Β-phase Structure Research Articles

Facile synthesis and characterization of Cu2Se thin films and self-powered p-Cu2Se/n-Si heterojunction with high-performance photoresponse

A facile, cost-effective, and scalable chemical vapor deposition technique was used to synthesize p-type Cu2Se thin films on glass and n-type Si substrates. Thorough characterization confirmed the films’ β-phase structure with the correct stoichiometric ratio and exceptional crystalline quality, exhibiting behavior akin to a degenerate semiconductor. Measurements unveiled a work function of 4.83 eV and a bandgap of 2.13 eV for Cu2Se. The fabrication of a p-Cu2Se/n-Si heterojunction was achieved by depositing the p-type Cu2Se thin film onto the n-type Si substrate. The resulting heterostructure displayed rectification behavior, and its energy band diagram resembled a Schottky diode. Further exploration into its photoelectric properties showcased the p-Cu2Se/n-Si heterostructure’s favorable self-powered attribute, characterized by fast, steady, reproducible, sensitive, and robust photoresponsive performance. Consequently, it proves highly suitable for applications in high-frequency photodetectors. Additionally, the p-Cu2Se/n-Si heterojunction’s photovoltaic power conversion efficiency exceeded the reported values of the CuO/Si and Cu2O/Si systems. Here, this study contributes significantly to the pivotal evaluation of p-Cu2Se/n-Si heterostructures for promising optoelectronic applications.

Design and application research of a flexible array plantar sensor based on P(VDF-TrFE)/SnO2NPS/GR for Parkinson’s disease diagnosis

ABSTRACT This paper introduces a flexible array Plantar sensor fabricated through the high-voltage electrospinning process of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ，incorporating stannic oxide nanoparticles （SnO2NPS）and graphene (GR) composite nanofilm. The surface morphology, β-phase crystal content, piezoelectric performance, composition, and structure of the composite piezoelectric films were evaluated using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and a vibration platform. Experimental findings reveal that P(VDF-TrFE)/SnO2NPS/GR composite films containing 5% SnO2NPS and 0.1% GR exhibit superior open-circuit voltage and short-circuit current, measuring 22.43 V and 12.95 uA, respectively. These values are approximately 1.59 times and 1.34 times higher than those of the 5% P(VDF-TrFE) composite film and about 2.37 and 2.16 times higher than those of pure P(VDF-TrFE). A flexible piezoelectric sensor was fabricated using this composite film, and the mechanical properties and electrical impedance behavior of the sensor were investigated and analyzed.A multi-channel foot pressure collection and classification system was established based on this sensor, and a Parkinson’s disease machine learning model for multi-channel foot pressure collection was investigated. Various machine learning models for Parkinson’s disease were compared, and a fine K Nearest Neighbors（KNN） Parkinson’s disease classification model with an accuracy of 97.1% was proposed. This offers a novel solution for Parkinson’s disease diagnosis and holds significant reference value.

Microstructure and Physico-Mechanical Properties of Biocompatible Titanium Alloy Ti-39Nb-7Zr after Rotary Forging

The evolution of microstructure, phase composition and physico-mechanical properties of the biocompatible Ti-39Nb-7Zr alloy (wt.%) after severe plastic deformation by rotary forging (RF) was studied using various methods including light optical microscopy, scanning and transmission electron microscopies, X-ray diffraction, microindentation, tensile testing and investigation of thermophysical properties during continuous heating. The hot-rolled Ti-39Nb-7Zr with initial single β-phase structure is subjected to multi-pass RF at 450 °C with an accumulated degree of true deformation of 1.2, resulting in the formation of a fibrous β-grain structure with imperfect 500 nm subgrains characterized by an increased dislocation density. Additionally, nano-sized α-precipitates formed in the body and along the β-grain boundaries. These structural changes resulted in an increase in microhardness from 215 HV to 280 HV and contact modulus of elasticity from 70 GPa to 76 GPa. The combination of strength and ductility of Ti-39Nb-7Zr after RF approaches that of the widely used Ti-6Al-4V ELI alloy in medicine, however, Ti-39Nb-7Zr does not contain elements with limited biocompatibility and has a modulus of elasticity 1.5 times lower than Ti-6Al-4V ELI. The temperature dependences of physical properties (elastic modulus, heat capacity, thermal diffusivity) of the Ti-39Nb-7Zr alloy after RF are considered and sufficient thermal stability of the alloy up to 450 °C is demonstrated.

