Oxygen vacancy enhanced room temperature ferromagnetism in Ar+ ion irradiated WO3 films

Room-temperature ferromagnetism in WO₃ films was enhanced by 130 keV Ar⁺ ion irradiation. The X-ray diffraction (XRD) and Raman measurements not only confirmed the monoclinic phase of the irradiated WO₃ films, but also showed that oxygen vacancy (V_O) defects were formed. The analysis of photoluminescence spectra strongly reconfirmed the presence of oxygen vacancy. X-ray photoelectron spectroscopy (XPS) measurements revealed that the contents of V_O and induced W⁵⁺ ions increase with increasing irradiation fluence and rich W⁵⁺-V_O defect complexes in the irradiated WO₃ films were formed. Further, the magnetic measurements exhibited a 2-fold enhancement in the saturation magnetization at the largest fluence of 3 × 10¹⁶ ions/cm². At lower irradiation fluence, a bound magnetic polaron model was proposed to reveal the ferromagnetic exchange coupling resulting from overlapping of V_O⁺ and V_O⁺⁺ defect states, and 5d¹ states of W⁵⁺. At high irradiation fluence, the carrier concentration reaches 1.02 × 10²⁰/cm³ and carrier-mediated exchange interactions result in the film's ferromagnetism.     

Fe doping effect of vanadium oxide films for enhanced switching electrochromic performances

In the present study, Fe-doped V₂O₅ films showing impressive electrochromic (EC) performance were developed using the sol-gel spin-coating method. To confirm the optimized Fe-doping effect on the V₂O₅ films for the EC performance, we adjusted the Fe atomic percentages to 0.0, 0.5, 1.0, and 1.5?at%, respectively. With the effect of Fe doping on the V₂O₅ films, the obtained films resulted in the formation of the oxygen vacancies. As the result, when the optimum Fe atomic percentage was 1.0?at%, the enhanced switching speeds (3.7?s for the bleaching speed and 2.0?s for the coloration speed) and enhanced coloration efficiency value (47.3?cm²/C) compared to the other films were implemented. This can be attributed to the improved electrical conductivity and Li⁺ diffusion coefficient that led to efficient generation of the EC reaction activity and narrowing the optical bandgap at the coloration state to increase transmittance modulation. Therefore, this unique film can be a promising EC material to improve the performance for the EC devices.     

Thermal and optical properties of hyperbranched fluorinated polyimide/mesoporous SiO2 nanocomposites exhibiting high transparency and reduced thermo-optical coefficients

A series of hyper-branched polyimide (HBPI)/mesoporous SiO₂ nanocomposite films were prepared from a fluorinated anhydride (6FDA), a fluorinated triamine (TFAPOB), and mesoporous SiO₂ nanoparticles (NPs). The anhydride-terminated precursor of HBPI was functionalized using a coupling agent prior to mixing with SiO₂ NPs. The morphologies and thermal-optical properties of the nanocomposite films were investigated, with particular focus on their optical transparency, refractive indices (n), and thermo-optical (TO) coefficients. The absolute values of TO coefficients (|dn/dT|) of HBPI film (50.8 ppm/K) were significantly reduced to 13.4 ppm/K by homogeneous dispersion of 15 wt% of SiO₂ NPs. The HBPI/SiO₂ composite films exhibited high thermal stability without significant weight loss of up to 400 °C in air. The films also exhibited small coefficients of linear thermal expansion (CTEs) within the range 30–40 ppm/K. In addition, enhanced interfacial interactions between SiO₂ and HBPI significantly improve the optical transparency with cutoff wavelengths shorter than 450 nm. The refractive indices of HBPI/SiO₂ composite films were found to range from 1.477 to 1.502, which agrees well with the calculated values. This study shows that the incorporation of SiO₂ NPs in multi-functional HBPI matrix is a promising approach to prepare high performance thermally stable films for thermo-optic applications.     

