Physical properties of carbon nanowalls synthesized by the ICP-PECVD method vs. the growth time

Investigation of the physical properties of carbon nanowall (CNW) films is carried out in correlation with the growth time. The structural, electronic, optical and electrical properties of CNW films are investigated using electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, UV–Vis spectroscopy, Hall Effect measurement system, Four Point Probing system, and thermoelectric measurements. Shorter growth time results in thinner CNW films with a densely spaced labyrinth structure, while a longer growth time results in thicker CNW films with a petal structure. These changes in morphology further lead to changes in the structural, optical, and electrical properties of the CNW.

Three-Dimensional (3D) Conductive Network of CNT-Modified Short Jute Fiber-Reinforced Natural Rubber: Hierarchical CNT-Enabled Thermoelectric and Electrically Conductive Composite Interfaces

Jute fibers (JFs) coated with multiwall carbon nanotubes (MWCNTs) have been introduced in a natural rubber (NR) matrix creating a three-dimensional (3D) electrically conductive percolated network. The JF-CNT endowed electrical conductivity and thermoelectric properties to the final composites. CNT networks fully covered the fiber surfaces as shown by the corresponding scanning electron microscopy (SEM) analysis. NR/JF-CNT composites, at 10, 20 and 30 phr (parts per hundred gram of rubber) have been manufactured using a two-roll mixing process. The highest value of electrical conductivity (σ) was 81 S/m for the 30 phr composite. Thermoelectric measurements revealed slight differences in the Seebeck coefficient (S), while the highest power factor (PF) was 1.80 × 10−2 μW/m K−2 for the 30 phr loading. The micromechanical properties and electrical response of the composite’s conductive interface have been studied in peak force tapping quantitative nanomechanical (PFT QNM) and conductive atomic force microscopy (c-AFM) mode. The JF-CNT create an electrically percolated network at all fiber loadings endowing electrical and thermoelectric properties to the NR matrix, considered thus as promising thermoelectric stretchable materials.

Comparison of Structural, Electrical and Thermoelectric Properties of Vacuum Evaporated SnTe Films of Varied Thickness

As a key type of promising thermoelectric (TE) material p-type Tin Telluride (SnTe) vacuum evaporated thin films synthesized at room temperature (RT) on a glass substrate, report a significant enhancement in the figure of merit (ZT) value. The thicknesses of the nanostructured thin films were kept about 145 nm and 275 nm. High-resolution X-ray diffraction (HRXRD) outlines the polycrystalline nature in both thin films. Surface morphology of these films is composed of grains of variable sizes as elucidated by scanning electron microscopy (SEM). This observation is further confirmed by atomic force microscopy (AFM) wherein the average roughness, surface skewness, and surface kurtosis parameters are used to analyze the surface morphology. Local microstructural features and crystalline structure have been confirmed from High-resolution transmission electron microscope (HRTEM) and the selected area electron diffraction (SAED) pattern, respectively. Four probes method was used to determine electrical measurements which confirm that the thin films have semi-metallic nature. Thermoelectric measurements carried out on these films resulted that the figure of merit increases as the thickness of the film increases. The maximum ZT value of ˜1.02 is obtained at room temperature for the thin film of thickness 275 nm.

Electrochemical Deposition and Thermoelectric Characterisation of a Semiconducting 2-D Metal-Organic Framework Thin Film

The electrical conductivity and porosity of the 2-dimensional metal-organic framework Cu₃(2,3,6,7,10,11-hexahydroxytriphenylene)₂ [Cu₃(HHTP)₂] make it a promising candidate for thermoelectric applications. In this work, we report the electrochemical synthesis of Cu₃(HHTP)₂ films by an anodization approach and an evaluation of its thermoelectric properties. The electrochemically synthesised Cu₃(HHTP)₂ thin films were transferred using a wet chemical method in order to perform electrical measurements. We are reporting the first thermoelectric measurements of this framework both in bulk and thin film form which resulted in Seebeck coefficients of -7.24 µV/K and -121.4 µV/K with a power factor of 3.15x10^-3 µW m^-1 for the film respectively. The negative Seebeck coefficients suggest that Cu₃(HHTP)₂ behaves as an n-type semiconductor.

Electrochemical Deposition and Thermoelectric Characterisation of a Semiconducting 2-D Metal-Organic Framework Thin Film

The electrical conductivity and porosity of the 2-dimensional metal-organic framework Cu₃(2,3,6,7,10,11-hexahydroxytriphenylene)₂ [Cu₃(HHTP)₂] make it a promising candidate for thermoelectric applications. In this work, we report the electrochemical synthesis of Cu₃(HHTP)₂ films by an anodization approach and an evaluation of its thermoelectric properties. The electrochemically synthesised Cu₃(HHTP)₂ thin films were transferred using a wet chemical method in order to perform electrical measurements. We are reporting the first thermoelectric measurements of this framework both in bulk and thin film form which resulted in Seebeck coefficients of -7.24 µV/K and -121.4 µV/K with a power factor of 3.15x10^-3 µW m^-1 for the film respectively. The negative Seebeck coefficients suggest that Cu₃(HHTP)₂ behaves as an n-type semiconductor.

