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In the current work, a new nanometric TiO 2 -based magnetic catalyst has been developed from an innovative material obtained from the treatment of iron and steel industrial wastes, i.e. Fly Ash. This magnetic material, " MaM ", contains iron in the chemical-mineralogical composition and it represent an excellent example of circular economy: the industrial waste is converted into a high technological valued product. Through a one-step hydrothermal activation, the precursor is transformed in a zeolite with good magnetic properties. These properties could be exploited in the environmental field, such as the degradation of emerging pollutants in aqueous media by coupling it with a photocatalyst. In particular, in this work, TiO 2 nanoparticles are synthesized through a sol-gel synthesis and then mixed with MaM by means of ultrasounds, in different pH conditions: acidic (0.1 M HNO 3), neutral and alkaline (0.1 M NaOH). The MaM -TiO 2 composites are subjected afterward to a mild thermal treatment. The synthesized devices are characterized by means of X-Ray diffraction measurements (XRD) and scanning electron microscopy (SEM-EDS), while their photocatalytic activity is evaluated through the abatement of methylene blue (MB) solutions, according to the ISO norm 10678:2010. Based on experimental evidence, alkaline conditions lead to a homogeneous covering of the supporting material and therefore they are preferred to achieve a good photocatalytic activity; eventually the same conditions appeared to be crucial for the possibility to recover and subsequently reuse the composite material. • Composite material made of TiO 2 and magnetic zeolite for environmental purposes. • Supporting material with magnetic and adsorption features synthesized from iron waste. • Synthesis in alkaline conditions enhance recovery and recycling of the composite powders. [ABSTRACT FROM AUTHOR]

It remains a challenge to enhance the multiferroic properties of perovskite materials. Herein, we demonstrate a facile sol-gel synthesis of BiFeO 3 and Bi 0.98 Ho 0.02 Fe 1- x Cr x O 3 (x = 0.01, 0.02, 0.03 and 0.04) nanoparticles with an average size range of 71–35 nm. The crystal phase and structure of as-synthesized powders are studied using Rietveld refinement, which reveal 100% perovskite phase with rhombohedral R3c structure. A saturated loop with small remnant magnetization (M r) reflects weak ferromagnetism in all the samples. The dc magnetization along with Mössbauer spectroscopy confirms ferromagnetic nature of the compounds. Further, it is to be noted that the co-doping enhances the saturation magnetization to almost three times more than that of pure BiFeO 3 and related mechanism was studied in details. Simultaneously, the ferroelectric polarization (P m) was found to increase from 0.44 μC/cm2 (pure BiFeO 3) to 2.08μC/cm2 (Cr doped Bi 0.98 Ho 0.02 FeO 3). The co-doped samples show high resistivity which is confirmed by the decrease of loss tangent (tanδ) from 3.6 to 0.17 due to the reduction of oxygen vacancies. The band gap of as prepared samples was also found to increase at higher Cr concentration. To the best of our knowledge, for the first time, we have attempted to enhance the multiferroic properties of BiFeO 3 using Cr and Ho as co-dopants. • Nanoparticles of Ho, Cr co-doped BiFeO 3 multiferroics are prepared by sol-gel route. • Remarkable decrease in particle size is observed with increase in Cr content. • 3-fold increment in M s is obtained for Bi 0.98 Ho 0.02 Fe 0.96 Cr 0.04 O 3 compared to BiFeO 3. • Doped samples exhibit enhanced electrical polarization and resistive behaviour. • A blue shift (530–455 nm) is observed in UV–Vis absorption spectra with Cr doping. [ABSTRACT FROM AUTHOR]

Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) ceramics with super large grain size (>50 μm) have been successfully fabricated by sol-gel method. The effects of pH value of precursor solution on microstructure, electric properties and fatigue behavior were systematically studied. BCZT ceramics with super large grain size (35–55 μm) were prepared by BCZT powders with large particle size (136–221 nm) by controlling the pH value. The grain size and densification of BCZT ceramics decrease with the increase of pH value of precursor solution. XRD results indicate that there is the coexistence of rhombohedral and tetragonal phase in BCZT ceramics synthesized by precursor solution with a pH of 3 and are the coexistence of orthorhombic and tetragonal phase in BCZT ceramics synthesized by precursor solution with a pH of 5 and 7. BCZT ceramics shows obvious diffuse ferroelectric-paraelectric phase transition characteristic and the diffuseness behavior enhances as the pH value increases. The remnant polarization and coercive electric field of BCZT ceramics reduce with the decreased grain size caused by the increase of pH value. The excellent piezoelectric properties (d 33 = 585.6 pC/N and d 33 ∗ = 898 pm/V) of BCZT ceramics have been obtained by super large grain size and the construction of phase boundary of tetragonal phase and orthorhombic phase. Furthermore, BCZT ceramics with large grain size still has high fatigue resistance to bipolar electric cycling. • BCZT ceramics with super large grain size (>50 μm) are obtained. • Enhanced piezoelectric properties (d 33 = 585.6 pC/N and d 33 ∗ = 898 pm/V) are obtained. • High piezoelectric response results from super large grain size and phase boundary. [ABSTRACT FROM AUTHOR]

