Search

Bi0.86Ba0.14CuSeO/xCu2–ySe (0.05 ≤ x ≤ 0.15; y = 0 and 0.2) composites were fabricated by spark plasma sintering, and the crystal structure and thermoelectric properties of the Bi0.86Ba0.14CuSeO/xCu2–ySe composites were studied. The composites contained Cu2–ySe (y = 0 and 0.2) nanoinclusions in a tetragonal Bi0.86Ba0.14CuSeO matrix. To increase the electrical conductivities of Bi0.86Ba0.14CuSeO, we introduced Cu2–ySe nanoinclusions with a high electrical conductivity into the matrix. The introduction of Cu2–ySe nanoinclusions reduced the structural distortion of CuSe4 tetrahedra and the effective mass, thereby enhancing the carrier mobility. A significant increase in electrical conductivities was achieved with increasing Cu2–ySe nanoinclusion, i.e., 117, 165, and 214 Ω−1cm−1 at 673 K for x = 0.05, 0.10, and 0.15 composites. The Cu2–ySe nanoinclusions reduced the lattice thermal conductivity because they strengthened the long–wavelength phonon scattering at the Bi0.86Ba0.14CuSeO/Cu2–ySe interface. The largest dimensionless figure–of–merit (0.33 at 673 K) was obtained for x = 0.15 composite, which was attributed to the highest electrical conductivity and the lowest lattice thermal conductivity.

Bulk-type pellet thermoelectric devices were fabricated by pressing tungsten (W)-doped V2O5 (WxV2-xO5) nanospheres that were synthesized by chemical reaction, and their performance was studied. The sizes of the synthesized WxV2-xO5 nanospheres (x = 0, 0.04, 0.08, and 0.12) were measured as 259 ± 25, 184 ± 16, 178 ± 16, and 180 ± 21 nm, respectively. The thermoelectric properties were analyzed by obtaining the thermoelectric figure of merit (ZT) using the measured thermal conductivity, electrical conductivity, and Seebeck coefficient in the temperature range of 300–773 K. The thermal conductivity was decreased by the W doping, while the electrical conductivity was increased. As a result, the ZT value increased with the doping concentration, and the maximum ZT value of the W0·08V1·92O5 pellet reached 4.73 × 10−3, which is 3.3 times larger than that of a pure V2O5 pellet at 773 K.

Bi0.925Ca0.075Cu1−xSeO (x = 0–0.10) samples were fabricated by combining a two–step solid–state reaction with spark plasma sintering, and the effect of Cu vacancies on the crystal structure and thermoelectric properties of Bi0.925Ca0.075Cu1−xSeO samples was investigated. Bi0.925Ca0.075Cu1−xSeO formed a single phase with a tetragonal crystal structure (P4/nmm space group). X–ray photoelectron spectroscopy (XPS) analysis revealed that the Cu ions existed as a mixture of Cu1+ and Cu2+ ions and that the Bi ions existed as a mixture of Bi3+ and Bi4+ ions. The relative concentrations of Cu2+ and Bi4+ ions increase with increasing Cu vacancy, which in turn reduce the carrier concentrations. The Cu vacancies enhance the thermoelectric power factor and reduce the lattice thermal conductivity. The largest dimensionless figure–of–merit (0.62) was obtained for Bi0.925Ca0.075Cu0.90SeO at 600 °C. In this work, we optimized the thermoelectric properties of Bi0.925Ca0.075CuSeO by enhancing the power factor and suppressing the thermal conductivity through the formation of Cu vacancies.

In this work, several X-ray and nuclear analysis techniques were used to examine ZnO materials co-doped with In and Ga, or IGZO materials. X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy revealed multi-scale defects in the materials. A nanoscale secondary Ga2Zn9O12 spinel phase, mesoscale grain boundaries, and atomic-scale lattice defects were detected. The lattice defects included oxygen vacancies, zinc vacancies, and complex defects. Positron annihilation spectroscopy and Doppler broadening spectroscopy provided evidence of interactions between charge carriers and defects sites, which explained the low thermal conductivities of the IGZO materials (κtotal ≈ 3.9 W/mK) at 773 K. This combination of X-ray and nuclear analytical techniques can be viewed as a novel approach for investigating the thermoelectric properties of materials with complex crystal structures that contain atomic-scale voids, nanoscale secondary phases, and mesoscale grain boundaries.

