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Cu3SbSe4-Based materials were fabricated through Sn-doping and AgSb0.98Ge0.02Se2 incorporation and their thermoelectric properties were investigated in the temperature range from 300 K to 675 K. A remarkable enhancement in thermoelectric performance was obtained, which can be ascribed to the synergistic adjustment of electrical and thermal transport. The introduction of AgSb0.98Ge0.02Se2 nanoparticles strengthened phonon scattering in the composites, resulting in a low thermal conductivity. Simultaneously, a high power factor was maintained. As a result, a maximum figure of merit of 1.23 was obtained at 675 K for the sample Cu3Sb0.96Sn0.04Se4–3 wt% AgSb0.98Ge0.02Se2, which is one of the highest values ever reported in the Cu3SbSe4-based system.

We report the realization of high thermoelectric performance in Cu3SbSe4-based materials through Sn-doping and inclusion of Cu3Sb0.94Sn0.06Se2.5S1.5 nanostructure. This significant enhancement in thermoelectric performance is attributed to simultaneous modulation of the electrical and thermal transport. Sn doping can reduce electrical resistivity, maintaining its high power factor. Cu3Sb0.94Sn0.06Se2.5S1.5 nanoparticles dispersed in the matrix can strengthen interface scattering at the phase boundaries, which can effectively scatter the heat-carrying phonons and thus yielding low lattice thermal conductivity. As a result, the figure of merit reaches ∼0.87 at 673 K for Cu3Sb0.96Sn0.04Se4–3% Cu3Sb0.94Sn0.06Se2.5S1.5.

Several p-type Cu12Sb4S13 composites Cu 12 Sb 4 S 13 based composites Cu 12 Sb 4 S 13 / x %InSb (0 ≤ x ≤ 4) have been prepared as environmentally-friendly thermoelectric materials. A high figure of merit ZT = 0.9 is obtained for the sample Cu 12 Sb 4 S 13 / 3% InSb at 723 K, which is ∼61% larger than that for pure Cu 12 Sb 4 S 13 at the same temperature. The excellent performance is due to the simultaneous enhancement in Seebeck coefficient and reduction in thermal conductivity across the whole temperature range investgated. We believe that this study could be highly applicable in guiding the performance enhancement of other state-of-the-art thermoelectric systems.

Pb-doped tetrahedrite Cu12-xPbxSb4S13 (x = 0, 0.25, 0.50, 0.75, 1.00, 1.25 and 1.50) samples were prepared and their thermoelectric properties were investigated in the temperature range from 300 K to 723 K. The results show that Pb is successfully doped in Cu(1) site, which brings about both 10–118% increase in Seebeck coefficient owing to the decrease of hole concentration and 87–168% decrease in thermal conductivity due to the enhanced phonon scattering by the dopant atoms. As a result, a maximum ZT = 0.8 at 723 K is achieved for Cu11PbSb4S13, which is ∼43% larger than that of pristine Cu12Sb4S13. Present results demonstrate that Pb is an effective dopant to elevate thermoelectric performance of Cu12Sb4S13.

Although single crystalline SnSe has high thermoelectric figure of merit ZT, the highest ZT reported for polycrystalline SnSe-based material is not larger than 1. Here we show that a record value of ZT = 1.26 at 880 K is achieved for polycrystalline SnSe based composites with PbTe nanoinclusions. Our results indicate that the high performance arises from simultaneous increase in power factor and thermal resistance. The increased power factor mainly originates from enhanced electrical conductivity due to increased carrier concentration; while the large (∼25%) reduction of thermal conductivity can be ascribed to both the interface scattering of phonons and inhibition of bipolar effect. Present result demonstrates that the introduction of proper nanoinclusions can effectively elevate the thermoelectric performance of polycrystalline SnSe compound.

Herein, nanoparticles SnSe are prepared by fusion method together with ball-milling technique and the effect of hot-pressing temperatures on the thermoelectric properties of the dense materials is explored. Due to the optimization of carrier concentration, the peak figure of merit (ZT) value of the compacted material reaches 0.73 for SnSe sample hot-pressed at 400°C and 450°C. The present investigation indicates that the thermoelectric performance of the SnSe compound can be significantly improved by sintering with suitable temperature.