Cobalt-zinc ferrite nanoparticles having composition Co 1-x Zn x Fe 2 O 4 were processed by sol-gel method with particle sizes ranging from 10.8 nm to 3.6 nm. The crystal structure, particle size, and magnetic properties were investigated by XRD, FTIR, TEM, and VSM techniques. Single domain nature was established from the coercivity versus particle size curve. The dependence of specific saturation magnetization with zinc concentration was discussed in terms of site occupancy of cations and supported by FTIR measurements. A few single domain nanoparticle compositions exhibiting low Curie temperatures and reasonably good magnetization were subjected to induction heating measurement to explore the possibility of using the materials for magnetic hyperthermia. The material, having the composition, Co 0.37 Zn 0.63 Fe 2 O 4 was shown to be an excellent candidate for conducting hyperthermia study with self-regulated temperature at 46 °C. • Nanoparticles of size from 3.6 nm to 10.8 nm were synthesized by sol-gel method. • The chelating agent, polyvinyl alcohol was found to be powerful in controlling the particle size. • The transition from multi-domain to single domain nanoparticle was established with zinc concentration. • The composition Co 0.37 Zn 0.63 Fe 2 O 4 was developed with Curie temperature, 46 °C. • Self regulated magnetic hyperthermia in the composition, Co 0.37 Zn 0.63 Fe 2 O 4 was achieved. [ABSTRACT FROM AUTHOR]

In this study, titanium dioxide (TiO 2) nanotubes were grown using an electrochemical method, and different annealing conditions were tested for the structural surface properties. La 0.8 Sr 0.2 Co 0.5 Ni 0.5 O 3 (LSCNO) perovskite film was prepared by the sol-gel process. TiO 2 nanotubes and LSCNO perovskite film were combined to form a PN-type heterojunction structure for use in a carbon monoxide (CO) sensor. The experimental results showed that the TiO 2 /LSCNO heterojunction structure had a PN junction rectifier and makes a better CO sensor at 200 °C for a 400 ppm CO concentration. The response of the CO sensors was 38.41%, with good recovery and reproducibility. Image 1 • High response CO sensor with TiO 2 /LSCNO heterocontact was prepared. • The CO sensor can operate at relatively low temperatures. • The response of the CO sensors is 38.41%, with good recovery and reproducibility. • The sensing mechanism of TiO 2 /LSCNO heterostructure is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we reported the effects of the order of plasma treatment and high temperature annealing on solution-processed amorphous indium magnesium zinc oxide (a-IMZO, In:Ga:Zn = 3:1:1) thin film transistors (TFTs). Specifically, we utilized two different processes to fabricate TFTs. In one process, the active layers were plasma-treated (PT, 10 W, 10min) before high temperature thermal annealing (TA, 400 °C), and in another process, the active layers were plasma-treated after high temperature annealing. The former achieves lower off-current (5.83 × 10−12 A) and larger on/off current ratio (2.2 × 107), because the oxygen-related ions in the N 2 O plasma treatment can passivate the surface of the active layer and reduce the residual organic groups. However, introducing of O2+ and O2− ions leads to an increase in interface defects. The latter sample reaches a mobility 1.97 cm2/V·s, as the generated nanopores during high temperature annealing provide path for more atomic oxygen to infiltrate the film during PT and the oxygen vacancies are reduced. However, the on-current drops sharply with plasma treatment power for the increase of oxidation depth. In addition, all the PT samples show small hysteresis and improved stabilities. Our study suggests that moderate plasma treatment can be adopted to improve the a-IMZO TFT device performances. • PTbTA sample achieves lower off-current and larger on/off current ratio. • I on of PTaTA sample increases significantly and achieves higher mobility. • All the samples indicate an amorphous structure. • All the PT samples show small hysteresis and improved stabilities. [ABSTRACT FROM AUTHOR]