Developing strong-yet-ductile light-weight medium-entropy alloy via the unusual oxide doping effect

High or medium entropy alloys (M/HEAs) possess outstanding mechanical and thermal properties, but their high mass density severely restricts their practical applications. In this study, we designed a novel light-weight MEA based on the TiAlCrNb-x(ZrO2) system. These ZrO2 particles doped can completely dissolve in the β-phase structure of the TiAlCrNb MEA, which contrasts with conventional ceramic strengthening introduced through powder metallurgy. Consequently, it promotes the formation of Ti3Al nanoparticles and simultaneously substantially reduces grain size, thereby achieving a remarkable strength-ductility combination with a high specific yield strength of 225/250 MPa/(g·cm−3) while maintaining an excellent tensile ductility of 19.5/10.1% in the newly designed TiAlCrNb-(1.2/1.5)(ZrO2) MEAs. This performance outperforms most other light-weight M/HEAs. Strengthened mechanisms analysis indicates that the strength increment is attributed to grain-refinement-induced Hall-Petch strengthening and solid-solution strengthening from the dissolved oxygen. The results offer insight into the innovative design of ultrastrong and ductile light-weight MEAs for advanced structural applications.

Effect of Poling on β-Phase Structure of Electrospun PVDF-TrFE Nanofiber Film

Effect of Poling on β-Phase Structure of Electrospun PVDF-TrFE Nanofiber Film

Ionic thermoelectric effect in Cu2-δSe during phase transition

The ionic Seebeck coefficient was studied in copper selenide with Cu1.99Se, Cu1.95Se and Cu1.8Se stoichiometry which was synthesized with a melt crystallization method. To measure the ionic Seebeck coefficient of copper ions, 0.15C6H12N4CH3I + 0.85CuI solid-state electrolyte was prepared. Electrolyte layers were pressed with copper selenide powder into a sandwich-like structure. At the temperature of 410 K, the materials have ionic Seebeck coefficient values close to each other, about 1100 μV/K. In the case of β-phase structure (Cu1.8Se material), changes in the measured Seebeck coefficient were observed—with decreasing temperature, the ionic thermopower firstly increased reaching about 1230 μV/K and then decreased to 950 μV/K at 355 K. In the Cu1.99Se material, a phase transition to the α-phase was observed during cooling. The ionic Seebeck coefficient values gradually increased from 1030 to 1220 μV/K at 370 K, when the material is in the low-temperature phase. The measured difference between the ionic thermopower of the two phases well matches calculations based on the entropy of the transition (presence part of the Seebeck coefficient) and different activation energies of ionic transport (transport part).Graphical abstract

Heteroepitaxial growth of β-Ga2O3 thin films on single crystalline diamond (111) substrates by radio frequency magnetron sputtering

In this work, we demonstrate the first achievement in heteroepitaxial growth of β-Ga2O3 thin films on single crystalline diamond (111) wafers using RF magnetron sputtering. A single monoclinic (β-phase) structure with a monofamily {01} plane was obtained. XRD pole figure shows (02) and (002) textures of the (01) β-Ga2O3 plane parallel to (111) diamond with six distinct rotational domains, confirming successful epitaxial growth. Collectively, this research provides valuable insights into the epitaxial growth of β-Ga2O3 on diamond via sputtering, paving the way for scalable β-Ga2O3/diamond heterostructures for future electronic and optoelectronic applications with not only high performance but also effective self-thermal management.

Photocatalytic degradation of malachite green using PVDF membranes doped with Fe3O4 nanoparticles: role of porosity and surface roughness

We report on a cost-effective and time-efficient approach to synthesize flexible membranes of polyvinylidene fluoride (PVDF) doped with varying concentrations of Fe3O4 nanoparticles (FNP). The membranes exhibit a uniform dispersion of FNPs, a β-phase structure, and porous morphology, as confirmed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements. Fourier Transform-Infra Red (FTIR) and x-ray Photon spectroscopy (XPS) analysis was also performed for the identification of structural and chemical parameters of PVDF:FNP membranes. Photocatalytic degradation of malachite green (MG) dye under ultraviolet (UV) irradiation was assessed using the PVDF:FNP membranes. The results demonstrate a significant enhancement in the degradation efficiency and rate constant of the photocatalytic process with the utilization of PVDF:FNP membranes compared to FNP alone. Among the various concentrations tested, the PVDF membrane with 7% FNP doping exhibited the highest degradation efficiency of 98.39% and a notable apparent rate constant of 0.07048 min−1 in 60 min. The improved photocatalytic performance can be attributed to the larger surface area and enhanced accessibility of active sites in PVDF:FNP membranes, facilitating better control of the reaction environment and reducing the recombination rate of electron–hole pairs. This study suggests that PVDF:FNP membranes hold great promise for water purification applications, offering flexible membranes with superior degradation efficiency and enhanced reusability.