Many methods have been focused on improving the thermoelectric performance of Cu3SbSe4 based materials. However, no effective way can simultaneously achieve the significant improvement of power factor and the remarkable reduction of thermal conductivity. In this work, we introduce AgSb0.98Sn0.02Se2 particles into Cu3Sb0.96Sn0.04Se4 matrix forming Cu3Sb0.96Sn0.04Se4/x wt%AgSb0.98Sn0.02Se2 (x = 0, 1, 3, 5, 7) nanocomposites by milling and spark plasma sintering technique. Due to the reduced thermal conductivity and enhanced carrier mobility, a record-high ZT value of 1.17 is obtained for the sample Cu3Sb0.96Sn0.04Se4/5wt%AgSb0.98Sn0.02Se2. The reduced thermal conductivity is attributed to the enhanced phonon scattering caused by the second phase AgSb0.98Sn0.02Se2 with multiscale size and the enhanced power factor originated from increased carrier mobility due to the reduced carrier concentration, which is caused by the new acceptor energy level related to the interfacial defects. Present results demonstrate that excellent thermoelectric performance can be realized in Cu3Sb0.96Sn0.04Se4 matrix with AgSb0.98Sn0.02Se2 particles embedded.

The electrical transport properties of p-doped semiconductors CdTe 15/16 M 1/16 (M=N, P, As, Sb) and Cd 15/16 TeM 1/16 (M=Na, K, Rb, Cs) with two configurations are investigated through first-principles calculations combined with Boltzmann transport theory under the relaxation time approximation. It is found that N and Cs atoms in the homogeneous structure induce much sharper electron densities of states (DOSs) and flatter energy bands at the valence band edges than the rest of doped elements, resulting in much larger Seebeck coefficients. The calculations reveal that most of the Seebeck coefficients and electrical conductivities are impacted unfavorably by the conglomeration of impurity atoms considered. Though the power factors for homogeneous doping of N and Cs are comparatively smaller, the electronic figures of merit are much larger at 800–1000 K than the rest ones due to much smaller electronic thermal conductivities, therefore probably enhancing the thermoelectric figures of merit. The results show that doping the elements with electronegativities distinct from the host atoms can enhance the Seebeck coefficients and the thermoelectric performances of bulk semiconductors efficiently if the energy levels of doped atoms resonate with those of host atoms and the arrangement of doped atoms is modulated appropriately to avoid deteriorating the sharpness of the DOS (or transport distribution).

Thermoelectric properties of BiSbTe-based composites dispersed with a small amount (

The anisotropy of the thermoelectric properties of Bi2Te3−xSex (0.3 ≤ x ≤ 0.9) is investigated at temperatures from 300 to 523 K. The results indicate that due to the anisotropic microstructures, the anisotropic resistivity ρ and thermal conductivity κ of Bi2Te3−xSex are obtained. For example, the resistivity ratio ρp/ρn (here subscript n and p denote the directions normal and parallel to the pressing direction, respectively) and thermal conductivity ratio κp/κn for Bi2Te3−xSex are around 1.55–2.25 and 0.53–0.79, respectively. As a result, a highly anisotropic figure of merit (ZT) is obtained. A maximum ZTn of ∼0.7 is obtained in the temperature range of 440–470 K for Bi2Te2.1Se0.9. Moreover, the maximum ZTp for Bi2Te2.6Se0.4 is ∼0.6 in the temperature range from 400 to 470 K.

The anisotropy of thermoelectric properties for (BixSb1-x)2Te3 (0.16 ≤ x ≤ 0.24) are investigated in the temperature range of 300K to 523K. Anisotropy ratiosof the specimens are around 0.72-0.93 and 1.0-1.26 for the resistivity and the thermal conductivity, respectively. In addition, a relation of k ⊥ ≈ k // /( 1−f ) is found to hold, suggesting the validity of the rule of mixture for its k and f. The maximum ZT=1.37 (at 416K) are achieved for (Bi0.16Sb0.84)2Te3. Besides, (BixSb1-x)2Te3 sample shows good mechanical properties. The compression strength for (Bi0.16Sb0.84)2Te3 is 60MPa and 65MPa in the two measured directions, which is 6 folds and 1.6 times as larger as that of commercial ingot parallel and normal to the solidification direction, respectively.

