Pre-annealing Temperature Research Articles

Controlling the synthesis conditions for the fabrication of Pb (Mg1/3Nb2/3) O3 nano powders to diminish undesirable pyrochlore structure

The main problem in fabrication of relaxor lead magnesium niobate (PMN; Pb(Mg1/3Nb2/3) O3) material is the formation of an undesirable pyrochlore phase (Pb1.86Mg0.24Nb1.67O6.5). This phase significantly impacts the electrical properties of the compound. Therefore, this article presents various experimental trials performed to minimize the formation of the undesirable pyrochlore phase during the preparation of relaxor lead magnesium niobate material. In this regard, a sol-gel pathway was utilized. The synthesis was conducted as follows; niobium ethoxide, metal nitrate and metal acetate were combined with 2-methoxyethanol to form transparent solution. The gel was then formed by heating the solution at 80 °C, to form the precursor powder. Subsequently, thermal treatment at elevated temperatures was performed to form the perovskite structure. The effects of several synthesis conditions such as the presence of surplus Mg2+ ions, excess of Pb2+ ion content, annealing and pre-annealing temperature, type of fuel and the annealing time, on the physicochemical properties and the structure of PMN phase were investigated. Thermal gravimetric analysis (TGA) results manifested that crystallization of PMN was occurred at a temperature of 580 °C. X-ray diffraction (XRD) profiles revealed that the ratio of the pyrochlore (Pb1.86Mg0.24Nb1.67O6.5) phase was significantly reduced by increasing the Mg2+ ion content up to 30%. The lowest concentration of the pyrochlore phase was predestined during a single annealing step at 900 °C for a period of 3 h, using an excess of 30% Mg2+ ion concentration. Rietveld refinement of the XRD data was conducted using Material Analysis Using Diffraction (MAUD) software. The refinement was performed to determine the crystal structure and lattice constants. From the refinement, the cubic structure was evinced with a lattice constant (a) of 4.048Å. Fourier transform infrared (FT-IR) spectroscopy of PMN nano powders annealed at 900 °C for 3 h demonstrated a spectrum characteristic of the most perovskite compounds with a common BO6 oxygen-octahedral structure. Additionally, X-ray photoelectron spectrum (XPS) provided the composition and the chemical states of the prepared PMN compound. Brunauer–Emmett–Teller (BET) surface area analysis revealed that the PMN material exhibited a large specific surface area (155.8 m2/g) with a small average pore radius (2.8 nm). High-resolution transmission electron microscopy (HR-TEM) images indicated that the PMN particles manifested a regular cubic structure with an average particle size of 43 ± 0.1 nm under the optimum conditions. The selected area electron diffraction (SAED) technique proved the polycrystalline nature of the formed ceramic material. From characterization results obtained in this work, this material shows potential candidate for various metrological applications, including piezoceramic for the ultrasonic transducer cores.

Photovoltaic Properties of Bismuth Vanadate/Bismuth Ferrite Heterostructures Prepared by Spin Coating

This study investigates the photovoltaic performance of bismuth vanadate (BiVO₄)/bismuth ferrite (BiFeO₃) heterostructures. By varying the pre-annealing temperature of the BiVO₄ layer, we have achieved the significant enhancement in the open-circuit voltage (Voc) with the spontaneous formation of the polarized Bi4V2O11 interfacial layer. X-ray diffraction analysis confirms a pure rhombohedral distorted perovskite structure for BiFeO₃ and a monoclinic crystallographic nature for BiVO₄. SEM analysis exhibits a porous structure with small spherical grains in the BiVO₄ layer, with the dense and smooth surface of the BiFeO₃ layer. The heterostructures observed in a red-shifted absorption edge are compared with the individual materials, which indicates an improved light absorption. Tauc plot analysis has yielded the direct bandgap values of 1.88 eV and 1.83 eV for the BiVO4 annealing temperatures at 150 and 500 °C, respectively. The overall power conversion efficiency (η) has remained low at 0.003 % and 0.005 %, demonstrating the potential of interfacial engineering to optimize the photovoltaic properties of BiVO₄/BiFeO₃ heterostructures.