When the equipment which is related to safety or important to power production is installed in nuclear power plant units (NPPs), verification of equipment Electromagnetic Susceptibility (EMS) must be performed. The low-frequency radiated magnetic field susceptibility (RS101) test is one of the EMS tests specified in U.S NRC (Nuclear Regulatory Commission) Regulatory Guide (RG) 1.180 revision 1. The RS101 test verifies the ability of equipment installed in close proximity to sources of large radiated magnetic fields to withstand them. However, RG 1.180 revision 1 allows for an exemption of the low-frequency radiated magnetic susceptibility (RS101) test if the safety–related equipment will not be installed in areas with strong sources of magnetic fields. There is no specific exemption criterion in RG 1.180 revision 1. EPRI TR-102323 revision 4 specifically provides a guide that the low-frequency radiated magnetic field susceptibility (RS101) test can be conservatively exempted for equipment installed at least 1 m away from the sources of large magnetic fields (>300 A/m). But there is no exemption criterion for equipment installed within 1 m of the sources of smaller magnetic fields (

There have been significant developments in the enhancement of the thermoelectric (TE) performances of p-type PbTe compounds; however, the TE performances of n-type compounds are not comparable with those of p-type ones. For optimizing the high performance, effective Fermi level tuning is critical. Here, we found that extrinsic doping caused complex defect configurations, resulting in unconventional lattice dynamics and abnormal electronic/thermal transport properties. From the formation energy calculation, the increase in the lattice parameter of PbTe compounds having excess Pb was correlated with the formation of interstitials (Pbint and Teint), Pb–Te antisite defects, and cluster-type defects [(PbTe–TePb), (Pb–Pb)Te, (Te–Te)Pb, and (Pbint–2PbTe)]. When we applied extrinsic n-type doping such as excess Pb and Bi doping, counterpart hole doping-type complex defects were easily generated. The charge compensation effects due to the intrinsic defects such as the VTe2+ and Pbint2+ point defects and cluster-type anionic defects such as Pbint–2(PbTe) resulted in an unconventional electrical transport behavior with respect to the excess Pb concentration in Pb1+xTe. Bi doping in Pb1−xBixTe also gave rise to complex cluster-type defects such as nBiPb–VPb (n = 2 and 3) simultaneously. The complex cluster-type defects not only suppressed the doping efficiency but also increased the scattering exponent in the Seebeck coefficient, resulting in the enhancement of the Seebeck coefficient. The charge compensation between the charged impurity and defect cluster doping was beneficial for fine tuning of the Fermi level for optimal carrier concentration.

Background/aim The antitumor effect of sustained calcium supply on Src degradation was investigated in the context of hormone-dependent breast cancer, followed by elucidation of the underlying mechanisms. Materials and methods Hormone-dependent T-47D breast cancer cells were used. Lactate calcium salt (LCS) was used as the source of sustained calcium supply, and the applicable concentration of LCS was determined by the colorimetric MTT assay. LCS-mediated deactivation of downstream signaling via Src degradation was identified by western blot and immunocytochemistry. Results Calcium-mediated degradation of Src decreased survival signaling via phosphoinositide 3-kinase and protein kinase B and resulted in significant inhibition of the clonogenic ability of hormone-dependent breast cancer cells. Tumor volume was significantly decreased in response to LCS injection in a heterotopic xenograft model, and immuno histochemistry revealed tumor necrosis. Conclusion Sustained supply of calcium inhibited survival signaling via degradation of Src in hormone-dependent breast cancer cells.