Abstract Ag-loaded TiO 2 -ZnO thin films, with low ZnO content, were synthesized by a one-step sol-gel process. The Ag content varied in the interval 0–4 mol% Ag. The films were deposited on glass substrates and post-annealed at 500 °C to induce crystallinity. By using the Tauc model, it was determined that the higher the Ag concentration the higher the optical band-gap energy of the films, a result attributed to the Burstein-Moss effect. Images obtained by scanning electron microscopy and transmission electron microscopy depicted aggregated particles with grain size close to 20–25 nm for the oxides with no Ag, whereas the particle size decreased with the addition of Ag. X-ray photoelectron spectroscopy measurements indicated the formation of the Ti4+ and Zn2+ oxidation states, while Ag was found in the metallic state. A depth profile analysis, performed by secondary ion mass spectrometry, confirmed the presence of Ti, Zn, and Ag in the films. X-ray diffraction patterns displayed the anatase phase of TiO 2. For (TiO 2) 0.95 -(ZnO) 0.05 thin films, a BET analysis showed that the specific surface area increased from 4.56 up to 48.84 m2/g as a consequence of Ag doping. The photocatalytic degradation of the materials under UV irradiation was assessed by using methylene blue as a model pollutant. For (TiO 2) 1-x -(ZnO) x compounds with no Ag, the highest response corresponded to x = 0.05. In addition, the optimum photodegradation was found for (TiO 2) 0.95 -(ZnO) 0.05 thin films with 2 mol% Ag. Graphical abstract Image 1 Highlights • Ag-doped TiO 2 -ZnO thin films were deposited by the sol-gel process. • The incorporation of Ag in the films was demonstrated by SIMS and XPS. • The maximum BET area was found for (TiO 2) 0.95 -(ZnO) 0.05 films doped with 2 mol% Ag. • (TiO 2) 0.95 -(ZnO) 0.05 films doped with 2 mol% Ag showed the highest photoactivity. [ABSTRACT FROM AUTHOR]

Structural, optical, temperature dependent magnetic and electrical properties have been investigated for the nanocrystalline NiFe 1.97 RE 0.03 O 4 (RE = La3+ and Sm3+) compound. Without any signs of a secondary REFeO 3 phase, the Rietveld refinement reveals a single-phase spinel structure possessing cubic symmetry for current samples. The decrease in lattice constant has been observed as a result of RE ions substitution. The TEM micrographs reveal nanosized particles with an average size of 35 ± 3 nm and 32 ± 3 nm for La3+ and Sm3+ substituted samples. EDX spectra of both samples show good compositional homogeneity. HRTEM micrographs of both samples show well resolved lattice fringes and their inter-planar spacing matches with that obtained from the Rietveld analysis of the XRD patterns. The concentration of Fe2+ and Fe3+ ions has been estimated from the XPS spectra analysis and it is found to be ∼ 22% and 78% for NiFe 1.97 La 0.03 O 4 and, 20% and 80% for NiFe 1.97 Sm 0.03 O 4 compound. The optical energy band gap for rare earth substituted samples is found to be more than that of pure nickel ferrite. The value of saturation magnetization (M s) and magneto-crystalline anisotropy constant (K 1) estimated from the "Law of Approach to Saturation" equation for rare earth substituted samples are found to be less than that of pure nickel ferrite. However, an enhanced value of coercivity has been observed with RE substitution. ZFC (zero field cooling) and FC (field cooling) DC magnetization curves measured at 100 Oe in the temperature range of 60–400 K reveal a combination of weak and intermediate forms of magnetic interaction between the particles for both samples. Temperature dependent analysis of saturation magnetization and coercivity employing modified Bloch's law and Kneller's relation supports the nanomagnetic behavior of both samples. Under an AC magnetic field of 14.92 kA/m and frequency 337 kHz, the SAR and ILP values have been found to be ∼ 331 W/g and 4.22 nHm2/kg for NiFe 1.97 La 0.03 O 4 and, ∼ 241 W/g and 3.21 nHm2/kg for NiFe 1.97 Sm 0.03 O 4. The dielectric relaxation data have been analyzed at various temperatures ranging from 40 to 300 0C over the frequency range 100 Hz-1 MHz using electrical impedance spectroscopy. The dielectric constant for rare earth substituted samples is found to be more and their AC conductivity is observed to be less than that of pure nickel ferrite. The analysis of temperature dependent AC conductivity employing Jonscher's power law suggests that the charge carrier's conduction mechanism of both samples follows the small polaron hopping mechanism below 200 0C, thereafter; it follows the correlated barrier hopping mechanism. The activation energy estimated by imaginary impedance spectra is found to be 0.411 eV and 0.398 eV for NiFe 1.97 La 0.03 O 4 and NiFe 1.97 Sm 0.03 O 4 which is more than that of pure nickel ferrite. The Cole-Cole plots at different temperatures suggest the presence of non-Debye-type relaxation. The modeling of Cole-Cole plots with equivalent circuits for both samples confirms the contribution of both grain and grain boundary in electrical conduction. The estimated stretching exponential factor by fitting the modified KWW (Kohlrausch-Williams-Watts) equation to the imaginary modulus curve reveals relatively more dipole-dipole interaction in NiFe 1.97 Sm 0.03 O 4 than that of the La3+ substituted sample. [Display omitted] • Samples crystallized to single phase cubic spinel structure with F d 3 − m space group. • ZFC-FC analysis reveals intermediate type magnetic interaction between particles. • SAR is estimated by initial slope, Box-Lucas and modified Newton cooling approach. • Nyquist plots reveal non-Debye type dielectric relaxation and NTCR type behavior. • Presence of considerable induced dipole-dipole interaction in current samples. [ABSTRACT FROM AUTHOR]