The thermoelectric properties of Fe-doped compounds (Zn1 � xFex)4Sb3 (x ¼ 0, 0.0025, 0.005, 0.01) have been studied at the temperatures from 7 K to 305 K. The results indicate that low-temperature (T < 300 K) thermal conductivity of the moderately doped (Zn1 � xFex)4Sb3 (x ¼ 0.0025 and 0.005) reduces remarkably as compared with that of Zn4Sb3 due to enhanced impurity (dopant) scattering of phonons. Electrical resistivity and Seebeck coefficient are found to increase first and then decrease obviously with the increase in the Fe content. Moreover, the lightly doped compound (Zn0.995Fe0.005)4Sb3 exhibits the best thermoelectric performance due to the improvement in both its thermal conductivity and Seebeck coefficient, whose figure of merit (at 300 K), ZT, is about 1.3 times larger than that of b-Zn4Sb3 obtained in the present study.

Nanocrystalline (Mg1−xCdx)3Sb2 (x = 0–0.3) and nominally (Mg0.7Cd0.25Ag0.05)3Sb2 with a mean grain size of ∼35 nm were prepared by mechanical alloying plus hot-pressing, and their transport and thermoelectric properties were investigated from 310 K down to 20 K. The results indicated that electric resistivity of (Mg1−xCdx)3Sb2 decreased with increasing Cd content x, which could be ascribed to increase in carrier concentration indirectly caused by lattice distortion after substituted. The much larger decrease in the resistivity of (Mg0.7Cd0.25Ag0.05)3Sb2 than that of (Mg1−xCdx)3Sb2 should originate from substantial increase in hole concentration due to introduction of acceptor impurity Ag. At lower temperature regimes, Mott's T−1/4 law was observed, which could be attributed to the severe potential disorder caused by lattice distortion upon doping. Seebeck coefficient of all the substituted and co-doped specimens decreased presumably due to increased carrier concentration. Moreover, thermal conductivity of (Mg1−xCdx)3Sb2 decreased monotonously with increasing x due to phonon scattering of the impurity (Cd) with greater atomic weight. The presence of slight precipitated elementary Sb and Cd phases should be responsible for the observed larger thermal conductivity of (Mg0.7Cd0.25Ag0.05)3Sb2 specimen. The values of the ZT for all the doped specimens enhanced. Especially, ZT of (Mg0.7Cd0.25Ag0.05)3Sb2 reach 0.01 at 300 K, which is several orders magnitude higher than that un-doped one and those doped slightly with Cd only. Present result indicates that thermoelectric properties of Mg3Sb2 system can be effectively improved by the proper substitution of element Cd and co-doped with element Ag.

Cadmium doped compounds (Cd x Ti 1− x ) 1+ y S 2 (0 ≤ x ≤ 0.075) were prepared by solid-state reaction, and their transport and thermoelectric properties were investigated from 4 K to 310 K. The results indicated that electric resistivity ρ increased first and then decreased with increasing Cd content; at low temperatures ρ – T curves for (Cd x Ti 1− x ) 1+ y S 2 ( x > 0) was found to obey the Mott's two-dimensional hopping law ln ρ – T −1/3 . Moreover, it was found that the absolute thermopower | S | for all the doped compounds increased significantly in the whole temperature range investigated, and lattice thermal conductivity of the doped compounds rose obviously. The increase of ρ and | S | can be ascribed to decrease in electron concentration due to Cd substitution for Ti, while the slight decrease in ρ and | S | at high doping level could be caused by simultaneous intercalation of some Cd (and Ti) atoms upon heavy doping. The larger lattice thermal conductivity of the doped compounds would imply enhancement of the acoustic velocity. Besides, experiments show that the figure of merit, ZT , of the doped compound is improved in almost the whole temperature range investigated due to great enhancement of its thermopower, and specifically it reaches 0.022 at 310 K for (Cd 0.05 Ti 0.95 ) 1+ y S 2 , which is about 23% larger than that of TiS 2 .