Low-temperature firing and microwave dielectric properties of MgNb2-xVx/2O6-1.25x ceramics

MgNb_2-xV_x/2O_6-1.25x (0.1≤x≤0.6) ceramics with orthorhombic columbite structures were prepared at low-temperature by a solid-phase process. The phase component, microscopic morphology, low-temperature sintering mechanism and microwave dielectric performance of MgNb_2-xV_x/2O_6-1.25x ceramics were comprehensively investigated. Low-temperature sintering densification of dielectric ceramics was achieved via the nonstoichiometric substitution of vanadium (V) at the Nb-site. In contrast to pure MgNb₂O₆ ceramics, the sintering temperature of MgNb_2-xV_x/2O_6-1.25x (x = 0.2) ceramics was reduced by nearly 300 °C owing to the liquid-phase assisted sintering mechanism. The liquid phase arises from the autogenous low-melting-point phase. Meanwhile, MgNb_2-xV_x/2O_6-1.25x (x = 0.2) samples with nonstoichiometric substitution could achieve a more than 900% improvement in the Q × f value, compared with stoichiometrically MgNb_2-xV_xO₆ (x = 0.1, 0.2) ceramics. Finally, MgNb_2-xV_x/2O_6-1.25x dielectric ceramics possess outstanding microwave dielectric properties: ε_r = 20.5, Q × f = 91000, and τ_f = -65 ppm/°C when sintered at 1030 °C for x = 0.2, which provides an alternative material for LTCC technology and an effective approach for low-temperature sintering of Nb-based microwave dielectric ceramics.     

Effects of V2O5 addition on the synthesis of columnar self-reinforced mullite porous ceramics

Spearhead columnar mullite was synthesized by in-situ reaction with V₂O₅ as additive. When the content of V₂O₅ was 7 wt%, the length of the spearhead columnar mullite was the longest with an aspect ratio of about 3.5. Furthermore, columnar self-reinforced mullite porous ceramics were prepared by a foam-gelcasting method, and the effects of V₂O₅ content on the rheological and gelling properties of mullite slurries as well as the microstructure, physical property and thermal insulation property of the prepared mullite porous ceramics were studied. The results showed that the flexural strength and compressive strength of the porous ceramics with 63% porosity prepared by using 2 wt% V₂O₅ additive were respectively as high as 13.9 and 41.3 MPa, and the thermal conductivity was about 1.04 W m^?1 K^?1.     

Replacement behavior of Ti and Mg and selective separation of MgxTi3-xO5 (x=1, 0.9, 0.75, 0.6) from Ti-bearing electric furnace smelting slag via super-gravity

Ti-bearing electric furnace smelting slag produced from direct reduction and electric furnace smelting process of vanadium titanomagnetite ore, contains a high TiO₂ content of 40–55 wt%. While a mass of Mg, Al, Ca and Si are closely mixed with Ti in the slag, which greatly limits the recovery of Ti resource from the slag. In this work, the replacement behavior of Ti and Mg in Mg_xTi_3-xO₅ was studied, and selective separation of various Mg_xTi_3-xO₅ phases from Ti-bearing electric furnace smelting slag was conducted via super-gravity. It was found that Mg could replace Ti in Ti₃O₅ and form the Mg_xTi_3-xO₅, and increasing of cooling rate greatly limited the doping of Mg into Mg_xTi_3-xO₅, the Mg_xTi_3-xO₅ was transformed from (MgTi₂)O₅ to (Mg_0.9Ti_2.1)O₅, (Mg_0.75Ti_2.25)O₅ and (Mg_0.6Ti_2.4)O₅ respectively. On this basis, various Mg_xTi_3-xO_{5 (x = 1, 0.9, 0.75, 0.6)} phases were selectively separated from the smelting slag via super-gravity, where the mass fraction of TiO₂ was increased from 78.69 to 90.32 wt% while that of MgO was decreased from 13.56 to 6.98 wt% with the increase of Ti/Mg ratio in Mg_xTi_3-xO₅. Moreover, the replacement mechanism of Mg and Ti was confirmed from characterization of crystal structure and lattice parameter of various separated high-purity Mg_xTi_3-xO₅ crystals.     

Fabrication of reduced Graphene Oxide supported Gd3+ doped V2O5 nanorod arrays for superior photocatalytic and antibacterial activities

