Mixed Oxide Method Research Articles

Mechanisms of enhanced performance in Zr4+/Ta5+ codoped rutile-TiO2 ceramics via broadband dielectric spectroscopy.

Aliovalent dopant codoped rutile-TiO2 materials have garnered attention due to their excellent performance properties, characterized by low loss tangent (tanδ), high dielectric permittivity (ε'), and stable ε' over a broad temperature range. This performance is primarily due to the electron-pinned defect-dipoles (EPDDs) of the complex defects [Formula: see text]Ti3+-[Formula: see text]Ti3+BTi. Notably, the excellent dielectric properties in ZrxTa2.5%Ti0.975-xO2 (Zr-TTO) ceramics can be achieved using the traditional mixed oxide method without the EPDDs, due to the absence of A3+ (acceptor doping ions). Instead, the existence of localized free electrons and oxygen vacancies ([Formula: see text]) in Zr-TTO structures, due to doping ions and the sintering process, was confirmed by X-ray photoelectron and Raman spectroscopies. These ceramics exhibited ε'~ 2 × 104 and tanδ < 0.03 at 1kHz and 25°C in the 2.5-10%Zr-TTO samples. Moreover, all ceramics demonstrated a maximum ε' change (∆ε') of less than ±15% over the temperature range suitable for X7R and X8R type ceramic capacitors. Significantly, the change in ε' related to relative humility was calculated to be less than ±0.5% over the range of 50-95% RH, indicating the environmental stability of the dielectric properties, which is essential for capacitor applications. Investigations suggested that at least four mechanisms contributed to this system: the intrinsic effect of ionic polarization, Ti4+ · e- -[Formula: see text]- Ti4+ · e- and Ti4+ · e- - [Formula: see text] defects, interfacial polarization at insulating grain boundaries, and non-Ohmic contact between the surface sample and the metal electrode.

Evaluating the significance of rare earth and iron doping on structure-property of lead titanate

The samples (Pb0.8Ln0.2 Fe0.2 Ti0.8O3, (Ln= La, Nd, Sm, Gd)) were synthesized successfully by mixed oxide method. A significant reduction in tetragonality is observed with the modification of structure. The grain size from FESEM study was observed to be decreasing with increase in ionic radii of rare earth ions. Specifically, the dielectric constant is found to be maximum for the Sm-doped sample. Conductivity studies at varying temperature and frequencies reveal the NTCR behaviour of these samples. In Sm, Nd and Gd doped samples, tunnelling of small polarons is responsible for conduction process whereas for La doped sample, the conduction process is mediated through the combined effect of small polaron tunnelling and bipolaron hopping. The Sm-doped sample exhibits highest remanent polarization. All the results of this comprehensive study provide valuable insights into the effect of dopant ions on various properties of the studied materials, paving the way for device applications.

Investigation of Piezoelectric Properties in Ca-Doped PbBa(Zr,Ti)O3 (PBZT) Ceramics.

The perovskite-structured materials Pb0.75Ba0.251-xCax(Zr0.7Ti0.3)O3 for x = 1 and 2 at.% were synthesized using the conventional mixed-oxide method and carbonates. Microstructural analysis, performed using a scanning electron microscope, revealed rounded grains with relatively inhomogeneous sizes and distinct grain boundaries. X-ray diffraction confirmed that the materials exhibit a rhombohedral structure with an R3c space group at room temperature. Piezoelectric resonance measurements were conducted to determine the piezoelectric and elastic properties of the samples. The results indicated that a small amount of calcium doping significantly enhanced the piezoelectric coefficient d31. The calcium-doped ceramics exhibited higher electrical permittivity across the entire temperature range compared to the pure material, as well as a significant value of remanent polarization. These findings indicate that the performance parameters of the base material have been significantly improved, making these ceramics promising candidates for various applications.