Abstract High dielectric and magnetic properties coexisted in one is important for the miniaturization and multifunction of electronic devices. Ni doped barium ferrites were successfully fabricated by sol-gel technique in this work. The microstructures and properties were investigated by the means of XRD, SEM, XPS, impedance analysis and magnetic property measurement systems. Results showed that main phase of M-type barium ferrite with hexagonal plate-like grains and Ni2+ ions substituting for Fe3+ as BaFe 12-x Ni x O 19 was formed. Ni2+ doping promotes the formation and grain growth of barium ferrite ceramics. The optimized sintering temperature was 1250 °C at which relatively perfect microstructure was formed. Giant permittivity above 20 k and low dielectric loss of ∼0.1 generated in the ferrite. Low H a of 14–13 kOe and H c of 145–111 Oe emerged and large saturation magnetization of 60–72 emu/g presented in Ni2+-doped barium ferrites ceramics. The coexistence of impressive dielectric and magnetic properties in Ni2+-doped barium ferrites ceramics, makes it potential candidate in the area of miniaturization and multifunction of electronic devices. Highlights • Ni doped ferrite as BaFe 12-x Ni x O 19 is fabricated successfully by sol-gel process. • Ni2+ is controlled to substitute for Fe3+ in down-spin site. • Fe2+/Fe3+ electron pair dipoles are controlled to form in Ni2+-doped ferrite. • High M s of ∼72 emu/g and giant permittivity of above 20 k coexist in doped ferrite. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles of high saturation magnetization with least particle size are essential candidates for certain biomedical applications like hyperthermia. The development of such nanoparticles requires stringent processing conditions in arriving at desired characteristics. Magnesium substituted cobalt ferrite nanoparticles of size around 4 nm were processed by sol-gel method with high saturation magnetization and characterized by techniques XRD, TEM, FESEM and FTIR in elucidating the structural parameters. Magnetic properties were discussed in terms of a proposed cation distribution and occupancy of magnesium was established from electrical resistivity measurements. [ABSTRACT FROM AUTHOR]

The pure single phase BiFeO 3 nanoparticles have been prepared by microwave-assisted sol-gel process and its structure and magnetic properties have been studied. X-ray diffractometer, infrared and transmission electron microscope results show that the synthesized BiFeO 3 nanoparticles at the calcining temperature of 450 °C exhibits a rhombohedrally distorted perovskite structure without secondary phase and the size is about 40 nm. Meanwhile, the pure single phase BiFeO 3 particles exhibit typical ferromagnetic properties at room temperature and the obvious large exchange bias phenomenon at 60 K. A exchange bias field (H E ) of 302 Oe at 60 K for pure single phase BiFeO 3 nanoparticles at calcining temperature 450 °C after field cooling at 20 KOe has been observed. The MT curve at H = 100 Oe shows that the FC and ZFC magnetization curves start to differ in the temperature range from 60 K to 300 K revealing spin glass behavior of BiFeO 3 nanoparticles at calcining temperature 450 °C, 500 °C and 550 °C. The ferromagnetic behavior is attributed to size of effects, which partially destroy the long-wavelength cycloid spin structure expected in bulk BiFeO 3. The exchange bias effect in single crystalline BiFeO 3 nanoparticles arises from co-existence of different magnetic phases of an antiferromagnetic core and a ferromagnetic surface. The ferromagnetic, exchange bias effect and spin glass behavior of BiFeO 3 nanoparticles are assigned to the uncompensated or canted spins at the ferromagnetic surface and an antiferromagnetic core of BiFeO 3 nanoparticles. [ABSTRACT FROM AUTHOR]

