Thermo-emf Measurements Research Articles

Ba-doped Pr2NiO4+δ electrodes for proton-conducting electrochemical cells. Part 2: Transport and electrochemical properties

Materials based on barium-containing Pr2NiO4+δ are considered as promising air electrodes for protonic ceramic electrochemical cells owing to a wide range of attractive properties. In the present work, we thoroughly analyze the transport properties of Pr2NiO4+δ upon its chemical modification by Ba-doping. In detail, electrical conductivity and thermo-EMF measurements of Pr2–xBaxNiO4+δ (where x = 0, 0.1, 0.2, and 0.3) allow the effects of charge carrier concentration and mobility on overall transport to be determined depending on the chemical composition and defect structure. Lower polarization resistances of the Ba-containing electrodes when used in symmetrical cells with a BaCe0.5Zr0.3Y0.1Yb0.1O3–δ proton-conducting electrolyte confirm the functional benefits of barium as a dopant. However, the obtained experimental results can be explained not only by the better transport properties of barium-containing Pr2NiO4+δ (shown in the second part of our research), but also by the improved chemical and thermal compatibilities resulting in a good interface quality in an electrolyte/electrode couple (shown in the first part).

Ionic and electronic transport of dense Y-doped barium stannate ceramics for high-temperature applications

The search for new oxide materials with pronounced proton transport is of great importance for the fabrication of electrochemical devices capable of realizing various energy conversion processes with high efficiency. The state-of-the-art proton-conducting oxides based on Ba(Ce,Zr)O3 have been proposed as the most promising electrolytes for such devices, although they suffer from a number of drawbacks. Here, we report an in-depth analysis of the transport properties of Y-doped barium stannates as relatively new proton-conducting compounds. In detail, the single-phase BaSn1–xYxO3–δ (0 ≤ x ≤ 0.4) ceramics were successfully prepared and their electrochemical properties were analysed using a number of characterization methods, including conductivity and thermo-EMF measurements depending on oxygen partial pressure as well as electrochemical impedance spectroscopy. The data obtained clearly indicate that the Y-doping degree affects the transport properties of BaSn1–xYxO3–δ. The weakly doped stannates (0 ≤ x ≤ 0.15) are identified as pronounced n- and p-type electron conductors, while the heavily doped stannates (0.2 ≤ x ≤ 0.4) exhibit a higher ionic conductivity and a wider electrolytic domain boundary, which allows them to be considered as new potential electrolytes with good grain boundary conductivity for application in both protonic ceramic fuel and electrolysis cells.

Microcontroller-based test system for determining the P-N type and Seebeck coefficient of the thermoelectric semiconductors

In this study, a microcontroller-based test system is designed and realized to determine the Seebeck coefficient (α) and electrical conductivity type of thermoelectric (TE) semiconductors. The test system uses Hot-Probe method, which benefits from the Seebeck effect. It is an embedded system based on the principle of measuring the Seebeck voltage (thermo-emf) produced once a temperature difference (ΔT) between the surfaces of the TE semiconductors is created. Seebeck coefficient of TE semiconductors can be determined depending on the thermo-emf and temperature measurements in the system. TE semiconductor electrical conductivity type (P or N) can also be determined according to the sign of the measured thermo-emf. The system consists of two major components, the main unit and the multifunctional probe. Thanks to the developed multifunctional probe, it is possible to provide the necessary heat for the temperature difference as well as Seebeck voltage and temperature measurements. In the main unit of the system, an 8-bit Atmega328 microcontroller is used and its software is developed with mikroC Pro for AVR. For various temperature differences between the surfaces of 9 P-type and 9 N-type TE semiconductors of various shapes and sizes obtained by Zone Melting (ZM), Hot Pressing (HP) and Hot Extrusion (HE) methods, the changes in thermos-emfs of the materials are investigated. In addition, Seebeck coefficient, P-N electrical conductivity type, and figure-of-merit (ZT) parameters of semiconductors, which are important for TE module production, are found. According to the experimental results, with the developed test system, the thermo-emf measurements can be made in an accuracy of ±0.1 mV within 0–100 mV range, and the temperature measurements can have accuracy of ±1 °C within 0–75 °C range. As a result, it is seen that the developed test system is a research device which can determine the Seebeck coefficient and P-N electrical conductivity type practically, quickly and reliably irrespective of the shape and size of TE semiconductors.