In the current report, pure V₂O₅, a series of Gd doped V₂O₅ (1 wt%, 3 wt%, 5 wt% and 10 wt%) and graphene integrated Gd–V₂O₅ photocatalysts have been prepared using a facile wet chemical approach. The effect of Gd⁺³ ions substitution and RGO support on V₂O₅ was studied by the different analytical techniques. X-ray diffraction (XRD) results showed the orthorhombic crystal structure of synthesized samples with crystallize size in range of 22–35 nm. Morphological analysis showed nanorods and nanorod arrays like appearance of V₂O₅, Gd–V₂O₅ and GdV-₂O₅/RGO, respectively. Gd–V₂O₅ and Gd–V₂O₅/RGO exhibited enhanced optical response in the visible region along with decrease in the band gap values for Gd doped V₂O₅ samples. BET surface area of Gd–V₂O₅ and Gd- V₂O₅/RGO was calculated as 12.39 g/m² and 15.35 g/m² that was found to be higher than pristine V₂O₅. To study the photocatalytic activity of synthesized photocatalysts, methylene blue (MB) was chosen as model pollutant. Among the Gd doped V₂O₅ samples, highest photocatalytic activity (45.62%) was achieved by optimal concentration of 5 wt% Gd–V₂O₅ that is accredited to effective separation of electron-hole pairs. While Gd–V₂O₅/RGO showed 2.1 times higher dye removal (97.12%) than unsupported Gd–V₂O₅, under the visible light irradiation. The significantly high photocatalytic activity of Gd–V₂O₅/RGO is due to the synergistic effect aroused by combined action of Gd⁺³ ions doping and advantageous properties of highly conductive and large surfaced graphene. Recycling experiments for V₂O₅ derivatives showed good stability and recyclability of photocatalysts. Additionally, Gd–V₂O₅/RGO was found to be more potential anti-bacterial agent than V₂O₅ and Gd–V₂O₅.     

Electrical conduction behavior in nonstoichiometric BaBixNb5O15±δ tungsten bronze ceramics

The BaBi_xNb₅O_15±δ (BB_xN, 0.98 ≤ x ≤ 1.02) ceramics were synthesized via solid-state reaction to investigate the effect of Bi³⁺ nonstoichiometry on their microstructure and electrical conduction behavior. The study of the relationship between structure and conductive behavior revealed two main conclusions: (1) as the concentration of Bi³⁺ content increased, from deficiency to excess, the oxygen vacancies decreased, and the lattice unit volume V gradually increased; (2) there was a low-frequency Warburg electrode response besides the medium-frequency grain boundary response and high-frequency grain response, and the Bi³⁺ introduction could reduce conductivity. In addition, the dielectric anomalies indicated by the T₁ peak and the T₂ peak at 300 °C and 500 °C are related to the Warburg electrode response and to the Bi vacancy and oxygen vacancy defects, respectively.     

Phase Equilibria of the SiO2–V2O5 system

The SiO₂–V₂O₅ system is one of the key systems for vanadium extraction and applications of vanadium oxides in the ceramic industries. However, only limited data in this system and contradictive results were reported from preceding studies. In the present study, high-temperature phase equilibrium experiments were conducted to construct the phase diagram of SiO₂–V₂O₅ system at temperature range of 660–1100 °C. Electron probe X-ray micro-analyzer (EPMA) was used to analyze the microstructure and composition of the phases presented in quenched samples. The liquidus temperatures in both SiO₂ and V₂O₅ primary phase field were determined. The eutectic temperature is confirmed to be within 670–680 °C and the eutectic composition comprises 1.9 wt% SiO₂. SiO₂ phase contains up to 1.4 wt% V₂O₅ in the temperature range investigated.     

Structural,morphological, and optical properties of W-doped VO2 thin films prepared by sol-gel spin coating method

Thermochromic VO₂ thin films were deposited on soda-lime glass via sol-gel method. Doping was done through adding tungstic acid solution to the vanadium solution precursor. Grazing incidence x-ray diffractometer (GIXRD) results showed that VO₂ and V₆O₁₃ phases were formed together in the heat-treated sample. According to the GIXRD result of the W-doped sample, only VO₂ remained. Field-emission scanning electron microscopy (FESEM) micrographs showed that the VO₂ grain size decreased from about 70 to about 25 nm for undoped film and 2 wt% W-doped films, respectively. Atomic force microscopy (AFM) results showed that the root mean square roughness for the film with 180 nm thickness was about 18 nm, and 2 wt% W-doped film had a smoother surface. Diffuse reflectance spectroscopy (DRS) results showed that the band gap energy for undoped, 1 wt% W- doped, and 2 wt% W-doped VO₂ thin films was 1.7, 1.3, and 0 eV, respectively. Four-point probe resistivity measurements showed a significant decrement, from approximately 1 MΩ at 15°C to <100 Ω at 80°C. Regarding Vis-NIR spectroscopy results, maximum optical transmission for undoped and W-doped films was approximately 75% and 35%, respectively.     

