In this study, PEDOT:PSS-based thermoelectric composites were fabricated using a multi-component doping strategy incorporating single-walled carbon nanotubes (SWCNTs), ferrocene, and cobalt oxide. The novelty of this work lies in the synergistic combination of polymer, carbon nanostructures, and metal oxide additives, which has been rarely explored in polymer thermoelectrics. Four samples were prepared—undoped PEDOT:PSS, PEDOT:PSS–SWCNT, PEDOT:PSS–ferrocene–cobalt oxide, and PEDOT:PSS–SWCNT–ferrocene–cobalt oxide—to systematically investigate the effects of each dopant and their combination on thermoelectric performance. Structural and compositional integrity of the composites was confirmed by Raman spectroscopy, which verified the presence of SWCNTs, cobalt oxide, and the PEDOT:PSS matrix. Electrical conductivity increased significantly with SWCNT incorporation, reaching 139.6 S/m in the fully doped sample. All composites exhibited positive Seebeck coefficients, confirming p-type behavior, while thermal conductivity remained within the typical polymer range (57.4–199.0 mW/m·K). The multi-component doping led to a dramatic improvement in the figure of merit (zT), reaching 3.158 × 10⁻4—nearly 90 times higher than pristine PEDOT:PSS. These results demonstrate that tailored multi-dopant engineering is a promising route for tuning the thermoelectric properties of polymer-based composites, providing insights for the development of flexible and high-performance thermoelectric materials.

In this study, chromium oxide doped zirconia-gadolinia (ZrO₂-Gd₂O₃) nanoceramics were synthesized. The objectives were to produce and characterize these nanoceramics and to investigate the effect of chromium oxide concentration on their color properties. The polymeric precursor technique was selected for synthesis, with polyvinyl alcohol (PVA) used as the polymeric precursor. Various analytical techniques—including thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), color spectrophotometry, and Brunauer–Emmett–Teller (BET) surface area analysis—were employed to evaluate the structural, thermal, and optical properties of the samples. FT-IR analysis revealed characteristic vibration bands corresponding to Cr–O, Zr–O, and Gd–O bonds in all samples. XRD results indicated the presence of the fcc-Zr₂Gd₂O₇ and o-GdCrO₃ phases. Notably, the degraded perovskite structure of GdCrO₃ was also detected. Elemental analysis via energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of all target elements in the samples. According to SEM and BET analyses, the nanoceramics exhibited both macroporous and mesoporous structures, suggesting particle agglomeration within the matrix. Color spectrophotometry results showed a shift in color from olive green to vivid green with increasing Cr₂O₃ content and decreasing ZrO₂ content, highlighting the influence of chromium concentration on the ceramics.

Today, energy needs, and energy consumption are increasing day by day. Both the danger of depletion of energy resources and the increase in energy consumption compared to previous years have led to intensification of studies in the fields of free energy systems. One of the most important features of free energy systems is thermoelectric systems that provide energy production using waste heat. In this study, ferrocene doping was aimed and additions such as PEDOT: PSS, SWCNT and cobalt oxide were made in addition to these materials. In this context, 7 samples were obtained by the polymer film method. The characterizations of the materials were made by using XRD, FTIR, SEM, UV-Vis-NIR, DSC and TGA devices. When examined the thermoelectric properties of the samples, thermal conductivity results of all samples were obtained depending on the temperature, but electrical conductivity and Seebeck results of only 4 of the 7 samples were obtained. As a result of the data, the sample 1 had the lowest thermal conductivity value, and the sample 6 had the highest electrical conductivity, Seebeck coefficient, and zT data. The most important point in this study was that the zT value increased approximately 100 times with the addition of ferrocene, SWCNT and cobalt oxide to the PEDOT:PSS polymer (comparison of sample 0 and sample 6).

Neodymium, gadolinium, and praseodymium doped barium-iron oxide ceramic materials were synthesized by polymeric precursor method. No carbon contents or the moisture was observed in infrared spectra of the ceramics. Neodymium and gadolinium doped ceramics were crystallized in cubic lattice form, while praseodymium doped ceramic was formed in hexagonal lattice. Same results were observed from SEM images, Neodymium and gadolinium doped ceramics had similar morphological structures, but praseodymium doped ceramics had slightly different morphology. Neodymium and gadolinium doped ceramics consisted of grain-like structure, while praseodymium doped ceramic material consisted of both grain-like and pillar-like crystal structures.