Alkali-Induced Phase Transition to β-Spodumene along the LiAlSi2O6-LiAlSi4O10 Join

Due to the refractory nature of α-spodumene (LiAlSi2O6) and petalite (LiAlSi4O10), two major lithium minerals, conventional lithium recovery processes involve a high-temperature pre-treatment (>1000 °C) to induce a phase transition to tetragonal β-spodumene, an open structure allowing easier access to lithium through ion exchange. Considering that these high temperatures are not dictated by thermodynamics but rather sluggish kinetics, the study investigates the mechanisms enhancing the rate of transformation to β-spodumene at lower temperatures while minimizing the growth of metastable hexagonal β-quartz typically observed at the onset of the conversion. The heat treatment of natural α-spodumene revealed that rapid growth of β-spodumene veinlets is achieved at ≤600 °C by activation of alkali-rich fluid inclusions, through a dissolution–recrystallization process. For petalite, the mechanism of the phase transition, initiated at ≈750 °C is a solid-state transformation keeping crystallographic coincidence with the mineral host. Synthetic growth experiments along the LiAlSi2O6-LiAlSi4O10 join indicate a compositional dependence on the resulting β-phase structure, where minor sodium doping strongly favors β-spodumene, as the tetrahedral framework of β-quartz does not allow the extent of deformation to accommodate the larger alkali. These findings open opportunities for energy-efficient lithium recovery pathways where the phase transition and ion exchange can be achieved simultaneously without a high-temperature pre-treatment.

Study on Enhancing the Thermoelectric Stability of the β-Cu2Se Phase by Mn Doping.

Cu2Se is a promising thermoelectric (TE) material due to its low cost, Earth abundance, and high thermoelectric properties. However, the biggest problem of Cu2Se is its unstable chemical properties. In particular, under the action of an electric field or gradient temperature field, the chemical potential of copper ions inside the material increases. When the external field is strong enough, the chemical potential of copper ions at the negative end of the material reaches the chemical potential of elemental copper. Under these conditions, copper ions must precipitate out, causing Cu2Se to be unstable, and making it unsuitable for use in applications. In this study, we prepared Cu2-xMnxSe (x = 0, 0.02, 0.04 and 0.06) series bulk materials by vacuum melting-annealing and sintered by spark plasma sintering (SPS). We investigated the effects of Mn doping on the composition, microstructure, band structure, scattering mechanism, thermoelectric properties, and stability of Cu2Se. The results show that Mn doping can adjust the carrier concentration, promote the stabilization of the β-phase structure and improve the electrical properties of Cu2Se. When x = 0.06, the highest power factor (PF) value of Cu1.94Mn0.06Se at 873 K was 1.62 mW m-1 K-2. The results of carrier scattering mechanism analysis based on the conductivity ratio method show that the sample doped with Mn and pure Cu2Se had the characteristics of ionization impurity scattering, and the scattering factor was 3/2. However, the deterioration in thermal conductivity was large, and a superior zT value needs to be obtained. The cyclic test results of high-temperature thermoelectric properties show that Mn doping can hinder Cu+ migration and improve its thermoelectric stability, which preliminarily verifies the feasibility of using the stable zirconia mechanism to improve the thermoelectric stability of Cu2Se.

Effect of Cold Drawing and Annealing in Thermomechanical Treatment Route on the Microstructure and Functional Properties of Superelastic Ti-Zr-Nb Alloy.