Strategies for inhibiting the growth defects of CZTSe thin film

Growth defects are imperfections that appear during crystal formation.It is found that there are particle migration and crystalline phase decomposition behaviors during the crystal growth of CZTSe. By studying different annealing process paths, a selenium-free pre-annealing process strategy was proposed. It has been observed that under the condition of pre-annealing at 350℃ without selenium, the migration behavior of each element can be effectively controlled as the temperature increases. This process facilitates the formation of alloy phases and inhibits the generation of heterophase during the crystallization process. Simultaneously, the low-temperature pre-annealing treatment helps to reduce the decomposition of CZTSe during the annealing process, thereby minimizing defects. The large grains formed can also mitigate the carrier recombination issue caused by grain boundaries. In addition, the impact of pre-annealing temperature on crystallization quality was investigated. It was observed that there is a temperature threshold for enhancing crystallization, which should not exceed 400℃. As a result, the efficiency of the cells prepared using this strategy increased by nearly 50 %.

Employing pre-annealing as a control tool for alloying in CdSeTe/CdTe stacks produced by evaporation in vacuum

Alloying plays a critical role in CdSeTe/CdTe stacks used as absorber structure in high efficiency solar cells. In this study, the effect of pre-annealing between CdSeTe and CdTe on the structural and optical properties of stacks was examined in detail. After the CdSeTe layers (before CdTe) were grown by vacuum evaporation, pre-annealing was applied at moderate temperatures in the range of 200°C–300 °C. According to both XRD patterns and Raman spectra, a clear effect of pre-annealing temperature on alloying ratios and phase formations between CdSeTe and CdTe was ascertained. It was observed from the surface images that the change in pre-annealing temperature affected the grain sizes and morphology, depending on the Se ratios in the alloying. It was found that the transmission spectrum shifted to the long wavelength region with the change in crystallization as a result of pre-annealing. In the PL spectra, the presence of transitions related to the phase structures revealed by the XRD results was detected. In consequence, pre-annealing at 250 °C presented more promising results for potential CdTe cell applications.

Low temperature nitriding behavior in annealed 2205 duplex stainless steel

ABSTRACT Low-temperature gaseous nitriding response of annealed 2205 stainless steel was investigated through a series of nitriding treatments at different temperatures in the range 380–430°C for 25 h. Reflected light microscopy, X-ray diffraction and hardness indentation were utilized to investigate the dependence of the formation of nitrides and cracks on pre annealing temperatures and subsequent nitriding parameters. For most annealing and nitriding conditions applied, the surface adjacent region of the steels was transformed into expanded austenite, or a mixture of expanded austenite and expanded ferrite, supplemented by the presence of iron-based nitrides. Nitriding at a relatively low temperature at a gentle nitriding potential was found to be acceptable as it resulted in a sound nitrided case, where neither chromium nitrides nor cracks developed. Annealing at a relatively low temperature can improve the threshold of nitriding temperature up to 400°C without cracking, while annealing at a high temperature promotes the formation of nitrides.

Optimizing Annealing Temperature Control for Enhanced Magnetic Properties in Fe-Si-B Amorphous Flake Powder Cores

In this study, we examined the optimal pre- and post-annealing conditions for soft magnetic composites (SMCs) using amorphous flake powders produced through ball milling of amorphous Fe-Si-B ribbons, leading to enhanced magnetic properties. The SMCs, which utilized flake powders created via melt spinning, displayed outstanding DC bias characteristics, as well as increased permeability, primarily due to high saturation magnetization and the flaky morphology of the powders. Pre-annealing was performed not only to remove residual stress formed during the melt spinning process but also to improve pulverizing efficiency, which ultimately affected the particle size of the flake powders. Core annealing was performed to reduce core losses and improve permeability by relieving the residual stress generated during the pressing process. As a result, pre-annealing and core annealing temperatures were identified as crucial factors influencing the magnetic properties of the SMCs. We meticulously analyzed the particle size, the morphology of the flake powder, and the magnetic properties of the SMCs in relation to the annealing temperatures. In conclusion, we demonstrated that flake powder SMCs achieved superior soft magnetic properties, including significantly reduced core loss and heightened permeability, through optimal pre- and core-annealing at 370 °C and 425 °C, respectively.