Magnetic doping effects on the superconductivity of Y1-xMxBa2Cu3O7-δ (M = Fe,Co, Ni)

The discovery of superconductivity in copper oxide compounds has attracted considerable attention over the past three decades. The high transition temperature (T_c) in these compounds, exhibiting proximity to an antiferromagnetic order in their phase diagrams, remains one of the main areas of research. It is believed that magnetic fluctuations provide substance for the exotic superconductivity observed in these compounds. The present study attempts to introduce Fe, Co and Ni magnetic impurities into the superconducting cuprate YBa₂Cu₃O_7-δ with the aim of exploring the T_c behavior. The solid-state synthesis method is exploited to prepare fully oxygenated Y_1-xM_xBa₂Cu₃O_7-δ (Y_1-xM_x-123) (M = Co, Fe, Ni) samples with low levels of doping (0.00000 ≤ x ≤ 0.03000). Systematic measurements are then employed to assess the synthesized samples using AC magnetic susceptibility, electrical resistivity and X-ray diffraction (XRD). The measurements revealed an increase in T_c as a result of magnetic substitution for Y. However, the study of non-magnetic dopings on the fully oxygenated Y_1-xM'_xBa₂Cu₃O_7-δ (Y_1-xM'_x-123) (M' = Ca, Sr) samples showed a decrease in T_c. Quantitative XRD analysis further suggested that the internal pressure could have minor effects on the increase in T_c. The normal state resistivity vs temperature showed a linear profile, confirming that the samples are at an optimal doping of the carrier concentration.     

Effect of Li2O–V2O5 on the low temperature sintering and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 ceramics

Li₂O–Nb₂O₅–TiO₂ based ceramic systems have been the candidate materials for LTCC application, due to their high dielectric constant and Q × f value and controllable temperature coefficient in the microwave region. However, the sintering temperature was relatively higher (above 1100 °C) for practical application. In this study, dielectric properties of Li_(1+x−y)Nb_(1−x−3y)Ti_(x+4y)O₃ solid solution were studied with different x and y contents and among them, the Li_1.0Nb_0.6Ti_0.5O₃ composition (x = 0.1, y = 0.1) was selected, due to its reasonable dielectric properties to determine the possibility of low temperature sintering. The effects of 0.17Li₂O–0.83V₂O₅, as a sintering agent, on sinterability and microwave dielectric properties of Li_1.0Nb_0.6Ti_0.5O₃ ceramics were investigated as a function of the sintering agent content and sintering temperature. With addition of 0.17Li₂O–0.83V₂O₅ above 0.5 wt%, the specimens were well densified at a relatively lower temperature of 850 °C. Only slight decrease in apparent density was observed with increasing 0.17Li₂O–0.83V₂O₅ content above 0.75 wt%. In the case of 0.5 wt% 0.17Li₂O–0.83V₂O₅ addition, the values of dielectric constant and Q × f reached maximum. Further addition caused inferior microstructure, resulting in degraded dielectric properties. For the specimens with 0.5 wt% 0.17Li₂O–0.83V₂O₅ sintered at 850 °C, dielectric constant, Q × f and TCF values were 64.7, 5933 GHz and 9.4 ppm per °C, respectively.     

Tailoring structure and piezoelectric properties of CaBi2Nb2O9 ceramics by W6+-Doping

Calcium bismuth niobate (CaBi₂Nb₂O₉) is a typical bismuth-layer structured piezoelectrics (BLSPs) with a high Curie temperature (T_C) of ～943 °C, but it has low piezoelectric coefficient and high-temperature resistivity which severely limits signal acquisition in the high-temperature piezoelectric vibration sensors. Ion-doping modification is regarded as an effective way to enhance electrical properties. In this work, W⁶⁺ donor-doping at Nb⁵⁺ site in the CaBi₂Nb_2-xW_xO₉ (x = 0, 0.020, 0.025, 0.030, 0.035 and 0.040) piezoelectric ceramics with T_C of 931 ± 2 °C were fabricated by the conventional solid-state reaction method. The effects of W⁶⁺-doping on crystal structure of CaBi₂Nb_2-xW_xO₉ as well as microscopic morphology and electrical properties of ceramics were investigated systematically. The tetragonality, isotropy and electrical properties of the ceramics were enhanced with the introduction of W⁶⁺ dopant. It was found that x = 0.025 was the optimal W⁶⁺-doping ratio that yielded remnant polarization of 8.0 μC/cm², electrical resistivity of 3.0 × 10⁶ Ω cm at 600 °C, piezoelectric coefficient (d₃₃) of 14.4 pC/N, and good thermal depoling property. Our work has established a feasible approach to tune the structure of CaBi₂Nb₂O₉ to improve piezoelectric properties for potential applications in high-temperature piezoelectric vibration sensors.     