In this study, a superelastic Ti-18Zr-15Nb (at. %) alloy was subjected to thermomechanical treatment, including cold rotary forging, intermediate annealing, cold drawing, post-deformation annealing, and additional low-temperature aging. As a result of intermediate annealing, two structures of β-phase were obtained: a fine-grained structure (d ≈ 3 µm) and a coarse-grained structure (d ≈ 11 µm). Cold drawing promotes grain elongation in the drawing direction; in a fine-grained state, grains form with a size of 4 × 2 µm, and in a coarse-grained state, they grow with a size of 16 × 6 µm. Post-deformation annealing (PDA) at 550 °C for 30 min leads to grain sizes of 5 µm and 3 µm, respectively. After PDA at 550 °C (30 min) in the fine-grained state, the wire exhibits high tensile strength (UTS = 624 MPa), highest elongation to failure (δ ≥ 8%), and maximum difference between the dislocation and transformation yield stresses, as well as the highest superelastic recovery strain (εrSE ≥ 3.3%) and total elastic + superelastic recovery strain (εrel+SE ≥ 5.4%). Additional low-temperature aging at 300 °C for 30-180 min leads to ω-phase formation, alloy hardening, embrittlement, and a significant decrease in superelastic recovery strain.

Effects of aluminum and oxygen additions on quenched-in compositional fluctuations, dynamic atomic shuffling, and their resultant diffusionless isothermal [formula omitted] transformation in ternary Ti–V-based alloys with bcc structure

Diffusionless isothermal ω transformation is a recently discovered ω transformation that occurs isothermally during aging near room temperature in Ti alloys with a bcc (β-phase) structure. Unlike conventional displacive phase transitions, the diffusionless isothermal ω transformation occurs in locally unstable nanoscale β-phase regions formed by quenched-in statistical compositional fluctuations. In the present study, the effects of Al and oxygen additions in ternary β-phase Ti–V-based alloys on the diffusionless isothermal ω transformation and its attempt process, called dynamic atomic shuffling, were studied. Elastic constant and internal friction measurements for Ti–16.6V–2.1Al and Ti–17.5V–2.5O (at.%) alloy single crystals and analysis of quenched-in compositional fluctuations using the thermodynamic theory of fluctuations indicated that the oxygen addition increases the β-phase stability, and it selectively increases the activation energy of dynamic atomic shuffling in locally unstable Ti-rich regions, which is caused by the strong attractive interaction between Ti and oxygen elements. As a result, oxygen addition suppresses the diffusionless isothermal ω transformation that occurs during aging at 298 K. In contrast, low β-phase stability, which promotes ω-phase nucleation, is retained by Al addition. Furthermore, dynamic atomic shuffling with a low activation energy is retained even though the average activation energy is enhanced by the Al addition, originating from the relatively weak atomic interaction between Ti and Al. Therefore, the diffusionless isothermal ω transformation cannot be suppressed by Al addition.

Temperature dependent intercalation of molten 1-hexadecanol into Brodie graphite oxide

Intercalation of very long molecules into the structure of multi-layered graphene oxide (GO) was studied using example of 1-hexadecanol (C16), an alcohol molecule with 16 carbon atoms. Brodie graphite oxide (BGO) immersed in excess of liquid C16 just above the melting point shows expansion of c-unit cell parameter from ∼6 Å to ∼48.76 Å forming a structure with two densely packed layers of C16 molecules in a perpendicular orientation relative to the GO planes (α-phase). Heating of the BGO-C16 α-phase in excess of C16 melt results in reversible phase transition into β-phase at 336–342K. The β-phase shows much smaller unit cell parameter of 29.83 Å (363K). Analysis of data obtained using vacuum-driven evaporation of C16 from the β-phase provides evidence for structure of β-phase consisting of five layers of C16 molecules in parallel to GO plane orientation. Therefore, the transition from α-to β-phase corresponds to change in orientation C16 molecules from perpendicular to parallel relative to GO planes and decrease in the amount of intercalated solvent. Cooling of the β-phase in absence of C16 melt is found to result in the formation of γ-phase with inter-layer distance of ∼26.5 Å corresponding to one layer of C16 molecules intercalated perpendicularly relative to the GO planes. Structures with one and two layers of C16 molecules parallel to GO planes were identified in samples with rather small initial loading of C16. Surprisingly rich variety of structures revealed in the BGO-C16 system provides opportunities to create materials with precisely controlled GO inter-layer distance.

