Cu2ZnSnS4 ceramic target: Determination of sintering temperature by TG–DSC

In this work, mixed powders of Cu₂S, ZnS and SnS₂ were used to sinter CZTS ceramic target. Thermal properties of Cu-poor and Zn-rich mixed powders were investigated by thermogravimetry and differential scanning calorimetry (TG–DSC). It has been found that the formation temperature of CZTS was not obvious in DSC curve. Obvious weight loss begun from 800 °C and a strong endothermic peak of melting appeared at around 880 °C depending on the relative tin content in mixed powders. For different compositions in Cu-poor and Zn-rich region, all TG and DSC curves showed similar profile as a function of temperature. To reduce volatilization and low melting point compound of SnS and Cu–Sn–S when sintering, a sintering temperature of 750 °C was adopted. CZTS targets (360 mm×80 mm) have been successfully fabricated with Cu-poor and Zn-rich composition, kesterite phase and high compactness of above 93%.     

Influence of copper concentration on sprayed CZTS thin films deposited at high temperature

In this study, Cu₂ZnSnS₄ (CZTS) thin films were deposited by spray pyrolysis technique at constant substrate temperature. The effects of the copper concentration on the structural, morphological and optical properties of the films were investigated. The copper concentration was varied from 0.15 to 0.25 M in the steps of 0.05 M. The structural studies revealed that the Cu poor film shows low intense peaks, but as Cu concentration increases a relatively more intense and sharper diffraction peaks (112), (200), (220), and (312) of the kesterite crystal structure were observed. Raman spectroscopy analysis confirmed the formation of phase-pure CZTS films. From the morphological studies, it is found that the grain size increased as the Cu concentration increases from 0.15 to 0.25 M. The optical band-gap values were estimated to be 1.61, 1.52 and 1.45 eV for copper concentration 0.15, 0.20 and 0.25 M, respectively. Photoelectrochemical cells using films of different copper concentrations were fabricated and the best cell exhibited an efficiency of 1.09% for 0.25 M of copper concentration.     

Effect of periodic precursor on sulfurization process of Cu2ZnSnS4 thin film

In this study, Cu₂ZnSnS₄ (CZTS) thin films were fabricated by periodically sequential depositions of metallic precursors by magnetron sputtering followed by sulfurization. The element compositions, crystal structures, and surface morphologies of the single-period precursor (Zn/Sn/Cu) and four-period precursor (Zn/Sn/Cu/Zn/Sn/Cu/Zn/Sn/Cu/Zn/Sn/Cu) during the sulfurization process were investigated. The experimental results showed that in the initial stage of sulfurization, the single-period precursor had a more efficient reaction with sulfur vapor below 300?°C because of its thicker metal layers. During the process of sulfurization, the CZTS phase first formed in the four-period film at 400?°C, owing to the wide distribution of the internal layer in the periodic thin film. With a further increase in temperature, the crystallinity of CZTS was enhanced and the secondary phases were reduced. A CZTS phase with Cu-poor and Zn-rich composition was confirmed in both thin films after complete sulfurization. The CZTS thin film with a four-period precursor showed a better degree of crystallization, and a single phase of CZTS was obtained more easily than in the single-period thin film. Therefore, using a periodic structure can promote the sulfurization reaction of Cu-Zn-Sn precursors and enhance the properties of CZTS thin films.     

Bandgap engineering of Cu2InxZn1−xSn(S,Se)4 alloy films for photovoltaic applications

