Rutile Phase Research Articles

EFFECT OF TEMPERATURE AND INCORPORATION OF CR ON THE MICROSTRUCTURE AND HARDNESS OF TITANIUM ANODIZED WITH HCL AND GLYCEROL

Currently, electrochemical anodizing is one of the most common processes in materials science, since, under the right conditions, it allows to modify the material surface without damaging it by means of redox reactions, generating an oxide layer that protects the material and improves its properties. In this paper, grade 2 titanium was anodized using a solution of hydrochloric acid, glycerol, and deionized water as electrolyte, and 0.5 M K2CrO4 as doping agent, with a voltage of 30 V for 4.5 h. After anodizing with and without chromium, annealing was performed at different temperatures (500[Formula: see text]C, 600[Formula: see text]C and 700[Formula: see text]C) to promote structural and microhardness changes. The samples were analyzed by FE-SEM observing that the formation of nanostructures changes according to the heat treatment, where samples at 700[Formula: see text]C with chromium begin to form nanorods and, compared to those without chromium, the nanorods are longer. The presence of Cr in anodized TiO2 at different temperatures was confirmed by EDS technique. Using XRD, the microstructure of TiO2 anodized with and without Cr was analyzed and anatase and rutile phases were found, with greater presence of anatase for samples with Cr. Finally, a maximum hardness of up to 10.27 GPa was obtained from the sample at 700[Formula: see text]C without chromium, which is higher compared to the values of coatings with Cr. However, the anatase phase could be stabilized at higher temperatures making it suitable for medical applications since the anatase phase is the most biocompatible.

Photo-Electrochemical Oxygen Evolution Activity in Nickel and Cobalt Antimonates

Renewable generation of fuels via solar energy offers promising pathways towards sustainable energy future. Its deployment hinges on the discovery of electrochemically durable materials with good solar-to-chemical conversion efficiency. Necessary visible spectrum photoresponse from electrochemically stable materials is however quite rare. On the other hand, the oxygen evolution reaction (OER) requires electrodes that are not only catalytically active, but also stable under harsh electrochemical environments. In this talk, we report on and theoretical understanding of photo-electrochemical behavior an amorphous and crystaline versions of Ni-Sb-Ox and Co-Sb-Ox oxide photoanodes discovered via high-throughput experimental screening [1,2]. The newly discovered amorphous phases meet the requirements of operational stability, visible photoresponse, and appreciable photovoltage. Guided by experimental X-ray absorption characterization of these systems we use density functional theory calculations to perform a prototype phase search to identify a broad family of stable and metastable mixed rutile and hexagonal-like phases for other compositions [3]. Detailed Pourbaix analysis of the identified phases show excellent electrochemical stability, consistent with experimentally measured electrolyte concentrations of photoelectrochemical cells. We analyze when he identified phases form favorable oxygen vacancies formation energies under the reducing synthesis conditions which match measured Ni K-edge x-ray absorption spectra. The calculated OER overpotentials for the most active sites decreases with increasing Ni/Co content, which captures the experimentally observed trend. Stable amorphous metal-antimonates photoanodes are important systems for computational understanding of both the structural and catalytic behavior of these complex oxides and elucidating the co-optimization of photo-electrochemical activity and durability. This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under award DE-SC0021266.[1] Zhou, L., Peterson, E. A., Rao, K. K., Lu, Y., Li, X., Lai, Y., Bauers, S. R., Richter, M. H., Kan, K., Wang, Y., Newhouse, P. F., Yano, J., Neaton, J. B., Bajdich, M., & Gregoire, J. M. Addressing solar photochemistry durability with an amorphous nickel antimonate photoanode. Cell Reports Physical Science, 3(7), 100959. (2022).[2] Zhou, L., Wang, Y., Kan, K., Lucana, D. M., Guevarra, D., Lai, Y., & Gregoire, J. M. Surveying Metal Antimonate Photoanodes for Solar Fuel Generation. ACS Sustainable Chemistry and Engineering, 21, 33. (2022).[3] Rao, K. K., Zhou, L., Lai, Y., Richter, M. H., Li, X., Lu, Y., Yano, J., Gregoire, J. M. Bajdich, M., Resolving Atomistic Structure and Oxygen Evolution Activity in Nickel Antimonates, (under review).