Heterogeneous microstructure design by pre-manipulating ferrite recrystallization in a cold rolled medium Mn steel

The medium Mn steel (MMS), which is regarded as the most representative candidate of the third generation advanced high strength steels, has received widely attention during the last several decades with respect to the exceptional advantage of low cost and excellent strength-ductility properties. In this study, a microstructural strategy of developing heterogeneous microstructures in a cold rolled MMS is presented. By pre-manipulating occurrence of the ferrite recrystallization, both the lamellar-shaped and granular-shaped ultra-fine retained austenite can be obtained after the two-step intercritical annealing process. Various amounts of recrystallized ferrite and difform martensite can be obtained by adjusting the pre-annealing temperature, which can effectively contribute to producing the two types of heterogeneous retained austenite, i.e., lamellar and granular in the following annealing process. The heterogeneous-structured retained austenite enables an excellent strength–ductility combination and reduced Lüders strain in the cold-rolled MMS.

The influence of annealing temperature on NH3-SCR performance of CexZr1-x/UiO-66 bimetal MOFs

MOFs possess large surface area and high porosity, but they will convert into derivatives when subjecting to high temperature due to its poor thermal stability. Herein, a series of Ce-Zr bimetal MOFs derivatives were prepared by directly pre-annealing of CexZr1−x/UiO-66 bimetal MOFs at different temperatures under air atmosphere. The as-prepared samples were used as catalysts for selective catalytic reduction of NOx with NH3. The catalytic activity test results indicated that pre-annealing temperature had an obvious promoting effect on NH3-SCR performance. C0.5Z0.5/U-400 catalyst achieved a NOx conversion of 92% at 350 ºC and a complete N2 selectivity in a wide temperature range of 150–500 ºC. Various characterization tools were employed to reveal the effects of pre-annealing temperature on the microstructure and chemical properties of C0.5Z0.5/U bimetal MOFs and its derivatives. The pre-annealing treatment could lead to a distinctive decrease in specific surface area, demonstrating that C0.5Z0.5/U bimetal MOFs gradually converted into derivatives and there was an obvious agglomeration phenomenon between derived metal oxides. But a relatively large specific surface area and fluffy porous microstructure could be obtained for pre-annealing C0.5Z0.5/U at 400 ºC for 2 h. It was conducive to exposure of more active sites, thus enhancing catalytic performance. Moreover, C0.5Z0.5/U-400 catalyst not only possessed a higher Ce3+/(Ce3+ + Ce4+) ratio and a better reduction ability, but also had more abundant oxygen vacancies to adsorb and activate reactant gases. In-situ DRIFTS results indicated that NH3-SCR reactions over C0.5Z0.5/U-400 catalyst followed both E-R and L-H mechanisms.

Performance optimization of nanometer-thin indium-tin oxide transistors by two-step air annealing

In this study, the influence of air annealing on nanometer-thin indium tin oxide (ITO) transistors was investigated. Compared with unannealed devices, the field-effect mobility and subthreshold swing of ultrathin ITO transistors with pre-annealing, post-annealing, and two-step annealing were greatly improved. Under a pre-annealing temperature at 200 °C and post-annealing temperature at 100 °C, the ultra-thin ITO transistors showed field-effect mobility of 34.2 cm2/Vs, steep subthreshold swing of 1.95 V/decade, and high Ion/Ioff ratio of 2.46 × 107. X-ray photoelectron spectroscopy revealed that the performance changes could be ascribed to the changes in the oxygen vacancies in the ITO channel under different annealing conditions. The dependence of subthreshold swing on the annealing process may be related to the absorption and release of water molecules from the ultrathin ITO surface. Overall, these results emphasize the importance of the annealing procedures for nanometer-thin ITO transistors.

