Chemical Solution Technique Research Articles

PZT based dual energy harvester using chemical solution deposition technique

The present finding reports the state-of-art thin film based dual energy harvester which can harvest both mechanical as well as magnetic energies. Dual energy harvester is realised with the help of Lead Zirconium Titanate (PZT) thin film and nickel (Ni) foil. Ferroelectric PZT has been grown with the help of chemical solution deposition technique under optimised conditions on Nickel cantilevers. The effect of damping mass on the resonating frequency of the PZT-60/Ni dual cantilever has been studied. The maximum power and voltage generated by dual energy harvester at the matching load impedance of 100 kΩ under resonance condition were about 117 × 102 mW/m3 and 52 mV respectively corresponding to an applied acceleration of 1.0 g. A change of about 0.5 mV/Oe voltage was achieved for PZT-60/Ni cantilever in the presence of magnetic field. The dual energy harvester prepared with the help of chemical solution technique is found to have profound response and hence enables the realization of self powered electronic devices by scavenging an ambient magnetic and mechanical energies for various wireless electronic applications ranging from medical implant to health monitoring areas.

Silver-impregnated vanadium pentoxide nanofillers for reinforcement in titanium-based missile surfaces

An optimal content of silver doped vanadium pentoxide nanofillers (Ag-V2O5 NFs) was envisaged for reinforcement in Ti-based surfaces for boosting up the operational performance of high-supersonic and hypersonic missiles. Bar-shaped Ag-V2O5 NFs developed at 1, 3, and 5 % doping contents synthesized via microwave-assisted chemical solution technique were investigated for morphological, crystallographic, structural, and compositional properties by employing FESEM, XRD, Raman, and FTIR spectroscopy. Owing to their solubility differences, a blend of orthorhombic α- and β-phases were identified as spectral fingerprints specific to the developed Ag-embedded vanadium oxide crystalline structures. The Williamson-Hall method estimated the average crystallite size of α-Ag3-VO4 and β-Ag0.35-V2O5 phase NFs as 31.4 and 29.9 nm, respectively. The best results of the developed Ag-V2O5 NFs for the surface material transpired for the monoclinic metastable β-Ag0.333-V2O5 phase at optimal 3 % doping content with 13.7 nm average crystallite size, 0.35 % lattice strain, and 4.113 g/cm3 mass density.

Influence of phase dominance on structural, magneto-dielectric, magnetic-electric properties of (Ba0.85Ca0.15Zr0.1Ti0.9)O3-CoFe2O3 composites

In this work, lead-free (1-x) Ba0.85Ca0.15Zr0.1Ti0.9)O3–xCoFe2O3 (BCZT-CFO, x = 00, 0.2,0.8 and 1) multiferroic composites have been prepared by chemical solution technique and sintered at 1300 °C. The article is focused on a systematic study of phase dominance effect on structure, microstructure, dielectric, magneto-dielectric, magnetic, electric, and magneto-electric properties of the BCZT-CFO composites. The XRD study confirms perovskite phase in BCZT, cubic spinal phase in CFO and mixed structural evolution in composite samples without any traceable secondary phase formation. William-Hall equation has been used to evaluate strain kinetics in pure and composite samples. The scanning electron micrographs show dispersion of smaller BCZT grains in larger CFO grains matrix. The dense microstructure has been observed for composite sample with ferrite phase dominance. The room temperature dielectric study reveals frequency-dependent dielectric dispersion characteristics for composites and pure CFO. The enhanced dielectric properties are observed for composite sample with ferroelectric phase dominance. The room temperature magneto-dielectric behavior has been observed for lead-free multiferroic composites. Under magnetic study, observed typical ferromagnetic M-H hysteresis loop reveals presence of long-range ferromagnetic ordering in pure CFO as well as in composite samples. The highest value of Ms ~ 38.2 emu/g and Mr = 1.2 emu/g has been measured for ferrite phase dominant composite sample. Higher coercive field Hc value has been observed for composite with ferroelectric phase dominance. Leakage current characteristic has been investigated at and above room temperature for prepared samples. The composite with ferrite phase dominance has shown higher leakage current characteristics. The enhanced magento-electric coupling coefficient has been measured for composite with higher ferrite phase concentration.