Controlling Composite TiO2 Powder Characteristics in the Solid-State Synthesis of BaTiO3 Powders for Improved Sintering and Permittivity: A Comparative Study

In this study, the anatase–rutile phase fraction of TiO2, which would play a vital role in the solid-state synthesis of BaTiO3, was controlled to form a composite phase. The composite TiO2 was applied to a solid-state synthesis reaction, and the tetragonality, dielectric properties, and microstructure of the resulting BaTiO3 powders were analyzed under different synthesis conditions of TiO2. Furthermore, a comparative analysis of solid-state-synthesized BaTiO3 powders prepared using anatase, rutile, and mixed (anatase + rutile) TiO2 was performed to elucidate the mechanism of improvement in the sintering behavior and dielectric properties of the BaTiO3 powder synthesized using the composite TiO2. As a result of applying composite TiO2, BaTiO3 powder with excellent tetragonality was synthesized. In addition, it is effective in powder growth and the control of powder morphology, so sintering and dielectric properties can be improved at relatively low temperatures.

Tailored auto-combustion synthesis and optical and structural characterization of TiO2:Dy3+(1–11 mol%) nanostructures for wLED and latent finger print applications

Un-doped and dysprosium (Dy3+) doped (1–11 mol%) titanium dioxide (TiO2) nanoparticles (NPs) were synthesized by low temperature solution combustion route. The structural, morphological and nanostructural characterization of NPs were performed by powder x-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis, respectively. Rarely found rutile to anatase phase transition was observed by Dy3+ doping in TiO2 NPs using PXRD. The energy gap (Eg) of un-doped and Dy3+ doped TiO2 NPs were estimated by diffused reflectance spectra (DRS) between 2.92 and 3.07 eV. The active vibrational Raman modes of pure TiO2 were observed at 141, 446 and 608 cm−1. The mode alleged at 229 cm−1 indicates the rutile phase of TiO2 caused by second order effect. Studies of CIE and CCT confirmed that the NPs may be used in wLED applications. A rise of asymmetry ratio from 1.326 to 1.3453 with dopant concentration was observed in the photoluminescence (PL) spectra. The optimized TiO2:Dy3+ (9 mol%) nanostructures were used for the visualization of latent finger prints (LFPs) on porous and non-porous surfaces from level I to level III of ridge features.

Study on Discharge Characteristics and Microstructural Evolution of PEO Coatings Based on an Al/Ti Tracer Substrate

In this study, samples underwent plasma electrolytic oxidation (PEO) treatment using Al/Ti tracer substrates for 5, 10, 20, 35, and 55 min. The ionization states were determined using Optical Emission Spectroscopy (OES). Microstructural and elemental analyses were conducted using scanning electron microscopy equipped with energy dispersive spectrometry (SEM-EDS). The structural organization and phase composition of the coatings were characterized using X-ray diffraction (XRD) and Raman spectroscopy, respectively. The research findings indicate that the early discharge stage is dominated by discharge within the pre-deposited Al layer, which undergoes gradual oxidation along the thickness direction, while Ti (0.25 wt%) is found on the coating surface. The power increase was 56% of the total increase from min 5 to min 10 of discharge. As discharge time increased, the spectral peaks corresponding to Ti gradually became stronger and were accompanied by gradual enhancement of the crystallinity of the anatase and rutile phases within the coating. The coating surface displayed closed and semi-closed pores in the middle of the discharge. After 55 min of discharge, amorphous SiO2 was observed and Ti content on the coating surface increased to 4.59 wt%.

