacitor has been extensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. A dielectric material with a dielectric permittivity of ε′ > 10 3 plays an important role in such development. ...
... This material is called giant dielectric or colossal dielectric material. CaCu 3 Ti 4 O 12 (CCTO) ceramics are giant dielectric materials that have attracted researchers' attention [1][2][3][4][5][6][7][8][9]. Although this material has an ε′ > 10 4 , the dielectric loss tangent (tanδ) value is 0.05 at 1 kHz [1,2], which is not applicable for use as an electric capacitor. ...
CaCu3Ti4O12/In0.05Nb0.05Ti0.90O12 (CCTO/INTO) composite ceramics with volume fraction ratios of 0.9/0.1 (10% INTO) and 0.8/0.2 (20% INTO) were prepared via a solid-state reaction method. XRD results indicated the mixed CaCu3Ti4O12 and TiO2 phases in the CCTO/INTO composite ceramics. The lattice parameter of the CCTO phase increased as the INTO composition increased, indicating the entry of some Nb5+ and/or In3+ ions into the CCTO lattice structure. The mean grain size of the CCTO/INTO composite ceramics was smaller than that of the CCTO ceramic, demonstrating that the grain boundary mobility of the CCTO phase was decreased by the INTO particles. Improved dielectric properties were achieved with a low dielectric loss tangent (0.029-0.046) in the CCTO/INTO composite ceramics, while high dielectric permittivities (5.0 × 103-8.6 × 103) were achieved. Nonlinear J-E behavior was demonstrated in the all-ceramic samples. The dielectric and nonlinear properties of the CCTO and CCTO/INTO composite ceramics originated from an internal barrier layer capacitor effect.
... Due to the enhanced semiconducting nature, metal oxide doping would cause the decrease of leakage current and the breakdown electric field [16,18]. In addition, many researchers seek for other strategies to enhance dielectric constant and decrease dielectric loss by modifying of the second phase, such as TiO 2 [19,20], Al 2 O 3 [21], CaTiO 3 [22] and so on [23][24][25][26][27]. CCTO ceramics modified by TiO 2 can obtain a giant dielectric constant (~6.81 × 10 4 ) with low dielectric loss (< 0.12) at room temperature [20]. Sonia et al. reported that the permittivity of CCTO could be enhanced to 81000 from 58000 at 1 kHz by altering the state of the grain boundary with Al 2 O 3 [21]. ...
... Fig. 6(b) shows that the dielectric constant of CCTO ceramics modified by 0.5% MgO possesses the similar trend with the pure ceramics. As displayed in Fig. 6(c-d), a plateau region of permittivity can be seen at higher temperature above 120°C for 0.4 and 1 kHz, as observed in many studies [19]. The dielectric constants of CCTO ceramics modified with 1% and 2% MgO change slightly with the increase of the temperatures, which indicates that dielectric constants of the two samples show low dependence on temperature. ...
... With the increase of frequency, the fast-growing region shifts to higher temperature, which has been reported in previous study [19]. The results show that dielectric constant of CCTO ceramics modified by 1% MgO exhibit a large dielectric constant in a wide temperature range, and the dielectric constant is almost independent on temperature. ...
Colossal permittivity material CaCu3Ti4O12 (CCTO) ceramics modified by MgO with the mass fraction of 0%, 0.5%, 1%, and 2% were synthesized using a sol-gel method followed by a conventional ceramic preparation process. The scanning electron microscope exhibits that all CCTO ceramics possess the high densities and large grain size. The results of dielectric measurement show that all the samples possess giant dielectric properties. The colossal dielectric constant of CCTO ceramics increases firstly and then decreases with the increase of mass fraction from 0% to 2% at room temperature, while the value of dielectric loss is opposite. Specifically, the sample with the mass fraction of 1% shows the highest density, largest grains and most obvious grain boundaries. 1% sample also shows better electrical properties with giant dielectric constant (~6.59 × 10⁴ at 1 kHz) and low dielectric loss (~0.06 at 1 kHz) at room temperature. In addition, the optimal sample with the mass fraction of 1% shows a more stable dielectric constant from 20 °C to 200 °C. The electrical properties of the CCTO ceramics have achieved good performance by the addition of MgO.
The crystal structure, microstructure, dielectric properties and energy storage properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics with various TiO2 (0%, 1%, 8%, 40%, 50%, 60%) addition ceramics were discussed. Although the perovskite structure remained in samples with low content of TiO2, the secondary phase Ba2Ti5.5O13 appeared in samples with high TiO2 content. According to SEM results, the addition of TiO2 resulted in a significant decrease in the average grain size. Wtih the addition of TiO2, the phase transition temperature, corresponding to Curie temperature (Tc) of BCZT ceramics shifts to lower temperature. Compared with the pure BCZT ceramic, the higher impedance and slimmer hysteresis loops were realized in ceramics with high TiO2 content. The relatively large energy storage density (Wrec ~0.52 J/cm3) together with energy storage efficiency (η ~74.84%) were achieved in ceramic with 40% TiO2 content. When the contentration of TiO2 further increases, the energy storage efficiency increased, but the energy storage density declined. The present research provides a method to improve the energy storage performance of BCZT ceramics.
Napier grass fibre was utilized for the development of biocomposite
through nanocrystalline cellulose (NCC). NCC was generated by 64 wt% sulphuric
acid in the hydrolysis cycle with 60 min time reaction. Biocomposite in film form
has been prepared by mixing Poly (lactic acid) (PLA) and NCC using a method of
solvent casting. In manufacturing of biocomposite films, NCC with different composition (0, 3, and 6 wt%) was used. The result of XRD analysis displayed an increase
of crystallinity for PLA/NCC film compared to pure PLA film. However, PLA/NCC
film with 6 wt% content of NCC (PLA/NCC-6) exhibited the highest percentage of
crystallinity (69%). The chemical interaction of the structure between the NCC filler
and the polymer matrix was studied using FTIR which confirmed by the presence of
hydrogen bonding and the same trend of spectra was observed due to existence of
PLA. PLA/NCC-3 demonstrated the lowest water absorption (0.37%) compared to
pure PLA and PLA/NCC-6 film.
