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Modified copper calcium titanate (MCCTO) or functional activated carbon (FANC) particles were added to functional polypropylene (FPP) or heat‐treated polypropylene (HTFPP) matrix to improve the performance of FPP as dielectric films. By testing and characterizing the prepared FPPwxMCCTOy, FPPwxFANCz, FPPwxMCCTOyFANCz and HTFPPwxMCCTOy, HTFPPwxFANCy and HTFPPwxMCCTOyFANCz films, It is found that the dielectric constant and discharge energy density of each FPPwxMCCTOy, FPPwxFANCz, HTFPPwxFANCz and HTFPPwxFANCz films reach the maximum when the MCCTO and FANC loads are close to 8 and 6 wt% respectively. FPPwxMCCTO8FANCz and HTFPPwxMCCTO8FANCz series films also obtain the maximum dielectric constant and discharge energy density at FANC load approaching 6 wt%. The discharge energy density of HTFPPw86MCCTO8FANC6 film prepared properly is 3.2 J/cm3, which is more than 3 times higher than that of FPP. When MCCTO and FANC loads are ≦8 and 6 wt% respectively, with the increase of additive content, More dense distribution of MCCTO and FANC was observed in FPPwxMCCTOy(or HTFPPwxMCCTOy), FPPwxFANCz(or HTFPPwxFANCz) and FPPwxMCCTO8FANCz(or HTFPPwxMCCTO8FANCz) series film sections. In this paper, we propose possible explanations for the apparent improvement in dielectric constant, discharge energy density and heat resistance of capacitive films after appropriate heat treatment or addition of appropriate MCCTO and/or FANC loads. [ABSTRACT FROM AUTHOR]

The objective of the research is to study wear resistance characteristics of ceramics reinforced polymer composites against the solid particles impact. The composite specimens were prepared with polymer and ceramic fillers at fixed proportion of 80:20 by hand-lay-up technique. Barium titanate and calcium copper titanate were mixed in the ratios of 100:0, 0:100, 50:50, 60:40 and 40:60 to use as hybrid filler. Erosion wear test was conducted as per ASTM standard at three different velocities (48, 70 and 82 m/s) and four distinct impinging angles (30°, 45°, 60° and 90°), respectively. The experimental result shows that the striking velocity and impinging angle of sand particles have noticeable effect on wear rate. Irrespective to velocity of particle, a higher value of wear rate was obtained at 60° of impact indicating a semi brittle behavior of ceramics. The eroded surfaces of the worn samples were analyzed with SEM to ascertain the failure mechanism of the developed composites. The formation of crack and crater, wear debris, micro-plowing and micro-cutting of the erodent particles on the composite surface were the predominant mechanisms causing the erosion loss. [ABSTRACT FROM AUTHOR]

Conventional charge storage devices made of ceramic materials have limited deformability and configurability due to their extreme stiffness. The high demand for compliant dielectrics has led researchers to look beyond conventional ceramics, despite their very high dielectric properties. In this work, a mechanically robust, highly‐flexible and ultra‐stretchable thermoplastic elastomeric material with dielectric characteristics has been fabricated by introducing calcium copper titanate [CaCu3Ti4O12] (CCTO) dielectric material onto macromolecular chains of styrene–isoprene–styrene (SIS) triblock copolymer via a solution‐based polymer processing technique. CCTO powders have been synthesized using sol–gel technique. The resulting composite is ultra‐stretchable with strain at break of ~3200% and has high dielectric permittivity of ~10. High dielectric property is attributed to the well‐dispersed dielectric CCTO fillers within the SIS matrix, which provide sites for interfacial polarization and space charge accumulation. The influence of CCTO on dielectric properties has also been validated using the modified Cole–Cole model. [ABSTRACT FROM AUTHOR]

With the development of electronic information technology, people have put forward more requirements for miniaturization and multifunctionality of electronic devices. Obtaining dielectric materials with good dielectric response is a research challenge. Calcium copper titanate (CCTO) ceramics have attracted widespread attention from researchers due to their high dielectric constant, good stability, and strong applicability. However, it has a significant dielectric loss, which limits its further development and application. Based on this, this paper systematically reviews the research progress of CCTO in terms of dielectric loss, focusing on the influence of different doping modification strategies on the dielectric loss characteristics. The selection of different sites, types, amounts, and properties of dopants has an important impact on dielectric loss, and controlling the grain size and grain boundary resistance can achieve low dielectric loss. The potential future development directions of CCTO mainly include the development of new doping strategies, research on doping modification mechanisms, and applications of materials in multiple fields. This work lays the foundation for the study of CCTO and its application in electronic devices, and is of great significance for the development of new materials and the improvement of their performance. [ABSTRACT FROM AUTHOR]

