This study introduces an innovative counter electrode for dye-sensitized solar cells (DSSCs), utilizing gamma-irradiated chitosan integrated with NiMoS₂ nanoparticles on graphene layers. The aim of the fabrication of this composite is to offer an efficient, cost-effective, and environmentally sustainable alternative to conventional platinum-based electrodes. The application of gamma irradiation is crucial in enhancing the solubility and reactivity of chitosan, thereby facilitating its interaction with NiMoS₂ and graphene. Electrochemical impedance spectroscopy (EIS) results indicate that the addition of 7%wt graphene oxide (GO) can reduce carrier resistance and improve conductivity as well as charge transfer properties. The DSSC performance of 7%wt Gam-NMS@rGO achieved a power conversion efficiency (PCE) of up to 8.101%. This enhanced efficiency is attributed to the synergistic interactions between NiMoS₂ and graphene, which optimize catalytic activity and enhance redox reactions. This research highlights the potential of Gam-NMS@rGO as a viable candidate for platinum-free counter electrodes in DSSCs, offering an environmentally friendly alternative with competitive performance metrics.

A hierarchical NiCo2O4@ZnS/MWCNT (NCO@Z-MWCNTs) nanocomposite was synthesized to serve as a platinum-free counter electrode for dye-sensitized solar cells (DSSCs). The nanocomposite comprised spinel NiCo2O4 nanorods, ZnS associated with the surface of the nanorods, and an interconnected multi-walled carbon nanotube (MWCNT) network, and it was synthesized via a low-temperature solution-based hydrothermal method. XRD confirmed the presence of cubic NiCo2O4 and zinc blende ZnS phases, while FESEM–EDS and XPS analyses verified the incorporation of ZnS and the formation of a conductive carbon framework interconnecting adjacent nanorods. ZnS, rather than acting as an isolated catalytic component, was considered to contribute additional sulfide-related surface sites and to modulate the interfacial electronic environment of the NiCo2O4 nanorods, which likely facilitated redox reactions involving the I−/I3− couple. Meanwhile, the MWCNT network established continuous electron transport pathways, effectively reducing interfacial resistance and enhancing charge-transfer efficiency. Thermogravimetric and electrochemical analyses revealed enhanced thermal stability, improved redox kinetics, and a significant reduction in charge-transfer resistance compared with pristine NiCo2O4.The optimized NCO@Z–MWCNT 9wt% counter electrode achieved a power conversion efficiency of 10.03% under AM 1.5 G illumination, exceeding that of the Pt reference device (9.6%). Overall, the improved performance was attributed to the combined contributions of ZnS surface modification and the conductive MWCNT network, which together enhanced charge transport and electrocatalytic activity. This work demonstrates a scalable strategy for developing cost-effective, durable, and high-performance counter electrodes for dye-sensitized solar cells.