Perovskite-type tellurium-doped nickel stannate nanorods for highly sensitive electrochemical detection of arsenic drug roxarsone in food and environmental samples

The synthesis of perovskite-type tellurium-doped nickel stannate nanorods (TNS NRs) using surfactant-assisted hydrothermal followed by annealing processes is reported for the first time in this paper. Various analytical techniques were utilized to characterize the surface morphology, crystallinity, electronic states, and elemental compositions. The XRD patterns and FE-SEM/HR-TEM analysis demonstrated that TNS NRs have a tetragonal rutile phase with nanorod morphology. The TNS NRs modified electrode demonstrated a significantly improved electrocatalytic performance in the detection of organoarsenic drug roxarsone (ROX). The modified TNS NRs electrode demonstrated a low reduction potential (−0.53 V vs. Ag/AgCl) and a high reduction peak current response compared to previously reported sensors. The exceptional electrocatalytic performance of TNS NRs was primarily attributable to their nanorod morphology and high surface area, which allowed for a large number of active sites with a rapid electron transfer rate, making them optimal for ROX detection. Under optimal conditions, the proposed sensor performed well analytically, with a detection limit of 0.8 nM and a large recovery finding of 99.9% (n = 3). In addition, the sensor's durability was demonstrated by its remarkable repeatability (RSD 2.1%), reproducibility, and 30-day storage capacity. In light of this, the present work shows a chemically viable method for designing electrocatalysts with tailored architecture and paves the way for the development of sustainable materials for environmental protection.

A prediction of the thermodynamic, thermophysical, and mechanical properties of CrTaO4 from first principles

AbstractIt is reported that the self‐forming CrTaO4 oxide scale can protect refractory high‐entropy alloys from oxidation, superior to Cr2O3. In this paper, the phase stability, mechanical, and thermal properties of three polymorphous phases of CrTaO4 are systematically investigated from first‐principles density functional theory calculations. The mechanical properties predicted using the strain–energy methods indicated that all three phases are mechanically stable. The temperature dependence of elastic constants and polycrystalline moduli of three phases demonstrated the thermal softening as temperature increase. The Helmholtz‐free energies as a function of volume and temperature are derived from phonon dispersions within the quasi‐harmonic approximation at six strained volumes. The calculated apparent bulk coefficients of thermal expansion of these three phases are evaluated, the highest value approximately 13.4× 10−6 K−1 within a temperature range of 500–2000 K for the rutile I41md phase. The lattice thermal conductivity calculated by the Debye–Callaway model suggested that the rutile type I41md phase has the lowest value of approximately 2.1 W/m/K at 1800 K. The other two phases, C2/m and P2/c, exhibit higher values due to relatively lower Grüneisen parameters and larger phonon velocities. The melting point of CrTaO4 is predicted to be between 1975 and 2449 K using ab initio molecular dynamics simulations. This work provides a comprehensive theoretical understanding of the thermodynamic, mechanical, and thermal properties for the new material CrTaO4 and serves as an example of a viable computational design strategy for improved oxidation resistance of refractory alloys at high temperatures.

Enhanced photocatalytic activity in RhB dye degradation by Mn and B co-doped mixed phase TiO2 photocatalyst under visible light irradiation

Here, we report synthesis of undoped, manganese (Mn) doped, boron (B) doped and Mn-B co-doped TiO2 nanoparticles (NPs) by a cost-effective sol-gel method. The structural properties, phase, micro-morphology and particle size of the synthesized nanoparticles have been characterized by X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. These studies revealed that undoped and mono (Mn/B) doped TiO2 NPs exhibit only anatase phase, whereas (Mn and B) co-doped TiO2 NPs exhibit anatase and rutile mixed phase structure. Furthermore, co-doping reduces the particle size, agglomeration in aqueous medium and the sample possesses crystal defects. UV–Visible diffusive reflectance spectroscopy (DRS) revealed that the co-doped sample demonstrates extended optical response in the visible wavelength range of the solar spectrum and is red shifted when compared to undoped and mono doped TiO2 NPs. The obtained optical band gap (2.11 eV) and the Urbach energy (1.12 eV) for the Mn and B co-doped TiO2 NPs suggest the formation of mid-gap energy states, which might make this NPs a suitable candidate for photocatalysis in the visible light spectrum. We investigated the photocatalytic degradation of rhodamine B (RhB) dye by the synthesized NPs under visible light irradiation. Our studies revealed that co-doped TiO2 photocatalyst can degrade 99% of RhB dye within 90 min of visible light irradiation and can retain 95% degradation efficiency up to the third consecutive cycles. Finally, we provide a plausible explanation for such enhanced visible light assisted photocatalytic performance.