Calcium copper titanate (CCTO)/polystyrene–polyethylene–polybutylene–polystyrene (SEBS) dielectric elastomers were prepared via blending method. A capacitive strain sensor using CCTO/SEBS as dielectric layer and polyaniline–dodecylbenzensulfonic acid (PANI–DBSA)/SEBS as electrodes was designed and manufactured by thermoforming process. X-ray diffractometer (XRD), scanning electron microscopy (SEM) and Raman spectra analyses were carried out; no impurities were found in the composite and CCTO particles were well dispersed. The dielectric tests showed that the samples filled with 20 wt% CCTO have their permittivity improved by 70%. The capacitive strain sensors have a stabilized capacitance variety range at different strain ranges or stretch speeds, and could remain synchronized after 500-time-stretching, showing high reproducibility. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir‐doped calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A gIr−1 for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO2. By substituting Ti with Ir in CCTO, metal‐oxygen (M‐O) covalency can be significantly increased leading to the reduced energy barrier for charge transfer. Further, highly polarizable CCTO perovskite referred to as "colossal dielectric", possesses low defect formation energy for oxygen vacancy inducing a high number of oxygen vacancies in Ir‐doped CCTO (Ir‐CCTO). Electron transfer occurs from the oxygen vacancies and Ti to the substituted Ir consequentially resulting in the electron‐rich Ir and ‐deficient Ti sites. Thus, favorable adsorptions of oxygen intermediates can take place at Ti sites while the Ir ensures efficient charge supplies during OER, taking a top position of the volcano plot. Simultaneously, the introduced Ir dopants form nanoclusters at the surface of Ir‐CCTO, which can boost catalytic activity for the acidic OER. [ABSTRACT FROM AUTHOR]

Calcium Copper Titanium Oxide (CCTO) Ceramics of composition CaCu3Ti4O12 has emerged as a lead-free ceramic supercapacitor with a large dielectric constant of 104–105 at room temperature. The CCTO microstructure is electrically heterogeneous composed of semiconducting grains and insulating grain boundaries. The origin of the large dielectric constant has therefore been widely attributed to barrier layer capacitance originated at grain boundaries. Our research is focused on understanding the stability and reproducibility of the measured electrical and dielectric properties when they are used as capacitor dielectrics because of the inconsistent results obtained when tested in ambient conditions. The origin of this inconsistency is investigated through the roles of testing atmosphere, sample thickness and doping with alumina on the stability and reproducibility of dielectric properties of CCTO. The solid state reaction method is used to fabricate phase pure and dense samples. AC impedance spectroscopy is used to study the roles of testing atmospheres, temperatures, microstructures, grain boundaries, sample thickness, alumina doping and frequency on the dielectric properties. It is shown that this approach of characterizing fundamental electrical properties of CCTO can be used to eliminate hysteresis to produce stable and reproducible dielectric properties. These perspectives are presented and discussed. [ABSTRACT FROM AUTHOR]

AC electrical measurements were carried out on iodine doped, CaCu 3 Ti 4 O 12-x I x (x = 0, 0.005, 0.05 and 0.2) ceramic specimens sintered at 1100 °C for 12 h in the temperature (300–450 K) and frequency (20 Hz - 1 MHz). The crystalline structure, microstructure, and oxidation state of various ions of pure and iodine-substituted sintered specimens were carried out through XRD, SEM, and XPS, respectively. The dielectric relaxations in grains, grain boundaries, and sample-electrode interfaces for different compositions were investigated through impedance and modulus spectroscopic techniques and were reported in the first part of the investigation. It revealed the involvement of similar types of charge carriers in conduction and relaxation processes in grains and grain boundaries, respectively. This second section emphasizes the dielectric and conduction properties of CaCu 3 Ti 4 O 12 (CCTO) with iodine doping at the anion site. The XPS study reveals that the concentration [ V O • • ] is reduced, and [ V M ″ ] gets increased with increasing concentration of iodine from x = 0.05 to 0.2. This observation also supports the point defect model as reported earlier for charge compensation of impurity defect I O • i.e., with increasing substitutions of iodine, the charge on I O • change from electronic to cationic vacancies, V T i / / / / or copper V C u / / or both to keep electrical charge neutrality. The metal ions get segregated at grain boundaries. This, in turn, will minimize hopping due to electrons between Ti4+ and Ti3+ or Cu2+ and Cu1+. As a result, it increases resistivity and minimizes dielectric losses for the higher concentration of iodine doping. Thus, a high concentration of iodine doping at the oxygen site promotes the formation of a barrier layer capacitor. [ABSTRACT FROM AUTHOR]

Abstract Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir‐doped calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A gIr−1 for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO2. By substituting Ti with Ir in CCTO, metal‐oxygen (M‐O) covalency can be significantly increased leading to the reduced energy barrier for charge transfer. Further, highly polarizable CCTO perovskite referred to as “colossal dielectric”, possesses low defect formation energy for oxygen vacancy inducing a high number of oxygen vacancies in Ir‐doped CCTO (Ir‐CCTO). Electron transfer occurs from the oxygen vacancies and Ti to the substituted Ir consequentially resulting in the electron‐rich Ir and ‐deficient Ti sites. Thus, favorable adsorptions of oxygen intermediates can take place at Ti sites while the Ir ensures efficient charge supplies during OER, taking a top position of the volcano plot. Simultaneously, the introduced Ir dopants form nanoclusters at the surface of Ir‐CCTO, which can boost catalytic activity for the acidic OER.