We report a rapid and low-cost approach for synthesizing the manganese bismuth (MnBi) magnetic phase using a pulsed microwave sub-atmospheric air plasma system, developed by modifying a conventional household microwave oven. The system operates in pulsed mode under reduced pressure (0.3–0.7 Torr), generating a stable plasma characterized by strong N2, OH, and H emission. This plasma acts as a highly localized heat source, enabling chamber temperatures up to 360 °C depending on pulse parameters. MnBi alloy formation was achieved within seconds by controlling the microwave pulse current and duration. Our results indicate that the magnetic properties of MnBi are highly sensitive to pulse parameters. Structural analysis via transmission electron microscopy and X-ray diffraction revealed a distinct phase evolution: while a moderate 30-minute treatment at the appropriate operating preset (current = 5.3 A; pulse duty cycle = 8 s ON / 24 s OFF) promoted a well-ordered polycrystalline phase, increasing the pulse duty cycle induced nanocrystallization and partial amorphization. This structural modification is identified as the primary factor leading to diminished magnetic performance. Field-emission scanning electron microscopy/energy dispersive spectroscopy and X-ray photoemission spectroscopy analyses of the surface and bulk interior revealed significant compositional gradients, highlighting the surface-localized nature of the plasma treatment and the diffusion-driven mechanism of MnBi formation. This study demonstrates the feasibility of microwave plasma as an efficient, inert-gas-free approach for rapid intermetallic phase synthesis and provides new insights into plasma-assisted alloying mechanisms.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising materials for photocatalysis and environmental remediation owing to their tunable electronic structures and high surface-to-volume ratios. However, their practical performance is often limited by nanosheet restacking and aggregation following liquid-phase exfoliation (LPE), particularly during solvent removal, leading to reduced accessible active sites and diminished adsorption efficiency. Here, we report a solvent-exchange-enabled strategy to obtain highly concentrated, stable aqueous WSe2 nanoflakes via LPE followed by controlled rotary evaporation to remove isopropanol. This approach yields aqueous dispersions with concentrations up to 0.70 mg mL−1 while preserving the exfoliated 2H-WSe2 phase and crystallinity, as confirmed by comprehensive structural and chemical characterization. The resulting colloidal WSe2 nanoflakes exhibit exceptionally rapid adsorption kinetics toward cationic dyes, achieving >95% removal of methylene blue (MB) and rhodamine B (RhB) within 1 min. A high maximum adsorption capacity of 197.3 mg g−1 for MB is obtained and follows the Langmuir isotherm model, indicating monolayer adsorption and underscoring the importance of maintaining a stable colloidal state to maximize accessible adsorption sites. Following adsorption, the WSe2 nanoflakes demonstrate measurable visible-light-driven photocatalytic activity following first-order kinetics (MB = 6.69 × 10−3 min-1 and RhB = 2.54 × 10-3 min-1), providing a secondary post-adsorption treatment effect. Transient absorption spectroscopy revealed the comparatively faster electron-hole recombination rate in WSe2 (a t50% ~0.032 ms) than the commercial photocatalyst, P25 TiO2 (t50% ~2.3 ms), and was used to rationalize differences in activity. Overall, this work establishes a scalable aqueous processing pathway for TMD nanosheets/nanoflakes and highlights their potential for adsorption-dominated wastewater remediation systems, combining ultrafast absorption kinetics with high adsorption capacity.

A novel CoNi2Se4@SiO2 core-shell nanostructure decorated with graphene quantum dots (CNS@Si-GQDs) was synthesized via a simple hydrothermal method and investigated as a Pt-free counter electrode for dye-sensitized solar cells (DSSCs). The optimized CNS@Si-GQDs electrode with 7 ppm GQD loading exhibited excellent electrocatalytic activity toward the I3- /I- redox reaction, delivering a photoelectric conversion efficiency (PCE) of 8.10%, slightly higher than that of the conventional Pt electrode (8.03%). The optimized device also achieved a high short-circuit current density (Jsc) of 18.67 mA cm- 2, with a Voc of 0.75 V and a fill factor (FF) of 0.57. Electrochemical impedance spectroscopy revealed that the CNS@Si-GQDs (7 ppm) electrode possessed the lowest charge-transfer resistance (Rct = 241.62 Omega cm2), significantly lower than those of the 3 ppm and 5 ppm electrodes, indicating enhanced interfacial electron-transfer kinetics and catalytic activity. Tafel polarization analysis further confirmed improved exchange current density and faster triiodide reduction kinetics after GQD incorporation. The enhanced electrochemical performance was attributed to the synergistic interaction between the conductive GQD network and the CNS@SiO2 core-shell structure, which increased the electroactive surface area, promoted electron mobility, and provided abundant catalytic active sites. Additionally, the SiO2 interfacial layer helped suppress charge recombination and stabilize the hierarchical nanostructure. This study demonstrates a scalable, low-cost, and efficient Pt-free strategy for next-generation DSSCs and provides insights into the design of advanced electrocatalysts for sustainable solar energy conversion.