Probing the effect of precursor concentration on the growth and properties of titanium dioxide nanocones for environment safe solar cells.

Environment friendly third-generation solar cells sensitized by dyes, quantum dots, and perovskites are seen as promising energy alternatives. Among the various strategies, employing one-dimensional nanostructures that exemplify the smallest dimension for efficient carrier transport rate from the active layer to electron transport layer (ETL) in photovoltaic devices is attempted in this work. We herein report the synthesis of well-aligned 1-D TiO2 nanocones as ETL for photovoltaic thin films by varying the precursor concentration (0.03M, 0.04M, 0.05M) to track the evolution of growth. The hydrothermal approach is exploited to grow oriented rutile TiO2 nanocones on fluorine doped tin oxide (FTO) under neutral conditions. The examination of phase, crystallinity, morphology, and opto-electronic properties of the well-structured nanocone arrays is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), ultra violet diffuse reflectance spectroscopy (UV-DRS), Brunnauer-Emmett-Teller (BET) surface area analysis, and field-dependent dark and photoconductivity analysis. The XRD pattern confirms the formation of the tetragonal rutile phase. SEM micrographs and UV-DRS spectroscopy reveals that the length of the nanocones and the energy gap is found to be maximum for 0.04M concentration with a well-defined excitation band at 316nm. Significantly, a strong light-trapping effect that decreases the incident light reflections and correspondingly increases the light absorption is unveiled through photoconductive studies for the TiO2 nanocones at 0.04M having a surface area of 81.767 m2/g. The investigation essentially suggests that the as-prepared one-dimensional nanostructures would serve as efficient photoanodes in environment safe third-generation solar cells.

Versatility Investigation of Grown Titanium Dioxide Nanoparticles and Their Comparative Charge Storage for Memristor Devices.

Memristive devices have garnered significant attention in the field of electronics over the past few decades. The reason behind this immense interest lies in the ubiquitous nature of memristive dynamics within nanoscale devices, offering the potential for revolutionary applications. These applications span from energy-efficient memories to the development of physical neural networks and neuromorphic computing platforms. In this research article, the angle toppling technique (ATT) was employed to fabricate titanium dioxide (TiO2) nanoparticles with an estimated size of around 10 nm. The nanoparticles were deposited onto a 50 nm SiOx thin film (TF), which was situated on an n-type Si substrate. Subsequently, the samples underwent annealing processes at temperatures of 550 °C and 950 °C. The structural studies of the sample were done by field emission gun-scanning electron microscope (FEG-SEM) (JEOL, JSM-7600F). The as-fabricated sample exhibited noticeable clusters of nanoparticles, which were less prominent in the samples annealed at 550 °C and 950 °C. The element composition revealed the presence of titanium (Ti), oxygen (O2), and silicon (Si) from the substrate within the samples. X-ray diffraction (XRD) analysis revealed that the as-fabricated sample predominantly consisted of the rutile phase. The comparative studies of charge storage and endurance measurements of as-deposited, 550 °C, and 950 °C annealed devices were carried out, where as-grown device showed promising responses towards brain computing applications. Furthermore, the teaching-learning-based optimization (TLBO) technique was used to conduct further comparisons of results.