Thermal Decomposition of Magnesium Borohydride: New Insights from Synchrotron X-ray Scattering

Magnesium borohydride [Mg(BH4)2] has been extensively investigated as a promising material with applications in energy storage, having properties favorable for both hydrogen and electrochemical storage processes. Recent efforts regarding hydrogen storage to determine conditions optimal for dehydrogenation and hydrogenation have focused on identifying environmental factors that promote various polyborane intermediate pathways. In the present study, we demonstrate the impact of the synthesis route, residual impurities, sample processing, and starting crystalline phase on the structural transformations and decomposition pathways of Mg(BH4)2. Using synchrotron powder X-ray diffraction (PXRD) and small-angle X-ray scattering (SAXS), we provide evidence of the residual dimethyl sulfide solvent coordinated inside the pores of γ-Mg(BH4)2 even after post-synthetic de-solvation. In situ temperature-resolved PXRD and temperature programed desorption (TPD) indicate that these impurity molecules are removed by heating to 100 °C in vacuo. Furthermore, when γ-Mg(BH4)2 is heated slowly under vacuum, we observe a γ- to α-phase transformation in place of the ε-Mg(BH4)2 “intermediate” structure, which provides a direct connection between the α- and γ-Mg(BH4)2 decomposition pathways. At higher temperatures (∼150 °C), Mg(BH4)2 transitions to the well-known β-phase structure. Although XRD results suggest that the crystalline structures of β-Mg(BH4)2 are identical regardless of the starting material, SAXS and transmission electron microscopy indicate that when the γ-phase is used as the starting structure, the resulting β-Mg(BH4)2 material exhibits intergranular (i.e., skeletal) porosity, not observed when annealed from the α-phase. These variations of the microstructure may contribute to differences in dehydrogenation mechanisms observed in TPD data among the three currently existing “as-synthesized” Mg(BH4)2 structural phases.

Structure dependent piezoelectricity in electrospun PVDF-SiC nanoenergy harvesters

Piezoelectric materials are undeniably one of the most critical advanced materials in the modern era that can be used as energy harvesters and sensors. In many of these applications, flexibility is a key factor in guaranteeing the proper performance and durability of the device. Polyvinylidene fluoride (PVDF) is a structure-dependent piezoelectric polymer that can provide the required flexibility and piezo-response in its electroactive β-phase structure. The present research aims to investigate the effect of SiC additive and process parameters on the β phase formation in electrospun PVDF fibers. For this purpose, PVDF/SiC nanocomposites were prepared by the electrospinning method, and the effects of PVDF solution concentration, SiC wt%, and electrospinning voltage on β-phase fraction were studied using response surface methodology (RSM) approach for experimental design. The uniform and bead-free morphology of the fibers was observed using scanning electron microscopy (SEM). The results showed that the highest β content could be obtained at low PVDF concentrations, high electrospinning voltage and high SiC wt%. The dominant crystalline phase was determined by XRD analysis, and the β-phase fraction in nanocomposites containing different SiC loadings was estimated using FTIR spectroscopy. The presence of SiC nanoparticles enhanced the piezoelectric behavior of PVDF/SiC nanocomposites due to the higher β-phase fraction and improved charge transfer in the vicinity of semiconductive SiC nanoparticles. The optimum sample containing 3.98 wt% SiC nanoparticles was composed of 95.9% β-phase and showed a normalized piezoelectric sensitivity of 0.4737 mV/N, which was improved by about 350% compared to pure PVDF fibers. The obtained results show that PVDF/SiC nanocomposite fibers can be a promising choice for nanoenergy harvesters or flexible sensors with high sensitivity to small external loads. • RSM optimization was performed on the fabrication process of PVDF-SiC fibers. • β fraction was increased with voltage and SiC wt% and decreased with PVDF concentration. • PVDF-SiC nanocomposite fibers generate a significant output voltage upon loading. • 350% increase was observed in piezoelectric sensitivity of optimized PVDF-SiC fibers. • The piezoresponse enhancement was due to higher β fraction and better charge transfer in the vicinity of SiC nanoparticles.

High-Aligned PVDF Nanofibers with a High Electroactive Phase Prepared by Systematically Optimizing the Solution Property and Process Parameters of Electrospinning