In this work, first-principles calculations based on density functional theory within the generalized gradient approximation (GGA) parameterized by Perdew, Burke, and Ernzerhof (PBE) are used to investigate dominant defects in Co-doped SrTiO3 as well as other dominant native defects in SrTiO3. Our calculations revealed that CoTi defect in 1- charge state is the most dominant defect under Ti-poor condition. This indicated that Co atom is likely to substitute on the Ti site to form the CoTi defect in the Co-doped SrTiO3 system whereas the VO defects in 2+ charge state is likely to form in SrTiO3 under O-poor condition due to its comparatively low formation energy. It means that the VO defects is unavoidable in SrTiO3 under this condition. Regarding Sr-poor condition, the dominant defects at the pinned Fermi-energy are VO and VSr defects in 2+ and 2- charge state, respectively. Our calculations show that the CoSr defect is unlikely to form in Co-doped SrTiO3 under all growth conditions. In addition, we found that Coi-VSr complex defect is more likely to form in Co-doped SrTiO3 than isolated defect of CoSr. To be confirmed, simulated Co K-edge x-ray absorption near-edge spectroscopy (XANES) spectrum of CoTi defect is in consistent with the measured XANES spectrum of 12.5% Co-doped SrTiO3 sample annealed in air. The effect of defect nature and formation on the functional properties of Co-doped SrTiO3 was revealed that Co preferentially substitutes at the Ti site (CoTi), consistent with XANES analysis, while oxygen vacancies are unavoidable under O-poor conditions. These defects significantly influence material performance: CoTi narrows the band gap, enhancing optical absorption; oxygen vacancies and mixed Co valence states promote room-temperature ferromagnetism; and vacancy-mediated dipoles improve dielectric permittivity. The combined theoretical and experimental results establish defect engineering as a key route for tuning multifunctional properties of SrTiO3-based oxides.

This work investigates the longitudinal spin Seebeck effect (LSSE) in ferromagnetic Fe/Pt bilayer systems, examining the role of Fe layer thickness and substrate type on spin current dynamics and signal characteristics. Thin Fe films (3-20 nm) were sputtered onto Si/SiO2 and Si(B) substrates and analyzed for their structural, magnetic, and spin transport behaviors. The study identifies an optimal Fe thickness below 5 nm for effective spin injection, corresponding to a spin diffusion length of 4.7 nm, a spin Hall angle of 0.094, and a spin injection coefficient of-1.6 V (K ohm m)(-1). Beyond 15 nm, the LSSE signal reverses due to dominant shunting effects. Substrate interactions significantly affect spin scattering, particularly at the Fe/Si(B) interface, where an insulating layer is necessary to stabilize magnetic and spin properties. These results provide insights into optimizing ferromagnetic metal-based LSSE systems for advanced spintronic applications.

The generation of pure spin current through thermal gradients, known as the spin Seebeck effect (SSE), has garnered significant interest in spintronics. In this study, we design and construct a permanent magnetic instrument setup to generate a variable external magnetic field using NdFeB permanent magnets to observe the SSE. The experimental setup is composed of three crucial components: the magnetic field, the temperature gradient, and electronic control systems. Si/yttrium iron garnet (YIG)/platinum (Pt) and Si/nickel (Ni) samples, prepared via sputtering techniques, were utilized for standard calibration purposes. The results show that the external magnetic field produced by NdFeB varies with the gap distance between the two magnetic poles, following an exponential decrease in field strength with increasing gap distance. The magnetic field at the center can be adjusted from +/- 20 to +/- 5000 Oe. The temperature gradient stabilizes after approximately 10 min, with a temperature difference ( Delta T ) between the heated and cooled sides ranging from 0 to 30 K. For instrument testing, we performed magnetic field and angle-dependent measurements on Si/YIG/Pt and Si/Ni samples. The results indicate that the magnetic field dependence of the permanent magnet instrument (PMI) does not exhibit the voltage loop switching seen with an alternative magnetic coil (AMC) but shows analogous behavior at high magnetic fields. Moreover, the angle dependence of both PMI and AMC yielded comparable results. In conclusion, our PMI setup procedures effectively facilitate the observation of the SSE.