Bandgap engineering of Cu₂In_xZn_1?xSn(S,Se)₄ alloy films for photovoltaic application has been investigated. Cu₂In_xZn_1?xSn(S,Se)₄ (0 ≤ x ≤ 0.6) alloy films with different In contents and a single kieserite phase were fabricated by using a simple low-cost sol-gel method. The influence of In content on the structure, morphology, and optical and electrical properties of Cu₂In_xZn_1?xSn(S,Se)₄ films was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), X-Ray photoelectron spectroscopy (XPS), optical absorbance, and room-temperature Hall measurements. The results of XRD, TEM, and XPS demonstrated the substitution of some Zn atoms by In in Cu₂In_xZn_1?xSn(S,Se)₄ films. The Hall measurements show that the carrier concentration of the Cu₂In_xZn_1?xSn(S,Se)₄ (0 ≤ x ≤ 0.6) decreases with increasing In content and that the p-type Cu₂In_xZn_1?xSn(S,Se)₄ films with preferable electrical properties can be obtained by adjusting the In content during film deposition. The optical measurements indicate that the bandgap of Cu₂In_xZn_1?xSn(S,Se)₄ films with kesterite structure can be continuously tuned in the range of 1.13–1.01 eV as x is increased from 0 to 0.6. Our results show that the Cu₂In_xZn_1?xSn(S,Se)₄ alloy is a potentially applicable material for bandgap grading absorption layers in high-power-conversion-efficiency solar cells.     

Direct dehydrogenation of n-butane over Pt/Sn/M/γ-Al2O3 catalysts: Effect of third metal (M) addition

A series of Pt/Sn/M/γ-Al₂O₃ catalysts with different third metal (M = Zn, In, Y, Bi, and Ga) were prepared by a sequential impregnation method for use in the direct dehydrogenation of n-butane to n-butene and 1,3-butadiene. In the direct dehydrogenation of n-butane, Pt/Sn/Zn/γ-Al₂O₃ catalyst showed the best catalytic performance. Catalytic performance decreased in the order of Pt/Sn/Zn/γ-Al₂O₃ > Pt/Sn/In/γ-Al₂O₃ > Pt/Sn/γ-Al₂O₃ > Pt/Sn/Y/γ-Al₂O₃ > Pt/Sn/Bi/γ-Al₂O₃ > Pt/Sn/Ga/γ-Al₂O₃. The catalytic performance increased with increasing metal–support interaction and Pt surface area of the catalyst.     

Properties of solution-processed MgInZnO semiconductor thin films and photodetectors fabricated at a low temperature using UV-assisted thermal annealing

Ultraviolet (UV) irradiation-assisted thermal annealing is used for the fabrication of Mg doped InZnO (MIZO) semiconductor thin films and metal-semiconductor-metal (MSM) type photodetectors on alkali-free glasses at a low temperature of 300 °C. In this study, the effects of UV irradiation time on the structural features and the optical and electrical properties of sol-gel derived MIZO thin films were investigated, and the photoresponse properties of MIZO photodetectors fabricated using UV-assisted thermal annealing (UV-TA) and conventional thermal annealing (CTA) were compared. The molar ratio of In:Zn was fixed at 3:2, and the Mg content was maintained at 20 at% ([Mg]/[In+Zn]) in the precursor solution. After a spin-coating and drying procedure was performed twice, the dried sol-gel films were heated on a hotplate at 300 °C and exposed to UV irradiation in ambient air. The UV irradiation time was adjusted to 1, 2, 3, and 4 h. All annealed MIZO thin films had a dense microstructure, uniform film thickness, and flat surface and exhibited good optical transmittance (> 86.0%). The mean resistivity decreased with increasing irradiation time, and the samples irradiated for 4 h exhibited the lowest mean resistivity of 4.4×10² Ω-cm. Current-voltage (I-V) characteristics showed that the MIZO photodetectors operated in the photoconductive mode. Under illumination with UVC light, the MIZO photodetectors exhibited an I_light-to-I_dark ratio of 7.7 × 10² and had a photoresponsivity of 5.0 A/W at a bias of 5 V.     

Enhanced photocatalytic activity of TiO2-ZnO thin films deposited by dc reactive magnetron sputtering

The effect of deposition conditions on the photocatalytic activity of TiO₂-ZnO thin films was studied. By using a (Ti)₉₀-(Zn)₁₀ alloy target, the samples were deposited at room temperature on glass substrates by dc reactive magnetron sputtering and post-annealed in air at 500 °C. The dependence of the physical properties of the films on the O₂/Ar gas ratio and the deposition working pressure was investigated. XRD patterns showed mainly the formation of the anatase phase of TiO₂. Optical absorption measurements exhibited a blue shift of the band-gap energy with increasing working pressure. XPS spectra indicated the presence of the Ti⁴⁺ and Zn²⁺ oxidation states, which correspond to TiO₂ and ZnO, respectively. The chemical state of Ti was further analyzed by means of the modified Auger parameter, α’, which gave a value of ca. 873 eV. The photocatalytic property of the films was assessed by the degradation of a methylene blue aqueous solution. The maximum photocatalytic performance was observed for the samples deposited at 3.0 mTorr and O₂/Ar gas ratio of 10/90. These results are explained in terms of the structural, optical, and morphological properties of the films.     