Effect of NMC-doping Concentration on the Structural Feature and Electrical Properties of Lithium Iron Phosphate Cathode for Use in Lithium-ion Batteries

T his study investigates the synthesis of Lithium Iron Phosphate (LFP) with NMC-doped cathode materials, aiming to enhance the performance of lithium-ion batteries. The NMC content was varied from 0.02 to 0.10wt%, and 1wt% of (NH4)3PO4 was added to all conditions to prevent phosphate loss during the calcination process. The composite powder was prepared using a straightforward mixed oxide method, with a calcination temperature of 600 °C for 5 hours under an argon gas flow. X-ray diffraction (XRD) analysis confirmed the successful formation of pure LFP with an orthorhombic crystal structure, devoid of any secondary phases. To further explore the impact of NMC doping on the structural characteristics, FTIR and Raman spectroscopy were employed. Results revealed that increasing NMC doping concentration beyond 0.02wt% led to the broadening of the PO43− symmetric stretching band at approximately 947 cm−1, indicating a higher degree of disorder in the LFP structures. This disorder was found to adversely affect electrochemical performance, resulting in decreased discharge capacity and increased impedance, as determined by electrochemical impedance spectroscopy (EIS), with higher concentrations of NMC and (NH4)3PO4. Scanning Electron Microscopy (SEM) analysis unveiled the presence of agglomerated particles ranging in size from 0.5 to 0.9 microns. Optimal conditions were identified with the addition of NMC doped at 0.02wt%, which exhibited a discharge capacity of approximately 119.41 mAh/g at 0.2 C, along with a low impedance of 200 Ohm. Moreover, the 0.02wt% sample demonstrated a promising linear trend in cycle performance, suggesting its potential for future applications in lithium-ion batteries.

Magnetoelectric, dielectric, and magnetic investigations of multiferroic NixCo1−xFe2O4−SryBa1−yNb2O6 composites

Magnetoelectric (NixCo1−xFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites with a 0–3 connectivity and different cation stoichiometries were synthesized via a classical mixed-oxide method. XRD patterns of all ceramics show reflections of the target phases SryBa1−yNb2O6 and NixCo1−xFe2O4. The influence of stoichiometry of the ferrimagnetic and ferroelectric phase on the magnetoelectric behavior was studied on composites with composition of (NixCo1−xFe2O4)0.3−(Sr0.5Ba0.5Nb2O6)0.7 and (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7. The magnetic Curie temperature increases with nickel content. However, the saturation magnetizations as well as the Curie temperatures of the composites are always lower than the ones of bulk NixCo1−xFe2O4 samples. The maximum magnetoelectric coefficient (αME) rises with increasing nickel content from 40 (x = 0) to 180 µV Oe−1 cm−1 (x = 1) in accordance with the dynamic magnetostriction coefficient. The evolution of αME of (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites shows an increase with strontium content up to y 0.5. Higher strontium content leads to a significant reducing of αME.

Synthesis and electrical characterization of Sb modified lithium bismuth titanate

Sb-modified lithium bismuth titanate Li0.5Bi0.3Sb0.2TiO3 is prepared following the mixed oxide method. The development of a new compound with a single-phase orthorhombic crystal structure is approved from the XRD analysis at environmental temperature. The electrical behavior like dielectric and electrical conductivity are analyzed in a wide temperature as well as frequency range by the impedance analyzer, which exhibits that these properties effectively depend on frequency and temperature. The ac conductivity versus temperatures plots obeys the Arrhenius relation and confirm the presence of the mixed type of conductivity process like space charge conductivity created from oxygen ion vacancies, ionic-polaronic conductivity, and so on, in the sample. Ac conductivity versus frequency spectra is as per Jonscher’s Universal Power law.

Structural and electrical characterization of Gd and Li modified Bismuth Sodium Strontium Titanate

Structural and electric characteristics of Gd, Li and Sr modified Bismuth Sodium Titanate i.e. (Bi0.5Na0.5)0.6(Gd0.5Li0.5)0.2Sr0.2TiO3 (BNGLST) composition is demonstrated. BNGLST was synthesized by the solid-state mixed oxide method using the stoichiometrically weighed constituent oxides and carbonates. The homogenously wet mixed powder was calcined at 1000 °C for 12h and compressed pellets were sintered at 1250 °C for 2h. X-ray diffraction was carried out to confirm the phase formation. Crystallographic information was extracted from the Rietveld refinement of the XRD data. Dielectric measurement was carried out from room temperature to 300 °C at 1 kHz − 1 MHz frequencies. The a.c. conductivity associated with oxygen ion conduction is discussed in detail as a function of temperature and frequency.