High-entropy engineering provides an effective strategy to enhance thermoelectric properties through increased lattice disorder induced by multielement doping. Recent multielement doping of GeTe-based alloys have significantly improved their thermoelectric performance, yet the vast compositional space of high-entropy GeTe makes identifying optimal compositions challenging. In this work, we investigate high-entropy GeTe alloys derived from the state-of-the-art Ge0.61Ag0.11Sb0.13Pb0.12Bi0.01Te system by partially adding Au to increase elemental and structural complexity without significantly degrading the electrical properties. Transmission electron microscopy confirms the presence of nanoscale lattice distortions and stacking faults that promote mass and strain fluctuations by enhancing phonon scattering. The Ge0.59Au0.02Ag0.11Sb0.13Pb0.12Bi0.01Te composition exhibits an ultralow lattice thermal conductivity of 0.22 W m-1 K-1 and achieves a maximum zT of 2.0 at 780 K. These findings demonstrate the effectiveness of high-entropy doping in tuning thermoelectric performance and advancing the development of next-generation GeTe-based thermoelectric materials.

This study revealed the atomic and electronic structures of Sn(SbTe2)2 and ZrW2O8 using X-ray absorption spectroscopy (XAS) coupled with density functional theory (DFT) calculations. The XAS analysis of Sn(SbTe2)2 revealed that Sn predominantly existed in the +4 oxidation state, with spectral features closely resembling those of SnO2. Sb was identified in the +3 oxidation state, consistent with the reference Sb2O3, while Te exhibited features characteristic of the -2 oxidation state, similar to those found in metal tellurides. These oxidation states suggest strong electron localization and structural stabilization effects within the ternary compound. The study of ZrW2O8 showed that Zr was predominantly 6-fold coordinated, which influenced its thermal properties. The DFT calculations indicated that both alpha- and beta-ZrW2O8 were wide-band-gap semiconductors, with band gaps of 3.35 eV and 3.51 eV, respectively. While the alpha-ZrW2O8 band gap was consistent with theoretical predictions, it remained lower than experimental values. The phase transition from the alpha to beta phase of ZrW2O8 led to increasing somewhat the energy band gap and enhancing p-type charge transport resulting in promising thermoelectric applications. These findings provided important atomic and electronic structural insights, revealing the mechanisms behind the low thermal conductivity in these materials. These results contributed to the design of advanced materials with optimized thermal properties, advancing energy efficiency and thermal management technologies.

The dielectric properties of (Ga, Al)-doped ZnO ceramics were studied by density functional theory (DFT) and experimental aspectes. In the first, the combustion method was used to prepare the pristine ZnO and Ga-, Al-doped, and codoped ZnO nanopowders, then calcined nanoparticles were characterized by x-ray diffraction technique (XRD), and field emission scanning electron microscopes (FE-SEM). Finally, the synthesized nanopowders were sintered and the dielectric properties of the ceramics were measured to reveal the effect of Ga and Al doping on ZnO. In case of the density functional theory (DFT) calculation which is conducted on the Vienna Ab initio Simulation Package (VASP) using generalized gradient approximation with Hubbard parameter (GGA+U), 4×2×2 supercells of pure ZnO and Ga-, Al-doped and codoped ZnO were modeled. The supercells were optimized, and then the density of states (DOS) were investigated. From the DFT results, doping Al and Ga shifts the Fermi level to higher states. Additionally, the semiconductive behavior of ZnO changes to a metallic character after Al and Ga doping. Thus, we found from the DFT calculation that it is possible that Al and Ga doping can improve the dielectric properties of ZnO. According to the results, we have successfully synthesized (Al, Ga)-doped ZnO ceramics. Interestingly, Ga-doped ZnO ceramics exhibited colossal dielectric response with low tanδ (about 0.83) and high ε′ (around 40,623). Ga doping in ZnO benefits dielectric properties more than Al doping and co-doping due to Ga's closer ionic radius to Zn, which minimizes lattice distortion and defects. This leads to improved stability of the ZnO lattice, reducing the formation of oxygen vacancies and enhancing dielectric performance. Therefore, it can be summarized that this work succeeds in the enhancement of dielectric properties of ZnO by Ga doping. As a result, ZnO could be a higher-efficiency dielectric material when it is doped by Ga.

