ZnS Phase Research Articles

Desulfurization kinetics of high lead and zinc sulfide containing slag with oxygen blowing

The desulfurization process of lead and zinc slag is an important smelting process to obtain lead and zinc. The aim of this paper is to study the desulfurization process of high lead and zinc sulfide containing slag with oxygen blowing. The predominance area diagrams of the Pb-Zn-Fe-S-O system (Pb/(Fe+Pb+Zn)=0.176, Zn/(Fe+Pb+Zn)=0.56) at various temperature were thermodynamically constructed. The physical properties, the chemical composition and the phase transformation of the desulfurization slag were investigated. The thermodynamic results indicated that lead, zinc, and iron can be oxidized to form high lead and zinc slag. The experimental results illustrated that the sulfur content in the oxidation slag can be reduced to less than 1% as temperature increased up to 1573 K. The XRD analysis of as-quenched slag shows the PbS and ZnS phase decreased, while zincite and spinel phase (ZnxFe3-xO4+y) emerged and increased as the reaction time increased. The desulfurization process of molten slag were considered to be the first-order reaction and the apparent activation energy was estimated to be 44.46 kJ/mol. Under the experimental conditions, the mass transfer in the gas and liquid phase was likely to be the restrictive step.

Investigation of ZnS films prepared with different solvents and zinc sources under different experimental conditions

Abstract ZnS films were prepared by chemical co-reduction method in this work. The influencing factors such as the kind of the solvent, reaction temperature and holding time on ZnS films were mainly investigated by repeated experiments. Experimental results show that, when using different solvents and zinc sources, the X-ray diffraction (XRD) peak intensities of ZnS products obtained by using ethanol as the solvent are much higher than those obtained by using ethylene glycol as the solvent. The ZnS film prepared from zinc source is uniform and compact with round particles arranged regularly. When using ethanol as the solvent, the target product ZnS phase is more easily obtained with ZnO as the zinc source. When holding at 140–180 °C for 20 h, with the increase of temperature the XRD intensity of ZnS phase increases, and the crystallinity becomes better with mostly ZnS spherical particles about 1 μm in diameter microscopically. Impurities ZnO appeared at higher temperature. The ZnS film with pure phase was obtained at 180 °C for 20 h with high XRD intensity and good crystallinity; The XRD peaks at 2θ angles of 28.654°, 48.674° and 56.561° correspond to the (1 0 2)/(0 0 6), (1 1 0)/(1 0 8) and (1 1 6) crystal planes; The extension of the reaction time favors the formation of the target product phase. The ZnS film prepared at 180 °C for 20 h has flat surface, uniform size and dense arrangement with the average resistivity of 0.048 kΩ·cm.

High figure of merit p-type transparent conducting thin film based on solution processed CuS-ZnS nanocomposite

Until now only n-type transparent conducting films (TCFs) have accomplished sufficient maturity while p-type TCFs are still in infancy which limits the success of all-transparent electronics. Considerable endeavors are made till date for development of new p-type TCFs with limited success. Here, we report a highly transparent and conducting p-type thin films (∼60 nm) based on CuS-ZnS nanocomposite deposited by simple chemical bath deposition method at ∼80 °C on glass substrates using different x values (0.1, 0.35, 0.6, 0.8) where x = Cu (mol %)/(Cu+Zn) (mol%). Grazing incidence X-ray diffractometry, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and atomic force microscopy are used to evaluate the structural and microstructural characteristics of the films. The existence of ZnS phase is seen only for x ≤ 0.6 due to a preferential deposition of CuS which helps to retain a significant visible light transparency for x = 0.6 with a small drop in the conductivity value as compared to CuS. Thus the film with x = 0.6 is found to have the optimum electrical properties with resistivity, hole concentration, and mobility values of 1.03×10−3 Ω-cm, 4.16 × 1022 cm−3, and 0.15 cm2/Vs respectively as well as an optical transmission value of 83% at 550 nm. An unprecedented figure of merit value of 9.2 × 10−4 Ω−1 is obtained for the optimized film which is not reported till date to our knowledge. A p-n heterojunction is fabricated using the optimized film on n-GaN which shows a rectification ratio of 3.06 × 104 at 2 V indicating a great potential as p-type TCF for flexible transparent electronics.

