Internal Barrier Layer Capacitor Research Articles

Microstructure, optical, dielectric, and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 ceramics

Microstructure features along with optical, dielectric and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 (x = 0, 0.3, 0.6, 0.9, and 1.0) ceramics were investigated systematically. With increase in Bi3+ doping content, Cd1-xBi2x/3Cu3Ti4O12 structure sightly distorted and eventually formed more stable configuration. Bi3+ doping also caused grain refinement and increased compactness of ceramics, whereas Bi-rich phase appeared at grain boundaries. Optical band gap (Eg) decreased due to increase in defect concentration. Dielectric loss (tanδ) dropped with increase in Bi3+ doping content while dielectric constant (ɛ′) remained high. The most optimal dielectric characteristics (the lowest tanδ of ∼0.033, giant ɛ′ of ∼10028 at 10 kHz and room temperature, the highest nonlinear coefficient (α of 4.62) and breakdown field strength (Eb of up to ∼9.23 kV/cm) were achieved at x = 0.9. Impedance spectra revealed semiconducting grains and insulating grain boundaries. Dielectric response evolution in Cd1-xBi2x/3Cu3Ti4O12 ceramics was described using internal barrier layer capacitor model. Electric modulus values indicated that low-frequency relaxation originated from grain boundaries. High energy barrier of grain boundaries was beneficial for enhancement of nonlinear properties of ceramics. Thus, Bi3+ doping improved both dielectric and nonlinear characteristics of Cd1-xBi2x/3Cu3Ti4O12 ceramics.

Effect of (Al3+/Ta5+) co-doped on dielectric properties of CdCu3Ti4O12 ceramics

In this work, dense CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] ceramics were prepared by a conventional solid phase method. The effect of Al[Formula: see text]/Ta[Formula: see text] dopants on the dielectric properties of CdCu3Ti4O[Formula: see text] ceramics was systematically investigated. Upon Al[Formula: see text]/Ta[Formula: see text] co-doping, the dielectric properties of CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] were significantly enhanced. Particularly, the CdCu3(Al[Formula: see text]Ta[Formula: see text]Ti[Formula: see text]O[Formula: see text] material displays a decent dielectric property, where dielectric constants ([Formula: see text]), loss tangent (tan [Formula: see text]) at a test frequency of 1[Formula: see text]kHz are able to satisfy the application temperature requirement of the Y6R capacitor. Surprisingly, the refined grains resulting from Al[Formula: see text]/Ta[Formula: see text] co-doping lead to heightened resistance at grain boundaries, which is closely associated with enhanced dielectric properties. Meanwhile, the giant dielectric property of the materials can be attributed to the effect of the internal barrier layer capacitance. The obtained results are expected to provide a new idea for obtaining high dielectric constant and low loss tangent in CdCTO-based materials and promote the practical application of such materials.

Doublet doped titanate ferroelectric system for capacitors and NTC thermistor applications

A simple negative temperature coefficient (NTC) thermistor Ba0.85Sr0.15Ti0.85Zr0.15O3 system is elaborated using a conventional solid-state reaction route. The structural analysis confirms that the elaborated pseudo-cubic system, which is indexed in the P4mm space group, exhibits one single phase. The dielectric properties and the electrical resistivity data are investigated over a large temperature range from 413 K to 673 K. In this temperature interval, the Steinhart–Hart equations are employed to confirm that Ba0.85Sr0.15Ti0.85Zr0.15O3 is a promising system for sensor application. Accordingly, the thermistor constant (β=10154 K), the sensitivity factor (-5.5 %/K≤α≤-2 %/K), the activation energy (Ea=0.875 eV), and the stability factor (SF=2.27) parameters are calculated to approve that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits an NTC-thermistor behavior. The temperature dependence of the electrical resistivity confirms that Ba0.85Sr0.15Ti0.85Zr0.15O3 reveals a semiconductor behavior. The dielectric investigation shows that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits a motivating dielectric properties (elevated dielectric constant value (105<ε’<106) and low dielectric losses (mostly < 0.007) with almost frequency independence between 20 Hz to 500 kHz). The colossal dielectric response of Ba0.85Sr0.15Ti0.85Zr0.15O3 is attributed to the internal barrier layer capacitor (IBLC) and the surface barrier layer capacitor (SBLC) effects. Such response suggests the suitability of Ba0.85Sr0.15Ti0.85Zr0.15O3 ceramic for high temperature capacitor applications.

