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This study reports on photoelectrical performance of the long-wave infrared HgCdTe high operating temperature (200-230 K) detector for the fast response time operating under unbiased conditions. The detailed analysis of the response time as a function of device architecture was conducted pointing out optimal working conditions and structure. The response time of the long-wave (xCd = 0.19) HgCdTe detector for temperatures reached by thermoelectrical cooling (200-230 K) was estimated at the level of τs < 0.6 ns for unbiased condition while responsivity Ri ~ 1.8 A/W and detectivity was assessed at the level of D* ~ 1.6 × 1010 cm Hz½/W. It was shown that extra series resistance Rseries < 10 Ω (resistance-capacitance time constant) plays a decisive role in order to reach τs < 1 ns meaning that device processing is much more important rather than fundamental limitations imposed by physics. [ABSTRACT FROM AUTHOR]

Lead-free Ba (1-x) Sr x TiO 3 (BST) ceramics were fabricated to convert near-room-temperature waste heat to electric energy for creating self-powered and ‘battery-less’ systems. In comparison to thermoelectrics that are specifically used for harvesting heat with stable temperature span, pyroelectric converters based on Olsen cycle mechanism can harvest heat with temperature-vibration environment. Large energy conversion density ( N D ) was obtained in BST ceramics within the narrower temperature gradient (< 60 °C). In terms of the diffused phase transition (DPT) in BST ceramics, the extra slim hysteresis loops processed relatively low coercive field ( E c ) and hysteresis loss, which can effectively enhance the N D owing to the wider electrical field interval. The effect of Curie temperature ( T c ) tuned by the ratios of Ba/Sr on N D and applicable range of temperature were also systematically examined. At the same electrical field difference (07 MV/m), the optimal energy conversion properties were gained around the T c , e.g., 0.36 J/cm 3 for BST66/ 3 4 ( T c = 23 °C) within a temperature range between 25 °C and 65 °C, and 0.48 J/cm 3 for BST72/28 ( T c = 43 °C) between 25 °C and 85 °C. [ABSTRACT FROM AUTHOR]

Recently, many novel superionic thermoelectric materials have been discovered along the concept of “phonon-liquid electron-crystal” (PLEC). Among them, Cu 2- x Se-based liquid-like materials are typical examples. In this study, a series of copper-deficient Cu 2- x Se (0.05 ≤ x ≤ 0.25) materials were synthesized and used to study the role of Cu vacancies on the electrical and thermal transport properties. The X-ray photoelectron spectroscopy (XPS) measurements suggest that the valence states of Cu and Se are independent on the Cu/Se atomic ratio. With increasing the content of Cu vacancies, the hole concentration is monotonously increased, leading to the improved electrical conductivity and reduced Seebeck coefficient. Based on the single parabolic band model analysis, it is found that changing the content of Cu vacancies does not obviously modify the material's electronic band structure and effective mass. Due to the presence of highly mobile Cu ions inside the crystal structure, the lattice thermal conductivities of all Cu 2- x Se (0.05 ≤ x ≤ 0.25) materials are very low with values around 0.39 W m −1 K −1 at 500 K. Because of the significantly reduced Seebeck coefficient and increased electronic thermal conductivity, the thermoelectric figure of merit zTs are decreased when increasing x from 0.05 to 0.25. At 750 K, a maximum zT of 0.46 is obtained in Cu 1.95 Se among all Cu 2- x Se (0.05 ≤ x ≤ 0.25) materials. [ABSTRACT FROM AUTHOR]