The primary purpose of this study was to observe the effects of graphene doping on the structure and the physical properties of n-type thermoelectric materials. Structural characterizations of the produced materials were measured by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR). Temperature-dependent thermal conductivity and the Seebeck coefficient measurements were applied via physical properties measurement system (PPMS). After XRD analyses, the diffractograms showed that the produced materials had crystalline forms. With respect to observing SEM micrographs, the homogenization of the samples usually increased with graphene doping. The results of temperature-dependent thermal conductivity and the Seebeck coefficient measurements revealed that graphene doping had a positive influence on both values.

Bu çalışmada toplamda doksan iki adet sesli komuttan oluşan bir yalıtık sözcüklü Türkçe konuşma tanıma sistemi tasarlanmış ve gerçekleştirilmiştir. Sistem, destek vektör makinesi (SVM) tabanlı olup, eğitimde kullanılan veri kümesi kaydedilen konuşmaların yapay olarak çeşitlendirilip artırılmasıyla elde edilmiştir.Farklı yapay veri oranlarının tanıma başarımı üzerindeki etkisi incelenmiştir

In this work, Au/4H–SiC Schottky diodes with different Bi2O3–x:PVA (x = Sm, Sn, Mo) thin insulator interface layer were produced for the fabrication of metal/insulator/semiconductor (MIS) structures. The effect of different Bi2O3–x:PVA interfacial layer deposited between metal and semiconductor on important optical and electrical parameters of Schottky diodes was investigated. The main electrical parameters of the prepared structures such as the saturation current (I0), the barrier height (ΦB0), ideality factor (n), and series and shunt resistance (Rs and Rsh) were obtained from the I‒V characteristics. The discrepancies in these parameters can be ascribed to the use of different nanomaterials as an interlayer. Moreover, the values of n, ΦB0, and Rs were also extracted by using Cheung and Norde functions and obtained results were compared with each other. The energy dependence of interface states [Nss vs (Ec − Ess)] was investigated by taking into account the voltage dependence of Φe(V) and n(V). In addition, Ln(I)–Ln(V) plots were drawn to specify the possible current transport mechanisms of the prepared structures. Experimental results show that the Schottky structures with (Bi2O3–Sn:PVA) and (Bi2O3–Sm:PVA) interlayers yield higher RR and Rsh values and lower Io values. This provides an evidence to performance increase in MS structures.

$$\hbox {Ag/Ru}_{0.03}{-}\hbox {PVA}$$ /n-Si structures were successfully prepared and their morphological and electrical properties were investigated. The obtained electrical results suggested that the complex dielectric constant ( $$\varepsilon ^{*}=\varepsilon ^{\prime }-{j\varepsilon ^{\prime \prime }}$$ ), complex electric modulus $$M^{*}=M^{\prime } + { jM}^{\prime \prime }$$ , loss tangent (tan $$\delta $$ ) and alternating current (ac) electrical conductivity ( $$\sigma _{\mathrm{ac}})$$ are all a strong function of the frequency (f) and applied voltage. The changes in these parameters are the results of the existence of the surface states ( $$N_{\mathrm{ss}})$$ or interface traps ( $$D_{\mathrm{it}} = N_{\mathrm{ss}})$$ , interfacial polymer layer, surface and dipole polarizations and hopping mechanisms. The values of $$\varepsilon ^{\prime }$$ and $$\varepsilon ^{\prime \prime }$$ show a steep decline with increasing frequency and then reach a constant value at high frequency, whereas the increments of $$M^{\prime }$$ and $$M^{\prime \prime }$$ with frequency are exponential. The tan $$\delta \, vs$$ . log f plot has a strong peak behaviour, especially in the accumulation region. These experimental results suggested that the $$\hbox {Ru}_{0.03}{-}\hbox {PVA}$$ interfacial layer could be used as a high dielectric material instead of conventional materials.

This study aims to observe the changes in the structural characterization and physical properties of calcium-praseodymium-cobalt oxide thermoelectric materials with graphene doping. Structural characterizations were examined via X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), and Fourier Transformed Infrared Spectroscopy (FTIR) measurements. Temperature-dependent thermal conductivity and Seebeck coefficient were measured by Physical Properties Measurement System (PPMS). In the SEM images, the samples were observed to be crystalline and showed enhanced fusion with graphene doping. There were no impurities in the samples according to the EDX results and all sample components were observed in these results. The properties and structures of the bonds in the XRD results were also visible in the FTIR results. According to the PPMS results, it was determined by measurements and graphs that graphene doping provided a significant and changeable effect to the thermoelectric materials.