Microstructure, optical, dielectric, and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 ceramics

Microstructure features along with optical, dielectric and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 (x = 0, 0.3, 0.6, 0.9, and 1.0) ceramics were investigated systematically. With increase in Bi3+ doping content, Cd1-xBi2x/3Cu3Ti4O12 structure sightly distorted and eventually formed more stable configuration. Bi3+ doping also caused grain refinement and increased compactness of ceramics, whereas Bi-rich phase appeared at grain boundaries. Optical band gap (Eg) decreased due to increase in defect concentration. Dielectric loss (tanδ) dropped with increase in Bi3+ doping content while dielectric constant (ɛ′) remained high. The most optimal dielectric characteristics (the lowest tanδ of ∼0.033, giant ɛ′ of ∼10028 at 10 kHz and room temperature, the highest nonlinear coefficient (α of 4.62) and breakdown field strength (Eb of up to ∼9.23 kV/cm) were achieved at x = 0.9. Impedance spectra revealed semiconducting grains and insulating grain boundaries. Dielectric response evolution in Cd1-xBi2x/3Cu3Ti4O12 ceramics was described using internal barrier layer capacitor model. Electric modulus values indicated that low-frequency relaxation originated from grain boundaries. High energy barrier of grain boundaries was beneficial for enhancement of nonlinear properties of ceramics. Thus, Bi3+ doping improved both dielectric and nonlinear characteristics of Cd1-xBi2x/3Cu3Ti4O12 ceramics.

Effect of thermal shock number and temperature on the dielectric characteristics of CaCu3Ti4O12 ceramics

The grain boundary (GB) with an internal barrier layer capacitance (IBLC) effect is the primary contributor to the high GB resistance of CaCu3Ti4O12 (CCTO) materials, which also directly determines their colossal dielectric properties. This paper investigates the effects of the thermal shock numbers and temperatures on the dielectric properties of CCTO materials. The findings indicate that increasing the thermal shock numbers can diminish the GB resistance and thus enhance the dielectric constant. Moreover, increasing the thermal shock numbers can reduce the dielectric loss in the low-frequency region, reducing the dielectric loss at 20Hz from 0.195 for the NC1 sample to 0.095 for the NC6 sample, a reduction of approximately 51%. In addition, increasing the thermal shock temperature improves the frequency stability of the dielectric constant in the high-temperature region by changing the GB resistance, although the dielectric constant decreases. Importantly, this thermal shock approach improves the dielectric properties of CCTO materials by affecting the ceramic GBs, which is instructive for studying the properties of other GB-dominated materials.

Role of oxygen vacancy on rapid densification and giant dielectric properties of flash sintered Ca2+ and Ta5+ co-doped TiO2 ceramics

(Ca, Ta) co-doped TiO2 ceramics were successfully prepared using flash sintering technology, and the effects of oxygen vacancies on the rapid densification and giant dielectric properties were studied. The results suggest that the maximum volume fraction of oxygen vacancies in flash-sintered samples is approximately 10%. Oxygen vacancies decrease the barrier energy level of atomic diffusion and provide convenient diffusion channels, resulting in rapid densification of the sample within 24 min at 1100 °C. All flash-sintered samples exhibit high relative density, exceeding 95%. Oxygen vacancies promote the electron-pinning defect dipole effect at low temperatures. As the temperature increases, carriers such as oxygen vacancies move to the grain boundary, forming an internal barrier layer capacitance effect. The optical dielectric constant reaches 7.25 × 104, and the dielectric loss drops to 0.09. Oxygen vacancy play an important role in both flash sintering technology and the giant dielectric properties of co-doped TiO2 ceramics.