The effects of N+ implantation under various conditions on CVD diamond films were analyzed with Raman spectroscopy, four-point probe method, X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), ultraviolet photoluminescence spectroscopy (UV-PL), Fourier transformation infrared absorption spec|troscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the N+ implantation doping without any graphitization has been successfully realized when 100 keV N+ ions at a dosage of 2×1016 cm−2 were implanted into diamond films at 550°C. UV-PL spectra indicate that the implanted N+ ions formed an electrically inactive deep-level impurity in diamond films. So the sheet resistance of the sample after N+ implantation changed little. Carbon nitride containing C≡N covalent bond has been successfully synthesized by 100 keV, 1.2×1018 N/cm2 N+ implantation into diamond films. Most of the implanted N+ ions formed C≡N covalent bonds with C atoms. The others were free state nitrogen, which existed in the excessive nitrogen layers. C(1s) XPS studies show the existence of three different C(1s) bonding states, corresponding to graphite, i-carbon and the carbon of C≡N covalent bonding state, respectively, which agrees well with the Raman results.

Insulating cubic BaTiO3(c-BT) polycrystalline thin films were synthesized on titanium covered silicon substrates using a novel low temperature technique called hydrothermal method. The films were hydrothermally formed by submerging the substrate in a 0.5M Ba(OH)2 aqueous solution sealed inside an autoclave, heating to 160°C with saturated vapor pressure around 0.8MPa and holding for various periods ranging from I to 9 hours. The surface of as-treated samples was dense, smooth pinhole-free with high homogeneity. Scanning electron microscopic (SEM) morphology showed the 6-hour-prepared films were composed of submicrocrystallines with grain size varied from 100 to 300nm in diameter. The films were characterized by X-ray diffraction (XRD), SEM, cross-sectional transmission electron microscopy (XTEM), Auger electron spectroscopy (AES) and Rutherford backscattering spectroscopy(RBS) analyses. The experimental results proved that hydrothermal method will become a valuable approach for fabricating perovs...

Bi-layered thin films of PZT(70/30) on BaRuO3 have been prepared on silicon substrate by ArF excimer laser deposition(PLD). BaRuO3 thin film crystallized into perovskite-like structure with (110) orientation and became highly conductive after atmospheric thermal annealing at 700°C for 30 minutes. It was found the subsequent PLD-deposited PZT film can be efficiently transformed to its perovskite structure by rapid thermal processing(RTP) at 700°C for 100sec

Boron nitride (BN) thin films were deposited on a Si (111) substrate using ArF pulsed excimer laser radiation for ablating a hexagonal BN (hBN) target and a de-gasdischarge for activating N2. The present phases in the films were determined by Fourier transformation infrared spectroscopy (FTIR). The results show that BN thin films containing largely cubic BN (cBN) phase on Si(111) substrates were successfully prepared by this de-gasdischarge assisted pulsed laser deposition (PLD). The effects of the de-gasdischarge and the chamber background gas on the formation of the cBN thin films were analyzed. The reasons for the phase evolution from hBN to cBN induced by the de-gasdischarge are discussed. The results suggested that the de-gasdischarge has two effects on the formation of cBN thin films. On one hand, it activated N2 and caused the formation of nearly stoichiometric BN films. On the other hand, it caused the activated ions to bombard the substrate and induced the formation of the cBN phase. The dual beam ion source assisted PLD method is proposed to be the most promising method in preparing cBN films.

Boron nitride (BN) thin films were deposited on Si(111) substrate using an ArF excimer laser for ablating the hexagonal boron nitride (hBN) target and a field-ionization source for activating N2. The phases present in the films were determined by Fourier transformation infrared spectroscopy (FTIR). The results show that BN thin films containing a large amount of cubic BN (cBN) phase on Si(111) substrate were successfully prepared by field-ionization source assisted pulsed laser deposition (PLD). It is clearly seen that activated N2 and ion bombardments seem necessary for the formation of cBN during the process of deposition using the field-ionization source assisted PLD method. Supplied as activated ions, nitrogen can easily form chemical bonds with boron atoms and can form nearly stoichiometric BN. The bombarding ions are supposed to have a strong influence on the formation of residual stress in BN films and this induces the formation of the cBN phase. The stoichiometric effect and largely the residual compressive stress in BN thin films seem the key factors determining the content of cBN phase.

Well-crystallized polycrystalline thin films of cubic barium titanate (BaTiO3) have been synthesized on Ti-covered Si substrates by exposing the substrates to a Ba(OH)2 aqueous solution at 160 °C and a low pressure less than 1 MPa. It was presumed that the film formation of BaTiO3 involved a dissolution-crystallization mechanism, which provides an attractive approach to produce other titanate films and powders. Also, we have used for the first time this hydrothermal technique to deposit epitaxial (001)-textured PbTiO3 thin films on SrTiO3(100) substrates.