Structural and electrical characterization of iron and lithium co-doped barium strontium titanate composite

This communication reports the effect of Iron (Fe) and Lithium (Li) co-doping on the structural, dielectric and electrical properties of Ba0.8Sr0.2TiO3; i.e. (Fe0.5Li0.5)0.1Ba0.7Sr0.2TiO3 (FLBST). The FLBST composite was synthesized by the solid-state mixed oxide method at 1400 °C for 12h. The crystalline phase formation has been confirmed by the X-ray diffraction technique and analyzed through the Rietveld Analysis using X’Pert Highscore plus software. From the XRD analysis, lattice parameters and the average crystallite size was calculated. The electrical properties of sintered (at 1450 °C for 2h) pellets were carried out in the temperature range of 30 °C–350 °C using impedance spectroscopy. Based on the real and imaginary part of the dielectric constant, i) the dipolar contribution which is dominant in 30 °C–150 °C is characterized by Curie-Weiss law and ii) contribution from defects and oxygen vacancies seen beyond 150 °C is described by Arrhenius equation.

Studies of Structural, Optical, and Electrical Properties of Eco‐Friendly Complex Ferroelectrics: BaTiO3–Bi0.5Na0.5TiO3

Some lead‐free complex compounds containing the two perovskite compounds BaTiO3 and Bi0.5Na0.5TiO3 of chemical composition (Ba1–xBix/2Nax/2)TiO3 (x = 0, 0.05, 0.1, 0.15) are fabricated using a cost‐effective mixed oxide method. Synthesis and characterization (electrical, ferroelectric, and optical) of the above‐defined complex ferroelectrics are reported in this article. Analysis of the X‐ray diffraction data/pattern reveals the formation of phase pure compounds with tetragonal symmetry. Determination of particle size is done using the Scherrer formula. A morphology study of sintered (at 1100 °C) pellets indicates that average grain size decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. Studies of Fourier transform infrared spectroscopy and ultraviolet–visible–near‐infrared spectroscopy reveal the type of chemical bonds present in the materials. The energy bandgaps of the compounds are found to be suitable for optical device applications. The frequency and temperature dependence of the dielectric study reveals that the dielectric constant increases and loss tangent decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. The analysis of the I–V plot and the field‐dependent polarization (P–E hysteresis loop) provide the low leakage current and existence of ferroelectricity at room temperature, respectively.

Improvement of the magnetoelectric response in NiFe2O4−Sr0.5Ba0.5Nb2O6 composites using LiNbO3 as sintering additive

Magnetoelectric (NiFe2O4)0.3−(Sr0.5Ba0.5Nb2O6)0.7 composites with addition of LiNbO3 as sintering additive were prepared by a classical mixed-oxide method. XRD patterns of ceramics sintered between 1000 and 1200 °C show the desired Sr0.5Ba0.5Nb2O6 and NiFe2O4 phases. SEM investigations confirm the 0–3 connectivity of the composite ceramics. The addition of 10 and 20 mol% LiNbO3 improves the densification of the composite ceramics and leads to an increase of the size of the Sr0.5Ba0.5Nb2O6 grains. Magnetic measurements show hystereses with low coercivities. Dielectric measurements were carried out depending on temperature and frequency. The samples with the LiNbO3 addition show significantly higher resistivity values (σDC). Magnetoelectric measurements were carried out in dependence of the magnetic DC-field, temperature, and frequency. The maximum magnetoelectric coefficient (αME) rises with the addition of LiNbO3 from 180 to 803 µV Oe−1 cm−1 (@900 Hz). Temperature dependent measurements show a continuously decreasing of αME with lower temperature.

Enhanced dielectric properties and improved thermal stability in TiO2-based ceramics by Cu and Nb co-doping