Advanced humidity sensing properties of CuO ceramics

This research explores the capacitive humidity sensing properties of CuO ceramic, selected for its simplicity as an oxide and ease of fabrication, in addition to its remarkable dielectric properties. The CuO sample was fabricated by sintering at 980 °C for 5 h. A microstructure with a relative density of 88.9% was obtained. X-ray diffraction confirmed the formation of a pure CuO phase. Broadband dielectric spectroscopy revealed that the observed giant dielectric properties at room temperature (RT) were attributed to extrinsic effects, including the internal barrier layer capacitor and sample-electrode contact effects. A key focus of this study was to examine the giant dielectric properties of CuO ceramic as a function of relative humidity (RH) at RT and frequencies of 102 and 103 Hz. It was observed that the capacitance of CuO continuously increased with rising RH levels, ranging from 30 to 95%. Notably, the maximum hysteresis errors were constrained to 2.3 and 3.3% at 102 and 103 Hz, respectively. Additionally, the CuO ceramic demonstrated very fast response and recovery times, approximately 2.8 and 0.95 min, respectively. The repeatability of the humidity response of the capacitance was also established. Overall, this research highlights the high potential of CuO as a giant dielectric material for application in humidity sensors.

Optimizing sintering conditions and microstructure for enhanced dielectric and humidity sensing properties of Na1/3Ca1/3Tb1/3Cu3Ti4O12 ceramics

This study investigated the impact of sintering temperature and resultant microstructure on the dielectric behavior and humidity sensing performance of Na1/3Ca1/3Tb1/3Cu3Ti4O12 (NCTCTO). The pure NCTCTO phase was obtained. Relative density and grain size tended to increase with the sintering temperature. The porous NCTCTO exhibited remarkable humidity sensing performance with minimal hysteresis error (2 %) and rapid response and recovery times (1.5 min). The dense NCTCTO ceramic with a high relative density of about 99 %, demonstrated significant giant dielectric properties, with ε′∼8500 and low loss tangent (0.08). The dielectric behavior was interpreted using the internal barrier layer capacitor model. The increase in ε′ with humidity was ascribed to the absorption of H2O molecules at the grain boundary, leading to increased interfacial polarization. This work delineates the critical influence of ceramic microstructure on the humidity sensing and giant dielectric properties of NCTCTO ceramics, paving the way for their application in advanced electronic devices.

Giant permittivity response and enhanced nonlinear electrical properties in a novel perovskite-like ceramic with multiple elements

Copper calcium titanate (CaCu3Ti4O12, CCTO) ceramics are receiving a great deal of attention for advanced electronic and energy storage device applications owing to their giant permittivity response and good temperature stability. However, the development and real applications of CCTO ceramics are generally restricted by their large dielectric loss and low breakdown electric field strength. In the present study, a novel type of perovskite-like Na1/3(Ca1/2Sr1/2)1/3(Bi1/2Y1/2)1/3Cu3Ti4O12 (NCSBYCTO) ceramics were designed via multiple elements strategy based on the high-entropy concept. Consequently, all the NCSBYCTO ceramics present a giant permittivity response (103∼104), good stability of temperature and frequency, and remarkable relaxation characteristics, especially the NCSBYCTO ceramic sintered at 1050 °C exhibits a relative balance between the giant permittivity of about 7.0 × 103–9.5 × 103 and the lower dielectric loss of approximately 0.043–0.294 at a frequency range of 104–106 Hz under room temperature. Furthermore, all the NCSBYCTO ceramics present an obvious nonlinear characteristic. More encouragingly, a higher breakdown field strength of around 2552.56 V/cm accompanied by a larger nonlinear coefficient of about 6.48 is achieved in the NCSBYCTO ceramic sintered at 1070 °C. A significant electrical heterogeneity structure and electron defect structure induced by the existence of mixed-valence Cu+/Cu2+ and Ti3+/Ti4+ are also found in the NCSBYCTO ceramics. The giant permittivity response, low dielectric loss and improved nonlinear properties can be considered the synergistic effect of the defect mechanism and the internal barrier layer capacitor model. This finding offers a route for designing giant permittivity ceramics with brilliant dielectric properties and nonlinear behaviors, which is expected to benefit dual-functional device applications of capacitors and varistors.