Effect of different crystalline phase of TiO2 on the catalytic activity of Ru catalysts in hydrogen evolution under acidic and alkaline media

Designing highly active and durable catalysts is considered to be crucial for enhancing hydrogen evolution reaction (HER) from water electrolysis. Although some studies indicate that anatase TiO2 is a promising candidate for electrolytic hydrogen evolution reaction, the influence of different crystalline phases of TiO2 on the supported Ru catalysts for electrocatalytic HER performance is rarely systematically explored. Herein, a series of Ru/TiO2-X (X = R (Rutile), A (Anatase), and P25) catalysts were prepared to investigate the influence of the rutile and anatase phases of TiO2 on the catalytic activity of Ru catalysts in HER. The findings demonstrate that the HER activity is much affected by the variation of the titania structure, when other factors are kept constant. The 15Ru/TiO2-R-H2 has superior HER performance with a small overpotential of 63 mV to achieve a current density of 10 mA cm−2 in acidic electrolyte and 99 mV in alkaline electrolyte compared to 15Ru/TiO2-A-H2 and 15Ru/TiO2-P25-H2. This might be attributed to the faster electron transfer and lower Fermi level caused by the oxygen vacancy (VO) and strong metal-support interaction (SMSI), along with the exposure of active sites afforded by the highly dispersed ruthenium nanoparticles on the rutile TiO2. Our results indicate that the presence of rutile TiO2 support alone is adequate to maintain Ru in its most active form and make it a more performing catalyst, compared to anatase titania and P25.

Structure phase-dependent dielectric and photodegradation properties of Co-doped TiO2 nanoparticles synthesized via co-precipitation route

This research pursued the effect of various calcination temperatures (300–1000 °C) on developing structural phases and the optical, dielectric, and photodegradation characteristics of cobalt-doped titanium dioxide nanoparticles (TiO2 NPs). The prepared NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared (FTIR) spectroscopy analysis, ultraviolet–visible light (UV–VIS) spectroscopy, and photodegradation of methylene blue in the presence of visible light. XRD analysis revealed the formation of a tetragonal anatase phase for the samples calcined at 300–600 °C, while the Co-doped samples calcined at 800 °C and 1000 °C displayed a tetragonal rutile phase. The optical band gap analysis indicated that doping in the host matrix produced lower band gap energy for all the prepared samples. Dielectric measurements showed that the rutile phase heated at 800 °C had a larger dielectric constant and dielectric loss than the un-doped TiO2 and the other cobalt-doped samples. Finally, the anatase Co-doped TiO2 exhibited a maximum MB degradation of 93 % in 90 min compared to un-doped TiO2, which only degraded 14 % and rutile-TiO2 NPs (62 % degradation). The underlying mechanism responsible for the diverse photodegradation performance displayed by the anatase and rutile phases of TiO2 NPs is discussed. Overall, these results demonstrate that cobalt doping and the crystalline phase of TiO2 NPs are vital parameters involved in optimizing the photocatalytic activity of TiO2.

Influence of layer number and sintering temperature on microstructural, tribological, and corrosion behavior of Al2O3–TiO2 multilayer coatings

The effects of layer number (2, 4, and 6-layer) and sintering temperature (800, 900, 1000, and 1100 °C) on the microstructure, wear, and corrosion properties of Al2O3–TiO2 multilayer coatings deposited on 316L stainless steel plates using the sol-gel dip coating technique were investigated. The wear characteristics were measured through ball-on-disc type dry sliding tests using an Al2O3 ball under a 1 N load, whereas the corrosion features were determined by potentiodynamic polarization tests conducted in a 3.5 wt% NaCl solution. Anatase, rutile, α-Al2O3, and γ-Al2O3 phases were obtained in the hybrid coatings, depending on the sintering temperatures. However, at 1100 °C, the coating did not adhere well to the substrate due to passive oxide film formation on the 316L plate, leading to spalling. Besides, the surface homogeneity deteriorated in the 6-layer coated sample due to higher organic removal and residual stresses. The corrosion rate decreased with the increasing number of layers, but the sensitivity to corrosion varied due to changes in surface properties. The 4-layer coated sample sintered at 1000 °C achieved the highest wear strength (improved by up to 71.1%) and corrosion resistance (increased by up to 90.4%) due to its decreased porosity and homogeneously distributed finer particles.