Effect of bath temperature on PbSe thin films prepared by chemical synthesis

Lead selenide (PbSe) thin films were deposited using chemical bath deposition techniques by varying bath temperatures (70–90°C) keeping deposition time and other parameters constant. The influence of the synthesis/bath temperature on structural and thermoelectric properties of as-deposited PbSe nanostructured film was investigated using x-ray diffraction, scanning electron microscope, Raman spectroscopy and thermo-emf measurement. The improvement of crystallinity of the PbSe films was studied using x-ray diffraction and Raman scattering. The structural parameters, such as the lattice constant (a), crystallite size (D), dislocation density (δ) and microstrain (ε) were evaluated from XRD spectra. The average crystallite size, as calculated from Scherrer's formula, increased from 22.45 to 24.87nm as the bath temperatures was varied from 70°C to 90°C. The dislocation density and microstrain were found to vary inversely with the crystallite size, whereas the lattice constant was found to slightly different with an increase in crystallite size. The scanning electron microscopy observation shows that with an increase in bath temperature, the grain size increases and they agglomerates. At the elevated bath temperatures individual particles agglomerate and lead to higher grain density and film crystallinity. The thermo-emf measurements have shown n-type conductivity in the as deposited films.

Physical properties of nanostructured (PbS)x(CuS)1−x composite thin films grown by successive ionic layer adsorption and reaction method

Nanostructured ternary semiconducting (PbS)x(CuS)1−x thin films were grown on glass substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature. The structural, morphological and optical characterizations of the films were carried out by X-ray diffraction, scanning electron microscopy and UV–Vis spectrophotometer respectively. The structural studies revealed that, (PbS)x(CuS)1−x films are nanocrystalline in nature and have mixed phase of cubic PbS and hexagonal CuS. The optical absorption measurements showed that band gap energy of (PbS)x(CuS)1−x can be engineered between 2.57 and 2.28eV by varying compositional parameter ‘x’. The room temperature dc dark electrical resistivity of PbS film is found to be 28.85Ωcm and it decreases when content of Cu in composite increases and becomes 0.05Ωcm for pure CuS. The thermo-emf measurements showed that the as deposited (PbS)x(CuS)1−x films are of n-type. The water angle contact measurements of (PbS)x(CuS)1−x, revealed that, films are hydrophilic in nature and it could be advantageous in electrochemical application.

Size Dependent Physical Properties of Nanostructured α-Fe2O3 Thin Films Grown by Successive Ionic Layer Adsorption and Reaction Method for Antibacterial Application

Thin films of nanostructured α-Fe2O3 with thickness of 156, 203 and 251 nm were deposited by successive ionic layer adsorption and reaction (SILAR) method onto glass substrates using FeCl3·6H2O and NaOH as cationic and anionic precursors. The X-ray diffraction studies revealed that, α-Fe2O3 thin films are nanocrystalline in nature with rhombohedral structure. The morphological properties were investigated by field emission scanning electron and atomic force microscopy. The optical studies showed that α-Fe2O3 exhibits direct as well as indirect optical band gap energy. The electrical resistivity of α-Fe2O3 at 305 K decreases from 11.76 × 102 to 9.46 × 102 Ω cm as film thickness increases from 156 to 251 nm. The thermo-emf measurements confirmed that α-Fe2O3 exhibits n-type conductivity. The nanocrystalline α-Fe2O3 exhibits antibacterial character against Staphylococcus aureus and its efficiency increases from 37.50% to 87.50% depending on crystallite size.