In this paper, we examined the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics fabricated by various routes and discussed the most important conditions affecting their dielectric behavior. We prepared feedstock powder using a molten salt route and compared it with a commercial powder. Both powders were sintered using SPS. For some samples, annealing was applied after sintering. Other samples were obtained by high-pressure forming and conventional sintering, using both powders. Phase composition, porosity and microhardness were evaluated in comparison with the literature. The results showed that a sintering temperature just below or equal to 1000 °C should be set for the SPS process. However, the best dielectric characteristics were obtained in samples prepared by high-pressure forming and conventional sintering, which showed a relative permittivity of 22,000 and a loss tangent of 0.13 at 1 MHz.

This report describes a comparative study of dye degradation under 20-W LED light using the perovskite photocatalyst Calcium Copper Titanate (CCTO) and its compositions (CaxCu3-xTi4O12) (x = 1, 1.5 and 2), synthesized by changing molar ratios of Ca2+ and Cu2+ ions. The 99.74% degradation of Rhodamine Blue (RhB) with composition (x = 1) within 6 h is reflected its better photocatalytic activity than the parent CCTO and other compositions. The band gap energy of the materials 2.18 eV (CCTO), 1.93 eV (x = 1), 2.40 eV (x = 1.5), and 2.55 eV (x = 2) are analysed with UV–Vis spectroscopy. The presences of Ca, Cu, Ti and O in the synthesized photocatalysts are confirmed with Elemental X-ray Dispersive (EDX) analysis. The cubic phases in the polyhedral shape of the materials are detected in X-ray diffraction and Scanning Electron Microscopy (SEM). This report further observes the defect density concentrations of the materials with Photoluminescence Spectroscopy (PL) and provides the approximate explanation of their dye degradation performance as photocatalysts. The rate constants are found in a first order reaction trend; where the composition (x = 1) shows about 1.683 × 10–2 min−1. The mechanistic understanding of the degradation process is also revisited and rationalized with different scavengers for the process. [ABSTRACT FROM AUTHOR]

The origin of abnormal ferroelectric and unusual piezoelectricity in the polycrystalline CaCu3Ti4O12 (CCTO) thin films deposited by RF-sputtering on Pt/Ti/SiO2/Si (100) substrates was explored. The CCTO thin films, deposited at room temperature followed by annealing at 600 °C for 2 h in a conventional furnace, have a cubic structure with lattice parameter a = 7.379 ± 0.001 Å and without any secondary phases. No polarization loss up to 1010 switching cycles, with a switched polarization ∆P of 30 µC/cm2 measured at 400 kV/cm was evidenced. The piezoelectric coefficient investigated by piezoresponse force microscopy (PFM) was approximately 9.0 pm/V. This may be the very first example of exploring the origin of ferroelectric behaviour for a material that possesses space charge polarization with highly resistive grain boundaries in the polycrystalline state.

Influence of acrylonitrile content and ceramic type on cure characteristics, mechanical, morphological, and dielectric properties of acrylonitrile butadiene rubber (NBR) vulcanizates was examined. Two types of ceramic filler, namely barium titanate (BT) and calcium copper titanate (CCTO), were synthesized by solid-state reactions. The ceramic powders were then characterized by X-ray diffraction, particle size analyzer, and scanning electron microscopy (SEM). Ceramic/rubber composites were then mixed in an internal mixer at 60 °C and a rotor speed of 60 rpm. Two acrylonitrile contents of NBR, namely 33 wt% and 42 wt%, were tested. Incorporation of ceramic fillers in NBR matrix and increasing acrylonitrile content shortened scorch and cure times, but increased minimum, maximum, and delta torque. Furthermore, SEM results revealed that the BT-filled NBR composites showed better filler–matrix interactions than the CCTO-filled NBR composites. This matches the better mechanical and dielectric properties of the BT-filled NBR composites. [ABSTRACT FROM AUTHOR]

Calcium copper titanate (CCTO) has been synthesized by high temperature solid‐state reaction from calcium carbonate, copper (II) oxide, and titanium dioxide as the starting materials. The formation and morphology of CCTO were confirmed by X‐ray diffraction, Fourier‐transformed infrared spectrophotometry, scanning electron microscopy (SEM), and particle size analysis. In order to develop flexible dielectric materials, acrylonitrile‐butadiene rubber (NBR)‐based composites were prepared with CCTO content varied from 0 to 120 phr (parts per hundred rubber). The cure characteristics of composites were assessed. High‐dielectric constant CCTO particles were blended into NBR to make composites with improved dielectric constant. Results showed that the NBR/CCTO composites had a high dielectric constant (10–20) with low dielectric loss (<0.4) and low conductivity (<10−3 μS/cm) at frequencies up to 106 Hz. However, the higher CCTO loadings had agglomeration in the NBR matrix, and thus tensile strength and elongation at break sharply deteriorated due to poor rubber‐filler interactions. The results showed lower storage modulus E′ and a reduction in Tg with the incorporation of CCTO in NBR matrix. Moreover, improved thermal stability of the NBR/CCTO composites was achieved. SEM was used to observe the dispersion of CCTO particles in NBR matrix. [ABSTRACT FROM AUTHOR]