Controlled synthesis, morphological, optical and electrical properties of copper-doped zinc oxysulfide nanostructures

Zinc oxysulfide nanostructures may have physical and chemical properties that are different from ZnS or ZnO. Therefore, Cu-doped oxysulfide nanostructures were prepared by vapor transport and their properties were characterized by various techniques. EDAX analysis confirmed the presence of Zn, S, O and Cu in the samples. XRD revealed the formation of mixed phases of hexagonal ZnS, orthorhombic ZnSO4, and hexagonal ZnO that is dependent on Cu content. The undoped sample has nanowire morphology. The increase in Cu doping changed the morphology form NWs to a mixture of NWs and nanoparticles (NPs), and then to NPs. The undoped oxysulfide sample has band gap of 4.08 eV, and the band gap decreased to 3.57 eV at 5% Cu doping. The PL intensity was enhanced upon Cu doping with 5 and 10 at% Cu while it weakened at higher Cu contents. The electrical resistivity decreased with Cu content and a thermally activated semiconducting behavior was reported for all samples.

Electrochemical deposition and characterization of ZnOS thin films for photovoltaic and photocatalysis applications

Electrochemical deposition of zinc oxysulphide (ZnOS) thin films for possible photovoltaic and photocatalysis applications has been carried out using zinc acetate and sodium thiosulphate precursors in a simple two-electrode deposition set-up. The deposited films were characterized for their structural, optical, morphological and compositional properties using glancing incidence X-ray diffraction (GIXRD), UV–Vis spectrophotometry, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy respectively. The detailed characterization results show that the ZnOS materials grown at different cathodic potentials of 1450 mV, 1500 mV and 1550 mV display desirable properties for the intended applications. Structural analysis shows that the films were formed by a combination of hexagonal ZnS and ZnO crystal phases. The energy bandgap estimated for the films across the explored potentials is in the range (2.68–3.26) eV for as-deposited films and (2.90–3.10) eV after annealing. These values and the transmittance were also shown to be increased significantly by reducing the deposition duration. SEM images show very compact and densely packed grains in the films while EDX results show Zn/S values of approximately unity and Zn/O values of approximately 0.1 across the deposition potentials explored, in both as-deposited and annealed conditions.

Photocatalytic degradation and ferromagnetism in mesoporous La doped ZnS nanoparticles

The influence of Lanthanum (La) doping on the crystalline phase, thermal, optical, photocatalytic degradation and ferromagnetic properties of mesoporous ZnS:La nanoparticles is investigated. BET surface studies confirm the presence of mesoporous in the ZnS and ZnS:La nanoparticles. Photocatalytic activity of 5 wt% La doped ZnS is evaluated by the degradation of Turquoise Blue H5G in aqueous solution under sunlight. The photomineralization and photostability are validated by TOC and ICP-OES analyses. Photoconductivity measurements confirm the production of photocharge carrier. The long range ferromagnetism in La doped ZnS nanostructures due to defects is formed by vacancies and lattice deformation. Morphology and the size of the nanoparticles are probed by field emission scanning microscope. TEM images confirm the hexagonal structure of the doped sample. The cubic structure of undoped ZnS and hexagonal structure of mesoporous La doped sample is confirmed by Raman modes. The thermal analysis of La doped nanoparticles is analyzed by using thermo gravimetric and differential scanning calorimetry method.