Gadolinium orthoniobate GdNbO 4 (GNO) and orthotantalate GdTaO 4 (GTO) thin films (∼100 nm) were prepared by sol-gel/spin-coating process on Al 2 O 3 substrates with Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) interlayer and annealing at 1000 °C. The precursors of films were synthesized using Nb or Ta tartrate complexes. We also report for the first time the FTIR, Raman spectra and morphology of tartrate GNO and GTO precursors annealed at various temperatures. The different phase transformation was determined in GNO or GTO precursors from fluorite T′-structure via orthorhombic O-GdNbO 4 or cubic C-GdTa 7 O 19 to monoclinic M-GdNbO 4 or M′-GdTaO 4 during annealing at 800–1200 °C. XRD results of GNO or GTO films confirmed the coexistence of M-GdNbO 4 or M′-GdTaO 4 phase in addition to O-GdNbO 4 (in GNO) or C-GdTa 7 O 19 (in GTO) as main phase at 1000 °C. The surface morphology and topography of thin films were investigated by the SEM and AFM analysis. GNO film was smoother with roughness of 7.31 nm in comparison with GTO (3.53 nm). The results of this work can contribute to the formation different polymorphs of these films for the application to environmental electrolytic thin film devices. [ABSTRACT FROM AUTHOR]

In this paper, we review the challenges and opportunities for foam materials and their composites as novel energy conversion materials. Specifically, foams with an exceptionally high specific surface area could be a perfect solution for advanced energy applications because the electrodes with limited reaction area between an electrolyte and an active material have been identified as one of the key factors affecting the low-level performance of Li-ion batteries, which is a major challenge hindering their commercial application. In the past decade, several electrode materials, structures, and fabrication processes have been developed and investigated with the intention of improving electrode performance. Among these processes, foam architecture is attractive as an electrode structure in Li-ion batteries as it has an intrinsic structural integrity with the ability to buffer stress caused by the large volume changes in high capacity anode materials during cycling. In this review, the electrochemical properties, reversible capacity, long cycle capability, high discharge capacity, battery lifetime, power density, energy efficiency, tensile strength, and mechanical properties of various foam electrode materials are discussed. The foremost objective of this review is to provide an overview on the latest research on improved electrode performance and current perspectives on porous electrode materials for future Li-ion batteries. [ABSTRACT FROM AUTHOR]

Currently, more attentions have been paid to the design and synthesis of three dimensional nanostructures. ZnO urchin-like shapes assembled by nanoparticles are grown on FTO glass substrates by sol-gel electrophoretic deposition of a colloidal sol containing zinc acetate (ZAD), triethylamine (TeA), and methanol. Based on observations from a time-dependent morphology evolution process, a three-step sequential growth model is recommended. The formation of urchin-like ZnO nanostructures depends on the type of media, sol concentration, and molar ratio of TeA/ZAD. Importantly, strong structure-induced photocatalytic performance enhancement for the degradation of methylene blue is obtained by these ZnO nanostructures compared to traditional ZnO film. The large specific surface area (48.4 m 2 g −1 ), strong light absorption ability, and nanoparticle shape affect the charge separation and transfer of urchin-like particles and hence enormously enhance the performance of photocatalyst. This work helps better understanding of the urchin-like shapes formed during sol-gel electrophoretic deposition and introduces an efficient way to enhance the photocatalytic efficiency of ZnO by changing the morphology. [ABSTRACT FROM AUTHOR]

The synthesis of mono-sized silica nanoparticle with mesostructures via sol-gel method by employing ammonium polycarboxylate (APC) surfactant has investigated. The major aim of this paper is to introduce APC as an appropriate surfactant to control nucleation and growth of nanoparticles during hydration and condensation steps of the sol-gel process. Dynamic light scattering (DLS) results indicated that the particle in the sol containing APC had an average particle size about 10 nm. The bonds of prepared silica nanoparticles were studied by IR spectroscopy and X-ray photoelectron spectroscopy (XPS). The result of scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) confirmed that applying APC could sufficiently induce the mass transfer during the synthesis process, this claim have also verified according to the particle size analysis. Resulting information also approved the synthesis of spherical and mono-sized nanoparticle with an average particle size of 25 nm. Furthermore, the synthesized nanoparticles possessed a mesostructured characteristic due to leaving of APC organic components during final heat treatment. N 2 adsorption/desorption porosimetry indicated that the particles were comprised of mesopores with an average pore size of 2.5 nm and specific surface area of 1015 m 2 g −1 . This strategy could be readily applied to prepare an engineered product of silica nanoparticles with uniform spherical morphology and mesostructure. [ABSTRACT FROM AUTHOR]

A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho 3+ ) lithium ferrites; Li 1.2 Co 0.4 Ho x Fe 2−x O 4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO 3 ) were appeared for x ≥ 0.06 indicating the solubility limit of Ho 3+ ions. The lattice constant ′ a′ increased from 8.351 to 8.360 Å upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 Å. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho 3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho 3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral ( v 1 ) and octahedral ( v 2 ) intrinsic vibrational bands at 627 cm −1 and 479 cm −1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants ( K o and K t ) were calculated and discussed with the tetrahedral (r A ) and octahedral (r B ) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 10 3 to 5.56 × 10 4 (Ω-cm) −1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho 3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li 1.2 Co 0.4 Ho 0.12 Fe 1.88 O 4 . The improved coercivity may suggest their utilization in perpendicular recording media applications. [ABSTRACT FROM AUTHOR]