ESR, XPS and NEXAFS spectra, as well as magnetic and electric properties of CaCu 3 Ti 4 O 12 synthesized by the solid-phase method within 6,12,24,48 and 60 h were studied. The analysis of magnetic susceptibility of CaCu 3 Ti 4 O 12 and magnesium-containing solid solutions of CaCu 3-3x Mg 3x Ti 4 O 12 revealed antiferromagnetic exchange interactions between Cu paramagnetic atoms, while the effective magnetic moment of copper atoms corresponds to the electronic state of Cu(II). In CaCu 3 Ti 4-4х Mg 4х O 12-δ samples within the whole concentration range the impurity phase MgTiO 3 was observed. The magnetic properties of calcium copper titanate were found to be inconsistent depending on the synthesis duration. The extreme point of magnetic susceptibility was found among samples synthesized within 48 h. Modelling and interpretation of the XPS spectra of CaCu 3 Ti 4 O 12 were performed. Based on the NEXAFS and XPS spectroscopy data, copper and calcium atoms in ceramics display oxidation state +2, while titanium atoms – Ti(IV). ESR spectra of CaCu 3 Ti 4 O 12 samples show an exchange-narrowing signal from copper (II) atoms at g = 2.15. In the ESR spectra of CaCu 3-3x Mg 3x Ti 4 O 12 the only intense exchange-narrowed line of Lorentzian form of Cu2+ ions is observed. The impedance spectroscopy study of electric properties of CaCu 3 Ti 4 O 12 found the media to feature temperature-dependent reach-through conductivity with activation energy of 0.79–0.71 eV. At 255–300°С, the dominant polarization process is in line with the Gerischer model. It indicates the formation of anionic-cationic associates accompanied by decreased low-frequency capacitance of the samples. With temperatures of over 300°С the samples start displaying ion-migrating polarization which contributes to higher capacitance and dielectric loss at low frequencies. As the temperature grows further to 400°С, the ion migration process gets to dominate within the whole frequency range under study. Based on the study, a conclusion was made on movable cations of copper participating in the polarization process at room temperature. [ABSTRACT FROM AUTHOR]

Calcium Copper Titanate Ceramics (CaCu3Ti4O12; CCTO) are useful as capacitors because of the large dielectric constant. This study investigated the effect of testing atmospheres such as air and dry N2 on the stability and reproducibility of the electrical properties displayed by CCTO ceramics. Solid‐state reaction method is used to synthesize phase pure CCTO powders, which are used to fabricate dense samples by sintering. Samples with different microstructures are obtained by sintering at different temperatures of 1070 and 1100°C. AC impedance spectroscopy is used to study the effects of testing atmospheres, temperatures, microstructures, and frequency on the dielectric properties of the sintered samples. Highly irreproducible dielectric properties are observed upon testing in ambient conditions. Stable and reproducible dielectric properties are only obtained in dry N2. Re‐exposing the same CCTO samples back into ambient air after treating in dry N2 restored irreproducibility. The results from this study suggested that the role of moisture/air in the ambient on the dielectric properties should not be over‐looked and is expected to play a key role in controlling the stability of dielectric properties of CCTO. This new approach of characterizing the CCTO ceramics can be used as guidelines to eliminate hysteresis due to ambient atmosphere and to produce stable and reproducible dielectric properties useful as capacitors. [ABSTRACT FROM AUTHOR]

Phase pure CaCu 3 Ti 4 O 12 CCTO ceramics are prepared by solid-state synthesis route. The effect of measuring atmospheres (air and dry N 2) on the stability and reproducibility of electrical properties of CCTO as a function of sample thickness (as-prepared to thinned down) is investigated. As-sintered CCTO prepared at 1080 °C for 5 h with an initial thickness of 2.31–2.32 mm is reduced subsequently by fine grinding to 1.835 mm and then to 1.65–1.5 mm. Large inconsistency in the impedance spectra is observed when the samples are measured in air despite the thickness variations. Stable and reproducible dielectric properties are obtained in dry N 2. A relatively closer resistivity (∼2 × 108 Ωcm at 23 °C in N 2) regardless of the sample thickness suggests the absence of any barrier layer at the sample surface. Increased space charge accumulation at grain boundaries (GBs) leading to much larger dielectric constant (ε′) was observed in air at 23 °C. A temperature (from 23 °C to 225 °C) and frequency (from 1 Hz to 1 MHz) independent and stable ε′ is observed when samples are tested in N 2. Much lower tan δ values with large ε′ are observed for both as prepared (0.010 ± 0.001 with ε′ of 9,663 ± 4 at 1.4 kHz) and the thinned down (0.015 ± 0.000 with ε′ of 9,352 ± 5 and 4.5 kHz) samples at 23 °C in N 2. [ABSTRACT FROM AUTHOR]

The stability and consistency of electrical properties displayed by calcium copper titanate (CaCu3Ti4O12–CCTO) ceramics are the most important concern when they are used as capacitor dielectrics. This study investigated the influence of exposure to air and dry N2 atmospheres on dielectric properties of the as-prepared CCTO as a function of temperature. Solid-state synthesis route has been used to fabricate the CCTO sintered pellets at 1100 °C for 5 h in air. Highly inconsistent impedance spectra and dielectric properties are observed in the frequency range from 1 Hz to 1 MHz when the samples are tested in air at 23 °C. In contrast, stable and consistent electrical properties are obtained by testing the samples under dry N2. Value of tanδ as small as 0.014 and a large dielectric constant (ε′) of 12,935 ± 2 at 2.2 kHz are obtained when samples are exposed and tested in dry N2 at 23 °C. The details concerning the possible underlying mechanisms responsible for dielectric properties of CCTO are reported in this article. [ABSTRACT FROM AUTHOR]