Enhanced dielectric and energy-storage properties in BiFeO3-modified Bi0.5(Na0.8K0.2)0.5TiO3 thin films

Lead free Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ thin films doped with BiFeO₃ (abbreviated as BNKT-xBFO) (x = 0, 0.02, 0.04, 0.08, 0.10) were deposited on Pt(111)/Ti/SiO₂/Si substrates by sol-gel/spin coating technique and the effects of BiFeO₃ content on the crystal structure and electrical properties were investigated in detail. The results showed that all the BNKT-xBFO thin films exhibited a single perovskite phase structure and high-dense surface. Reduced leakage current density, enhanced dielectric and ferroelectric properties were achieved at the optimal composition of BNKT-0.10BFO thin films, with a leakage current density, dielectric constant, dielectric loss and maximum polarization of < 2 × 10⁻⁴ A/cm³, ~ 978^, ~ 0.028 and ~ 74.13 μC/cm² at room temperature, respectively. Moreover, the BNKT-0.10BFO thin films possessed superior energy storage properties due to their slim P-E loops and large maximum polarization, with an energy storage density of 22.12 J/cm³ and an energy conversion efficiency of 60.85% under a relatively low electric field of 1200 kV/cm. Furthermore, the first half period of the BNKT-0.10BFO thin film capacitor was about 0.15 μs, during which most charges and energy were released. The large recoverable energy density and the fast discharge process indicated the potential application of the BNKT-0.10BFO thin films in electrostatic capacitors and embedded devices.     

Densification,mechanical and thermal properties of ZrC1 − x ceramics fabricated by two-step reactive hot pressing of ZrC and ZrH2 powders

Densification behavior, mechanical and thermal properties of ZrC_1 ? x ceramics with various C/Zr ratios of 0.6–1.0 have been investigated by two-step reactive hot pressing of ZrC and ZrH₂ powders at 30 MPa and 1500–2100 °C. The two-step reactive hot pressed ZrC_1 ? x ceramic has a higher relative density (> 95.3%) than that (91.9%) of stoichiometric ZrC sintered at 2100 °C. A cubic Zr₂C-type ordered phase forms in the ZrC_1 ? x sample obtained at a ZrC/ZrH₂ molar ratio of 0.6 at a relatively low temperature of 1100 °C. The decrease in C/Zr ratio is beneficial to densification of ZrC_1 ? x ceramic, however, excess grain growth occurs after sintering above densification temperature. The elastic modulus and Vickers hardness decrease with decreasing the C/Zr ratio. With decreasing the C/Zr ratio, both thermal conductivity and specific heat decrease due to the enhanced scattering of conducting phonons and electrons by carbon vacancies.     

New insight into the modification of Li-rich cathode material by stannum treatment

In this work, Sn is used to dope the Li-rich cathode material to improve the electrochemical performance of Li ion battery. After Sn treatment, the lattice parameters a, c and lattice volume V become larger. Compared with the pristine sample, the Sn-contained samples show longer plateaux at about 4.5 V in the first charging process, which means that Sn can activate the Li₂MnO₃ component. Meanwhile, with appropriate content of Sn doping, the sample exhibits enhanced rate capability and cycling stability. Especially, the sample S10 shows the best electrochemical performance, with a capacity retention of 88.66% after 100 cycles at 1 C (1 C=250 mA g⁻¹). The mechanisms of Sn doping have also been investigated. The increased activation of Li₂MnO₃ is due to the improved conductivity of Li₂MnO₃ phase by Sn doping, and the enhanced electrochemical performance is mainly ascribed to the increased ability of Li ion diffusing into bulk phase and the improved structure stability during the prolonged charge-discharge cycles. It is suggested that Sn doping is an effective way to improve the electrochemical performance of Li-rich cathode material.     