Transparent conductive ZnO films doped with 0–6 mol% of Al 3+ (or AZO films) and AZO- rGO (rGO - reduced graphene oxide, ∼0–0.5 g/L) nanocomposite films were deposited on silica glass substrates by sol-gel multilayer spin-coating, with annealing at 250 °C in vacuum. The effects of the processing conditions on the structure, optical and electrical properties of the AZO-rGO films, as well as the AZO thin films for comparison, were investigated by XRD, Raman spectroscopy, TEM and SEM, UV-Vis-NIR spectroscopy, and with the four-point prober and Hall effect measurements. Al 3+ ions and rGO sheets existed in the composite films, and both of more Al 3+ amount and more rGO could result in worse crystallinity of ZnO. More amount of rGO led to more rGO flakers existed in the surface of the AZO-rGO films. Increasing Al-doping amount could not obviously affect the optical transmittances of the AZO-rGO films, but lead to the UV absorption edge of the films slightly blue-shifted. Optical transmittances of the AZO-rGO films decreased obviously with increasing the rGO ratio, but slightly decreased with increasing the annealing time. The minimum sheet resistance R □ could be obtained when Al-doping amount was ∼2 mol% and rGO ∼0.25 g/L: 50.1 kΩ/□ for the AZO film and 15.2 kΩ/□ for the AZO-rGO film. Addition of rGO could improve the electric conductivity of AZO films. Longer time of vacuum-annealing could also improve the electric conductivity of the AZO-rGO films. For the AZO-rGO film doped with 2 mol% Al 3+ and 10 mg rGO after vacuum-annealing for 12 h, Hall mobility was ∼17.7 cm 2 /Vs and the carrier concentration was ∼10.6 × 10 19 /cm 3 . [ABSTRACT FROM AUTHOR]

Double perovskite Sr 2 CrReO 6 (SCRO) powders were prepared using a sol-gel process and molten-salt synthesis (MSS) method and then followed by annealing at different temperatures in N 2 (or Ar) atmospheres. They were characterized by powder X-ray diffraction and then followed by structural Rietveld refinements. The results reveal that at room temperature all the SCRO powders crystallize in a tetragonal phase structure with space group of I 4/ m. The Cr/Re cationic ordering degrees (η) at B-site in the sol-gel derived SCRO powders annealed in Ar and N 2 atmospheres, were about 68.9 % and 45.3 % respectively. The η values for the SCRO powders prepared by MSS method under the molar ratios of product-to-flux with 1:100, 1:80, and 1:50, were 67.4 %, 57.0 % and 54.3 %, respectively. All the SCRO powders exhibited ferromagnetic behaviors at room temperature and their saturation magnetization (M S) values at 2 K were in range of 0.52–0.67 μ B /f.u., smaller than the theoretical value of 1.0 μ B /f.u. That can be ascribed to the anti-site defects as well as the surface spin disorders in these SCRO powders. The sol-gel derived SCRO powders had a bead-like morphology and their average composition is slight Cr-rich and Re-deficient with a chemical formula of Sr 2 Cr 1+x Re 1−x O 6+δ , whereas the SCRO powders prepared by MSS method exhibited a spherical morphology and their average composition is slight Cr-rich and Sr-deficient with a chemical formula of Sr 2−y Cr 1+y ReO 6+δ. XPS spectra confirm a mixed valence states of Cr3+ and Cr6+ ions in the sol-gel derived SCRO powders, while only Cr3+ ions present in the SCRO powders prepared by MSS method. The Sr2+ ions and a mixed Re4+ and Re6+ ions exist in all the SCRO powders, and three kinds of oxygen species are present as lattice oxygen (O2-), adsorbed oxygens, and the oxygens in hydroxyl groups, respectively. The sol-gel derived SCRO powders had a higher M S but a smaller H c in comparison with the powders prepared by MSS method, which enables them to have promising applications in future spintronic devices. [Display omitted] • Sr 2 CrReO 6 (SCRO) powders were synthesized by sol-gel process and MSS method. • SCRO powders crystallize in a tetragonal crystal structure with I 4/ m space group. • SCRO powders exhibit ferromagnetic behavior at room temperature. • Their saturation magnetization (M S) values at 2 K are in range of 0.52–0.67 μ B /f.u. • XPS spectra identify the valence states of the constituent elements in the powders. [ABSTRACT FROM AUTHOR]