Self-cleaning functionalized FeNi/NiFe2O4/NiO/C nanofibers with enhanced microwave absorption performance

Microwave absorbing materials with enhanced microwave absorption performance and self-cleaning function are of great interest for military applications and human health caused by electromagnetic radiation pollution. Herein we report the synthesis of FeNi/NiFe₂O₄/NiO/C nanofibers (NFs) via electrospinning technique using nickel acetylacetonate (Ni(acac)₂), ferric acetylacetonate (Fe(acac)₃), and N, N-dimethylformamide (DMF)/polyacrylonitrile (PAN) solution as precursor. We also show the abilities of the materials to attenuate electromagnetic microwave and their ease of self-cleaning performance. X-ray diffraction patterns and HRTEM images reveal that the materials possess FeNi, NiFe₂O₄, NiO and graphite. HAADF-STEM images show that the magnetic nanoparticles distribute uniformly along the fibers. Contrast experiments had been conducted on different calcination temperatures to elucidate the impedance matching and loss mechanism. Based on the results of the experiment, excellent microwave absorption was exhibited by blending the NiFe₂O₄/NiO/CNFs and FeNi/NiFe₂O₄/NiO/CNFs into paraffin at 50 wt% and 5 wt%, respectively. Moreover, the contact angles (CA) of the as-prepared fiber films calcined at 650, 750 and 950 °C were 143°, 141° and 144°, respectively, indicating that fiber films exhibited excellent hydrophobicity and self-cleaning function. It suggested that the as-obtained NFs had an excellent application prospect in self-cleaning microwave absorbing materials.     

Effect of Ar/O2 ratio on double-sided electrochromic glass performance

This paper reports the qualities of WO₃ film and NiO film added to a counter electrode and their use in a double-sided electrochromic glass device. A mixture of argon and oxygen gasses with ratios of Ar/O₂ of 1.5, 2, 3, and 5 were used for the deposition of the working electrode of WO₃ film for EC glass. The structure of double-side EC glass consists of glass/ITO/NiO/electrolyte/WO₃/ITO/glass/ITO/WO₃/electrolyte/NiO/ITO/glass layers. The working electrode of WO₃ film controls the color presented, the applied voltage controls the color depth, and the counter electrode controls the transparency in the bleached state. The double-sided EC glass with double WO₃ films and double NiO films have faster coloration/bleaching rates than do single-sided EC glass. A mixture of Ar/O₂ ratio of 3.0 has the best coloration/bleaching property of the ratios tested. Compared to the single-sided EC glass, the double-sided EC glass has lower transmittance of about 72% and 6% than the 78% and 12% during coloration and bleaching states in the visible light region with +1.5 V and ?3.5 V applied.     

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.     

Microstructure,ferroelectric and piezoelectric properties of Bi4Ti3O12 platelet incorporated 0.36BiScO3-0.64PbTiO3 thick films for high temperature piezoelectric device applications

Bi₄Ti₃O₁₂ (BiT) platelet incorporated 0.36BiScO₃-0.64PbTiO₃ (BS-PT) thick films were successfully developed for high temperature piezoelectric device applications. Their microstructure and ferroelectric and piezoelectric properties were systematically investigated to demonstrate the effect of the BiT template. It was found that the incorporation of BiT template was not responsible for textured grain growth of the BS-PT thick films; however, it could result in grain growth and densification of the BS-PT thick films by optimizing the sintering temperature and amount of BiT template. In particular, a 4 wt% BiT-incorporated BS-PT thick film sintered at 1000°C exhibited a pure perovskite structure and excellent piezoelectric properties of d₃₃ (440 pC/N) and k_p (53%), despite the presence of micro-pores caused by molten BiT. The BS-PT thick film, exhibiting good ferroelectric characteristics of P_r of 39.4 μC/cm² and E_c of 3.0 kV/mm at 1 kHz, also had an extremely high T_c of approximately 402°C. This implies that the BiT platelet incorporated BS-PT thick film is applicable for high temperature piezoelectric devices.     