Poly(vinylidene fluoride) (PVDF)-electrosprayed nanofibers have been the subject of much research due to their flexibility and piezoelectric properties compared to other piezoelectrics, for example, ceramics or other polymeric materials. The piezoelectric performance of PVDF is mainly related to the presence of β-phase. This study aims to determine the influence of working and formulation parameters on the generation of β-phase, morphology, and crystal structure of PVDF nanofibers. In addition, this research innovatively analyzes the effect of the dispersion state of PVDF molecular chains in the solvent on the electrospinning results. The morphology and crystal structure of PVDF nanofibers were determined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). Beadless nanofibers are obtained when the PVDF concentration reaches the semi-diluted regime entangled in dimethylformamide (DMF) or DMF/acetone solution. The optimization of the process parameters (static collector, tip to collector distance—25 cm, flow rate—1 mL/h, applied voltage—20 kV) allows the increase in the β-phase fraction from 68.3% ± 1.2% to 94.5% ± 0.6% for a PVDF concentration of 25 w/v% in a DMF/acetone mixture (2/3 v/v). With these same parameters applied to a rotating collector, it was observed that the piezoelectric performance is at maximum for a maximum β-phase fraction of 90.6% ± 1.1%, obtained for a rotational speed of 200 rpm. The effect of orientation of PVDF nanofibers on piezoelectric properties was quantitatively discussed for the first time; the piezoelectric properties are independent of the alignment of the nanofibers.

Atomic-scale characterization of structural damage and recovery in Sn ion-implanted β-Ga2O3

β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ-phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ-Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ-phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability.

Synthesis of nanostructure Ta2O5 coatings using plasma reactive sputtering technique for optical filter application

Titanium bentoxide Ta2O5 deposited on glass substrates by were heated to 400 °C for 1, 2 and 6 hours. The as-deposited Ta2O5 films deposited by DC reactive sputtering show amorphous structure, the structure improved to crystalline after increasing annealing temperature. When the annealing time rises to 6 hours, Ta2O5 films with β-phase structure was obtained. The basic and optical properties of arranged films have been considered utilizing XRD and UV-Visible spectroscopy. The XRD comes about appeared that all films are polycrystalline in nature with orthorhombic structure and favored introduction along (0140) plane. The crystallite size was calculated using Scherrer formula and it is found that the 2 hrs sputtering time, 3Kv, 10Amp and 4×10-2mbar. Maximum crystallite size was (27.5nm). The absorbance and transmittance spectra have been recorded in the wavelength extend of (300-1000) nm in arrange to think about the optical properties. The optical energy gap for permitted direct electronic move was calculated using Tauc condition with regard to vitality of photon. It is found that the band gap increases with increasing annealing times and its ranges between 3.2 eV and 3.75 eV for the prepared Ta2O5 thin films.

Influence of the rf power and oxygen content on structural, electrical, and optical properties of V2O5 thin films prepared via reactive radio frequency sputtering

Herein, V2O5 thin films were deposited through O2-reactive radio frequency (RF) magnetron sputtering using a metallic vanadium arget without external heating on a glass substrate. The influence of the RF power and O2 content on phase formation was investigated, and the percentage of the phase volume was related to the electrical and optical properties of the films. These films were composed of a mixture of α and β phases of V2O5, and the coexistence of monoclinic (βм) and tetragonal (βт) symmetries of the β-phase structure was observed. The phase of the film deposited at 100 W RF power with 10% O2 was βт. Increasing the RF power to 150 W led to the development of the βм phase in the film. At 200 W, the obtained film was a mixture of βм- and α-V2O5 phases, and the film produced with an O2 content of more than 10% was a mixture of three phases: βт-, βм-, and α-V2O5. Further increase in the O2 content decreased the βм-phase volume but increased the βт-phase volume. The electrical resistivity and optical properties depended on the phase volume. Furthermore, the relationship between the phase volume and film properties is presented.

Influence of manufacturing processes on β-phase precipitates and corrosion properties of Zr-1Nb alloys

Zr-1Nb alloys manufactured by the alternate sequences between hot working and β-quenching were investigated in addition to an industry-fabricated Zr-1Nb material. Second phase particles, particularly composition and crystallography structure of β-phase precipitates, were characterized by electron microscopy. Pure steam corrosion test was performed to evaluate corrosion properties of the three Zr-1Nb alloys. Cross-sectional morphology and structure of the oxide films formed on the corroded alloys were analysed by scanning electron microscope and Raman spectroscopy. The results demonstrate strong effect of processing sequence on the β precipitates and corrosion properties. With the processing sequence of hot working and β-quenching, fine β-Nb particles are formed fully via precipitation from the Nb-supersaturated α-Zr grains, benefiting corrosion resistance. With the reverse sequence, the β phase and corrosion behavior are found dependent on hot working temperature in the phase regime of (α-Zr + β-Zr). Correlation between manufacturing processes and corrosion behavior is discussed in the light of second phase particles and oxides characterization.