Tb-doped and (Zn,Tb)-codoped Ba 0.75 Sr 0.25 TiO 3 (BST) crystalline powders were prepared via a sol-gel process. Photoluminescence spectra of the samples were recorded at room temperature. When excited by 320 nm ultraviolet light, several emission peaks were detected, including four characteristic emission peaks of Tb 3+ located at 488 nm, 543 nm, 589 nm and 624 nm. Further research indicates that the various Tb 3+ doping concentrations range from 1 to 2 at. % can result in the different intensities of emission peaks depending on their positions. The intensities of emission peaks at 488 nm and 624 nm decrease with increasing the concentration of Tb 3+ , while the intensity of the peak at 543 nm has a relatively slow response to the variation of Tb 3+ concentration. The concentration quenching phenomena were observed in all the emission peaks, and the quenching concentration of Tb is different depending on the peak position. In addition, PL emission peak intensities are enhanced by (Zn,Tb)-codoping, which is understood by a charge compensation mechanism of defects. According to CIE coordinates, green-emitting phosphors based on BST crystalline powders were obtained. The experimental results imply a potential green light application of Tb-doped and (Zn,Tb)-codoped BST materials. [ABSTRACT FROM AUTHOR]

Mn-Co-Zr substituted BaM ferrite with enhanced saturation magnetization (Ms) was prepared by so-gel method for high-frequency applications. The substituted single-phase BaM ferrite is prepared by heat treating at 1100 °C for 4 h. We used SEM, XRD and VSM (vibrating sample magnetometer) to study the sample's morphology, phase and magnetic properties. SEM result shows the ferrite particle size is reduced from 250 nm to 35 nm as substitution x = 1.2. Though BaM ferrite is traditionally a permanent magnetic material, VSM measurements indicate it becomes soft magnetic material after substituting the Mn-Co-Zr ions. The coercivity (Hc) and Ms are 3658 Oe and 58.8 emu/g for x = 0.2, and it becomes 317 Oe and 48.7 emu/g for x = 1.2. Vector network analyzer (VNA) was employed to investigate the high-frequency electromagnetic properties of the ferrite. It was found that the resonance peak decreases as x increases. The reflection loss (RL) is smaller than 10 dB for frequency ranges of 7.2–12.2 GHz and smaller than 20 dB for 9.1–10.6 GHz. The maximum RL is 23 dB at frequency of 9.7 GHz for x = 1.2. Mn-Co-Zr substituted BaM ferrite might be a good candidate for electromagnetic compatibility and for other applications at high frequencies. [ABSTRACT FROM AUTHOR]

Calcium sulfate (CaSO 4 ) powders doped with different amounts of manganese (Mn 2+ ) ions were synthesized by sol-gel process. The Mn concentration was changed from 0 to 5%. Here we attempted to fabricate Mn doped CaSO 4 samples and characterized them for their optical and structural properties. The Ultraviolet–Visible analysis (UV–Vis), infrared spectroscopy (FT-IR) and powder X-ray diffraction (XRD) have been used to characterize the optical properties, phase evolution and crystallinity of the obtained samples. X-ray diffraction patterns revealed that CaSO 4 powders obtained were crystallized. The crystallites sizes of the obtained CaSO 4 powders were found to be from 321.3 to 417.7 Å. The transmittance has decreased from 67 to 42% and the band gap of pure CaSO 4 has been found to 3.94 eV and it is shifted to 3.71 eV for 5% Mn doped CaSO 4 . The results obtained in this study were discussed comparatively with those cited in the literature. [ABSTRACT FROM AUTHOR]

Polycrystalline Bi 4 YFeTi 3 O 15 thin films were prepared on (111)Pt/Ti/SiO 2 /Si through a sol-gel process. X-ray diffraction analysis shows the films have a single-phase four-layered Aurivillius structure with the space group of Fmm 2. As expected, the Bi 4 YFeTi 3 O 15 films exhibit the coexistence of ferroelectric and weak ferromagnetic properties with the remanent polarization (2 P r ) ∼ 53.62 μC/cm 2 and the saturated magnetization ( M s ) ∼ 0.50 emu/cm 3 at room temperature. More interestingly, both dielectric relaxation behavior and room-temperature magneto-dielectric effect were observed in the Bi 4 YFeTi 3 O 15 films, probably resulting from the coexistence of Fe 2+ and Fe 3+ . The conduction mechanism of the films from 10 to 300 kV/cm is dominated by Ohmic mechanism, space-charge-limited current (SCLC), and trap-filled-limit (TFL) current, respectively. The leakage current density remains lower than 1.03 × 10 −5 A/cm 2 under the poling field below 300 kV/cm at 300 K. [ABSTRACT FROM AUTHOR]