Structural, electrical and optical properties of nanostructured Cd1−xFexS thin films deposited by chemical spray pyrolysis technique

Multi-component nanostructured thin films of Cd1−xFexS were successfully deposited onto glass substrates from aqueous solutions of ferric chloride, cadmium chloride and thiourea using chemical spray pyrolysis technique. The structural, compositional and morphological studies were carried out by using X-ray diffractometer (XRD), energy dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. The structural study revealed that, CdS, FeS and Cd1−xFexS films are nanocrystalline in nature with hexagonal lattice. The optical characterization shows that the band gap of the spray deposited CdS film is 2.20eV and it increases with ‘x’ and becomes 2.44eV for FeS. The electrical resistivity of Cd1−xFexS thin films is of the order of 106Ωcm and shows variation depending on ‘x’. The thermo-emf measurement confirms n-type conductivity of Cd1−xFexS thin films.

Effect of annealing on physical properties of CBD synthesized nanocrystalline FeSe thin films

Nanocrystalline FeSe thin films were successfully prepared by solution growth method using ferric chloride and sodium selenosulphate as cationic and anionic precursors along with complexing agent oxalic acid. The thickness dependent physical properties of FeSe thin films prepared by varying deposition time are discussed. The FeSe films of thickness 161nm were further annealed to investigate its impact on physical properties. The X-ray diffraction studies showed that, as deposited FeSe films are nano crystalline in nature and their crystallinity increases with thickness as well as with annealing temperature. The morphological studies showed that FeSe exhibits granular surface with channel like features at higher thickness. The electrical resistivity and thermo-emf measurements confirmed that, FeSe films are semiconducting in nature with P-type conductivity. The activation and band gap energies of FeSe films are found dependent on film thickness as well as on annealing temperature.

Structural, electrical and optical properties of nanocrystalline Cd1−xFexSe thin films deposited by chemical spray technique

Nanocrystalline Cd1−xFexSe thin films were successfully deposited onto glass substrates at temperature 573K from aqueous solutions of ferric chloride, cadmium chloride and selenium powder using the chemical spray technique. The structural, morphological, compositional, electrical and optical characterizations were carried out using X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), atomic force microscopy (AFM), resistivity and optical absorption measurement techniques. The deposited Cd1−xFexSe thin films are nanocrystalline in nature with hexagonal lattice. The optical band gap of CdSe thin film is of the order of 1.85eV and it increases with the compositional parameter ‘x’ and becomes 2.60eV for FeSe thin film. The electrical resistivity of Cd1−xFexSe thin films is of the order of 106Ωcm and shows variation depending on ‘x’. The thermo-emf measurement confirms n-type conductivity of Cd1−xFexSe thin films.

Physical properties of nanostructured Mn3O4 thin films synthesized by SILAR method at room temperature for antibacterial application

Nanocrystalline Mn3O4 thin films of thickness 63, 99 and 141nm were synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates at room temperature using MnCl2.4H2O and NaOH as cationic and anionic precursors. The grazing incidence X-ray diffraction measurements confirmed that as grown Mn3O4 films are orthorhombic in nature. The FESEM and AFM analysis shows that Mn3O4 films are nanocrystalline in nature with porous morphology. The optical absorption measurements showed that Mn3O4 exhibit direct optical band gap energy that changes from 2.70 to 2.86eV depending on crystallite size. The electrical resistivity and thermo-emf measurements confirmed that SILAR grown Mn3O4 films are semiconducting in nature with p-type conductivity. The antibacterial efficiency of films against Escherichia coli increases from 18.64% to 94.91% as crystallite size of Mn3O4 increases.

Thickness dependent physical properties of chemically deposited nanocrystalline MgSe thin films deposited at room temperature by solution growth method

Chemical bath deposition method has been employed to deposit nanocrystalline magnesium selenide thin films of thickness 104–292nm onto glass substrates at room temperature. The deposition bath consists of magnesium chloride, triethanolamine (TEA) and selenium dioxide. The as deposited films were characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption, electrical resistivity and thermo-emf measurements. The X-ray diffraction (XRD) studies revealed that the crystallinity of the magnesium selenide thin film increases with thickness. SEM studies reveal that MgSe films exhibit uniform distribution of round shaped grains over the entire substrate surface.The optical band-gap and electrical resistivity of MgSe film decrease as the film thickness increases. Such type of dependence is attributed to the quantum size effect that is observed in nanocrystalline semiconductors.The thermo-emf measurement confirms its p-type conductivity.