TiO2/halide perovskite interface: The impact of surface state passivation on energy alignment and photovoltaic performance of perovskite solar cells

In perovskite solar cells (PSCs) trap-assisted recombination is the dominant mechanism limiting the cell performance. Here to overcome this challenge we apply the band gap tuning and surface passivation strategy for reducing the recombination losses at the interface between the TiO2 layer and perovskite absorber. The TiO2 surface was modified by SO42− anions and Cd2+ cations using a low-cost chemical solution technique. X-ray photoelectron spectroscopy analysis revealed that the chemical modification of the TiO2 surface leads to the downward shift of the valence band maximum pointing out the increased conduction electron density and resulting in minimizing the barrier losses at the interface. Electrochemical impedance measurements proved that the modification of the TiO2 surface significantly decreases the charge transfer resistance at the interface with perovskite light absorber. As a result, open circuit voltage and fill factor parameters of the PSCs were enhanced and the hysteresis is decreased. Moreover, the surface passivation significantly improves the air stability of PSCs indicating that the stability of the whole device critically depends on the TiO2/perovskite interface structure. Thus, our study provides valuable guideline toward the designing of hetero-interfaces to enhance both the power conversion efficiency and stability of PSCs.

Non-vacuum Preparation of wse2 Thin Films via the Selenization of Hydrated Tungsten Oxide Prepared using Chemical Solution Methods

ABSTRACTIt is known that tungsten oxide may be reacted with selenium sources to form WSe2 but literature reports include processing steps that involve high temperatures, reducing atmospheres, and/or oxidative pre-treatments of tungsten oxide. In this work, we report a non-vacuum process for the fabrication of compositionally high quality WSe2 thin films via the selenization of tungsten oxide under milder conditions. Tungsten source materials were various hydrated WO3 and WO2.9 compounds that were prepared using chemical solution techniques. Resulting films were selenized using a two-stage heating profile (250 °C for 15 minutes and 550 °C for 30 minutes) under a static argon atmosphere. Effects of the starting tungsten oxide phase on WSe2 formation after single and double selenization cycles were investigated using Raman spectroscopy and X-ray diffraction (XRD). After two selenization cycles, hydrated WO3 was converted to (002)-oriented WSe2 that exhibits well-resolved peaks for E12g and A1g phonon modes. Only a single selenization cycle was required to convert amorphous WO2.9 to WSe2. All selenizations in this work were achieved in non-reducing atmospheres and at lower temperatures and shorter times than any non-laser-assisted processes reported for WO3-to-WSe2 conversions.

Narrow Band Gap Ternary Absorber Layer for Solar Cell for Small Business Enterprises in Equatorial Africa

According to recent studies, on the Daily nation newspaper, in Kenya of 6 th January 2017 featured the story, the number of people doing the same thing in surrounding villages was so high that many of them had to leave their phones behind at the charging centre (for up to three days) before returning to pick them. To fight darkness, up to 80 percent of Africans depend on personal generators, candles and kerosene (paraffin) lamps to provide basic lighting. Let’s not even talk about all the other things we desperately need electricity for – iron clothes, pump water, charge mobile phones etc. In this article, we shall focus on the types of solar cell materials that can be used to fabricate solar cell to be installed on roof tops to generate electricity used by individuals and households. Photovoltaic devices are used to convert solar radiation energy into electrical forms of energy for various uses. Current research is geared towards using thin films with wide band gaps to allow optimum penetration of radiation within the VIS - NIR region. Inorganic wide band gap, Cd x Zn 1- x S thin films and narrow band gap, PbS thin films were optimized through chemical solution technique in this study. Wide band gap thin films of Cd x Zn 1- x S were grown at about 82 0 C while those of narrow band gap thin films of PbS were grown at room temperature utilizing aqueous conditions. Their optical constants were investigated and found to be suitable for solar cells applications.