TiO2-based ceramics have application potential in multilayer ceramic capacitors because of its large dielectric constant and low dielectric loss. In this work, Cu2+, Nb5+ co-doped TiO2 ceramics (CNTO) with colossal permittivity and low loss were designed and prepared via an oxide mixed method, and the effect of Cu2+, Nb5+ co-doped amount on dielectric properties were systematically investigated. Remarkably, the compositions of (Cu1/3Nb2/3)0.005Ti0.995O2 and (Cu1/3Nb2/3)0.01Ti0.99O2 exhibit large dielectric permittivity (εr) of ∼27,060 and ∼41,200 accompanied with low dielectric loss (tan δ) of ∼0.011 and ∼0.032 at 1 kHz, respectively. Based on dielectric properties, relaxation behavior assessments and X-ray photoelectron spectroscopy analysis, we confirmed that the high dielectric permittivity of CNTO ceramics mainly originates from the electron-pinned defect-dipole (EPDD) effect. Moreover, the temperature stability value of εr keeps stable of ±7.5% at 1 kHz from −200 to 200 °C for (Cu1/3Nb2/3)0.005Ti0.995O2 and from 10 to 200 °C for (Cu1/3Nb2/3)0.01Ti0.99O2 ceramics, which separately meet the X9F and Z9F capacitor requirements, respectively. The findings presented in this work might have important strategic significance for promoting the miniaturization of electronic components.

Electrical conduction mechanism in multiferroic Gd doped GaFeO3

A detail analysis on the structural, morphological, dielectric, conductivity, ferroelectric, magnetic and electrical behaviour of Gd doped GaFeO3 prepared by mixed oxide method is presented. XRD analysis, by using Rietveld refinement method, validates that all the samples have single phase orthorhombic structure. Decrement in the grain size with rise in Gd content is found from FESEM analysis. The dispersive characteristic of dielectric constant is described by the Maxwell-Wagner model and Koop's theory. The value of εr is found to increase with Gd content. The modified Debye formula is used to fit εr with frequency data, which indicates the existence of more than one relaxation processes. The frequency dependant ac conductivity curve is found to obey Jonscher's power law and the conduction mechanism for all the samples is explained by of small polaron hopping (SPH) transport model. The modulus and impedance spectra confirms the presence of non- Debye type of relaxation. The presence of semicircular curves of complex impedance plot suggests the effect of grain boundary contribution to the conduction process for all the samples at low temperatures. The value of remanent polarization is found to fall with Gd content. From M-H loop, magnetisation at M (30kOe) is found to rise while non-saturation is found to decrease with Gd content and analysed on the basis of Law of Approach.

Effects of Na Excess on the Crystal Structure Ferroelectric and Piezoelectric Properties of (Bi0.487Na0.427K0.06Ba0.026)TiO3 Lead-Free Piezoceramics

In this research, (Bi0.487Na0.427K0.06Ba0.026)TiO3 ceramics were prepared by conventional solid-state mixed-oxide method to incorporate Na excess according to the chemical formula (Bi0.487Na0.427+ x K0.06Ba0.026)TiO3, where x = 0.0, 0.005, 0.010, 0.015 and 0.020. The crystal structure, dielectric, ferroelectric and piezoelectric properties were systematically investigated with respect to the amount of Na excess. X-ray diffraction data identified pure perovskite structure for all compositions. The pseudocubic structure was observed for x = 0.0 − 0.005 before it transformed to rhombohedral structure at x ≥ 0.015. The grain size tended to be larger with increasing Na excess amount. Increasing x also led to a substantial increase in ferroelectric-relaxor transition temperature (T F-R) from 80 °C (x = 0) to 110 °C (x = 0.020). With increasing x from 0 to 0.020, the standard polarization-electric field (P-E) hysteresis measurements revealed a reduction in remanent polarization (P r) together with an increase in coercive field (E c), which was further confirmed by the remanent P-E hysteresis measurements. In addition, the piezoelectric constant (d 33) was also found to steadily decrease as x increased. The observation of increased T F-R and E c along with a decrease in d 33 and P r indicated a stabilization of ferroelectric order induced by Na excess. This research highlights the importance of sufficient control over A-site stoichiometry and how it affects the ferroelectric and piezoelectric properties of BNT-based ceramics.

Phase Transition, Thermal Expansion and Electrical Properties of BNLT-BT Ceramics Near the Morphotropic Phase Boundary

Lead-free ceramics based on bismuth sodium lanthanum titanate (Bi0.4871Na0.4871La0.0172TiO3: BNLT) and barium titanate (BaTiO3: BT) were prepared by a modified two-step mixed-oxide method. Effects of BT content on the phase transition, thermal expansion behavior, mechanical and electrical properties of lead-free BNLT-BT ceramics were studied. The Burn’s temperature and local polarizations were estimated from the thermal expansion data. Various aspects of understanding the polarization behavior and other effects in this system have also been investigated and discussed. The 0.96BNLT-0.04BT ceramics have shown the d33 value of 135 pC/N. The coercive field (E c) and remanent polarization (P r) were found to be 24 kV/cm and 9.0 µC/cm2, respectively. This may be useful in the future development of multifunctional lead-free materials in electronic applications.