CaCu2.9Mg0.1Ti4.2-xGexO12 ceramics with x = 0, 0.1, and 0.2 were fabricated to study the electrical and dielectric properties, nonlinear current-voltage properties, humidity sensing properties. The main phase of CaCu3Ti4O12 (CCTO) was obtained in the sintered ceramics with dense microstructure and slight change in grain size. All sintered ceramics showed high dielectric permittivity (epsilon ' > 10(4)) at frequencies below 10(5) Hz, while the loss tangent was reduced by a factor of 3 (from 0.034 to 0.010 at 1 kHz and 25 degrees C), as x increased from 0 to 0.1. The temperature dependence of epsilon ' was also reduced. Furthermore, the enhanced nonlinear coefficient (alpha = 4.8-5.9) and breakdown electric field (E-b = 227-755 V/cm) were achieved. The dielectric and nonlinear properties originated from the electrically heterogeneous microstructure, which was confirmed by impedance and admittance spectroscopies. Both the resistance and activation energy of the insulating internal barriers were higher than that of the semiconducting core grains. Furthermore, these two parameters of the doped samples were larger than that of the undoped sample (x = 0). It was found that a low frequency epsilon ' was strongly dependent in the relative humidity in the range of 11-95 %RH, which could be applied in a humidity sensor. Accordingly, the hysteresis error was also calculated to determine the possibility of application in humidity sensors.

A novel tungsten disulfide-molybdenum copper oxide composite supported with graphene quantum dots (WM@GQDs) has been synthesized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs) using a simple and low-cost ultrasonication method. The unique structure of WM@GQDs exhibits excellent power conversion efficiency due to its high catalytic activity and charge transport properties. In addition, the graphene quantum dots (GQDs) provide more active sites in the zero-dimensional materials for an I/I3− redox reaction which can improve the electrical and optical properties of the composite. The results indicate that the amount of GQDs in the composite affect the effectiveness of solar devices. When 0.9%wt of GQDs was used, the WM@GQDs composite achieved an efficiency of 10.38%, which is higher than that of the expensive platinum CE under the same conditions. The mechanism behind the improved power conversion efficiency (PCE) of the composite sample is also discussed in detail. Therefore, WM@GQDs can be an efficient material to replace platinum in DSSCs as a CE.

Low dissipation factor (tan delta) 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 tan delta of 0.015-0.043 with very high dielectric permittivities of 7.0-9.1 x 104 at 1 kHz. Notably, the temperature coefficient in the range of +/- 15 % was obtained in the temperature range of - 60-200 degrees 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 tan delta was primarily caused by the IBLC effect associated with a high resistance of the insulating part and defect dipoles.

Novel MoWO4 with ZnO nanoflowers was synthesized on multi-walled carbon nanotubes (MW-Z@MWCNTs) through a simple hydrothermal method, and this unique structure was applied as a counter electrode (CE) for dye-sensitized solar cells (DSSC) for the first time. The synergetic effect of ZnO nanoflowers and MoWO4 on MWCNTs was systematically investigated by different techniques. The amount of MWCNTs was optimized to achieve the best DSSC performance. It was found that the 1.5% MW-Z@MWCNTs composite structure had the highest power conversion efficiency of 9.96%, which is greater than that of traditional Pt CE. Therefore, MW-Z@MWCNTs-based CE can be used to replace traditional Pt-based electrodes in the future.