PHOTOLUMINESCENCE EMISSION OF Cu DOPED ZnS MICROSTRUCTURES SYNTHESIZED BY THERMAL EVAPORATION

Cu doped ZnS microstructures were prepared by the thermal evaporation method using ZnS powder and CuCl2.2H2O powder as precusor materials. The microstructures was characterized by using X-ray diffraction (XRD) analysis. The XRD studies indicated that there are two phases (ZnS and ZnO) at the undoped sample, but most of the samples are only having wurtzite (hexagonal) phase of ZnS after doping. The photoluminescence emission and photoluminescence excitation of ZnS and Cu2+ doped ZnS microstructures have been studied. The photoluminescence excitation spectra of ZnS microstructures is present around 374 nm. After doping of Cu2+ ion the absorption wavelength shifted towards the lower wavelength, this blue shift in the absorption edge is a measure of increased band gap. The emission spectrum of pure ZnS has a green emission band centred at around 520 nm. After doping with Cu2+ ion the luminescence centers were transferred to 516 nm and a strong blue peak at 440 nm appears. The reasons of these will be discussed in this paper.

TiO2-coated ZnS films as photoanode for dye-sensitized solar cell: effect of zinc nitrate hexahydrate concentration on the performance

This work is concerned with the use of TiO2-coated ZnS films as a photoanode in dye-sensitized solar cell (DSSC). The ZnS layer has been coated on TiO2 films via immersion technique. The influence of ZnS precursor concentration on the properties of the sample has been investigated. The effect of the precursor concentration on the performance of the device has also been studied. The XRD analysis reveals that anatase and ZnS phase exists in TiO2-coated ZnS sample. The samples absorb light in UV region but reflect more light in the visible region. The FESEM analysis reveals that the morphology of the TiO2-coated ZnS is nanograss. The device utilizing 0.03 M ZnS precursor demonstrates the highest η of 1.323% due to the smallest bulk and charge transfer resistance and also due to longest carrier lifetime.

Formation of zinc sulfide species during roasting of ZnO with pyrite and its contribution on flotation

In this paper, formation of zinc sulfide species during roasting of ZnO with FeS2 was investigated and its contribution on flotation was illustrated. The evolution process, phase and crystal growth were investigated by thermogravimetry (TG), X-Ray diffraction (XRD) along with thermodynamic calculation and scanning electron microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDS), respectively, to interpret the formation mechanism of ZnS species. It was found that ZnS was initially generated at about 450 °C and then the reaction prevailed at about 600 °C. The generated FexS would dissolve into ZnS and then form (Zn, Fe)S compound in form of Fe2Zn3S5 when temperature increased to about 750 °C. This obviously accelerated ZnS phase formation and growth. In addition, it was known that increasing of ZnO dosage had few effects on the decomposition behavior of FeS2. Then, flotation tests of different zinc oxide materials before and after treatment were performed to further confirm that the flotation performances of the treated materials could be obviously improved. Finally, a scheme diagram was proposed to regular its application to mineral processing. It was systematically illustrated that different types of ZnS species needed to be synthetized when sulfidization roasting-flotation process was carried out to treat zinc oxide materials.

Synthesis of ZnS Quantum Dots for QDs-LED hybrid device with different cathode materials

In this study, a chemical method was used to synthesise ZnS quantum dots (QDs) with low cost and simple process. A fixed molar ratio 1:1 of zinc chloride and sodium sulfide has been used for preparing two samples A and B. The X-ray diffraction (XRD) analyses prove the cubic phase of ZnS with an average particles size of (3-29) nm According to UV-Vis. spectra analyses, a large blue shift over 32 and 48 nm was observed, while the band gaps energy (Eg) were 3.55 and 3.8 eV for A and B samples respectively. The emission spectrum of quantum dots carries more evidence on the presence of shallow at 373 and 367 nm originated from the interstitial Zn and traps at 428 and 439 nm, whose origin ascribed to defects zinc vacancy (VZn), while 541 nm was due to sulfide vacancy (VS). QDs-LED hybrid devices were fabricated using ITO/PEDOT: PSS/Poly-TPD/ZnS-QDs/layers with two types of cathode materials LiF and Al. Using LiF as cathode in addition to the Al gives good enhancement to light generation in compares with that of Al cathode only. The spectra 350-700 nm appeared a wide emission band according to the EL measurement.