Correlation between Phase Evolution, Physical and Electrical Properties of (Bi0.5(Na0.80K0.20)0.5)1- x (Ba0.7Sr0.3) x TiO3 Lead-Free Piezoelectric Ceramics

The (Bi0.5(Na0.80K0.20)0.5)1- x (Ba0.7Sr0.3) x TiO3 or (BiNK)1- x (BaS) x T (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol fraction) lead-free piezoelectric ceramics were firstly made by a conventional one step mixed-oxide method and sintered at 1125 °C for 2 h with a heating rate of 5 °C/min. All samples showed optimum relative densities of ∼97–98%. The XRD result indicated that no impurity phase was detected in all fabricated samples. SEM images indicated that all ceramics possessed irregular shaped grains. It was also found that BST added content had an effect on electrical properties of BNKT ceramics. The highest piezoelectric coefficient (d33 = 164 pC/N) with good dielectric (εr = 1577, tanδ = 0.0855) and ferroelectric properties (Pr = 11.38 µC/cm2, Ec = 19.89 kV/cm) were obtained for (BiNK)0.98(BaS)0.02T sample.

Enhanced electro-strain with high electrostrictive performances of Bi0.5Na0.4K0.1TiO3 based lead-free piezoelectric ceramics by Ba(Fe0.5Nb0.5)O3

Complex piezoelectric ceramics of (1-x)[0.97(Bi0.5Na0.4K0.1)TiO3–0.03(Ba0.7Sr0.3)TiO3]-xBa(Fe0.5Nb0.5)O3 or (1-x)[0.97BNKT-0.03BST]-xBFN were investigated, where the x value was between 0 and 0.03. All compositions were synthesized via a conventional mixed oxide method. X-ray diffraction and Raman spectroscopy techniques indicated that all ceramics exhibited a coexistence of rhombohedral (R) and tetragonal (T) phases without any impurity phase. However, the T phase became dominant at higher BFN contents. The maximum temperature (Tm), the ferroelectric to ergodic relaxor phase transition temperature (TF-R), and Burn’s temperature (TB) decreased with increasing BFN content, while the dielectric constant at Tm was enhanced for the x = 0.01 ceramic. The BFN additive interrupted ferroelectric ordering, which led to constriction in the hysteresis loops as well as large electric field-induced strains (Smax = 0.42%), a normalized strain coefficient (d*33 = Smax/Emax = 846 pm/V), and an electrostrictive coefficient (Q33 = 0.0432 m4/C2) for the x = 0.01 ceramic under a moderate applied electric field of 50 kV/cm. These results indicated that this ceramic had the potential for electromechanical applications.

Enhanced room temperature relative permittivity and low dielectric loss ferroelectric double perovskite for energy storage applications

The polycrystalline ceramic oxide, BaBi1.2Fe0.8TiO6 is synthesized by a mixed oxide method at 1000 °C. XRD and Rietveld's analysis suggests a tetragonal system and P4mm space group. The closely spaced dense micro grains of various shapes and sizes in scanning electron micrograph (SEM) image support the polycrystalline single-phase compound. The UV–Visible spectroscopy results in a convenient value of threshold wavelength (610 nm), absorption bandgap energy (2.23 eV), and reflectance bandgap energy (2.31 eV) which are good responses to the IR and visible range and its possible application in photocatalytic devices. The room temperature (RT) polarization loop shows non-zero remanent polarization, i.e. ferroelectric property of the compound. Relatively higher room temperature dielectric permittivity (ɛr = 2455) with low loss tangent (tanδ) = 0.247 at 100 Hz, phase transition (Td > 200 °C), and Curie (Tc > 470 °C) temperature values are supporting to be as good dielectric material for ceramic capacitors. Transport property shows lower RT current density is in order of 1E-9 at 300 V/cm. The compound follows the Arrhenius equation and results in imminent values of activation energy in ac conductivity (Ea = 0.847 eV at 100 Hz) and dc conductivity (Ea = 0.838 eV) analysis. Based on the results, the present compound is likely to be used as a dielectric material in ceramic capacitors, energy and memory storage devices, and photocatalytic devices.