Abstract Herein, we report an electrochemical property of giant dielectric quaternary oxide CaCu 3 Ti 4 O 12 (CCTO) nanocubes. Single crystalline nanostructures of CCTO are synthesized by simple molten salt method. X-ray diffraction (XRD), Field-emission scanning electron microscopy (FESEM), High resolution transmission electron microscopic (HRTEM) techniques are used to study the structural and morphological properties. XRD and HRTEM analysis confirm the formation of phase pure and single crystalline CCTO nanocubes. Detailed electrochemical performance of as synthesized samples has been carried out by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. Electrochemical properties of three different CCTO nanstructure synthesized at 800 °C for three different holding time (30 min, 1 h and 5 h) has been compared. CCTO nanocube electrodes provide maximum areal capacitance of 1185 mF cm−2 at a scan rate of 10 mV s−1 in aqueous KOH solution. An all-solid-state symmetric device has been fabricated by using CCTO nanocubes. The device delivers maximum areal capacitance 76 mF cm−2 at a scan rate of 10 mV s−1. Furthermore, the electrodes exhibit an excellent cycling stability with 94.8% capacitance retention even after 3000 cycles of charging discharging at a current density 10 mA cm−2. The present investigation explores possible use of single crystalline CCTO nanocubes as next generation supercapacitor material having a double perovskite structure. Graphical abstract Molten salt synthesis route of single crystal Calcium Copper Titanate towards symmetric supercapacitor applications fx1 Highlights • CCTO is prepared via molten salt route at different temperatures. • Characterization of as-prepared samples are carried out by XRD, XPS, FESEM and HRTEM. • Electrochemical performance of CCTO nanocube shows best result among the three samples. • Symmetric supercapacitor device has been fabricated by CCTO nanocubes. [ABSTRACT FROM AUTHOR]

Abstract Thermal stability of calcium copper titanate was studied by differential scanning calorimetry, thermogravimetry and high-temperature mass spectrometry. Calcium copper titanate (CCTO) had no thermal effects and mass losses caused by thermal dissociation or any phase transitions, besides melting, in the temperature range of 298–1423 K. The melting point of calcium copper titanate is 1398 K. The endothermic effect at 1250 K was associated with the decomposition of copper (II) oxide segregated in the intergrain space of the CaCu 3 Ti 4 O 12 -CuO ceramics. In this connection, we proposed a simple method for estimating the content of copper oxide in the CaCu 3 Ti 4 O 12 -CuO composite. The processes of evaporation of CaCu 3 Ti 4 O 12 in the temperature range of 1500–2100 K were studied by high-temperature mass spectrometry. In the temperature range of 1500–1750 K, easily volatilized copper oxide was evaporated selectively from the calcium copper titanate. At the temperature of 2100 K, atomic calcium and titanium oxides, TiO and TiO 2 , were present in the vapor. [ABSTRACT FROM AUTHOR]

The development of clean, sustainable and renewable energy sources is now the key to the urgent need to solve energy problems in countries around the world. How to efficiently store energy to reduce energy loss and reduce the burden on the environment is a hot topic of research. Traditional dielectric materials have low dielectric constants, low energy storage density and high dielectric losses, which seriously restrict their further development and application. Calcium copper titanate (CCTO) has become a new generation of capacitors and energy memories due to its high dielectric constant, good stability, fast dielectric response and other characteristics. It has an important role in the miniaturization, lightweighting and energy saving of electronic devices. Based on this, this paper firstly introduces the crystal structure, dielectric and photocatalytic properties of CCTO, then systematically analyses and compares the synthesis techniques of CCTO, followed by a summary of its performance enhancement strategies in electrical, optical, magnetic, thermal and acoustic aspects, and finally discusses the applications of CCTO in various fields and provides an outlook on potential future development directions. This review provides a foundation for the research and development of CCTO-based systems and is instructive for the development of CCTO in power conversion and energy storage. [Display omitted] • Intensively introduced and compared the eight synthesis techniques for CCTO. • Systematically analyzed and evaluated the four property enhancement strategies. • Comprehensively summarized the applications of CCTO in the eight scenarios. • This work has implications for clean and sustainable development of energy storage. [ABSTRACT FROM AUTHOR]