Herein, the effect of AgSbTe2 microstructure on the thermoelectric conversion efficiency of an AgSbTe2-based alloy was studied. The as-sintered sample exhibited material separation into a multiphase mixture of cubic Sb-rich AgSbTe2 (Ag21Sb28Te51), monoclinic Ag2Te with an inhomogeneous distribution, and an Sb-rich zone. The samples were subjected to heat treatment for 24 h at 523, 573, and 673 K. The results indicated that AgSbTe2 was metastable against Ag2Te and Sb2Te3 at 573 K. The accelerated kinetics induced the separation of AgSbTe2 into less-Sb-rich δ’-AgSbTe2 and Sb2Te3 with sub-µm sizes. The observations also revealed that AgSbTe2 was stable against Ag2Te and Sb2Te3 at 673 K. Micrometer-scale Ag2Te precipitates and rhombohedral Sb2Te3 phases were dissolved in the main matrix. Furthermore, single-phase δ-AgSbTe2 was stabilized with nanoscale precipitates of Ag2Te and Sb-rich nanodots. The thermoelectric transport properties of the heat-treated samples were investigated. The results indicated that the thermoelectric performance of the single-phase metastable structure with nanoscale precipitates was superior to that of the multiphase structure. Multiphase AgSbTe2 exhibited a low thermal conductivity; however, the effective Seebeck coefficient was balanced by the presence of multiple phases. This resulted in a low thermoelectric power factor. Metastable single-phase AgSbTe2, with Ag2Te and Sb-rich nanodots, exhibited a high Seebeck coefficient with a slightly low p-type conductivity. This resulted in a high thermoelectric power factor, and the presence of nanoscale precipitates lowered the thermal conductivity. It was concluded that the thermoelectric performance of metastable single-phase δ-AgSbTe2 was superior to that of multiphase AgSbTe2.

Oxygen content in n-type Bi2Te3-based alloys plays a crucial role in determining the thermoelectric properties. We aimed to control the residual oxygen that originated from the ball milling process; for this, sintering processes such as spark plasma sintering (SPS) and plasma activated sintering (PAS) were utilized. The reduction of oxygen content was successfully achieved with PAS, leading to improved electrical properties. With the removal of residual oxygen, the carrier concentration increased, resulting in reduced electrical resistivity. The phonon thermal conductivity was reduced due to the grain size of this sample, which was smaller than that of the hot-pressed (HP) samples. An enhanced value of the dimensionless figure of merit (ZT) of 0.83 at 473 K, an increase of 25.2% compared with that of the HP samples, was achieved. The selection of the appropriate sintering process should be considered to remove oxygen content, as well as to minimize grain growth.

Distributed Control System (DCS) communication networks, which use Fast Ethernet with redundant networks for the transmission of information, have been installed in digitalized nuclear power plants. Normally, failover tests are performed to verify the reliability of redundant networks during design and manufacturing phases; however, systematic integrity tests of DCS networks cannot be fully performed during these phases because all relevant equipment is not installed completely during these two phases. In additions, practical verification tests are insufficient, and there is a need to test the actual failover function of DCS redundant networks in the target environment. The purpose of this study is to verify that the failover functions works correctly in certain abnormal conditions during installation and commissioning phase and identify the influence of network failover on the entire DCS. To quantify the effects of network failover in the DCS, the packets (Protocol Data Units) must be collected and resource usage of the system has to be monitored and analyzed. This study introduces the use of a new methodology for verification of DCS network failover during the installation and commissioning phases. This study is expected to provide insight into verification methodology and the failover effects from DCS redundant networks. It also provides test results of network performance from DCS network failover in digitalized domestic nuclear power plants (NPPs).

The anisotropy of thermoelectric properties and microstructures in Bi2Te2.7Se0.3 fabricated by repressing (hot deformation) is investigated. The initial particle and grain size decreased with high-energy ball milling time, which affected the degree of grain orientation during the hot deformation process. To achieve high-performance thermoelectric properties, the anisotropic TE properties are optimized with the control of the degree of grain orientation, carrier concentration and temperature-dependent transport properties. By optimizing synthesis processes, we achieved a highly anisotropic figure of merit (ZT), with peak ZT values of 0.7 and 1.05 at 423 K, in the out of plane and in-plane directions, respectively. The in-plane ZT of the hot deformation sample was enhanced by 24% compared with that of the as-pressed sample (ZT = 0.85) due to reduced electrical resistivity and thermal conductivity, which was attributed to the significant anisotropy in grain orientation.