Improved stress relaxation stability of a heat-resistant Al-Cu-Mg-Ag alloy with good mechanical properties by a pre-annealing/solution-aging treatment

Good stress relaxation stability enables heat-resistant aluminum alloys to serve well at high temperatures. From the viewpoint of simultaneous regulation of microstructure and precipitates, a deliberate pre-annealing (200–400 ℃) followed by solution-aging (T6) treatment was proposed to improve the stress relaxation stability of an Al-Cu-Mg-Ag heat-resistant aluminum alloy in this work. A peak effect on the stress relaxation stability was found with a pre-annealing temperature of 325 ℃, which is associated with larger-sized grains and finer-sized precipitates of the alloy. This interesting peak phenomenon is attributed to a good balance of recrystallization and precipitation. Moreover, the regulated microstructure surprisingly assisted the 325 ℃ pre-annealing+T6 treated alloy with good tensile properties. The proposed heat treatment method provides a route for developing high-performance heat-resistant aluminum alloys.

Pre-annealing for improved LPCVD deposited boron-doped poly-Si hole-selective contacts

We demonstrate the beneficial effect of a pre-annealing step prior to the boron diffusion on passivation and contact resistivity of industrially LPCVD deposited poly-Si/SiOX hole-selective contacts. We investigate the influence of the pre-annealing temperature on passivation quality, measured as implied open-circuit voltage and recombination current density, and on changes in crystallinity, characterized by Raman spectroscopy. A clear increase in passivation quality is observed on planar and textured surfaces as well as for various poly-Si thicknesses (100–230 nm) and thermal SiOX growth temperatures (600–800 °C). On planar surfaces and without the use of atomic hydrogenation, we report an increase in iVOC of around 5 mV with every additional increase of pre-annealing temperature by 50 °C (>900 °C) leading to an iVOC of 720 mV (J0 = 9.3 fA/cm2). After atomic hydrogenation, the effect of the pre-annealing is less pronounced. Nevertheless a gain in iVOC (reduction in J0) of 5–10 mV (2–5 fA/cm2) is achieved when comparing samples without pre-annealing with samples after a pre-annealing at 1050 °C. On textured surfaces on the other hand, this trend is more pronounced after atomic hydrogenation, for which a pre-crystallisation at 1050 °C leads to an iVOC (J0) of 705 mV (16.8 fA/cm2), which is a gain (reduction) of 24 mV (21.7 fA/cm2) compared to samples without a pre-annealing step.

Enhancement of phase transition properties of ultrathin VO2 thin films on microsphere array by vacuum thermal pre-annealing

Vanadium dioxide (VO2) thin films were fabricated on SiO2 microsphere array surface by vacuum thermal pre-annealing and rapid thermal oxidization annealing of magnetron sputtering vanadium films. The effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin films were investigated. The resistance transition ranges of phase transition are improved from 7.58 to 10.23 as the increasing of vacuum thermal pre-annealing temperature. The phase transition temperature decreases and the width of thermal hysteresis loop keeps constant. We analyzed the effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin film in the light of vanadium thin film shrinking effects. The results are important for fabrication of ultrathin VO2 film on microsphere array and application in optical regulation field.

Effect of pre-annealing of Mo foil substrate on CZTSSe thin films and Mo(S,Se)2 interface layer

Cu2ZnSn(S,Se)4 (CZTSSe) thin film deposited on flexible Mo foil substrate has advantage of high mass specific power and good ductility. However, a thick Mo(S,Se)2 interface layer is easily to be formed between CZTSSe and Mo foil substrate. The ohmic contact property of CZTSSe/Mo is deteriorated by the formation of Mo(S,Se)2. In this work, the Mo foil substrate was pre-annealed to inhibit the growth of Mo(S,Se)2 interface layer. CZTSSe thin films were prepared on the pre-annealed Mo foil substrate by sol-gel and selenization methods. The pre-annealing treatment of Mo foil substrate leads to the oxidation of Mo. During the high temperature selenization process, the MoOx acts as a buffer layer to suppress the formation of the Mo(S,Se)2 interface layer. With the increase of the pre-annealing temperature of the Mo foil substrate, the thickness of the Mo(S,Se)2 interface layer decreases, and the resistance of CZTSSe/Mo(S,Se)2/Mo structure decreases. The ohmic contact properties of CZTSSe/Mo can be improved by the pre-annealing treatment of metal Mo foil substrates.