The microstructure,ferroelectric and dielectric behaviors of Na0.5Bi0.5(Ti,Fe)O3 thin films synthesized by chemical solution deposition: Effect of precursor solution concentration

Fe-doped Na_0.5Bi_0.5TiO₃ (NBTFe) thin films were prepared directly on indium tin oxide/glass substrates using a chemical solution deposition method combined with sequential layer annealing. The X-ray diffraction, scanning electron microscopy and insulating/ferroelectric/dielectric measurements were utilized to characterize the NBTFe thin films. All the NBTFe thin films prepared by four precursor solutions with various concentrations of 0.05, 0.10, 0.20 and 0.30 M exhibit polycrystalline perovskite structures with different relative intensities of (l00) peaks. A large remanent polarization (P_r) of 33.90 μC/cm² can be obtained in NBTFe film derived with 0.10 M spin-on solution due to its lower leakage current and larger grain size compared to those of other samples. Also, it shows a relatively symmetric coercive field and large dielectric tunability of 36.34%. Meanwhile, the NBTFe thin film with 0.20 M has a high energy-storage density of 30.15 J/cm³ and efficiency of 61.05%. These results indicate that the electrical performance can be controlled by optimizing the solution molarity.     

Influence of precursor solution concentration on the microstructure,leakage current and dielectric tunability of Zn-doped Na0.5Bi0.5TiO3 thin films prepared by metal organic decomposition

Zn-doped Na_0.5Bi_0.5TiO₃ (Zn: NBT) thin films were prepared from precursor solutions with different concentrations (0.08, 0.20 and 0.35 M) via a metal organic decomposition process. The effects of the mole concentration of precursor solution on crystallization and electrical properties were investigated. All the films exhibit polycrystalline perovskite structure. The increasing degree of predominant (110) orientation with the decrease of the concentration is ascribed to the highly diluted of the solution, leading to the local grain-on-grain growth. Compared with other films, the 0.20 M-film exhibits a strong nonlinear dependence of the dielectric constant on the applied voltage due to the improvement of crystallinity and insulating property. Furthermore, the effect of applied voltage on the dielectric tunability for 0.20 M-film is discussed. A higher tunability of 36.8% and figure of merit of 7.4 in Zn: NBT film can be observed at ±16 V and 100 kHz.     

Effects of element chemical states and grain orientation growth of ITO targets on photoelectric properties of the film

A study was carried out to compare element chemical states and grain orientation growth between two ITO targets, which were respectively sintered at 1560 °C (target A#) and 1600 °C (target B#). The lower sintering temperature can be beneficial to increase mass content ratio of In₂O₃ to SnO₂, reduce the production of Sn²⁺ ions and the component of O-In as well as increase oxygen holes, and can also promote grain orientation growth of In₂O₃ and In₄Sn₃O₁₂ phase. Three groups of ITO films were deposited at 230 °C using these targets to investigate the effects of sputtering parameters on the photoelectric properties of ITO films. Under different sputtering pressures, the sheet resistance for target A# has higher sensitivity to low O₂ flow, while target B# displays higher sensitivity to high O₂ flow. In the case of sputtering pressure of 0.5 Pa, ITO films for target A# displays the highest visible transmittance. In addition, annealing process could decrease the sheet resistance and improve the transmittance of ITO films because of its effect on the crystallinity and surface morphology of ITO films.     

Synthesis and characterization of Bi1.5Zn0.92Nb1.5−xSnxO6.92−x/2 pyrochlore ceramics

The morphological, compositional, structural, dielectric and electrical properties of Bi_1.5Zn_0.92Nb_1.5?xSn_xO_6.92?x/2 ceramics have been investigated by means of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), temperature and frequency dependent dielectric constant and temperature dependent conductivity measurements for Sn-contents in the range of 0.00 ≤ x ≤ 0.60. It was shown that single phase of the pyrochlore ceramics can only be obtained for x ≤ 0.25. Above this value a ZnO phase appeared in the XRD patterns and SEM micrographs as well. An increase in the lattice constant and in the temperature coefficient of dielectric constant and a decrease in the dielectric constant values with increasing Sn content was observed for the ceramics which exhibited a single phase formation. A temperature dependent but frequency invariant dielectric constant was observed for this type of ceramics. The lowest electrical conductivity and highest dielectric constant was observed for the sample which contains 0.06 Sn. The Bi_1.5Zn_0.92Nb_1.5?xSn_xO_6.92?x/2 pyrochlore ceramic conductivities are thermally active above 395 K. For temperatures greater than 395 K, the conductivity activation energy which was found to be 0.415 eV for the pure sample increased to 1.371 eV when sample was doped with 0.06 Sn.     