Defect engineering in rare-earth-doped SrTiO3 ceramics: Route to colossal capacitance material up to X9R capacitor standard

With the advent of the electronic information era, capacitors have become a hot research topic due to their economic and strategic significance. Such microelectronic components play an irreplaceable role in important fields such as scientific research and military industries. Therefore, there is an urgent need to develop dielectric materials capable of withstanding more demanding conditions. In this work, a defect engineering method was incorporating Tm3+ rare earth ions into strontium titanate were proposed, resulting in a colossal dielectric permittivity, low dielectric loss, and excellent frequency and temperature stability. For the sample with x=0.01, the dielectric permittivity exceeds 345,804, the dielectric loss is below 0.011, and the dielectric permittivity variation within the temperature range from −55–200°C is less than 15%, which meets the ELA X9R capacitor standard (X: −55 °C, 9: +200 °C, R: Δεr ≤ ± 15%). The excellent performance is ascribed to the electron pinning defect dipole effect (EPDD) and internal barrier layer capacitor effect (IBLC), which is verified by XPS and impedance spectra. A deeper understanding of these mechanisms could help to reveal the origin of the colossal capacitance and thus contribute to the design of materials with colossal capacitance.

Structural and Dielectric Properties of Titania Co-Doped with Yttrium and Niobium: Experimental Evidence and DFT Study

This work explores the impact of the sintering temperature and co-dopant contents on the microstructure and dielectric properties of (Y0.5Nb0.5)xTi1−xO2 (0.025 ≤ x ≤ 0.10) ceramics synthesized by the solid state reaction method. The physical mechanism underlying the colossal electric permittivity was systematically investigated with experimental methods and first principles calculations. All specimens exhibited the characteristic tetragonal structure of rutile, besides secondary phases. A niobium- and yttrium-rich secondary phase emerged at the grain boundaries after heating at 1500 °C, changing the main sintering mechanism. The highest value of the electric permittivity (13499 @ 60 °C and 10 kHz) was obtained for (Y0.5Nb0.5)0.05Ti0.95O2 sintered at 1480 °C, and the lowest dissipation factor (0.21@ 60 °C and 10 kHz) for (Y0.5Nb0.5)0.1Ti0.90O2 sintered at 1500 °C. The dielectric properties of Y3+ and Nb5+ co-doped TiO2 are attributed to the internal barrier layer capacitance (IBLC) and electron-pinned dipole defect (EPDD) mechanisms.

Combined transport and dielectric models and experimental characterization based on impedance spectroscopy for studying the microstructural and transport properties of electro-ceramic perovskites

Collective investigations on the electrical resistivity, complex dielectric permittivity, complex impedance, conductivity, and electric modulus properties of La0.55Ca0.45Mn0.8Nb0.2O3 (LCMNO) are conducted. The impedance spectroscopy (IS) technique is reviewed to examine the electrical and dielectric responses of the material according to the carrier displacement, including core-shell structure, grain boundary effects, dielectric relaxation (local relaxation), and long-range conduction (non-local relaxation). This technique can correlate the electrical and dielectric responses with the ceramics’ microstructural effects (grain boundary and grain (core-shell) zones). For LCMNO, the electrical resistivity study confirms the presence of a metal-semiconductor transition at TM-SC=66 K. It points towards a gradual crossover from the thermally activated Small Polaron Hopping (SPH) to the Variable Range Hopping (VRH) process at low temperatures and for T> TM-SC. The dielectric results confirm the presence of various types of polarization effects. The occurrence of a dipolar reorientation is attributed to long-range electrical conduction. In addition, the accumulation of the activated charge carriers increases the Maxwell-Wagner polarization resulting from an internal barrier layer capacitor (IBLC) microstructure. The electric modulus study confirms the existence of a correlation between the mobile charge carrier’s motions. From the complex impedance, dielectric, and electric modulus, it is possible to label a material’s conductive and dielectric natures (non-Debye-relaxation-type).