Characterization of c-oriented BaFe12O19 films synthesized by ion beam deposition on Al2O3 (102) substrate

In this work, textured c-oriented BaFe12O19 films were synthesized by ion-beam deposition on Al2O3 (102) substrates. The texturing of the films was achieved by special deposition regime, based on the periodic interruptions of the process. These interruptions promoted spontaneous formation of (00 l) nuclei on the surface. After resumption of deposition these surface nuclei covered with next portion of the material. During the next break in deposition, nuclei (00 l) are again formed on the surface. By the end of the process, the entire volume of the film is filled with such nuclei; therefore, after crystallization annealing, the films become textured. It was found that the duration of pauses in the deposition affects the microstructure of hexaferrite and the optimal value of the time interval is proposed. To further increase the texture degree of the films, it was proposed to introduce the operation of preliminary annealing into the synthesis process. It was established that with an increase in the pre-annealing temperature from 300 to 900°C, the saturation magnetization, residual magnetization, and coercive force change nonmonotonically with a maximum at 500 °C. The microstructure of the film surface was also affected by the pre-annealing regime. An explanation for these effects is proposed and associated with the formation of the α-Fe2O3 (102) interlayer and the diffusion of aluminum from substrate to the film. The X-ray diffraction patterns of the obtained films do not differ, and all reflexes of hexaferrite are represented by the {00 l} set.

Shape memory effect in metallic glasses

Shape memory effect in metallic glasses

INFLUENCE OF STRUCTURAL FEATURES OF ZNO FILMS ON OPTICAL AND PHOTOELECTRIC CHARACTERISTICS OF INVERTED POLYMER SOLAR ELEMENTS

In this work we investigated the effect of preliminary annealing of zinc acetate solution films on the morphology, structure, optical properties of the formed ZnO films and also on the photovoltaic properties of polymer solar cells based on the obtained ZnO films. It was found that the pre-annealing temperature significantly affects the morphology and structure of the obtained ZnO films. At pre-annealing temperatures below 200 oC the films have a strongly relief morphology (wrinkled morphology), while at pre-annealing temperatures above 200 oC the surface morphology of the films is smooth. The relief of ZnO films affects the photocurrent density of solar cells. Cells based on ZnO films with wrinkled morphology showed a higher photocurrent compared to smooth morphology, which is due to strong light scattering and, as a result, the optical path of light in the photoactive layer is increased due to multiple reflection of light in the wrinkled structure of ZnO. In addition, with increasing pre-annealing temperature, the photovoltage of solar cells and the rate of recombination of charge carriers increases, but the diffusion coefficient of charge carriers decreases, which indicates an increase in the density of defects in the crystal lattice of ZnO. Thus, it has been shown that smooth or highly relief thin ZnO films with controlled properties can be obtained from a zinc acetate solution.

Growth of AZTSe thin films by rapid thermal processing and numerical simulation of p-CZTSe/n-AZTSe thin film heterojunction

In this work, we adopted a rapid thermal processing (RTP) for selenization and studied the influence of selenization time on vacuum evaporated multi-stacked precursor’s to form Ag2ZnSnSe4 (AZTSe) thin films. The RTP selenization temperature, pre-annealing temperature and pre-annealing time were optimized in our previous study on Ag2ZnSnSe4 films and found to be 400 °C, 250 °C and 20 min, respectively. From energy-dispersive X-ray (EDX) study, the Ag/(Zn + Sn), Zn/Sn, and Se/metals ratios are observed to vary in the range (0.81–0.99), (1.13–1.62), and (1.03–0.94) with an increase in selenization time from 1 to 5 min, respectively. The multi-stacked thin films selenized at 400 °C for 1 min was found to be nearly stoichiometric. The photoelectron spectroscopic analysis reveals that the elements Ag, Zn, Sn, and Se exhibit + 1, + 2, + 4, and -2 oxidation states, respectively. The X-ray diffraction (XRD) study shows the formation of single-phase AZTSe with (112) plane as a strong orientation for 1-min RTP selenization. Morphological studies reveal the growth of larger grains with a mean grain size of ~ 0.5 µm. It was observed that the AZTSe thin film grown with 1-min RTP selenization has an optical band gap of 1.37 eV. These films have electrons as a majority charge carrier (n-type) with highest mobility and resistivity values of 79.4 cm2(Vs)−1 and 2.61 × 104 Ωcm, respectively. The numerical simulation was carried out on p-CZTSe/n-AZTSe-based solar cells with the obtained experimental data of AZTSe films in the present study using Solar Cell Capacitance Simulator (SCAPS-1D) software, and it shows the maximum power conversion efficiency (ƞ) of 16.84%.