Boron and rare earth stabilized graphene (Gr) doped polyvinylidene fluoride (PVDF) nanofibers were synthesized by electro‐spinning method. The structural and morphological properties of the nanofibers were characterized. The morphological and structural behavior of the samples containing different amounts (0%, 0.1%, 0.3% and 0.5%) of Gr and different doping material such as boron (B) and rare earth elements (REEs), were found to be different from each other. Scanning electron micrographs (SEM) of the synthesized nanofibers exhibit that, the addition of the Gr into pure PVDF caused a marked decrease in the diameters of nanofibers. So much so that the average diameter of pure PVDF nanofibers was about 500 nm while the average diameters of the Gr doped nanofibers was merely 58 nm. To the energy dispersive X‐ray (EDX) Analysis, suitable and specified elements were determined for each samples. The X‐ray diffraction (XRD) patterns show that crystallinity of the nanofibers increased with the increasing content of Gr. In addition, the XRD peaks β crystalline phase in G‐doped PVDF was more intense than the ones in pure PVDF and the most intense one was observed at 0.3% G‐doped PVDF. Boron doping contrary to Gr addition result in the increase of α phase. Differential thermal analyses (DTAs) data showed that Gr and B doping increased the melting point of PVDF materials. In addition, the dielectric properties of these samples showed that the value of ε ’ increased with increasing the rate of Gr. Thus, the P‐G 0.3% and P‐G 0.5% materials have the largest dielectric constants. POLYM. COMPOS., 40:3623–3633, 2019. © 2019 Society of Plastics Engineers

In this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0≤x≤0.3, 0≤y≤0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15–300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25×10-5, 5.3×10-6, 8.6×10-5 and 9×10-6 for sintered powders from undoped, Ni and B doped powders, respectively.

Three different thicknesses (50, 150 and 500 nm) Zn-doped polyvinyl alcohol (PVA) was deposited on n-4H-SiC wafer as interlayer by electrospinning method and so, Au/(Zn-doped PVA)/n-4H-SiC metal–polymer–semiconductor structures were fabricated. The thickness effect of Zn-doped PVA on the dielectric constant (\(\varepsilon ^{\prime }\)), dielectric loss (\(\varepsilon ^{{\prime }{\prime }}\)), loss-tangent (tan \(\delta \)), real and imaginary parts of electric modulus (\(M^{\prime }\) and \(M^{{\prime }{\prime }})\) and ac electrical conductivity \((\sigma _{\mathrm{ac}})\) of them were analysed and compared using experimental capacitance (C) and conductance (\(G/\omega \)) data in the frequency range of 1–500 kHz at room temperature. According to these results, the values of \(\varepsilon ^{\prime }\) and \(\varepsilon ^{{\prime }{\prime }}\) decrease with increasing frequency almost exponentially, \(\sigma _{\mathrm{ac}}\) increases especially, at high frequencies. The \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) values were obtained from the \(\varepsilon ^{\prime }\) and \(\varepsilon ^{{\prime }{\prime }}\) data and the \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) vs. f plots were drawn for these structures. While the values of \(\varepsilon ^{\prime }\), \(\varepsilon ^{{\prime }{\prime }}\) and tan \(\delta \) increase with increasing interlayer thickness, the values of \(M^{\prime }\) and \(M^{{\prime }{\prime }}\) decrease with increasing interlayer thickness. The double logarithmic \(\sigma _{\mathrm{ac}}\) vs. f plots for each structure have two distinct linear regimes with different slopes, which correspond to low and high frequencies, respectively, and it is prominent that there exist two different conduction mechanisms. Obtained results were found as a strong function of frequency and interlayer thickness.