Physical properties of MgSe thin films grown by chemical bath deposition method: effect of molar concentration of MgCl2

In the present paper, we have reported the effect of molar concentration of Mg salt on physical properties of MgSe thin films deposited by chemical bath deposition process. The MgSe thin films have been characterized for their structural, morphological and optical studies. We have observed that the films are nanocrystalline in nature with cubic lattice. The optical band gap energy of MgSe is changed from 2.82 to 2.65 eV depending on Mg ion concentration in deposition bath. The electrical resistivity of MgSe film varies from 56 × 102 to 41 × 102 Ω cm depending on Mg ion concentration in reaction bath. The thermo-emf measurement has confirmed p-type conductivity of MgSe.

Structural, optical and electric properties of nanocrystalline MgSe thin films deposited by chemical route using triethanolamine as a complexing agent

Semiconducting nanocrystalline thin films of magnesium selenide have been prepared using economic chemical bath deposition technique onto glass substrates at room temperature. The deposition bath consists of magnesium chloride, triethanolamine, hydrazine hydrate and selenium dioxide. The quantity of triethanolamine in the deposition bath was varied to study its effect on growth process as well as on physical properties of MgSe. The deposited films were characterized using X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. The effect of complexing agent (TEA) on optical and electrical properties is reported. It was found that as the triethanolamine in deposition bath increases, optical band-gap and electrical resistivity decreases. The thermo-emf measurement shows p-type nature of MgSe.

Polyaniline–CuO hybrid nanocomposites: synthesis, structural, morphological, optical and electrical transport studies

Thin films of semiconducting polyaniline (PANi) nanofibers reinforced with copper oxide (CuO) nanoparticles (NPs) were prepared on glass substrate using spin coating technique. Polyaniline (PANi) have been synthesized by chemical oxidative polymerization method with monomer aniline in presence of (NH4)2S2O8 as an oxidant at 0 °C. The copper oxide (CuO) nanoparticles were synthesized by sol–gel method. Physical properties of nanocomposite (NCs) films were characterized and analyzed by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, Two probe resistivity measurement technique and Thermo-emf measurement. Structural analysis showed that the crystal structure of CuO is not disturbed in the PANi–CuO hybrid nanocomposite. Surface morphology study shows the uniform distribution of CuO nanoparticles in PANi matrix. FTIR and UV–Visible studies confirm the presence of polyaniline in emeraldine base form in the composites and suggest incorporation of CuO in polymer. Two probe electrical resistivity measurements of nanocomposites (NCs) film revealed that the resistivity of PANi increases with increasing content of CuO NPs.

Properties of spray deposited Cu2ZnSnS4 (CZTS) thin films

A new solar absorber material, Cu2ZnSnS4 (CZTS) in thin film form has been deposited onto glass substrates using spray pyrolysis technique. The thickness dependent (244–754nm) structural, morphological, optical and electrical properties of CZTS films have been studied. The X-ray diffraction studies revealed the formation of polycrystalline CZTS films. The surface morphological studies revealed the formation of smooth, compact and uniform CZTS surface. Absorption coefficient was of the order of 104cm−1 and depending on film thickness and the direct transition was observed with band gap in the range from 1.6 to 1.67eV. The thermoemf measurement revealed that the CZTS films exhibit p-type electrical conductivity.

Aqueous chemical growth of Cu2ZnSnS4 (CZTS) thin films: Air annealing and photoelectrochemical properties

In present investigation, Cu2ZnSnS4 (CZTS) thin films have been deposited on to glass substrates by novel chemical successive ionic layer adsorption and reaction (SILAR) method. The effect of air annealing in the temperature range between 573 and 773K on the structural, morphological, optical and electrical properties has been studied. The X-ray diffraction studies revealed the formation of polycrystalline CZTS films. The surface morphological study showed smooth, compact and uniform film formation after annealing formation. The band gap was in between range from 1.5 to 1.8eV depending on annealing temperature. The thermo emf measurement revealed that the CZTS exhibits p-type electrical conductivity. Further, photoactivity of CZTS thin films was tested by forming the photoelectrochemical cell.