Optical constants and dispersion parameters of La-doped ZnS nanocrystalline films prepared by sol–gel technique

The structure, morphology and particle size of La-doped ZnS nanocrystalline films were investigated by XRD, SEM and FTIR. XRD showed that the obtained films are nanocrystalline corresponding to the hexagonal ZnS phase with the particle size 3.44–15.13 nm. Optical properties of La-doped ZnS nanocrystalline films were investigated by UV–vis absorption technique. The band gap energy of nanocrystalline films was found to be 2.93 to 2.77 eV. Wemple – Didomenico single effective oscillator model was used to study the dispersion of nanocrystalline films refractive index. The red shift in the absorption band edge of the La-doped ZnS samples provides possibility for improving the solar energy application of ZnS.

Efficient Charge Separation in Plasmonic ZnS@Sn:ZnO Nanoheterostructure: Nanoscale Kirkendall Effect and Enhanced Photophysical Properties.

Tetravalent Sn doped ZnO nanocrystals show excellent plasmonic absorbance in the visible region. Plasmonic ZnS@Sn:ZnO core-shell heterostructures have been synthesized by the anion exchange process where the O2- is exchanged by S2- anion. An increase of sulfur concentration induces interior hollow structures arising from the different diffusion rates of O2- and S2- ions. Gradual transformation of wurtztie ZnO nanocrystals in the anion exchange process stabilizes the wurtzite crystalline phase of ZnS. Carrier concentration and various types of intrinsic defect states in both ZnO and ZnS result in ultraviolet, blue, and green emissions. The coexistence of exciton-plasmon coupling in the same nanoparticle and efficient electron-hole separation in type II heterostructure increases the photocatalytic activity and photo current gain.

Investigation of the nanoscale two-component ZnS-ZnO heterostructures by means of HR-TEM and X-ray based analysis

This article is devoted to the spectroscopic characterization of ZnS-ZnO nanoscale heterostructures synthesized by the microwave-assisted solvothermal method. The synthesized samples were investigated by means of X-ray powder diffraction (XRPD), high energy resolution fluorescence detected X-ray absorption near-edge-structure (HERFD-XANES) spectroscopy, valence-to-core X-ray emission spectroscopy (VtC-XES) and high resolution transmission electron microscopy (HR-TEM) as well as energy dispersive X-ray spectroscopy (EDX). The average crystallite size estimated by the broadening of XRPD peaks increases from 2.7 nm to 3.7 nm in the temperature range from 100 °C to 150 °C. HR-TEM images show that nanoparticles are arranged in aggregates with the 60–200 nm size. Theoretical estimation shows that the systems synthesized at higher temperatures more prone to the agglomeration. The full profile Reitveld analysis of XRPD data reveals the formation of hexagonal zinc sulfide structure, whereas electron diffraction data reveal also the formation of cubic zinc sulfide and claim the polymorphous character of the system. High energy resolution Zn K-edge XANES data unambiguously demonstrate the presence of a certain amount of the zinc oxide which is likely to have an amorphous structure and could not be detected by XRPD. Qualitative analysis of XANES data allows deriving ZnS/ZnO ratio as a function of synthesis temperature. EDX analysis depicts homogeneous distribution of ZnS and amorphous ZnO phases across the conglomerates. A complementary element-selective valence to core X-ray emission spectroscopy evidences formation of two-component system and confirms estimations of ZnS/ZnO fractions obtained by linear combination fit of XANES data.

Nanoscale Characterization of Growth of Secondary Phases in Off-Stoichiometric CZTS Thin Films.