• Chromium ions substitute Ca and Ti sites in the Ca 1-x Cr x Cu 3 Ti 4 O 12 thin films. • The band gap increased with reduced grain size and oxygen vacancy concentration. • The Ca 0.8 Cr 0.2 Cu 3 Ti 4 O 12 thin film had the best dielectric and nonlinear properties. • Both intrinsic and external mechanisms contribute to excellent electrical properties. In the present work, the optical and dielectric properties, microstructures, and nonlinear electrical performances were systematically investigated for Ca 1-x Cr x Cu 3 Ti 4 O 12 (x = 0.00 - 0.40) thin films prepared on Pt/Ti/SiO 2 /Si substrates using the sol-gel method. X-ray photoelectron spectroscopy (XPS) verified that Cr3+ and Cr6+ were present in the thin films. Additionally, the content of secondary phase of titanium oxide (TiO 2) increased, the grain size decreased, and the surface roughness improved with the increase in the doped content of Cr. Due to the reduced grain size and oxygen vacancy concentration, the optical energy band gap increased from 2.92 to 3.54 eV. The change in the dielectric constants (Ɛ r) of the thin films followed the internal barrier layer capacitor model. Doping was found to decrease the dielectric loss (tan δ) and enhance the nonlinear properties, which was due to the presence of TiO 2 secondary phase, high density, reduced grain size, incremental potential barrier height and grain boundary resistance. The Ca 0.8 Cr 0.2 Cu 3 Ti 4 O 12 thin film had a high Ɛ r of around 9340, low tan δ of around 0.012 at 1 kHz, nonlinear coefficient of about 4.64, and breakdown field of ca. 89 kV/mm. These results indicated that the doping of an appropriate amount of Cr could effectively modify the microstructure of CaCu 3 Ti 4 O 12 thin films and improve their optical and electrical properties. [ABSTRACT FROM AUTHOR]

Abstract CaCu 2.9 Ni 0.1 Ti 3.9 Ni 0.1 O 12 (CCNTNO) polycrystalline powder of giant dielectric constant material was successfully obtained by solid-state reaction. The sample, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Raman spectroscopy, confirmed to be a pure phase CCTO associated with large grains surrounded by small ones of nearly cubic shape. The effect of Ni doping on optical properties of CaCu 2.9 Ni 0.1 Ti 3.9 Ni 0.1 O 12 has been determined. Furthermore, the dielectric constants of these co-doped ceramics (CCNTNO) were higher than that of CCTO pure prepared under the same conditions of synthesis. The grain size and the dielectric constant depended absolutely on doped and sintering time. Results confirm that co-doping CCTO by Ni in both copper and titanium sintered enhanced the grain growth as the sintered time is higher than 6 h. Especially ceramic sintered at 1100 °C for 12 h shows excellent abnormal growth grain with approximately 50–100 μm sized crystallites which displayed extraordinarily high dielectric constants up to 105 at 25 °C (most exceptional behavior). Based on these results, internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples. Loss factor and resistivity of these ceramics were equally interpreted. It must be noted also that the resistivity decreased largely if the sintering time is around 12 h as evidenced in the impedance plots. Highlights • Synthesis of new Ni-CCTO composition were Ni doped both Cu and Ti sites. • Comparative study between CaCu 3 Ti 4 O 12 and CaCu 2.9 Ni 0.1 Ti 3.9 Ni 0.1 O 12. • Adding of Ni-doping ions in CCTO both in Cu and Ti sites enhanced the grain size. • Enhancement of dielectric properties of CaCu 2.9 Ni 0.1 Ti 3.9 Ni 0.1 O 12. • Perfect correlation of dielectric properties, grain boundaries and resistance. [ABSTRACT FROM AUTHOR]

In this paper the microstructure and chemical composition of CaCu3Ti4O12 multilayer elements fabricated using low temperature cofired ceramics procedure were characterized by scanning electron microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The multilayer elements were obtained in the process encompassing: tape casting, laser cutting, screen printing, isostatic lamination and cofiring of ceramic tapes with internal conductive films at 940°. The compatibility of CaCu3Ti4O12 with three commercial Ag and Ag-Pd thick film pastes was confirmed. The results of scanning electron microscope and energy dispersive spectroscopy analysis revealed close to the stoichiometric composition of CaCu3Ti4O12 grains and significant enrichment in oxygen of grain boundaries. X-ray photoelectron spectroscopy studies showed that main oxidation states of the component elements were Cu2+, Ti4+, and Ca2+. [ABSTRACT FROM AUTHOR]

The problem of detecting the toxic hydrogen sulfide (H 2 S) gas at part per million levels in air by means of simple solid state gas sensors is relevant to environmental and gas processing industries. In this work, high-performance H 2 S gas sensors are developed based on nickel-doped calcium copper titanate (Ni-doped CCTO) thin films synthesized by a sol-gel method. From gas-sensing measurements, the response of Ni-doped CCTO sensing films increased substantially with increasing Ni doping level from 1.5 to 7.3 wt%, revealing a catalytic effect of Ni on the surface reactions with adsorbed H 2 S molecules. In particular, 7.3 wt% Ni-doped CCTO sensors offered a high response of 120 for 10 ppm of H 2 S at the optimal operating temperature of 250 °C, an order of magnitude higher than that of undoped one. In addition, the response time dropped significantly from ∼80 s to ∼4 s while the recovery time slightly improved as the Ni doping content increased from 0 to 7.3 wt%. Moreover, the Ni-doped CCTO sensors exhibited good reproducibility and high H 2 S selectivity against ethanol, H 2 , NO 2 and NH 3 . Therefore, the Ni-doped CCTO sensors are highly promising for sensitive and selective detections of H 2 S. [ABSTRACT FROM AUTHOR]