Narrow Band Gap Ternary Absorber Layer for Solar Cell for Small Business Enterprises in Equatorial Africa

According to recent studies, on the Daily nation newspaper, in Kenya of 6th January 2017 featured the story, the number of people doing the same thing in surrounding villages was so high that many of them had to leave their phones behind at the charging centre (for up to three days) before returning to pick them. To fight darkness, up to 80 percent of Africans depend on personal generators, candles and kerosene (paraffin) lamps to provide basic lighting. Let’s not even talk about all the other things we desperately need electricity for – iron clothes, pump water, charge mobile phones etc. In this article, we shall focus on the types of solar cell materials that can be used to fabricate solar cell to be installed on roof tops to generate electricity used by individuals and households. Photovoltaic devices are used to convert solar radiation energy into electrical forms of energy for various uses. Current research is geared towards using thin films with wide band gaps to allow optimum penetration of radiation within the VIS - NIR region. Inorganic wide band gap, CdxZn1-xS thin films and narrow band gap, PbS thin films were optimized through chemical solution technique in this study. Wide band gap thin films of CdxZn1-xS were grown at about 82°C while those of narrow band gap thin films of PbS were grown at room temperature utilizing aqueous conditions. Their optical constants were investigated and found to be suitable for solar cells applications.

Rectification of sulphur deficiency defect in CdS based films by introducing a novel modification in the SILAR cyclic process

In the present study, a novel modification is introduced in the dipping process of the SILAR (successive ionic layer adsorption and reaction) technique which is one of the important chemical solution techniques, generally used for the deposition of cadmium sulphide films. This study clearly establishes that this improved SILAR (ISILAR) technique enables one to rectify the sulphur deficiency, generally present in CdS films and there by obtain a near stoichiometric undoped and doped CdS thin films. In the present work, Fe doped CdS thin films are also deposited on glass substrates using this ISILAR technique. In this ISILAR technique, during the automated dipping process, a fresh anionic solution bath replaces the used one when the supply of S2− ions from this anionic solution declines to an optimized threshold value. As a result of this modification, the stoichiometric deviation drastically reduces from 12.9% to 3.3% for CdS films and from 20.2% to 0.6% for CdS:Fe films. The underlying mechanism for this observed improvement in the stoichiometry is elaborated in this article. The CdS films deposited using this ISILAR technique exhibit better transmittance values compared to several reported values. The XRD studies reveal that the deposited films have good crystalline quality. The magnetic studies show that at higher Fe doping (15 at.%) level, a ferromagnetic nature is observed in the lower applied magnetic field region. The optical band gap decreases gradually with the increase in the Fe doping level and this result is found to be supported by photoluminescence results.

New superconductor LixFe1+δSe (x ≤ 0.07, Tc up to 44 K) by an electrochemical route.

The superconducting transition temperature (Tc) of tetragonal Fe1+δSe was enhanced from 8.5 K to 44 K by chemical structure modification. While insertion of large alkaline cations like K or solvated lithium and iron cations in the interlayer space, the [Fe2Se2] interlayer separation increases significantly from 5.5 Å in native Fe1+δSe to >7 Å in KxFe1−ySe and to >9 Å in Li1−xFex(OH)Fe1−ySe, we report on an electrochemical route to modify the superconducting properties of Fe1+δSe. In contrast to conventional chemical (solution) techniques, the electrochemical approach allows to insert non-solvated Li+ into the Fe1+δSe structure which preserves the native arrangement of [Fe2Se2] layers and their small separation. The amount of intercalated lithium is extremely small (about 0.07 Li+ per f.u.), however, its incorporation results in the enhancement of Tc up to ∼44 K. The quantum-mechanical calculations show that Li occupies the octahedrally coordinated position, while the [Fe2Se2] layers remain basically unmodified. The obtained enhancement of the electronic density of states at the Fermi level clearly exceeds the effect expected on basis of rigid band behavior.