Manipulation of luminescence activity by interfacial engineering via surface treatment of TiO2 nanorods in the core/shell/mixed halide CH3NH3PbI3-xClx perovskite heterostructures

Efficient charge transfer between the various layers in a solar cell requires proper modification of interfaces. Multi-step hydrothermal processing have been adopted for the fabrication of Core/shell TiO2/SrTiO3 nanorod array on the Fluorine-doped Tin Oxide and TiO2 surfaces. Nanorods were treated with strontium for surface passivation via hydrothermal technique which is found to be critical in tuning the optoelectronic properties. For individual layers in thin films, various experimental techniques were used to study structural, morphological, optical and spectroscopic properties. Raman spectroscopy, reveal presence of rutile and anatase phase for TiO2 nanorods which corelates with the crystal structure of compact layer and nanorods. Afterwards a perovskite layer was deposited on top of nanorods to study photo-luminescence response which successfully revealed that strontium treatment of nanorods suppresses the recombination of charge carriers. The observations and results discussed in this article will be helpful in improving the optoelectronic properties of the material and could lead to improved efficiency of perovskite solar cells.

Effect of anodizing time on the structural color and photocatalytic properties of the TiO2 films formed by electrochemical method

Environmentally friendly materials are gaining more and more importance day by day. Structural colored materials without chemical pigments have become popular in this respect. It was aimed to produce structurally colored, photocatalytic TiO2 film coatings on the Titanium substrates using the anodizing method. Since the TiO2 structure, which has photocatalytic properties, is not covered with any coating such as paint, the function of cleaning the environment with solar energy is preserved. The crystallite sizes of the anatase and rutile phases were found between 22.18 and 22.18 nm. The highest photocatalytic efficiency was obtained at the sample anodized for 60 s with 60% efficiency. The surface morphologies of the samples were transformed into a worm-like morphology after anodization for 600 s. These regular indentations of the worm-like structure create extra coherent light scattering in the red region, similar to the photonic crystal surfaces. So, the main outcome is that the obtained colors can be controlled by Photonic Crystal morphologies. Also, extremely eco-friendly, multifunctional TiO2 film coatings with both structural color and photocatalytic properties were obtained.

Investigating the crystallization behavior of TiO2 during annealing: Molecular dynamics simulations

TiO2 is a dielectric material with excellent photocatalytic and photochemical properties. The conversion of TiO2 from an amorphous to crystalline phase significantly improves the photocatalytic activity of TiO2. However, the crystallization behavior of TiO2 during annealing has been little studied in the field of molecular dynamics. In this paper, the crystallization behavior of TiO2 during annealing under different conditions was analyzed using molecular dynamics simulation. To investigate the phase transition process of TiO2, the melting point temperature of the system was calculated by mean square displacement at about 2400 K. The effect of size on structural stability was explored. The radial distribution function and x-ray diffraction curves revealed that the anatase phase appeared over 800 K. Moreover, with the increase in annealing temperature, the anatase content in TiO2 first increased and then decreased, and the rutile phase gradually increased. At a specific temperature, a structure is formed where rutile and anatase coexist. Anatase atoms compete with rutile atoms, and by increasing the temperature, anatase is converted to rutile. The amorphous structure is reduced at high temperatures, improving the crystalline quality. The crystallization behavior of the amorphous structure can improve the photocatalytic efficiency of TiO2. TiO2 nanometers have good prospect for application. Therefore, studying the crystallization behavior of TiO2 is essential.

Nanostructured Vanadium Dioxide Materials for Optical Sensing Applications.

Vanadium dioxide (VO2) is one of the strongly correlated materials exhibiting a reversible insulator-metal phase transition accompanied by a structural transition from a low-temperature monoclinic phase to high-temperature rutile phase near room temperature. Due to the dramatic change in electrical resistance and optical transmittance of VO2, it has attracted considerable attention towards the electronic and optical device applications, such as switching devices, memory devices, memristors, smart windows, sensors, actuators, etc. The present review provides an overview of several methods for the synthesis of nanostructured VO2, such as solution-based chemical approaches (sol-gel process and hydrothermal synthesis) and gas or vapor phase synthesis techniques (pulsed laser deposition, sputtering method, and chemical vapor deposition). This review also presents stoichiometry, strain, and doping engineering as modulation strategies of physical properties for nanostructured VO2. In particular, this review describes ultraviolet-visible-near infrared photodetectors, optical switches, and color modulators as optical sensing applications associated with nanostructured VO2 materials. Finally, current research trends and perspectives are also discussed.