Giant dielectric properties and temperature stability of triple–doped AlxIn0.05−xTa0.05Ti0.9O2 ceramics

AlxIn0.05−xTa0.05Ti0.9O2 ceramics with x ranging from 0 to 0.05 were synthesized using a conventional solid–state reaction method. All samples achieved a pure rutile–TiO2 phase. Additionally, the lattice parameters of the samples increased with higher Al doping concentrations. The ceramics exhibited a dense microstructure and uniform dispersion of dopants. Raman spectroscopy revealed a decrease in oxygen vacancies in the structure with increasing Al3+ concentration. The presence of Ti3+ in the structure was confirmed by X–ray photoelectron spectroscopy. The dielectric properties of all samples were investigated as functions of frequency and temperature. The triple–doped AITTO ceramics demonstrated a high dielectric constant (ε′) of ∼2×104 and low dielectric loss (tanδ) ranging from 0.029 to 0.04, along with excellent temperature stability of ε′ at 1 kHz, showing a Δε′/ε′30 of less than ±15% over a temperature range of −60 to 210 °C. Notably, the tanδ of the triple–doped AITTO ceramics remained below 0.04 even at 200 °C. Impedance spectroscopy was utilized to analyze the electrical properties of the grains and grain boundaries. The observed dielectric properties are attributed to the formation of electron–pinned defect–dipoles, along with the impacts of both internal and surface barrier layer capacitors.

High insulation resistivity and low dielectric loss in (Ta, Al)‐codoped BaTiO3 colossal permittivity materials

AbstractLow insulation resistivity is a key factor limiting the practical application of colossal permittivity (CP) ceramics in electronic components. In this study, BaTiO3–0.01Ta2O5–xAl2O3 (BTAx, x = 0.005, 0.01, 0.015, 0.02) CP ceramics with high insulation resistance were successfully prepared by sintering in N2. In particular, BTA0.015 ceramic exhibits CP (εr = 2.01 × 105, 1 kHz), low dielectric loss (tanδ = 0.044, 1 kHz), high insulation resistivity (ρv = 1.4 × 109 Ω cm, DC voltage (DC) 100 V), and superior frequency and thermal stability (20 Hz–1 MHz, room temperature–350°C). The polarization mechanism, dielectric and insulating properties were investigated by different atmosphere processing, scanning electron microscopy (SEM) X‐ray photoelectron spectroscopy (XPS), and impedance analysis. Moderate doping of Al2O3 facilitates the construction of electron‐pinned defect dipoles, which improves the dielectric properties. In addition, the ceramics feature an extremely fine grain size, which is conducive to suppressing the long‐range migration of delocalized electrons. The combination of electron pinning defect dipole effects and internal barrier layer capacitance effects are the responsible for the giant dielectric constant. This research shows that the defect dipole‐dependent polarization can be employed to design highly insulating BaTiO3‐based CP ceramics.

Microstructure and dielectric properties of Na and Ni co-substituted CaCu3Ti4O12 ceramics with high dielectric constant and low loss