In this study, the effect of Ag defects on the lattice and thermoelectric properties of Ag-doped BixSb2−xTe3 (BST) alloys are systematically investigated. Using density-functional calculations, we reveal that Ag impurity defects occupying interstitial sites in the BST affect the formation of intrinsic defects in the host materials. Ag interstitial defects, which are responsible for increasing the lattice parameter of the c axis, lower the formation energies of BiTe and SbTe acceptor defects more effectively in the Bi-rich BST than in the Bi-poor BST. In addition, these Ag interstitials induce the formation of AgBi and AgSb in BixSb2−xTe3. Therefore, Ag-induced defect interactions can be used to finely optimize the defects and doping density by varying the Bi content. Furthermore, the phonon thermal conductivity is reduced with the formation of nanoscale twin structures with various stacking faults. Finally, a high figure of merit of 1.4 at 423 K is achieved for p-type BST alloys.

CuAgSe is a promising thermoelectric material whose p-type and n-type thermoelectric figure of merit, Z T , values are relatively high (0.95 and 0.70, respectively). It exhibits native n-type conduction, while p-type conduction is present in non-stoichiometric CuAgSe. Here, we report that the carrier type in CuAgSe semiconductors can be effectively controlled by changing the growth process or doping. We were able to switch the carrier type of CuAgSe from the native n-type to the non-stoichiometric p-type by increasing the soaking time during growth. In contrast, the n-type conduction was always observed when Ni, Co, and Zn were doped into the host lattices. We obtained a maximum Z T value of 0.69 at 623 K in undoped n-type CuAgSe. Zn is a promising dopant for n-type CuAgSe with a Z T value of 0.68 at 623 K, which can be further optimized. Our work provided a simple and effective technique for producing both single-phase n- and p-type CuAgSe.

Thermoelectrics directly converts waste heat into electricity and is considered a promising means of sustainable energy generation. While most of the recent advances in the enhancement of the thermoelectric figure of merit (ZT) resulted from a decrease in lattice thermal conductivity by nanostructuring, there have been very few attempts to enhance electrical transport properties, i.e., the power factor. Here we use nanochemistry to stabilize bulk bismuth telluride (Bi2Te3) that violates phase equilibrium, namely, phase-pure n-type K0.06Bi2Te3.18. Incorporated potassium and tellurium in Bi2Te3 far exceed their solubility limit, inducing simultaneous increase in the electrical conductivity and the Seebeck coefficient along with decrease in the thermal conductivity. Consequently, a high power factor of ∼43 μW cm–1 K–2 and a high ZT > 1.1 at 323 K are achieved. Our current synthetic method can be used to produce a new family of materials with novel physical and chemical characteristics for various applications.

Solid solutions of magnesium silicide and magnesium stannide were recently reported to have high thermoelectric figure-of-merits (ZT) due to remarkably low thermal conductivity, which was conjectured to come from phonon scattering by segregated Mg2Si and Mg2Sn phases without detailed study. However, it is essential to identify the main cause for further improving ZT as well as estimating its upper bound. Here we synthesized Mg2(Si,Sn) with nanoparticles and segregated phases, and theoretically analyzed and estimated the thermal conductivity upon segregated fraction and extraneous nanoparticle addition by fitting experimentally obtained thermal conductivity, electrical conductivity, and thermopower. In opposition to the previous speculation that segregated phases intensify phonon scattering, we found that lattice thermal conductivity was increased by the phase segregation, which is difficult to avoid due to the miscibility gap. We selected extraneous TiO2 nanoparticles dissimilar to the host materials as additives to reduce lattice thermal conductivity. Our experimental results showed the maximum ZT was improved from ∼0.9 without the nanoparticles to ∼1.1 with 2 and 5 vol % TiO2 nanoparticles at 550 °C. According to our theoretical analysis, this ZT increase by the nanoparticle addition mainly comes from suppressed lattice thermal conductivity in addition to lower bipolar thermal conductivity at high temperatures. The upper bound of ZT was predicted to be ∼1.8 for the ideal case of no phase segregation and addition of 5 vol % TiO2 nanoparticles. We believe this study offers a new direction toward improved thermoelectric performance of Mg2(Si,Sn).