In this work, Sr and Zn co-doped calcium copper titanate having nominal formula Ca 0.90 Sr 0.10 Cu 3 Ti 3.95 Zn 0.05 O 12 has been synthesized and systematically studied for structure, dielectric and electrical properties. The phase purity of the prepared composition has been confirmed by X-ray diffraction (XRD) pattern and various structural parameters are presented here with Rietveld refinement data. The Scanning electron microscopy (SEM) image revealed the presence of homogeneous fine-grained microstructure investigated in the prepared ceramic. The impedance data well fitted with 2 R-CPE model confirmed the non-ideality of the system. Dielectric studies have shown the existence of two relaxation processes in low and high frequency domains. Low frequency dielectric response proposed as a combination of Maxwell-Wagner relaxation and intrinsic defect (V o ++ ) while high frequency behavior has been interpreted in terms of polaronic relaxation caused by hopping process of an electron between Ti 3+ and Ti 4+ states. The frequency dependent behavior of conductivity has been well fitted to Dong’s model and interpreted in term of Overlapping Large Polaron Tunneling (OLPT) mechanism. The various parameters; relaxation angular frequency (ω 1 ) of Debye process, ionic hopping frequency (ω 2) , dc conductivity (σ o ), cole- cole parameter (α) and frequency exponent (s) have been determined by Dong’s Model fitting. [ABSTRACT FROM AUTHOR]

Calcium copper titanate(CCTO)/polyurethane composite films with high dielectric constant, low dielectric loss and super flexibility were fabricated by incorporating CCTO ceramic powders into millable polyurethane elastomer (MPU) matrix using a rubber milling combined with hot compression molding method. The composite films show uniform microstructures and the dielectric constant is as high as 35.2 while the dielectric loss is only 0.041 when CCTO content reaches 40 vol% at 100 Hz and room temperature (RT). Moreover, it is important to note that this film has stable dielectric constant and dielectric loss in a relatively wide temperature range (from 0 °C to 70 °C), which is significantly import to the practice use of electronic devices based on CCTO composites. In addition, the flexibility of the film could be retained even when the CCTO content is up to 40 vol% and the elongation at break of this composite film is as high as 159.1%. Theoretical analysis indicates that the experimental data are in good conformity to the effective medium theory (EMT) model with a derived n = 0.21, suggesting more close association of the dielectric constant with the CCTO filler size and shape. [ABSTRACT FROM AUTHOR]

Rapid synthesis of long calcium copper titanate (CCTO) nanorods was carried out by sequential annealing. CCTO thin films have been deposited on p-Si substrate by RF sputtering technique and afterwards, the samples were thermally treated using a preheated furnace by varying the annealing temperature from 850 °C to 1100 °C. CCTO nanorods of 12 µm lengths and 400–600 nm diameters were synthesized at 1100 °C. Based on the FESEM observations, a plausible growth mechanism has been proposed to explain the formation of nanorods. The (220) XRD peak of the CCTO film became prominent for the annealing temperature of 950 °C. The presence of nanoscale crystals in amorphous matrix has been observed by HRTEM studies. The elemental mapping of CCTO nanorod has shown a spatial variation of elements throughout the nanorod. The oxide and interface charge density was found to be increased with the rise in annealing temperature. [ABSTRACT FROM AUTHOR]

In this study, M n F e 9 n + 3 O 15 n + 4 ( 0 ≤ n ≤ 1 ) (M = Ba, Sr), (n = 0, Fe 3 O 4 ) and (n = 1, M = Ba, Sr, barium-strontium hexaferrites (BaFe 12 O 19 - SrFe 12 O 19 )), CaCu 3 Ti 4 O 12 (CCTO) and Phosphorus-doped graphitic carbon nitride (P-g-C 3 N 4 ) were synthesized by co-precipitation-calcination, semi-wet sol-gel and specific heat program methods, respectively. Morphology and crystal structure of synthesized powders were characterized by SEM and XRD, respectively. To investigate the absorption properties, the scattering parameters were measured by a vector network analyzer. Type and wt% of M n F e 9 n + 3 O 15 n + 4 ( 0 ≤ n ≤ 1 ) (M = Ba, Sr), wt% of CCTO and wt% of P-g-C 3 N 4 were selected as factors at the Taguchi method and optimized to obtain a nanocomposite with higher microwave (MW) absorption efficiency. The minimum reflection loss (RL) (higher absorption efficiency) was reached less than −30 dB (absorption >99.9%) for optimized sample with optimal conditions, including 1 wt% of Fe 3 O 4 , 3 wt% of CCTO, 1 wt% of P-gC 3 N 4 with only 1 mm thickness at the 8–12 GHz frequency range (X-band). [ABSTRACT FROM AUTHOR]

In order to develop high-performance dielectric materials, poly(arylene ether nitrile)-based composites were fabricated by employing surface-hydroxylated calcium copper titanate (CCTO) particles. The results indicated that the surface hydroxylation of CCTO effectively improved the interfacial compatibility between inorganic fillers and the polymer matrix. The composites exhibit not only high glass transition temperatures and an excellent thermal stability, but also excellent flexibility and good mechanical properties, with a tensile strength over 60 MPa. Furthermore, the composites possess enhanced permittivity, relatively low loss tangent, good permittivity-frequency stability and dielectric-temperature stability under 160 °C. Therefore, it furnishes an effective path to acquire high-temperature-resistant dielectric materials for various engineering applications.