Bismuth Ferrite Enhanced ZnO Solid State Dye-sensitised Solar Cell

ZnO dye sensitized solar cells have been reported to be plagued with issues of dye aggregation which increased current recombination. This dye aggregation has been linked to the pH 5 ruthenium-based dye solutions, which is below ZnO's point of zero charge of pH 9, resulting in positive surface charges on ZnO which form Zn2+ - dye complexes. In this paper, a heterogeneous architecture of ZnO and bismuth ferrite (BiFeO3 or BFO) is synthesized using a technique which allows the synthesis using purely chemical solution techniques. BFO is a perovskite studied extensively for its multiferroic properties and its potential for anomalous photovoltages. The solid state solar cells are sensitized with N719, and uses copper thiocyanate (CuSCN) as a hole conductor. The ZnO-BFO-N719-CuSCN heterogeneous architecture solar cell showed efficiencies which increased ca four-fold to 0.38% and Jsc which doubled to 1.38mA/cm2 compared to ZnO-N719-CuSCN architectures. We will report that the addition of BFO improved performances due to the reduction of dye aggregation due to BFO's pzc of pH 6.5 which is close to the pH 5 of the dye solution, as well as BFO's role as an electron blocking layer which prevents the back tunneling of electrons from ZnO to CuSCN.

Shape uniformity control of metal–organic framework nanodisks via surfactant and substrate synergetic scissoring effects and their fluorescence sensing properties

A surfactant and substrate synergetic chemical solution technique was promoted to synthesize uniformly shaped MOF nanodisks. The hexaprismatic nanodisks of {[Eu2(MFDA)2(HCOO)2(H2O)6]·H2O}n (Eu-MFDA_HND, H2MFDA = 9,9-dimethyl fluorene-2,7-dicarboxylic acid) were obtained on a supported substrate in the presence of sodium dodecyl sulfate. The surfactant and substrate worked together to produce the uniform hexaprismatic shaped products, but in contrast, mixed products of defected hexaprisms and irregular nanoparticles were obtained without the substrate. Also, the dehydrated Eu-MFDA_HND crystals showed a much higher fluorescence quenching efficiency towards 2,4-DNT as compared to their corresponding bulk crystals. This effective morphology-scissoring technique may help the shape control of other functional MOF materials and benefit their application in the fields of catalysis, sensing, optoelectronic microdevices, micromechanical devices, etc.

Effect of a Second Annealing Process on the Properties of BaTiO3 Thin Films on Polycrystalline Nickel Substrates Grown by Polymer-Assisted Deposition

Ferroelectric BaTiO3 thin films were successfully deposited on nickel foils by a chemical solution technique named polymer-assisted deposition. It is found that a second annealing in oxygen using a rapid thermal annealing furnace would strongly affect the electric properties of the as-prepared thin films. Dielectric and ferroelectric properties have been systematically studied. The correlation between the second annealing conditions and dielectric properties was established and discussed. Optimized second annealing condition was found.

Perovskite enhanced solid state ZnO solar cells

This paper will report on the design, fabrication and testing of a solid-state perovskite enhanced ZnO solar cell. The p-type perovskite material used is bismuth ferrite (BFO) which has an absorption range within the blue range of the visible light spectrum. The solid state solar cell, was sensitized with N719 dye and used a CuSCN hole conductor. A disadvantage of ZnO is its poor chemical stability in acidic and corrosive environments. As chemical solution techniques were used in depositing BFO, a buffer method using an aminosilane ((3-aminopropyltrimethoxysilane or H2N(CH2)3Si(OCH3)3)) coating was used to provide a protective coating on the ZnO nanorods before the BFO film was spin coated onto the ZnO nanorods. The photovoltaic performance of the solar cells were tested using a Keithley 2400 source meter under 100mW/cm2, AM 1.5G simulated sunlight, where improvements in Jsc and efficiency were observed. The BFO was able to harness more electrons and also acted as a buffer from electron recombination.

Influence of Nano-Filler Loading on the Nano-MgO Dielectrics

In this study, we investigated the effect of MgO nanofiller content to the dielectric layer properties of nano-MgO film. Nano-MgO film was successfully deposited with particle size in the range of 42 to 92 nm by simple chemical solution technique. The film produced shows some surface modification as the nanofiller content increased. With the nanofiller loading increasing from 0 wt% to 3 wt%, relative permittivity values were varied. NanoMgO films with 1 wt% filler content have high relative permittivity value while film with 2 wt% was good in morphology.