Structural and Electrocaloric Investigation of the Lead and Strontium Modified Bismuth Sodium Titanate Ceramics

The Structural and Electrocaloric characteristics of Pb and Sr Modified Bismuth Sodium Titanate, i.e. Bi0.25Na0.35Sr0.3Pb0.1TiO3 (BNSPT) is reported. BNSPT Ceramics was synthesised by the traditional solid-state mixed oxide method. Stoichiometry-weighted constituent oxide and carbonates are mixed for 2 h in an acetone media and then calcined at 800 °C for 6 h. X-ray diffraction confirms the formation of a single-phase crystal structure. Further, lattice parameters were calculated using the Reitveld refined data and crystallite size was calculated by Debye-Scherrer’s equation. The dried powder was compacted in to pellets and sintered at 1250 °C for 2 h. The temperature dependence of maximum polarization was obtained from the P-E loop at a different temperature range from room temperature to 200 °C. The Electrocaloric properties of the BNSPT were measured by 500 V/cm using the Standard Thermodynamics Maxwell relation.

Shielding effectiveness performance of polyaniline-NiFe2O4:Cu composites for sub-8 GHz applications

Herein, NiFe2O4 doped Cu was synthesized using a mixed-oxide method to investigate its potential for creating composites with high microwave shielding effectiveness. The compound NiFe2−xCuxO4 was synthesized with x values of 0.1, 0.3 and 0.5, respectively. After sintering at 1250 °C for 4 h, single-phase Ni ferrite was formed. To analyze the phase composition and the structure of the synthesized compound, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed. The study's findings showed that NiFe2−xCuxO4 did not exhibit a second phase. To create composites with high microwave shielding effectiveness, polyaniline-NiFe2O4:Cu composites were fabricated using a hot-pressing technique, with compositions of NiFe1.9Cu0.1O3.95, NiFe1.7Cu0.3O3.85 and NiFe1.5Cu0.5O3.75 with the aniline, The weight ratios of Cu-added nickel ferrite and aniline were changed from 1:1 to 1:3, and epoxy resin was used. Using a two-port vector network analyzer, the polyaniline-NiFe2O4:Cu composites’ microwave shielding effectiveness performance was examined in the range between 0 and 8 GHz. The study found that the shielding effect of the composites could be easily modified by changing the amount of polyaniline present in the specimens for the appropriate frequency bands. At 6.82 GHz, using a sample with a thickness of 2.0 mm, a minimum shielding effect performance of − 29.74 dB was achieved. Overall, the results of this study demonstrate the potential of polyaniline-NiFe2O4:Cu composites as effective microwave shielding materials.

Dielectric relaxations and low dissipation factor with excellent temperature stability of Ti1-x(Co1/3Ta2/3)xO2 ceramics

Low dissipation factor (tanδ) and excellent temperature stability of high dielectric permittivity are obtained in Ti1-x(Co1/3Ta2/3)xO2 ceramics, which were prepared using a mixed oxide method. The unit cell of the rutile TiO2 structure expanded due to relatively larger ionic radii of the co–dopants. The dopants homogeneously appeared in the microstructure of the TiO2 ceramics. Highly dense sintered–ceramics without second phase exhibit low tanδ of 0.015–0.043 with very high dielectric permittivities of 7.0–9.1 × 104 at 1 kHz. Notably, the temperature coefficient in the range of ±15 % was obtained in the temperature range of −60–200 °C. The electrically heterogeneous microstructure was studied using impedance spectroscopy. The contributions of extrinsic and intrinsic factors were separated by the dielectric relaxations in low and high–frequency ranges, respectively. The dielectric relaxations were well fitted using a modified Cole-Cole model. A low–frequency relaxation was well described based on the Maxwell-Wagner relaxation model. A high permittivity was originated from the intrinsic (i.e., defect dipoles) and extrinsic (internal barrier layer capacitor, IBLC) effects. A low tanδ was primarily caused by the IBLC effect associated with a high resistance of the insulating part and defect dipoles.