The presence of secondary phases is one of the main issues that hinder the growth of pure kesterite Cu2ZnSnS4 (CZTS) based thin films with suitable electronic and junction properties for efficient solar cell devices. In this work, CZTS thin films with varied Zn and Sn content have been prepared by RF-power controlled co-sputtering deposition using Cu, ZnS and SnS targets and a subsequent sulphurization step. Detailed TEM investigations show that the film shows a layered structure with the majority of the top layer being the kesterite phase. Depending on the initial thin film composition, either about ~1 μm Cu-rich and Zn-poor kesterite or stoichiometric CZTS is formed as top layer. X-ray diffraction, Raman spectroscopy and transmission electron microscopy reveal the presence of Cu2-xS, ZnS and SnO2 minor secondary phases in the form of nanoinclusions or nanoparticles or intermediate layers.

The Critical Role of Thioacetamide Concentration in the Formation of ZnO/ZnS Heterostructures by Sol-Gel Process.

ZnO/ZnS heterostructures have emerged as an attractive approach for tailoring the properties of particles comprising these semiconductors. They can be synthesized using low temperature sol-gel routes. The present work yields insight into the mechanisms involved in the formation of ZnO/ZnS nanostructures. ZnO colloidal suspensions, prepared by hydrolysis and condensation of a Zn acetate precursor solution, were allowed to react with an ethanolic thioacetamide solution (TAA) as sulfur source. The reactions were monitored in situ by Small Angle X-ray Scattering (SAXS) and UV-vis spectroscopy, and the final colloidal suspensions were characterized by High Resolution Transmission Electron Microscopy (HRTEM). The powders extracted at the end of the reactions were analyzed by X-ray Absorption spectroscopy (XAS) and X-ray diffraction (XRD). Depending on TAA concentration, different nanostructures were revealed. ZnO and ZnS phases were mainly obtained at low and high TAA concentrations, respectively. At intermediate TAA concentrations, we evidenced the formation of ZnO/ZnS heterostructures. ZnS formation could take place via direct crystal growth involving Zn ions remaining in solution and S ions provided by TAA and/or chemical conversion of ZnO to ZnS. The combination of all the characterization techniques was crucial to elucidate the reaction steps and the nature of the final products.

STRUCTURAL, SURFACE MORPHOLOGICAL AND MAGNETIC STUDIES OF Zn1−xFexS (x=0.00–0.10) DILUTED MAGNETIC SEMICONDUCTORS GROWN BY CO-PRECIPITATION METHOD

We have fabricated Zn[Formula: see text]FexS ([Formula: see text], 0.02, 0.04, 0.06, 0.08 and 0.10) diluted magnetic semiconductors using co-precipitation method. X-ray diffraction patterns depict that Zn[Formula: see text]FexS appears as a dominant phase with cubic zinc blende structure and nanoscale crystallite size. In addition, a secondary phase of rhombohedral ZnS also appears; however, no additional phase arises that primarily belongs to Fe dopant. Using Debye–Scherrer relation, the crystallite size is found to be in the range of 20–27[Formula: see text]nm, which is in good agreement with the crystallite size calculated using the Williamson–Hall (WH) plot method. The appearance of secondary phase provoked to study the residual strain using Stokes–Wilson equation, which is nearly consistent to that observed using WH plot method. The surface morphology, revealed using scanning electron microscopy, depicts non-uniform surface structure with a variety of grains and void dimensions. Hysteresis loops measured for Zn[Formula: see text]FexS at room temperature (RT) illustrate a paramagnetic behavior at higher fields; however, small ferromagnetic behavior is evident due to the small openings of the measured hysteresis loops around the origin. The measured RT ferromagnetism reveals the potential spintronic device applications of the studied diluted magnetic semiconductors.