Cu 10.5 Zn 1.5 Sb 4 S 13 tetrahedrite compound was prepared by mechanical milling of Cu 2 S, ZnS and Sb 2 S 3 powders and spark plasma sintered (SPS) to dense samples. The phase formation, chemical homogeneity, thermal stability of the compound and the thermoelectric properties of the sintered samples were evaluated. Single phase tetrahedrite with the crystallite size of 40 nm was obtained after 30 h of milling followed by annealing at 573 K for 6 h in an argon atmosphere. In-situ high-temperature X-ray diffraction studies revealed that the phase is stable up to 773 K. The Seebeck coefficient of the sintered samples of density >98% shows p-type behavior with maximum thermopower of 170 μV/K at 573 K. The electrical resistivity (ρ) decreases with temperature up to 475 K and then increases. A low thermal conductivity of 0.5 W/(m⋅K), in combination with moderate power factor gave a maximum ZT of ∼0.038 at 573 K in Cu 10.5 Zn 1.5 Sb 4 S 13 sample having a grain size of ∼200 nm. [ABSTRACT FROM AUTHOR]

The purpose of this work is to describe, with numerical simulation, the space charge behavior in polymeric materials. Particular intent is accorded to the variation of the thermo-electrical constraints. The simulation is performed for a range of the electric field from 10 to 110 MV/m and the space charge behavior was described at various temperatures: 0, 27, 60 and 100 ° C. In general, the numerical results show a predominance of the temperature effect, vs. the electric field, on the space charge behavior. The dynamic of the electrical charges is different under 100 ° C, a forehead is observed on their distribution in the sample. Strong electric field enhancements are remarked in the dielectric, they exceed 38% of the applied field under 100 ° C. Only 1.3% of augmentations are observed under room temperature even with higher applied field of 110 MV/m. Both experimental and theoretical Current-Field characteristics, plotted in log-log scale, show linear behavior with slopes greater than one. The different values of slope indicate space charge limited conduction; a change is remarked at 40 MV/m which can defines the beginning of the high fields regime in the case of the studied polymer (Polyethylene Naphthalate). [ABSTRACT FROM PUBLISHER]

Highly dispersed olive-like NiS particles were synthesized in a liquid-liquid biphasic system at room temperature, where nickel xanthate in organic solvents (toluene and benzene) and sodium sulfide in water solution were used as nickel and sulfide sources, respectively. NiS particles were formed at the stabilized phase interface. The structures, chemical composition and optical characteristics of the products were investigated by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. The organic solvents obviously influenced the morphology of the NiS particles. The olive-like NiS with smooth surface and sharp ends was obtained at benzene/water interface, while spindle-like NiS particles with rough surface and circle ends were formed when using toluene as a solvent. Analogously, chainlike Bi2S3 nanowires were produced at chloroform/water interface. The effect of the experiment parameters including reaction time, solvent and concentration of reactants on the size and morphology of the products was discussed in detail and a possible formation mechanism was suggested. [ABSTRACT FROM AUTHOR]

Electretic state and radiation absorption of nanocomposites consisting of polymer matrix and metal particles filler obtained in result of electric explosion are investigated. Stable thermoelectrets of polymer metal-filled systems that have better electert properties than traditional polymer materials are obtained. Suggested method of composite polymer system creation enables to obtain shielded materials with better radiative absorption, resistant to external actions, cost-efficient. [ABSTRACT FROM AUTHOR]

The present work deals with transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermally stimulated discharge current (TSDC) study of inorganic metal oxide (ZnO) nanoparticles and its thermoelectrets. The thermoelectrets were prepared by applying different electric polarizing field ( E) at constant polarizing temperature ( T), for constant polarization time ( t). The TSDC study was carried out in the temperature region of 313-473 K. It was observed that the conductivity of ZnO samples increases with the increase in temperature and polarizing field. The dependence of TSDC data on polarizing agents, i.e. field and temperature shows Arrhenius type of behviour and is explained on the basis of variable range hopping mechanism. [ABSTRACT FROM AUTHOR]

This paper describes the results of thermally stimulated discharge conductivity study of activated charcoal-polyvinyl chloride (PVC) thin film thermoelectrets. TSDC has been carried out in the temperature range 308-400°K and at four different polarizing fields. Results are discussed on the basis of mobility of activated charcoal and polyvinyl chloride chains. [ABSTRACT FROM AUTHOR]