The aim of this study is to improve the electrical property of Ag/n-Si metal–semiconductor (MS) structure by growing an Ru-doped PVP interlayer between Ag and n-Si using electrospinning technique. To illustrate the utility of the Ru-doped PVP interface layer, current–voltage (I–V) characteristics of Ag/n-Si (MS) and Ag/Ru-doped PVP/n-Si metal–polymer–semiconductor (MPS) structures was carried out. In addition, the main electrical parameters of the fabricated Ag/Ru-doped PVP/n-Si structures were investigated as a function of frequency and electric field using impedance spectroscopy method (ISM). The capacitance–voltage (C–V) plot showed an anomalous peak in the depletion region due to the special density distribution of interface traps/states (Dit/Nss) and interlayer. Both the values of series resistance (Rs) and Nss were drawn as a function of voltage and frequency between 0.5 kHz and 5 MHz at room temperature and they had a peak behavior in the depletion region. Some important parameters of the sample such as the donor concentration atoms (ND), Fermi energy (E F ), thickness of the depletion region (WD), barrier height (Φ B0 ) and R s were determined from the C−2 versus V plot for each frequency. The values of N D , W D , Φ B0 and R s were changed from 1 × 1015 cm−3, 9.61 × 10−5 cm, 0.94 eV and 19,055 Ω (at 0.5 kHz) to 0.13 × 1015 cm−3, 27.4 × 10−4 cm, 1.04 eV and 70 Ω (at 5 MHz), respectively. As a result of the experiments, it is observed that the change in electrical parameters becomes more effective at lower frequencies due to the Nss and their relaxation time (τ), dipole and surface polarizations.

Au/ZnO/n-Si (MIS) structures were fabricated by using the RF sputtering method and their complex dielectric constant (epsilon*= epsilon'-j epsilon"), electric modulus (M*=M' + jM") and electrical conductivity (sigma = sigma(dc) + sigma(ac)) values were investigated as a function of frequency (0.7 kHz-1 MHz) and voltage (- 6 - ( + 6 V)) by capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements to get more information on the conduction mechanisms and formation of barrier height between Au and n-Si. The In sigma-Inf plots have two different regions corresponding to low-intermediate and high frequencies. Such behavior of In sigma-Inf plots shows that the existence of two different conduction mechanisms (CMs) at low-intermediate and high frequencies. Moreover, the reverse bias saturation current (I-0), ideally factor (n), barrier height (Phi(B0)) were determined from the forward bias I-V data and they were found as a strong function of temperature. The value of n especially at low temperature is considerably higher than unity. The values of (Phi) over bar (B0) and standard deviation(sigma(s)) were found from the intercept and slope of (Phi) over bar (B0)-q/2kT plots as 0.551 eV and 0.075 V for the region I (80-220 K) and 1.126 eV and 0.053 V for the region II (220-400 K), respectively. The values of (Phi) over bar (B0) and effective Richardson constant (A*) were found from slope and intercept of activation energy plots as 0.564 eV and 101.084 Acm(-2) K-2 for the region I and 1.136 eV and 41.87 Acm(-2) K-2 for the region II, respectively. These results confirm that the current-voltage-temperature (I-VT) characteristics of the fabricated Au/ZnO/n-Si SBDs can satisfactorily be explained on the basis of TE theory with double GD of the BHs.

In this study, we investigate the effect of the addition of poly vinyl alcohol (PVA), a polymer filler, which is known to promote the strength of unit mass, corrosion strength and the flexibility of the final product together with boric acid as a cross linking agent to concrete polymer composites by viscosity, setting time, compressive and bending strength tests in accordance with Turkish standards. The addition of PVA and boric acid caused 4% increase in 28 days’ compressive strength results. The bending strength on the other hand, the bending strength decreased by 45%. The samples were also investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD) methods. The experiments repeated with higher filler concentrations showed that porosity of the final concrete was significantly decreased resulting a much higher quality end product.

Electrical and dielectric properties of Au/n-Si metal-semiconductor structures with high dielectric have been examined by capacitance/conductance-voltage (C/G-V) measurements in the frequency range of 5-500 kHz at room temperature. Voltage-dependent profiles of interface states (N-ss) and resistance (R-i) were extracted from the C and G data using the low-high-frequency capacitance and Nicollian-Brews methods, respectively. The real and imaginary components of the complex dielectric constant (epsilon', epsilon ''), electric modulus (M' and M ''), and ac conductivity (sigma(ac)) were calculated from the C and G data. All parameters have a strong relation with frequency and voltage, especially at low frequencies due to Maxwell-Wagner relaxation and N-ss. The observed peaks in the N-ss-V and R-i-V plots can be ascribed by the special distribution of N-ss at M/S interface. These results confirmed that [2% graphene cobalt-doped (Ca3CO4Ga0.001Ox] interlayer has high-dielectric constant and can be used an interlayer instead of the traditional SiO2 at M/S interface to increase their capacitance or more charges/energy storage and reduce both the values of N-ss and series resistance (R-s). The values of a are almost constant at lower-intermediate frequencies, but they start to increase at high frequencies that are corresponding to the dc and ac conductivity, respectively.