We found that Na is a good source to develop twin structures in the Bi-Te system, such as Ag as noted in a previous study. The twin boundaries had a considerable influence on reductions of the lattice thermal conductivity due to phonon scattering by the nano-ordered layers and on reductions of the electrical resistivity owing to the defects generated by the substitution of Na into the cation sites. Here, we report the enhanced thermoelectric properties of a Na-doped p-type Bi0.5Sb1.5Te3 alloy. Measurements show that the electrical resistivity and the Seebeck coefficient decrease with Na doping due to an increase in the free carrier (hole) concentration and that the lattice thermal conductivity decreases with Na doping. The achieved maximum ZT value was 1.20 at 423 K, which is approximately 20% higher than that of Bi0.5Sb1.5Te3 under the same fabrication conditions. These results were achievable by controlling the morphology of the twin structure and the carrier concentration by means of Na doping.

The thermoelectric performance of CuCr1-xMgxO2 materials in terms of multi-scale defects induced at various Mg dopant concentrations (x = 0–0.3) was thoroughly studied in this paper. At 748 K and for x = 0.05, 0.15, and 0.30, we report the following power factors and thermal conductivities: 175, 213, and 2.3 μW/m K2 and 7.85, 5.60, and 3.82 W/m K, respectively. In the low doping regime (x

This study investigates the thermoelectric performance of a bulk-type pellet nanodevice fabricated with pressed V2O5 nanospheres synthesized by chemical reaction and sized 258 ± 27 nm. The following thermoelectric properties in the 300–773 K temperature range were analyzed: thermal conductivity (λ), electrical conductivity (σ), Seebeck coefficient (S), and figure of merit (ZT). The bulk-type pellet thermoelectric device exhibited a higher S and lower σ compared to the film-type device at 300 K. With increasing temperature, the absolute value of S and λ slightly decreased but the σ value increased. The power factor (PF) and ZT value at 773 K were 1.43 × 10−6 Wm−1K−2 and 1.4 × 10−3, respectively.

The electromagnetic interference (EMI) generated from sources in power units can interfere with digital Instrument and Control (I&C) systems. When EMI is emitted with conducted and radiated noise, it interferes with the signals of the I&C systems. Since the digital I&C systems are efficient and competitively priced, the analogue I&C systems have been upgraded and replaced with digital I&C systems, but these systems have less EMI immunity. When safety-related I&C systems are installed in the units, the verification of equipment EMI should not be done in site-specific tests but in test facilities. There are needs to do the overall site-specific EMI assessment of I&C systems depending on the reactor types from thirteen operating units. This study evaluated the margin between plant emission limits and the highest composite plant emissions of the EMI. When the non-safety-related I&C equipment or systems are placed in the units, there are no individual test levels of the radiated electrical field. If need be, the level should comply with the test levels of the radiated electrical field on the safety-related I&C systems. This paper presents the test levels of radiated electrical fields to non-safety-related I&C equipment or systems.

We report the enhanced thermoelectric properties of Ce-doped AgSbTe2 (AgSb1−xCexTe2) compounds. As the Ce contents increased, the proportion of heterophase Ag2Te in the AgSbTe2 gradually decreased, along with the size of the crystals. The electrical resistivity and Seebeck coefficient were dramatically affected by Ce doping and the lattice thermal conductivity was reduced. The presence of nanostructured Ag2Te heterophases resulted in a greatly enhanced dimensionless figure of merit, ZT of 1.5 at 673 K. These findings highlight the importance of the heterophase and doping control, which determines both electrical and thermal properties.

The crystal structure of AgSbTe2 has been refined using first-principles calculations, from which the ordering of the cations, Ag and Sb, was confirmed. The spontaneous formation of two (D4 and L11) phases at ambient and elevated pressure was demonstrated theoretically. The compound was also prepared and its high-pressure structural deformation sequence, ranging from ambient to 50.9 GPa, was observed with synchrotron radiation at room temperature. The compound underwent a pressure-induced amorphization (PIA) at 24.6 GPa and then started recrystallizing at 49.2 GPa. The bulk modulus (B0) and pressure derivative of the bulk modulus (Bp) were determined experimentally to be 56.3 ± 5.1 GPa and 4.3 ± 0.8, respectively. We suggest that large displacements of Te atoms to Ag vacancy positions are responsible for PIA and the recrystallization.