Fabrication of CaLa4(Zr0.05Ti0.95)4O15 thin films by RF magnetron sputtering

Crystalline CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films deposited on n-type Si substrates byRF magnetron sputtering at a fixed RF power of 100 W, an Ar/O₂ ratio of 100/0, an operating pressure of 3 mTorr, and different substrate temperatures were investigated. The surface structural and morphological characteristics analyzed by X-ray diffraction and atomic force microscopy were sensitive to the deposition conditions, such as the substrate temperature. The diffraction pattern showed that the deposited films had a polycrystalline microstructure. As the substrate temperature increased, the quality of the CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films improved, and the kinetic energies of the sputtered atoms increased, resulting in a structural improvement of the deposited CaLa₄(Zr_0.05Ti_0.95)₄O₁₅ thin films. A high dielectric constant of 16.7 (f=1 MHz), a dissipation factor of 0.19 (f=1 MHz), and a low leakage current density of 3.18×10⁻⁷ A/cm² at an electrical field of 50 kV/cm were obtained for the prepared films.     

Tuning electrical properties of PZT film deposited by Pulsed Laser Deposition

The variation of the chemical composition and properties of PZT films as a function of oxygen pressure and laser fluence during pulsed laser deposition is used to tune the electrical properties of the PZT thin films. It is found that the deposition using a 248 nm laser fluence of 1.7 J/cm² and an oxygen pressure of 400 mtorr results the PZT films very similar to that of target material. Changing the laser fluences or oxygen pressure, affects the lead content of the deposited film. In the range of oxygen pressure 50–200 mtorr, the Zr/Zr+Ti and Ti/Zr+Ti ratio varies with oxygen pressure while the Pb/Zr+Ti ratio is almost uniform. Using oxygen pressure as a control parameter to tune the chemical compound and electrical properties of the deposited PZT films, the remnant polarization of the PZT films is tuned in the range of 6.6–42.2 µC/cm², the dielectric constant is controlled in the range of 29–130, and the piezoelectric constant d₃₃ is controlled in the range of 3.82–4.96 pm/V for a 40 nm thick PZT film.     

Preparation of (0 2 0)-oriented BaTi2O5 thick films and their dielectric responses

Barium dititanate (BaTi₂O₅) thick films were prepared on a Pt-coated Si substrate by laser chemical vapor deposition, and ac electric responses of (0 2 0)-oriented BaTi₂O₅ films were investigated using several equivalent electric circuit models. BaTi₂O₅ films in a single phase were obtained at a Ti/Ba molar ratio (m_Ti/Ba) of 1.72–1.74 and deposition temperature (T_dep) of 908–1065 K as well as m_Ti/Ba = 1.95 and T_dep = 914–953 K. (0 2 0)-oriented BaTi₂O₅ films were obtained at m_Ti/Ba = 1.72–1.74 and T_dep = 989–1051 K. BaTi₂O₅ films had columnar grains, and the deposition rate reached 93 μm h^?1. The maximum relative permittivity of the (0 2 0)-oriented BaTi₂O₅ film prepared at T_dep = 989 K was 653 at 759 K. The model of an equivalent circuit involving a parallel combination of a resistor, a capacitor, and a constant phase element well fitted the frequency dependence of the interrelated ac electrical responses of the impedance, electric modulus, and admittance of (0 2 0)-oriented BaTi₂O₅ films.     