In order to see effects of interfacial (with and without different graphene (GP) + Ca1.9Pr0.1Co4Ox-doped PVA) layer on the electrical characteristics of conventional Au/n-Si (MS) contacts. Therefore, Au/(GP + Ca1.9Pr0.1Co4Ox-doped PVA)/n-Si (MPS) structures were fabricated with different rates of (%3 GP, %7 GP) PVA and were fabricated on same n-Si wafer. Au/n-Si (MS), Au/PVA/n-Si, Au/%3GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si and Au/%7GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si structures were fabricated and their main electrical characteristics compared each other by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of with and without GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si at room temperature were studied to investigate its main electrical parameters. The energy density distribution profile of the interface states (Nss) was obtained from the forward bias I–V data by taking into account voltage dependent ideality factor (n(v)) and effective barrier height (Φe) and they increase from at about mid-gap energy of Si to bottom of conductance band edge. In addition, voltage dependent profile of resistivity of the structure was obtained from I–V data for four different structures. The analysis of experimental results reveals that the existence of GP + Ca1.9Pr0.1Co4Ox-doped PVA interfacial layer improves the performance of MS structure. In order to determine the dominant current-transport mechanism (CTM) in the whole forward bias region of these structures, the double logarithmic forward bias I–V plots were also drawn. These plots exhibit two distinct linear region with different slopes which are corresponding to intermediate and high forward bias voltages. The slope of these plots show that in the region 1 (low biases) the dominant CTM is trap-charge-limited current (TCLC), whereas in the region 2 (high biases) is space-charge-limited current (SCLC) for four diodes.

In order to interpret the electrical characteristics of fabricated Au/ZnO/n-Si structures as a function of frequency and voltage well, their capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements were carried out in a wide range of frequencies (0.7 kHz–2 MHz) and voltages (± 6 V) by 50 mV steps at room temperature. Both the C–V and G/ω–V plots have reverse, depletion, and accumulation regions such as a metal–insulator/oxide semiconductor (MIS or MOS) structures. The values of doped-donor atoms (N D), Fermi energy level (E F), barrier height (ΦB), and series resistance (R s) of the structure were obtained as a function of frequency and voltage. While the value of N D decreases with increasing frequency almost as exponentially, the value of depletion width (W D) increases. The values of C and G/ω increase with decreasing frequency because the surface states (N ss) are able to follow the alternating current (AC) signal, resulting in excess capacitance (C ex) and conductance (G ex/ω), which depends on their relaxation time and the frequency of the AC signal. The voltage-dependent profiles of N ss were obtained from both the high–low frequency capacitance and Hill-Colleman methods. The other important parameter R s of the structure was also obtained from the Nicollian and Brews methods as a function of voltage.

Au/graphene oxide (GO)-doped PrBaCoO nanoceramic/n-Si capacitors were fabricated and their admittance measurements were carried out between 1 kHz and 1 MHz at room temperature. Experimental results showed that the capacitance (C) and conductance (G/w) values are strong functions of frequency and applied bias voltage. C–V plot revealed two distinctive peaks at low frequencies which are located at about 0 and 2 V, such that the first peak disappears towards high frequencies. The energy density distribution profile of the interface/surface states (D it/N ss) and their relaxation time (τ) and capture cross section (σ p) of the sample were obtained by using the admittance method. In addition, the voltage-dependent profile of N ss and resistance were obtained by using low–high frequency capacitance and Nicollian-Brews method, respectively, and they also reveal two distinctive peaks, respectively. Two peaks’ behavior in the forward bias C–V, N ss–V and R i–V plots confirmed the existence of two different localized regions of N ss between Si and interfacial layer. The series resistance (R s) of the device decreased with increasing frequency from 175 Ω at 1 kHz to 72 Ω at 1 MHz. As a result, the mean value of D it was found about 5 × 1013 eV−1 cm−2 which is reasonable for an electronic device.