Calcium copper titanate (CaCuTiO, CCTO) thin films have been deposited on platinized silicon [(111)Pt/Ti/SiO/Si] substrate through a sol-gel spin coating technique and annealed at 600-900°C with a variation of 100°C per sample for 3 h. The activation energy for crystalline growth, as well as optimal annealing temperature (900°C) of the CCTO crystallites was studied by x-ray diffraction analysis (XRD). Thickness dependent structural, morphological, and optical properties of CCTO thin films were observed. The field emission scanning electron microscopy (FE-SEM) verified that the CCTO thin films are uniform, fully covered, densely packed, and the particle size was found to be increased with film thickness. Meanwhile, quantitative analysis of dielectric properties (interfacial capacitance, dead layers, and bulk dielectric constant) of CCTO thin film with metal-insulator-metal (M-I-M) structures has been investigated systematically using a series capacitor model. Room temperature dielectric properties of all the samples exhibit dispersion at low frequencies, which can be explained based on Maxwell-Wagner two-layer models and Koop's theory. It was found that the 483 nm thick CCTO film represents a high dielectric constant ( ε = 3334), low loss (tan δ = 3.54), capacitance ( C = 4951 nF), which might satisfy the requirements of embedded capacitor. [ABSTRACT FROM AUTHOR]

CaCu3Ti4O12 (CCTO) perovskite has been widely investigated because of its excellent dielectric properties, i.e. huge and constant permittivity upon varying temperature and frequencies, which are really attractive in wireless communication devices. These characteristics have been originally demonstrated in single crystals and ceramics. Hence, huge efforts have been focused on the fabrication and investigation of CCTO thin films. First attempts have been performed by pulsed laser deposition technique, nevertheless the chemical vapor deposition methods are preferred for large area industrial production. In this context, here is described the Metal Organic Chemical Vapor Deposition (MOCVD) approach for the growth of CCTO complex oxide. High quality CCTO thin films are fabricated on several substrates, varying from single crystals (LaAlO3 and SrTiO3) to electrodes (Pt and IrO2). The present MOCVD process is based on a molten mixture of the Ca(hfa)2•tetraglyme, Ti(tmhd)2(O -iPr)2, and Cu(tmhd)2 precursors as multi-component source. The deposited CCTO films are epitaxial on single crystal substrates, while polycrystalline films have been found on metal electrodes. A correlation among structural/morphological properties of CCTO films with deposition conditions and substrate nature is discussed. Moreover, the effects of the structural properties on the dielectric properties are also investigated. [ABSTRACT FROM AUTHOR]

This work presents a study on the dielectric and magnetic properties of the yttrium ferrite/calcium copper titanate composites. Their structural properties were analyzed by X-ray diffraction, density, and scanning electron microscopy. Impedance and microwave measurements were performed to obtain the permittivity of the composites at different frequencies. The dielectric constant, at 300 K and below 1 MHz, shows a value of about 4 × 103and at 2.4 GHz a value of 32 was measured. The generalized Looyenga mixture law was used to describe the variation of dielectric constant with the filler volume fraction in low and high frequency regions. Magnetic measurements shows a relation of hysteresis loops based on the concentration of yttrium ferrite. A maximum of 37 emu/g for the saturation magnetization was obtain at 300 K. [ABSTRACT FROM PUBLISHER]

In this paper we study CaCu 3 Ti 4 O 12 doped with Ni on copper site. We focus particularly on the effect of the substitution amount and the sintering parameters on the grain growth, morphological evolution, dielectric constant and resistivity. Compositions with formula CaCu 3-x Ni x Ti 4 O 12 with x = 0, 0.05, 0.075, 0.1, 0.2 and 0.3 were prepared by conventional solid state reaction method. The samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Dielectric measurements were taken at room temperature in the 10 2 Hz −10 7 Hz frequency range. XRD analysis confirmed the formation of a single phase material in the samples calcined at 1000 °C for 12 h with x ≤ 0.2 and indicated the presence of secondary phases such as CuO, CaTiO 3 and TiO 2 in other with x > 0.2. In all compositions, structure remained cubic. The dielectric properties such as permittivity, loss factor and resistivity of these ceramics were improved and interpreted. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir-doped calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A g Ir -1 for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO 2 . By substituting Ti with Ir in CCTO, metal-oxygen (M-O) covalency can be significantly increased leading to the reduced energy barrier for charge transfer. Further, highly polarizable CCTO perovskite referred to as "colossal dielectric", possesses low defect formation energy for oxygen vacancy inducing a high number of oxygen vacancies in Ir-doped CCTO (Ir-CCTO). Electron transfer occurs from the oxygen vacancies and Ti to the substituted Ir consequentially resulting in the electron-rich Ir and -deficient Ti sites. Thus, favorable adsorptions of oxygen intermediates can take place at Ti sites while the Ir ensures efficient charge supplies during OER, taking a top position of the volcano plot. Simultaneously, the introduced Ir dopants form nanoclusters at the surface of Ir-CCTO, which can boost catalytic activity for the acidic OER., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)