Loose-parts monitoring system (LPMS) monitors loosened or detached parts and foreign parts inside the pressure boundary of a reactor coolant system. If any object is detected, the LPMS identifies the object's characteristics, and can contribute to improving plant safety, since it can identify loosened metal objects, which have a potential to cause severe damage to internal components of the steam generator chamber. The most significant problem of a traditional LPMS is the high false alarm rate. The most developed systems used more sophisticated methods for event identification. With these sophisticated systems, the false alarm rate could be reduced to below 1%. Even though the LPMS resulted in a false alarm rate of less than 1%, there is still a high false alarm rate when the unit increases or decreases power. As the unit increases power, the coolant starts to heat the metal structure, which causes false alarms. Plant operators should continuously identify all alarms, including false alarms, until the metal structure reaches thermal balance. It is difficult to discriminate between valid and false alarms, since the signal pattern by thermal shocks and structure friction is similar to that by loose metal impacts. The false alarm rate can be reduced to almost 0% by applying an algorithm to discriminate between the false and valid alarms. In this paper, an efficient algorithm is proposed to discriminate against signatures which are not related to loose-parts events, especially when the unit increases or decreases power. The algorithm can discriminate the signal pattern by the impact of loose parts against the signal pattern induced by thermal shocks and structure friction. The algorithm was validated in field tests by the proven automatic gun, and the false alarm rate was minimized.

The thermoelectric properties of the Ge1−xMnxTe compounds were investigated in the temperature range from 300 K to 773 K. The crystal structure of the compound was gradually changed with Mn, changing from a rhombohedral to a cubic-like cell. The Seebeck coefficient and the electrical resistivity were increased with Mn. From the Hall coefficient measurement, the reduction of the carrier concentration was confirmed and was responsible for the change of the electrical properties. The thermal conductivity was also reduced with Mn. The maximum dimensionless figure of merit, ZT, was obtained for x = 0.05 composition, where the value was ZT = 1.3 at 773 K. The evolution of the crystal structure with Mn attributed to the change of the thermoelectric properties. The Mn-doped compound which has a more cubic phase than a rhombohedral exhibited superior thermoelectric properties to the pure rhombohedral phase. Open image in new window

In this paper, we propose an algorithm to visualize radio wave environment based on the measured Received Signal Strength Indication(RSSI) and 3D geographic information. We estimate the source position using the circumcenter of the triangle and visualize the radio wave environment using the empirical propagation models. A mode seeking algorithm(mean-shift clustering) is used to seek the peak points and the center of gravity is utilized to reduce the estimation errors. Our approach finds its applications in the radio wave monitoring systems for the efficient utilization of radio resources.

The Electromagnetic Interference(EMI) generating from corona discharge of transformer area can interference the digital Instrument and Control(I&C) systems located nearby transformers. When the potential gradient of the electric field around the conductor is high enough to form a conductive region but not high enough to cause electrical breakdown to nearby objects, the EMI of corona discharge emits with the conducted and radiated noise and it interferences the signals of the I&C systems. Since digital I&C systems have an efficiency and competitive price, the analog I&C systems have been upgraded and displaced with the digital I&C systems but which have less EMI Immunity. There was no assessment to I&C systems by EMI generating corona discharge nearby transformers. When the safety-related I&C systems are installed in plants, the verification of equipment EMI should be done not in site-specific test but in test facilities. There are the need to do the site-specific EMI evaluation of corona discharge nearby transformers. This paper assesses the margin between plant emission limits and the highest composite plant emission of corona. When the non safety-related I&C systems are placed in transformer area, it suggests the appropriate radiated susceptibility level to EMI of corona discharge.

Utilities have recently been debating the respective pros and cons of implementation of a multi-phase upgrade during several normal outages versus a single major upgrade implementation during a prolonged outage. We have studied these approaches and have been developing the basic design of nuclear power plants (NPPs) instrumentation and control (I&C) upgrade since early 2008. As part of this study, analyses of the NPPs I&C systems were conducted and the need for upgrading the systems was raised. One of the primary concerns regarding the system upgrade is a cost-benefit implementation, which will influence the upgrade approach. From this viewpoint, the I&C upgrade must consider economic factors such as I&C vendor cost, architecture engineering cost, installation cost, utility cost, and other transition costs such as training and procedure development. This paper presents a comparison study of economical aspects including cost evaluation between the aforementioned upgrade implementations and suggests a solution for I&C upgrade approach.