Fly ash (FA) and sugarcane bagasse ash (SCBA) are the wastes from lignite power plants and sugar industries, usually disposed of as landfills. In this research, these wastes were effectively utilized as a construction material, namely geopolymer. The effect of the SCBA (0–40 wt.%) addition to the FA geopolymers was investigated. The compressive strength of the FA geopolymers was reduced with the SCBA addition. The reduction was mainly due to the presence of the highly stable and non-reactive quartz (SiO2) phase in SCBA. The SCBA was not dissolved in the alkaline activated solution and hence did not contribute to the geopolymerization process. The unreacted SCBA particles remained in the geopolymer matrix but did not provide strength. However, if the amount of SCBA was about 10 wt.% or less, the impact on the characteristics and properties of FA geopolymers was minimal. Furthermore, this research also studied the dielectric properties of the FA geopolymer/SCBA composites. The relatively large dielectric constant (ε′ = 3.6 × 103) was found for the pristine geopolymer. The addition of SCBA decreased the ε′ slightly due to high carbon content in SCBA. Nevertheless, the variation in ε′ was mainly controlled by the geopolymerization process to form the aluminosilicate gel structure.

The (Zn, Nb)-codoped TiO2 (called ZNTO) nanopowder was successfully synthesized by a simple combustion process and then the ceramic from it was sintered with a highly dense microstructure. The doped atoms were consistently distributed, and the existence of oxygen vacancies was verified by a Raman spectrum. It was found that the ZNTO ceramic was a result of thermally activated giant dielectric relaxation, and the outer surface layer had a slight effect on the dielectric properties. The theoretical calculation by using the density functional theory (DFT) revealed that the Zn atoms are energy preferable to place close to the oxygen vacancy (Vo) position to create a triangle shape (called the ZnVoTi defect). This defect cluster was also opposite to the diamond shape (called the 2Nb2Ti defect). However, these two types of defects were not correlated together. Therefore, it theoretically confirms that the electron-pinned defect-dipoles (EPDD) cannot be created in the ZNTO structure. Instead, the giant dielectric property of the (Zn0.33Nb0.67)xTi1−xO2 ceramics could be caused by the interfacial polarization combined with electron hopping between the Zn2+/Zn3+ and Ti3+/Ti4+ ions, rather than due to the EPDD effect. Additionally, it was also proved that the surface barrier-layer capacitor (SBLC) had a slight influence on the giant dielectric properties of the ZNTO ceramics. The annealing process can cause improved dielectric properties, which are properties with a huge advantage to practical applications and devices.

In this work, we have studied optical and dielectric properties of (Ga, Cu)-doped ZnO nanoparticles in both theoretical and experimental aspects. In an experimental approach, we have synthesized ZnO, Ga-doped ZnO, Cu-doped ZnO, and (Ga, Cu)-codoped ZnO nanopowder by using combustion method, then calcined nanoparticles were investigated by XRD, SEM, TEM, and UV-vis spectroscopy techniques. In the case of the first-principles calculation, 2×2×2 supercell of ZnO and (Ga, Cu)-co-doped ZnO is modeled. These systems consist of 32 atoms while two-Zn atoms are removed and replaced by Ga and Cu. Thus, it is 12.5% mole (Ga, Cu)-co-doped ZnO, same doping percentage to experiment part. In the study, density functional theory (DFT) study is conducted on VASP using GGA with Hubbard parameter (GGA+U). The supercells are firstly optimized. Then, the study carries on by density of states, and band structures calculation. To summarize, we have successfully fabricated (Ga, Cu)-co-doped ZnO nanoparticles with the particle size of 40 – 50 nm, then, optical, and dielectric properties of Ga and Cu doping on ZnO are studied. From the explored results, it can be concluded that this work successes in enhancement dielectric properties and optical properties of ZnO by Ga and Cu doping. As a result, ZnO could be a higher efficiency dielectric material and photocatalyst under Sun irradiation when it is doped by Ga and Cu ions.

(Co, Nb) co-doped rutile TiO2 (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO2 phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO2 with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ ≈ 36,105 and a low loss tangent of tanδ ≈ 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoVoTi complex defect. On the other hand, the substitution of TiO2 with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.