Polycrystalline thin films of BaTiO 3 with a resistivity of 10 3 Ω cm were fabricated on Ti-covered silicon substrates by a hydrothermal method at temperatures as low as 160°C. The films were formed by submerging the substrates in a 0.5 M Ba(OH) 3 aqueous solution sealed inside an autoclave, heating to 160°C with a saturated vapor pressure around 0.8 M Pa, and holding for various periods from 1 up to 24 h. The film thickness increased as the treatment prolonged within a certain period. The subsequent firing in air at 600°C was found to raise the resistivity substantially. The structure and properties of the films were characterized by using x-ray diffraction, scanning electron microscopy, cross-sectional transmission microscopy, Auger electron spectroscopy, Rutherford backscattering spectroscopy, and spread resistance probing. The film growth mechanism involved in hydrothermal kinetics was discussed. Three ways for hydrothermally synthesizing thick BaTiO 3 films have been recommended.

High electrical conductive BaRuO 3 thin films with (110) perovskite orientation have been successfully fabricated on Si(100) substrates by pulsed ArF excimer laser deposition and post-annealing. The resistivity of the films at room temperature is in the range of 10 −2 –10 −3 Ω cm. Auger electron spectroscopy (AES) measurement shows that the compositions uniformly distributed throughout the film. Rutherford backscattering spectroscopy (RBS) analysis indicates that the chemical stoichiometric ratio is well consistent with the ideal one as in BaRuO 3 .

To enhance thermoelectric performance by utilizing topological properties of topological insulators has attracted increasing attention. Here, we show that as grain size decreases from microns to ∼80 nm in thickness, the electron mobility μ increases steeply from 12–15 cm2 V−1 s−1 to ∼600 cm2 V−1 s−1, owing to the contribution of increased topologically protected conducting surfaces. Simultaneously, its lattice thermal conductivity is lowered by ∼30%–50% due to enhanced phonon scattering from the increased grain boundaries. As a result, thermoelectric figure of merit, ZT, of all the fine-grained samples is improved. Specifically, a maximum value of ZT = ∼0.63 is achieved for Bi2Se3 at T = ∼570 K.

In situ crystallized BaTiO/sub 3/ thin films have been successfully prepared on Ti-covered silicon substrates at low temperature of 160/spl deg/C by hydrothermal method. The surface of the samples was dense, homogeneous and highly insulating, the films had good adherence to the substrate while exhibited dark-blue color. X-ray diffraction (XRD) characterization and spreading resistance probes (SRP) measurements showed that a multi-layer structure of cubic BaTiO/sub 3//amorphous BaTiO/sub 3-x//Ti/Si was formed, while it became tetragonal BaTiO/sub 3//Ti/Si after rapid thermal annealing (RTA) at 600/spl deg/C for 60 sec. Thus, it can be seen that hydrothermal method for preparing perovskite thin films will become an excellent low-temperature processing with great significance.

In Pb-free β-Zn4Sb3 based composites incorporated with (Bi2Te3)0.2(Sb2Te3)0.8, we concurrently realize ∼30% increase in thermoelectric power factor through an energy filtering effect caused by carrier scattering at interface barriers, and ∼15% reduction in thermal conductivity due to interface scattering, allowing the figure of merit to reach 1.1 at 648 K in the composite system with 1 vol. % of (Bi2Te3)0.2(Sb2Te3)0.8.

The thermoelectric properties of Bi-doped compounds (Zn1−xBix)4Sb3 (x=0,0.0025,0.005,0.01) were studied experimentally as well as theoretically. The results indicate that low-temperature (T

The effects of Ca substitution for Y on the electrical transport and thermoelectric properties of Y1−xCaxCoO3 (0⩽x⩽0.1), prepared by using the sol-gel process, were investigated in the temperature range from 300to780K. The results indicated that direct current electrical resistivity ρ of Y1−xCaxCoO3 decreased remarkably with increasing Ca content x as x⩽0.01, which could mainly be attributed to the increase of hole concentration due to substitution of Ca2+ for Y3+. The temperature dependences of the resistivity for Y1−xCaxCoO3 were all found to be basically consistent with small-polaron hopping conduction model. Although Seebeck coefficient S of Y1−xCaxCoO3 at low temperatures T