Preparation of Na and Ni co-substituted CaCu3Ti4O12 (CCTO) ceramics through sol-gel method is carried out to enhance the dielectric properties. On the morphology and dielectric properties of CCTO ceramic, the effects of Na and Ni co-substitution are investigated. The results demonstrate that at room temperature, Na and Ni co-substituted Ca0.993Na0.007Cu2.95Ni0.05Ti4O12 exhibits significantly increased grain size and consequently a high dielectric constant exceeding 12000 across a broad frequency range (1–105 Hz). Meanwhile, its dielectric loss is reduced to 0.016 at 1 kHz, a phenomenon that can be ascribed to the raised resistance and activation of grain boundary. Furthermore, Ca0.993Na0.007Cu2.95Ni0.05Ti4O12 also yields a breakdown field strength of 2.3 kV/cm. The giant dielectric response can be explained by the internal barrier layer capacitor model. These excellent comprehensive performances not only contribute to obtain simultaneously low dielectric loss and high breakdown strength for CCTO ceramics with high dielectric constant, but also can facilitate the practical application of CCTO ceramics in advanced capacitors.

(Zn2+ + Cd2+) co-doped CaCu3Ti4O12 ceramics with enhanced dielectric permittivity and reduced dielectric loss tangent

The present study systematically investigated the structure, dielectric properties, and electrical response of Ca1-xCdxCu3-yZnyTi4O12 (x = y = 0, 0.025, 0.05, and 0.10). The XRD analysis indicates the presence of a CaCu3Ti4O12 phase in all the sintered ceramics, with no indications of impurity phases found. Achieving high dielectric permittivity and low loss tangent can be accomplished through codoping with Zn2+/Cd2+. At room temperature and 1 kHz, the Ca0.95Cd0.05Cu2.95Zn0.05Ti4O12 ceramic has a high dielectric constant of ∼1.61 × 105 and a low loss tangent of ∼0.03. In addition, codoping ions can enhance the stability of dielectric permittivity with respect to temperature variations. The utilization of impedance spectroscopy as a technique confirms the heterogeneous microstructure observed in sintered materials. The results of this investigation suggest a potential association between the internal barrier layer capacitor model and the underlying cause of the colossal dielectric characteristics observed in Ca1-xCdxCu3-yZnyTi4O12 materials. The analysis of X-ray photoelectron spectroscopy indicates the presence of Cu+ and Ti3+ species, which could potentially exert a significant impact on the development of n-type semiconducting grains in Ca1-xCdxCu3-yZnyTi4O12 ceramics. This influence is attributed to the existence of oxygen vacancies. Theoretical simulations revealed that a Zn atom is situated in proximity to a Cd atom within the CCTO structure. Furthermore, our findings indicate that the oxygen vacancy does not interact with the dopants. Our electron density analysis suggests that the presence of Cu+ and Ti3+ ions, as observed by XPS measurements, is a consequence of the existing oxygen vacancy.

Enhancing grain boundary contributions to improve the dielectric properties of (In0.5Nb0.5)0.05Ti0.95O2 ceramics by Bi aided sintering

The internal barrier layer capacitance effect substantially contributes to the colossal permittivity in In and Nb co-doped TiO2 (INTO) ceramics. Therefore, enhancing grain boundary density and ceramic compactness can efficaciously reduce their low-frequency dielectric loss. In this investigation, Bi2O3 addition was utilized to aid sintering and refine grains for INTO ceramics. The results reveal that Bi-doped INTO ceramics, in contrast to their undoped counterparts, exhibit a more refined and compact grain structure with a significant increase in the quantity of grain boundaries. Moreover, a noticeable reduction in low-frequency dielectric loss from above 0.1 to below 0.05 and enhanced frequency stability of permittivity from below 10 Hz to approximately 10 kHz were observed, along with a decrease in the sintering temperature to 1300 °C. In comparison to undoped INTO ceramics, Bi doping also enhances the withstand voltage capability by a factor of 1.5–4 for Bi-doped INTO ceramics. However, as the sintering temperature of Bi-doped INTO ceramics increases and the grain size enlarges, their breakdown voltage gradually decreases, but the non-linear coefficient of current-voltage characteristics progressively increases. Analysis of complex impedance spectra confirms that the increased grain boundary density and resistance in Bi-doped INTO ceramics is the primary factor for the enhanced dielectric properties and withstand voltage capability.