Enhancement of photosensitivity by annealing in Bi2S3 thin films grown using SILAR method

Bi2S3 thin films were grown by successive ionic layer adsorption and reaction method (SILAR) onto the glass substrates at room temperature. The as prepared thin film were annealed at 250°C in air for 30min. These films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrical measurement systems. The X-ray diffraction patterns reveal that Bi2S3 thin film have orthorhombic crystal structure. SEM images showed uniform deposition of the material over the entire glass substrate. The optical energy band gap observed to be decreased from 1.69 to 1.62eV for as deposited and annealed films respectively. The I–V measurement under dark and illumination condition (100W) show annealed Bi2S3 thin film gives good photoresponse as compared to as deposited thin film and Bi2S3 thin film exhibits photoconductivity phenomena suggesting its useful in sensors device. The thermo-emf measurements of Bi2S3 thin films revealed n-type electrical conductivity.

Novel process for synthesis of α-Fe2O3: microstructural and optoelectronic investigations

Novel chemical synthesis method has been successfully employed for the preparation of n type α-Fe2O3 nanoparticles. Thin films of annealed Fe2O3 powders processed on glass substrates using spin coating technique. The effects of process temperature on the structural, morphological, electrical transport and optical properties were studied. X-ray diffraction study revealed formation of single phase nanocrystalline hexagonal α-Fe2O3. Microstructural analysis confirms nanostructured morphology. Dc electrical conductivity measurement reveled the semiconducting nature with room temperature electrical conductivity increased from 10−4 to 10−3 (Ω cm)−1 as process temperature of Fe2O3 increased from 400 to 700 °C respectively. The n-type electrical conductivity is confirmed from thermo-emf measurement with no appreciable change in thermoelectric power after increasing processing temperature. The decrease in the band gap energy from 3.88 to 2.62 eV was observed after increasing process temperature.

Characterization of nanostructured Mn3O4 thin films grown by SILAR method at room temperature

A novel successive ionic layer adsorption and reaction method has been successfully employed to grow nanostructured conducting nearly transparent thin films of Mn3O4 on to glass substrates at room temperature using MnCl2 and NaOH as cationic and anionic precursors. The structural and morphological characterizations of the as deposited Mn3O4 films have been carried out by means of X-ray diffraction (XRD), Field Emission Scanning Electron Micrograph (FESEM), EDAX, Atomic Fore Microscopy (AFM) and Fourier Transform Infrared Spectrum (FTIR) analysis. The optical absorption and electrical resistivity measurements were carried out to investigate optical band gap and activation energy of Mn3O4 films deposited by SILAR method. The optical band gap and activation energy of the as deposited film is found to be 2.70 and 0.14 eV respectively. The thermo-emf measurements of Mn3O4 thin film confirm its p-type semiconducting nature.

Preparation and characterization of CdS–Bi2S3 nanocomposite thin film by successive ionic layer adsorption and reaction (SILAR) method

CdS, Bi2S3 and CdS–Bi2S3 nanocomposite thin films were grown by successive ionic layer adsorption and reaction method (SILAR) onto the glass substrates at room temperature. These films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical measurement systems. A comparative study was made between CdS, Bi2S3 and CdS–Bi2S3 nanocomposite thin films. The XRD patterns reveal that CdS, Bi2S3 and CdS–Bi2S3 nanocomposite thin film have hexagonal, orthorhombic and mixed phase of hexagonal CdS and orthorhombic Bi2S3 crystal structure, respectively. SEM images showed uniform deposition of the material over the entire glass substrate. The energy band gap for CdS, Bi2S3 and CdS–Bi2S3 thin films were revealed from the optical studies and were found to be 2.4, 1.6 and 1.69eV, respectively. The thermoemf measurements of CdS–Bi2S3 nanocomposite thin film revealed n-type electrical conductivity, while the I–V measurement of CdS, Bi2S3 and CdS–Bi2S3 nanocomposite thin film under dark and illumination condition (100mW/cm2) exhibited photoconductivity phenomena suggesting its applicability in photosensors devices.