Desorption of zinc by the kaolin from Suzhou,China

This paper studied the influence of copper concentration, pH, temperature, and the ratio of solid to solution on desorption of Zn in the kaolin from Suzhou, China in a background solution of 0.01 M CaCl₂ by batch extraction experiments. At 0, 5, 50, 100 mg/l Cu concentration, for each 0.5 increase in pH between about 1.80 and 3.04% desorption decreases 3.80, 13.87, 9.97, and 7.65%, respectively. The pH₅₀ (pH at 50% Zn desorption) is found to follow the sequence: Cu (5 mg/l, pH₅₀ = 2.60) < Cu (50 mg/l, pH₅₀ = 2.70) < Cu (100 mg/l, pH₅₀ = 2.95) < Cu (0 mg/l, pH₅₀ = 10.65). The free energy change (ΔG) values, the values of enthalpy change (ΔH), and entropy change (ΔS) have been calculated. There were no large differences in the desorption of Zn from 25 to 50 °C. The concentration of Zn in solution after desorption equilibrium increases and percent desorption decreases when the solid to liquid ratio increases from 0.025 to 0.2. The kaolin possibly cannot be used for the landfill clay liner.     

Growth and properties of Cu3SbS4 thin films prepared by a two-stage process for solar cell applications

Cu₃SbS₄ is a promising material for thin film heterojunction solar cells owing to its suitable optical and electrical properties. In this paper, we report the preparation of Cu₃SbS₄ thin films by annealing the Sb₂S₃/CuS stacks, produced by chemical bath deposition, in a graphite box held at different temperatures. The influence of annealing temperature on the growth and properties of these films is investigated. These films are systematically analyzed by evaluating their structural, microstructural, optical and electrical properties using suitable characterization techniques. X-ray diffraction analysis showed that these films exhibit tetragonal crystal structure with the lattice parameters a=0.537 nm and b=1.087 nm. Their crystallite size increases with increasing annealing temperature of the stacks. Raman spectroscopy analysis of these films exhibited modes at 132, 247, 273, 317, 344, 358 and 635 cm⁻¹ due to Cu₃SbS₄ phase. X-ray photoelectron spectroscopy analysis revealed that the films prepared by annealing the stack at 350 °C exhibit a Cu-poor and Sb-rich composition with +1, +5 and −2 oxidation states of Cu, Sb and S, respectively. Morphological studies showed an improvement in the grain size of the films on increasing the annealing temperature. The direct optical band gap of these films was in the range of 0.82–0.85 eV. Hall measurements showed that the films are p-type in nature and their electrical resistivity, hole mobility and hole concentration are in the ranges of 0.14–1.20 Ω-cm, 0.05–2.11 cm² V⁻¹ s⁻¹ and 9.4×10²⁰–1.4×10¹⁹ cm⁻³, respectively. These structural, morphological, optical and electrical properties suggest that Cu₃SbS₄ could be used as an absorber layer for bottom cell in multi-junction solar cells.     

Investigation of optical,structural, FTIR and magnetic properties of Sn substituted Zn0.98Mn0.02O nanoparticles

Zn_0.98Mn_0.02O and Zn_0.98−xMn_0.02Sn_xO (x=2% and 4%) nanoparticles have been successfully synthesized via sol–gel method. X-ray diffraction (XRD) confirmed the hexagonal wurtzite structure of the samples and also successful Sn doping without any secondary phases. The microstructure of ZnMnO was significantly altered where the morphology was turned from mixed plate-like structure to spherical like structure by Sn substitution which was confirmed by electron microscope images. The energy dispersive X-ray (EDX) analysis confirmed the presence of Sn and Mn in Zn–O nanoparticles. The observed narrowing of energy gap (red shift) from 3.85 eV (Sn=0%) to 3.66 eV (Sn=4%) was discussed based on size effect and generation of free carrier concentrations. The improved optical properties of Sn–Zn–Mn–O evidenced for developing opto-electronic devices with better conversion efficiency. The shift of lattice mode (position) around 527–548 cm⁻¹ and the change in shape of the band demonstrated the presence of Sn in Zn–Mn–O. The decrease of UV emission intensity and increase of defect related blue and green emissions indicated the possible generation of white light sources and display devices. The superior magnetic property of Sn doped Zn_0.98Mn_0.02O was explained by the intrinsic exchange interaction between Zn/Mn/Sn ions through the defects induced by Sn.