Effect of Zn/Sn molar ratio on the microstructural and optical properties of Cu2Zn1-xSnxS4 thin films prepared by spray pyrolysis technique

Quaternary kesterite Cu2ZnSnS4 (CZTS) compound is one of the most promising semiconductor materials consisting of abundant and eco-friendly elements for absorption layer in thin film solar cells. The effect of Zn/Sn ratio on Cu2Zn1-xSnxS4 (0≤x≤1) thin films were studied by deposited by varying molar volumes in the precursor solution of zinc and tin was carried out in proportion of (1-x) and x respectively onto soda lime glass substrates kept at 573 K by using chemical spray pyrolysis technique. The GIXRD pattern revealed that the films having composites of Cu2ZnSnS4, Cu2SnS3, Sn2S3, CuS and ZnS phases. The crystallinity and grain size were found to increase by increasing the x value and the preferential orientation along (103), (112), (108) and (111) direction corresponding to CZTS, Cu2SnS3, CuS, and ZnS phases respectively. Micro-Raman spectra exposed a prominent peak at 332 cm−1 corresponding to the CZTS phase. Atomic force microscopy was employed to study the grain size and roughness of the deposited thin films. The optical band gap was found to lie between 1.45 and 2.25 eV and average optical absorption coefficient was found to be greater than 105 cm−1. Hall measurements exhibited that all the deposited Cu2Zn1-xSnxS4 films were p type and the resistivity lies between 10.9×10−2Ωcm and 149.6× 10−2Ωcm.

MORPHOLOGY, PHASE AND PHOTOLUMINESCENCE OF ZnS MICROSTRUCTURES GROWN BY THERMAL DEPOSITION AT DIFFERENT TEMPERATURE OF SUBSTRATES

In this paper, we present about influent of temperature at the possitions where we puted the silica substrates on morphology, phase and photoluminescence of ZnS microstructures by thermal evaporation of ZnS powder in Ar gas ambient at atmospheric pressure. From X-ray diffraction pattern (XRD), the prepared microstructures have wurtzite (hexagonal) structures for ZnS phase and appear ZnO phase at lower temperature areas. The morphology of the microstructures change depending on substrate temperatures. The photoluminescence spectrum (PL) at room temperature shows that the shift from ultraviolet (UV) emission at high substrate temperature to strong blue emission at lower substrate temperature. The reasons of these peaks will be discussed in detail.

Zinc molarity effect on Cu2ZnSnS4 thin film properties prepared by spray pyrolysis

In the present work, Cu2ZnSnS4 (CZTS) thin films were deposited by spray pyrolysis, the effect of zinc molarity on films structural, optical and electrical properties was investigated. CZTS films were grown by pneumatic spray pyrolysis with various zinc salt molarities. The structural properties reveal that all prepared CZTS films have a kesterite structure with a preferential orientation along (112) plan with the presence of secondary phases. Film composition and structural property vary with Zn molarity: at relatively low Zn molarity CuS secondary phase is formed, while with increasing Zn molarity ZnS secondary phase is formed. The crystallite size increases from 25 to 125 nm with increasing Zn molarity. Films transmission spectra show low transmission in the visible range, whereas the band gaps varies slightly with Zn salt molarity, it lies between 1.3 and 1.37 eV. Hall Effect measurements were employed to determine the electrical properties of CZTS films. The films conductivity is a p type, it is reduced with increasing Zn molarity due to the reduction of free carriers concentration caused by carriers loss at ZnS/CZTS interface and the presence of the resistive ZnS phase.

X-ray spectroscopic diagnostics of the structure of quantum dots based on zinc and manganese sulfides and oxides

The microwave synthesis of quantum dots (QDs) based on zinc and manganese sulfides and oxides in a water-ethanol medium is proposed. The sample synthesized is characterized by X-ray diffraction (XRD), photoluminescence, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The XRD analysis shows the presence of the hexagonal ZnS phase of wurtzite type with an average nanocrystal size of 4.5 nm and manganese oxide Mn3O4 (hausmannite phase) with an average particle size of 12.5 nm in the sample under study, but does not provide the unambiguous conclusion about the doping of ZnS nanoparticles with Mn atoms. Although the analysis of the zinc and manganese K-edge XANES spectra suggests that the synthesized QD sample is a ZnMnS solid solution (~11%), a significant amount of a by-product (manganese oxide Mn3O4 of the hausmannite phase, ~89%) is formed.