Investigations of structural, optical and transport property of Sb-doped SnO2 compounds for optoelectronics application

Recently extensive research into the potential uses of oxide materials doped with non-magnetic elements in optoelectronic and spintronic devices has been carried out. In this work, the structural, optical and transport property of the Sn1−xSbxO2 (x = 0–0.10) compounds were studied by using X-ray diffraction (XRD), Raman spectroscopy, UV–vis photo-spectrometer and Hall-effect measurements. For preparation of the samples, the solid-state reaction technique was utilized. Based on the measurement and analysis of the XRD data, it was revealed that these prepared materials were crystallized in a single tetragonal rutile phase of SnO2. Moreover, the XRD data indicated that the solubility limit of Sb was only upto 8 % and thereafter secondary phase of Sb2O3 starts to appear. Using the equation developed by Debye and Scherrer, it was discovered that these samples had an average crystallite size that fell somewhere in the range of 32–36 nm. The microstructural investigation using a scanning electron microscope show a nano meter range sphere-shaped morphology. The rutile phase of SnO2 has been reconfirmed by Raman spectroscopy, and it further shows that there is no lattice disorder upon inclusion of Sb into the SnO2 lattice. An analysis of the optical property by means of a UV–vis Photo-spectrometer indicates that the value of optical band gap reduces as the amount of Sb doping in the material increases. Whereas, the optical transmittance value was found to decrease. The Hall effect measurement indicate the p-type behaviour of these samples and the carrier concentration of holes rises with Sb doping concentration.

Facile synthesis of Ni0.5Zn0.5Fe2O4/MXene composite powders for high-performance asymmetric supercapacitors

Ni0.5Zn0.5Fe2O4/Ti3C2Tx MXene composite powders were prepared by solution combustion synthesis method. The various amounts of Ti3C2Tx MXene sheets were dispersed in the precursor solution containing the metal nitrates as oxidant and glycine as fuel in water solvent. The effects of Ti3C2Tx MXene contents (25, 50, 75 wt%) on the structural, microstructural, and electrochemical properties were studied by various characterization methods. The Ni0.5Zn0.5Fe2O4 particles covered the Ti3C2Tx MXene sheets at the lower contents. However, the Ti3C2Tx MXene was delaminated to the rutile and anatase TiO2 phases without losing the sheetlike morphology at its higher contents. The Ni0.5Zn0.5Fe2O4 and Ti3C2Tx MXene had the specific capacity of 598 and 680C g−1, respectively, which was enhanced to 1614C g−1 at 1 Ag−1 for the Ni0.5Zn0.5Fe2O4–25 wt%Ti3C2Tx MXene. The hybrid capacitor made of the Ni0.5Zn0.5Fe2O4–25 wt% MXene composite powders as positive electrode and activated carbon as negative electrode showed the energy density of 53 Whkg−1 at the power density of 1335 Wkg−1 by applying a current density of 1 Ag−1.

Correlation of metal-to-insulator transition and strain state of VO2 thin films on TiO2 (110) substrates

We explore the possibility of tuning the metal-to-insulator transition (MIT) of crystalline VO2 thin films by strain engineering. We deposit high-quality VO2 epitaxial films of different thicknesses on TiO2 (110) substrates by pulsed laser deposition. The strain state of the deposited film varies with its thickness. This allows us to correlate the MIT characteristics with the strain state of the VO2 film by a careful characterization of the structural and electrical properties. Thin VO2 films on TiO2 (110) substrates are almost fully strained up to thicknesses of about 20 nm and exhibit tensile strain along the c axis of the (high-temperature) metallic rutile phase leading to an increase in the MIT temperature by as much as 30 °C in comparison to the almost fully relaxed 300 nm-thick VO2 film. The strain gradient within the thicker samples leads to a continuous serial switching of layered regions of the VO2 film from the insulating to the metallic state with increasing temperature.