Chemical Solution Deposited Magnesium Oxide Films: Influence of Deposition Time on Electrical and Structural Properties

Magnesium oxide thin films have been deposited on glass substrate using simple chemical solution technique. Film thickness was varied (171, 238, and 506nm) by controlling the deposition time. The electrical behaviour of MgO films showed leakage current density below 10-7 A/cm2 for voltage range from -10V to 10V. Resistivity value of the film was found to be increased due to the large grain boundary produced in the film. The formation of island like structure was detected at film thickness of 506nm which composed of nanoparticle MgO. The 238nm film was found to be suitable thickness of dielectric layer due it electrical properties and structural properties which include resistivity, leakage current density, roughness and particle size respectively.

Microstructure modification of La2Zr2O7 buffer films for coated conductors by metal organic decomposition

La2Zr2O7 (LZO) film directly deposited on Ni-5 at.%W by a chemical solution technique, metal organic decomposition (MOD), indicated a poor texture characteristic, which would result in high-angle grain boundaries in subsequent YBa2Cu3O7−δ (YBCO) associated with weak-link behavior. Different ultrathin MOD-LZO, Y2O3, and CeO2 seed layers (~several nanometers) with various annealing temperature were inserted to improve the crystallographic alignment. The relation between the texture and annealing temperature was systematically investigated. A CeO2 seed layer allows us to grow high quality LZO epitaxial films with values of full width at half-maximum around 5.61° and 5.13° for the Φ-scan of (222) and rocking curve of (400) LZO, respectively, which is comparable to the microstructure of films grown using physical vapor deposited Y2O3 as a seed layer. This buffer template, serving for YBCO coated conductors, could potentially decrease the overall fabrication cost.

Enhancement in Dielectric Constant and Structural Properties of Sol-Gel Derived MgO Thin Film using ZnO/MgO Multilayered Structure

High dielectric constant, low porosity and nano-dimension particle of single layer magnesium oxide, MgO and multilayer ZnO/MgO were synthesized at different MgO solution molar concentration by the simple chemical solution technique. The MgO molar concentration was found to alter the properties of both single and multilayer films. Observation reveals the surface morphology change form uniform to agglomerate and porous structure with corresponding increase in molar concentration. The increment in particle size and the formation of agglomerated particle were observed by FESEM (JEOL JSM-J600F). The best prepared dielectric film for both single and multilayer is the film that deposited using 0.4 molar concentration MgO solution due to its high dielectric constant, uniform film, and the particle is in nanometer dimension with nonorod like structure.

Polyvinyl Alcohol 폴리머 용액법으로 합성한 스포듀민 분말의 특성연구

【LAS-system ceramic powder, spodumene ( $Li_2O{\cdot}Al_2O_3{\cdot}4SiO_2$ ), was successfully synthesized by a chemical solution technique employing PVA(polyvinyl alcohol) as an organic carrier. The PVA content affected the microstructure of porous precursor gels and the crystalline development. The optimum PVA content contributed to homogeneous distribution of metal ions in the precursor gel and it resulted in the synthesis of glass free $\beta$ -spodumene powder having a specific surface area of $7.57\;m^2/g$ . The agglomerated $\beta$ -spodumene powders were also enough soft to grind to fine powders by a simple ball milling process. The microstructures of the densified powder compacts were strongly dependant on the minor phases of spodumene solid solution and amount of liquid phase, which were formed from the inhomogeneous precursors.】

A chemical solution approach for superconducting and hard epitaxial NbC film

Epitaxial NbC thin films were grown by a chemical solution technique, polymer assisted deposition. High quality epitaxial NbC film showed a transition temperature of 10 K and a hardness of 19.54 GPa.

Ultrathin epitaxial superconducting niobium nitride films grown by a chemical solution technique

Ultrathin epitaxial superconducting NbN (18 nm) films, exhibiting a superconducting transition temperature of 14 K and a critical current density as high as 5.2 MA cm(-2) at 5 K under zero magnetic field, were grown on SrTiO(3) (STO) by a chemical solution technique, polymer assisted deposition (PAD).