Giant dielectric response and relaxation behavior of Bi3+/W6+ co-doped TiO2 ceramics.

With the rapid development of electronic information technology, dielectric ceramics are widely used in the field of passive devices such as multi-layer ceramic capacitors. In this paper, (Bi2/3W1/3)xTi1-xO2 (BWTOx) ceramics with superior dielectric properties have been prepared by using a traditional solid-state method. Remarkably, at a (Bi2/3W1/3)4+ doping level of 0.01, a (Bi2/3W1/3)0.01Ti0.99O2 ceramic achieved a giant dielectric permittivity of ∼1.5 × 104 and a low loss tangent of ∼0.07 at 1 kHz, as well as a good temperature independence, which could satisfy the operating temperature standards for X9R capacitors. The abnormal dielectric relaxation in the low temperature region can be explained by the interface polarization. Data based on the complex impedance spectroscopy and X-ray photoemission spectroscopy results indicate that the colossal permittivity of BWTOx ceramics is mainly ascribed to the internal barrier layer capacitance effect. The findings of this work could provide valuable insights for achieving large dielectric constants and good temperature stability simultaneously in BWTOx and other related electronic ceramic materials.

Pioneering dielectric materials of Sn-doped Nb0.025Ti0.975O2 ceramics with excellent temperature and humidity stability for advanced ceramic capacitors.

In this study, the rutile TiO2 system, widely acclaimed for its superior properties, was enhanced through co-doping with isovalent Sn4+ ions and 2.5% Nb5+ donor ions, diverging from traditional acceptor doping practices. This novel doping strategy was implemented by employing a conventional solid-state reaction method, resulting in the synthesis of Sn-doped Nb0.025Ti0.975O2 (Sn-NTO) ceramics. These ceramics demonstrated remarkable dielectric characteristics, with a high dielectric constant (ε') ranging from ∼27 000 to 34 000 and an exceptionally low loss tangent between 0.005 and 0.056 at ∼25 °C and 1 kHz. Notably, the temperature coefficient of ε', , aligned with the stringent specifications for X7/8/9R capacitors. Furthermore, the Sn-NTO ceramics exhibited a stable Cp response across various frequencies within a humidity range of 50 to 95% RH, with ΔCp (%) values within ±0.3%, and no hysteresis loop was detected, suggesting the absence of water molecule adsorption and desorption during humidity assessments. This behavior is primarily attributed to the effective suppression of oxygen vacancy formation by the Sn4+ ions, which also affects the grain growth diffusion process in the Sn-NTO ceramics. The observed heterogeneous electrical responses between semiconducting grains and insulating grain boundaries in these polycrystalline ceramics are attributed to the internal barrier layer capacitor effect.

The influence of extrinsic structural factors on the dielectric properties of CaCu3Ti3.90Cr0.10O12 ceramics

In this study, CaCu3Ti3.90Cr0.10O12 was produced via a solid-state reaction method. The phase formation and crystal structure analyses indicate a body-centered cubic structure with the space group Im3. There were no observed secondary phases. A microstructural study revealed that, with the sintering time fixed at 3 h, the average grain size increases as the sintering temperature was raised from 1090 °C to 1110 °C. Interestingly, the dielectric permittivity of CaCu3Ti3.90Cr0.10O12 ceramics increases from 3.53×104 to 8.04×104 as the sintering temperature was increased. In addition, the loss tangent of the CaCu3Ti3.90Cr0.10O12 ceramic decreases from 0.086 to 0.043. Impedance spectroscopy reveals the construction of an internal barrier layer capacitor structure in CaCu3Ti3.90Cr0.10O12 ceramics. The presence of Cu+ and Ti3+ in the CaCu3Ti3.90Cr0.10O12 system is shown by X-ray photoelectron spectroscopy, indicating a charge compensation mechanism produced by the oxygen vacancy within the CaCu3Ti3.90Cr0.10O12 ceramics. Interfacial polarisation may be the most significant contributor to the high dielectric permittivity of these ceramics.