Cobalt Sulfide as Photoelectrode of Photoelectrochemical Hydrogen Generation from Water

This study aimed to synthesize and characterize cobalt sulfide deposited on FTO by hydrothermal method and investigate its photoelectrochemical (PEC) water splitting performance. Cobalt sulfide thin films were produced by annealing at two different temperatures, namely, 400 and 500 °C. X-ray diffraction (XRD) and Fourier transform Raman spectroscopy were used to characterize the phase structure. Scanning electron microscopy was used to observe the morphology. Ultraviolet-visible spectroscopy and linear sweep voltammetry analyses were used to determine the thin-film band gap and evaluate the PEC water splitting performance, respectively. From the XRD and Raman analyses, all the samples produced consisted of mixed phases of Co3S4 and Co9S8. However, each sample contained different percentage phases. The sample annealed at 400 °C contained more Co9S8, whereas that annealed at 500 °C contained comparable amounts of Co3S4 and Co9S8. The morphologies of pre-annealed samples showed vertical flakes with diameters around 200-250 nm and flake thickness around 25-50 nm. When the temperature was increased from pre-annealing temperature to 400 and 500 °C, several flakes were destructed and formed spherical-like clusters. The Tauc plot from absorption analysis showed that the samples annealed at 400 and 500 °C produced similar band gaps at ~2.0 eV. The PEC performance analysis results show that annealing at 400 °C produced the highest photocurrent density of 10 μA/cm2 at a potential of -0.7 V.

Spin-coated hbox {Cu}_2hbox {ZnSnS}_{4} solar cells: A study on the transformation from ink to film

In this paper, we study the DMSO/thiourea/chloride salt system for synthesis of pure-sulfide hbox {Cu}_2hbox {ZnSnS}_{4} (CZTS) thin-film solar cells under ambient conditions. We map out the ink constituents and determine the effect of mixing time and filtering. The thermal behavior of the ink is analyzed, and we find that more than 90% of the solvent has evaporated at 250,^{circ }hbox {C}. However, chloride and sulfoxide species are released continually until 500,^{circ }hbox {C}, suggesting the advantage of a higher pre-annealing temperature, which is also commonly observed in the spin-coating routines in literature. Another advantage of a higher pre-annealing temperature is that the worm-like pattern in the spin-coated film can be avoided. We hypothesize that this pattern forms as a result of hydrodynamics within the film as it dries, and it causes micro-inhomogeneities in film morphology. Devices were completed in order to finally evaluate the effect of varying thermal exposure during pre-annealing. Contrary to the previous observations, a lower pre-annealing temperature of 250,^{circ }hbox {C} results in the best device efficiency of 4.65%, which to the best of our knowledge is the highest efficiency obtained for a pure-sulfide kesterite made with DMSO. Lower thermal exposure during pre-annealing results in larger grains and a thicker hbox {MoS}_2 layer at the CZTS/Mo interface. Devices completed at higher pre-annealing temperatures display the existence of either a Cu-S secondary phase or an incomplete sulfurization with smaller grains and a fine-grain layer at the back interface.

High‐Efficiency CsPbI2Br Perovskite Solar Cells with Dopant‐Free Poly(3‐hexylthiophene) Hole Transporting Layers

AbstractCsPbI2Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI3, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI2Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI2Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI2Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.