In this paper, a comparative analysis of PBTI induced device degradation in nanowire n-channel junctionless and inversion mode Multiple-Gate MOSFET(MuGFETs) has been performed. It has been observed that the threshold voltage is increased after PBTI stress and the threshold voltage variation of junctionless device is less significant than that of inversion mode device. However the degradation rate of junctionless device is less significant than that of inversion mode device. The activation energy of the device degradation is larger in inversion mode device than junctionless device. In order to analyze the more significant PBTI induced device degradation in inversion mode device than junctionless device, 3-dimensional device simulation has been performed. The electron concentration in inversion mode device is equal to the one in junctionless device but the electric field in inversion mode device is larger than junctionless device.

Recently SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. For thermoelectric device applications, it is necessary to have n-type materials with comparable ZT value. Here, we report that n-type SnSe single crystals were successfully synthesized by substituting Bi at Sn sites. In addition, it was found that the carrier concentration increases with Bi content, which has a great influence on the thermoelectric properties of n-type SnSe single crystals. Indeed, we achieved the maximum ZT value of 2.2 along b axis at 733 K in the most highly doped n-type SnSe with a carrier density of −2.1 × 1019 cm−3 at 773 K., The good thermoelectric figures of merit of p-type tin selenide single crystals are actively studied. Here, the authors show that n-type SnSe can also reach a figure of merit of around 2, at high temperatures, when doped with bismuth.

The effect of Sb addition on the thermoelectric properties of the AgPb18Sb1+xTe20 (x = 0 − 1) compounds (LAST-18 compounds) has been investigated in a temperature range between 323 K and 723 K. The measured thermoelectric properties were compared with LAST-18 (x = 0 composition) previously reported and fabricated using the same procedure. All samples showed a negative Seebeck coefficient, which implies the major carrier is the electrons. The carrier concentration of the samples with additional Sb was larger than that of the LAST-18 compounds, indicating that Sb is acting as a donor element in the LAST compounds. From the results of XRD, the Seebeck coefficient, and Hall measurement, the solubility limit of Sb in LAST was estimated. The maximum dimensionless figure of merit, ZT, was obtained for the x = 0.2 composition, where the value was ZT = 1.33 at 723 K. The enhancement of ZT was attributed to the increment of the carrier concentration, resulting in a dramatic reduction of electrical resistivity compared with LAST-18.

The L-shaped 2-5-3-7 algorithm, combining efficient Singaporean and Korean procedures with divisibility rules of primes 2, 3, 5, and 7, helps students identify LCMs and GCFs.

An InGaZnO thin film transistor with different gate lengths and widths have been fabricated and their device degradations with device sizes have been also performed after negative gate bias stress. The threshold voltage and subthreshold swing have been decreased with decrease of gate length. However, the threshold voltages were increased with the decrease of gate lengths. The transfer curves were negatively shifted after negative gate stress and the threshold voltage was decreased. However, the subthreshold swing was not changed after negative gate stress. This is due to the hole trapping in the gate dielectric materials. The decreases of the threshold voltage variation with the decrease of gate length and the increase of gate width were believed due to the less hole injection into gate dielectrics after a negative gate stress.

A thermoelectric material with sufficient performance at high temperatures is a key factor for thermoelectric generation from solar-thermal energy (I. R. radiation). In this study, we analyzed CoSb 3 skutterudite compounds as a thermoelectric material at high temperatures and synthesized filled skutterudites with two types of filler atoms: 1) Yb- and La-fillers with a different electronegativity ( X ) from the Sb atoms and 2) the In-filler with nearly the same electronegativity ( X ) as the Sb atoms. All the samples were sintered with the spark plasma sintering method, and their thermoelectric properties were investigated. From the results, the Yb atoms were the most effective in decreasing the thermal conductivity of this system due to their very different electronegativity ( X ) value from the Sb atoms and lower melting temperature than that of the La-filler. In addition, In-filled compositions had high power factor values while the In-free composition had the lowest power factor value due to its lower melting temperature. The addition of La atoms for filling was not effective in reducing the thermal conductivity of this filled skutterudite system due to its higher melting point. A maximum ZT value of 0.9 at 782 K was obtained in the In 0.1 Yb 0.2 Co 4 Sb 12 specimen.