Multi-electrochromism behavior and electrochromic mechanism of electrodeposited molybdenum doped vanadium pentoxide films

Molybdenum doped vanadium pentoxide (Mo doped V₂O₅) films are prepared by cathodic electrodeposition on indium tin oxide substrate from Mo doped V₂O₅ sol. As an anodic and cathodic coloration electrochromic material, the electrodeposited Mo doped V₂O₅ film presents a better cycling stability, reversibility and multi-electrochromic behavior (orange-yellow-green-blue) with an optical modulation of 60-90% in the spectral region 550-900 nm, which can be expected as a result of enhanced electron intervalence transfer between Mo⁶⁺ and V⁵⁺, V⁴⁺ states, in addition to V⁵⁺ and V⁴⁺ transition. The electrochromic mechanism of Mo doped V₂O₅ films is investigated with atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The surface roughness of the film increase at the different coloration states due to the increasing crystallinity degree. The change of the interlayer spacing for the host V₂O₅ and the change of the C and Li element states verify the insertion of organic solvent into the interlayer of the host V₂O₅ and some of the Li⁺ ions into the sites in the V-O layers. The electrochromic kinetics process indicates that the electrochromism of Mo doped V₂O₅ films can be considered as a reversible reduction/oxidation process accompanying the insertion/extraction of Li⁺ ions and electrons.     

Solution combustion synthesis of iron-deficient Sc2-xFexO3 (x = 0.17-0.47) nanocrystals with bixbyite structure: The effect of spatial constraints

In this paper, nanopowders based on iron-deficient Sc_2-xFe_xO₃ (x = 0.17–0.47) nanocrystals with bixbyite structure and crystallite size of 3.7–38.9 nm were successfully synthesized via solution combustion. Variable glycine-to-nitrate (G/N) ratio was the main controlling factor. A wide range of experimental and computational methods were used to analyze the impact of spatial constraints on the resulting solid-state products. It was found that solution combustion mode greatly influenced on the temperature and gaseous products in the reaction zone. Volume (G/N = 0.4–0.8, T_max = 1179–1511 °C), self-propagating (G/N = 1.0–1.4, T_max = 614–957 °C) or smoldering (G/N = 0.2, T_max = 443 °C) combustion modes were acquired during the synthesis depending on G/N ratio. It was shown that the formation of impurity phases of am-Fe₂O₃ (T_max < 850 °C), c-Fe₃O₄ (900 °C < T_max < 1500 °C) or c-FeO (T_max > 1500 °C) was possible, depending on the combustion temperature. Besides, the combustion mode affected the porous and surfacial structure of resulting mesoporous nanopowders – specific surface area and total pore volume varied in ranges of 1.7–82.8 m²/g and 0.0088–0.1538 cm³/g, consequently. Chemical composition and unit cell parameters of Sc_2-xFe_xO₃ showed the positive deviation from Vegard's law. The average sizes of the interpore thickness (h) depending on G/N ratio were found from values of specific surface area and pycnometric density of nanopowders, which made it possible to establish the presence of spatial constraints for the crystals' growth of Sc_2-xFe_xO₃ at h values below 10 nm. Analysis of aspect (h/D) ratio allowed to determine synthetic parameters which led to mono- or polycrystalline structure of interpore space in resulting Sc_2-xFe_xO₃-based nanopowders. The results and patterns established in this paper allowed to synthesize a new type of foam-like functional materials based on rare-earth ferrites.     

Effect of laser power density on the electrochromic properties of WO3 films obtained by pulsed laser deposition

Pulsed laser deposition (PLD) was used to prepare tungsten trioxide (WO₃) films on ITO substrates with a varying laser power density of 4.0–5.5 W/cm². XPS indicated that when the laser power density decreased, the peak positions of the W 4f and O 1s orbits shifted slightly to low energy due to the difference in oxygen vacancies. As the laser power density decreased, W⁶⁺ gradually replaced the lattice position of O^2?, increasing oxygen vacancies in the lattice. The transmittance modulated values (ΔT) were over 44% at 830 nm, indicating strong absorption by the WO₃ thin films in the near-infrared ray. The switching time of the WO₃ thin films between bleached states and coloured states decreased as the laser power density increased due to the amorphous structure, morphology, and lower oxygen deficiency at a high power density. The high ΔT and very fast switching time of t_b (1.09 s) and t_c (6.01 s) demonstrated the excellent electrochromic (EC) properties of the WO₃ films prepared by PLD.