Layered Manganese Bismuth Tellurides with GeBi4Te7– and GeBi6Te10–type Structures: Towards Multifunctional Materials

<p>The crystal structures of new layered manganese bismuth tellurides with the compositions Mn0.85(3)Bi4.10(2)Te7 and Mn0.73(4)Bi6.18(2)Te10 were determined by single-crystal X-ray diffraction, including the use of microfocused synchrotron radiation. These analyses reveal that the layered structures deviate from the idealized stoichiometry of the 12<i>P</i>-GeBi4Te7 (space group <i>P</i>3<i>m</i>1) and 51<i>R</i>-GeBi6Te10 (space group <i>R</i>3<i>m</i>) structure types they adopt. Modified compositions Mn1–<i>x</i>Bi4+2<i>x</i>/3Te7 (<i>x </i>= 0.15 – 0.2) and Mn1–<i>x</i>Bi6+2<i>x</i>/3Te10 (<i>x </i>= 0.19 – 0.26) assume cation vacancies and lead to homogenous bulk samples as confirmed by Rietveld refinements. Electron diffraction patterns exhibit no diffuse streaks that would indicate stacking disorder. The alternating quintuple-layer [M2Te3] and septuple-layer [M3Te4] slabs (M = mixed occupied by Bi and Mn) with 1:1 sequence (12<i>P </i>stacking) in Mn0.85Bi4.10Te7 and 2:1 sequence (51<i>R </i>stacking) in Mn0.81Bi6.13Te10 were also observed in HRTEM images. Temperature-dependent powder diffraction and differential scanning calorimetry show that the compounds are high temperature phases, which are metastable at ambient temperature. Magnetization measurements are in accordance with a MnII oxidation state and point at predominantly ferromagnetic coupling in both compounds. The thermoelectric figures of merit of n-type conducting Mn0.85Bi4.10Te7 and Mn0.81Bi6.13Te10 reach <i>zT </i>= 0.25 at 375 °C and <i>zT </i>= 0.28 at 325 °C, respectively. Although the compounds are metastable, compact ingots exhibit still up to 80% of the main phases after thermoelectric measurements up to 400 °C.</p>

Layered Manganese Bismuth Tellurides with GeBi4Te7– and GeBi6Te10–type Structures: Towards Multifunctional Materials

<p>The crystal structures of new layered manganese bismuth tellurides with the compositions Mn0.85(3)Bi4.10(2)Te7 and Mn0.73(4)Bi6.18(2)Te10 were determined by single-crystal X-ray diffraction, including the use of microfocused synchrotron radiation. These analyses reveal that the layered structures deviate from the idealized stoichiometry of the 12<i>P</i>-GeBi4Te7 (space group <i>P</i>3<i>m</i>1) and 51<i>R</i>-GeBi6Te10 (space group <i>R</i>3<i>m</i>) structure types they adopt. Modified compositions Mn1–<i>x</i>Bi4+2<i>x</i>/3Te7 (<i>x </i>= 0.15 – 0.2) and Mn1–<i>x</i>Bi6+2<i>x</i>/3Te10 (<i>x </i>= 0.19 – 0.26) assume cation vacancies and lead to homogenous bulk samples as confirmed by Rietveld refinements. Electron diffraction patterns exhibit no diffuse streaks that would indicate stacking disorder. The alternating quintuple-layer [M2Te3] and septuple-layer [M3Te4] slabs (M = mixed occupied by Bi and Mn) with 1:1 sequence (12<i>P </i>stacking) in Mn0.85Bi4.10Te7 and 2:1 sequence (51<i>R </i>stacking) in Mn0.81Bi6.13Te10 were also observed in HRTEM images. Temperature-dependent powder diffraction and differential scanning calorimetry show that the compounds are high temperature phases, which are metastable at ambient temperature. Magnetization measurements are in accordance with a MnII oxidation state and point at predominantly ferromagnetic coupling in both compounds. The thermoelectric figures of merit of n-type conducting Mn0.85Bi4.10Te7 and Mn0.81Bi6.13Te10 reach <i>zT </i>= 0.25 at 375 °C and <i>zT </i>= 0.28 at 325 °C, respectively. Although the compounds are metastable, compact ingots exhibit still up to 80% of the main phases after thermoelectric measurements up to 400 °C.</p>