Conducting Ag and Al co-doped ZnO (ZnO:Al:Ag) nanostructures were synthesized using sol-gel process. The effects of Ag incorporation on the structural, optical, electrical, and photoluminescent properties of ZnO:Al:Ag nanostructures were studied. The crystalline quality of the nanostructures was found to be improved by Ag doping concentration of 0.3% owing to compensation for vacancies created by Al 3+ via Ag + . The electrical properties were enhanced for Ag doping concentration of 0.3%. This may be due to an improvement of the crystalline quality. The optical band-gaps (E g ) of the nanostructures are significantly lower than that of undoped ZnO. The E g of the nanostructures slightly decreased to its minimal value with Ag doping, and was found to be about 3.19 eV for R Ag/Zn = 0.3%; the material then retained its initial value of 3.22 eV (R Ag/Zn = 0%) for higher Ag doping. With Ag doping, the value of work function (WF) increased from 4.67 eV for R Ag/Zn = 0% to 4.99 eV for R Ag/Zn = 0.3% due to substitution of Ag + into Zn 2+ sites. An absorption peak in the blue region was observed in the Ag-doped nanostructures; this peak redshifted with the increase of the doping concentration. The photoluminescence (PL) intensity in the near band edge (NBE) region was the highest for the Ag/Zn ratio of 0.3%, whereas the maximum PL intensity in defect region was obtained for the Ag/Zn ratio of 0%. [ABSTRACT FROM AUTHOR]

Li 4 Ti 5 O 12 /hierarchical porous carbon matrixes composites are successfully prepared by a facile and fast polymers assisted sol–gel method, aiming to promote both electronic and ionic conductivity. As indicated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis, three less expensive cost and available water soluble polymers (e.g. PAA, CMC, and SA) can homogeneously react with Li–Ti–O precursor to incorporate into interior of nano-scale lithium titanate and provide a continues conductive network after pyrolysis. In addition, the results of scanning electron microscopy and transmission electron microscopy also prove that the Li 4 Ti 5 O 12 nanoparticles are firmly embedded in porous carbon matrix with no obvious agglomeration. EIS measurement and cyclic voltammetry further reveal that the facilitated electrode kinetics and better ionic transport of Li 4 Ti 5 O 12 /hierarchical porous carbon matrixes composites than that of Li 4 Ti 5 O 12 . The c-CMC-LTO exhibits a superior capacity of 92 mAh g −1 and retains its initial value with no obviously capacity decay over 200 cycles under an ultra-high C rate (50 C). [ABSTRACT FROM AUTHOR]

TiO 2 nanocrystals were prepared by sol–gel/solvothermal processing and modified by the addition of W precursor before the solvothermal step. The W: Ti nominal atomic ratio (R W ) was fixed to 0.16 and 0.64. Surface modification of TiO 2 occurred for R W = 0.16 while for R W = 0.64 nanocomposites with WO 3 nanocrystals were obtained after heat-treatment at 500 °C. Pure TiO 2 proved to be very poorly performing in acetone sensing in all the operating conditions. Instead, the addition of both W concentrations largely enhanced the sensor response. It ranged over two orders of magnitude of conductance variation for all the tested concentrations at as low as 200 °C operating temperature. The results showed that it is possible to enhance the performance of an otherwise almost inactive oxide like TiO 2 by proper combination with another more active oxide like WO 3 . [ABSTRACT FROM AUTHOR]

In this work, multifunctional superhydrophobicity coatings have been produced on germanium, brass, steel and copper substrates with the help of simple sol–gel spray coating method. A simple testing, artificially simulated corrosive solution continuously exposes with coating surface for six months, it reveals the excellent anti-corrosion performance against corrosive salt solution at room temperature. The as-prepared superhydrophobic coating surface shows outstanding long-term durability, mechanical stability, self-clean ability, thermal stability and acid resistance. We will present how the sol–gel spray coating approach has been integrated into advanced multifunctional material to improve their stability performances against critical conditions and to extend their applications by introducing additional functionalities. [ABSTRACT FROM AUTHOR]

Calcium doped zinc oxide nanorods on ZnO seed layers were grown by hydrothermal method. Photoinduced bicolour laser treatment was done on the samples and the effective second order nonlinear coefficient ( d eff ) has been measured. The morphology of the samples was investigated by the field emission scanning electron microscope (FESEM) images. The structural parameters acquired from X-ray diffraction (XRD) patterns have been correlated with the measured d eff . The results have revealed that 15 mol% Ca doped ZnO nanorod showed maximum d eff because of the Lorentz local field established along the length of the nanorod. The aspect ratio and stress play a significant role in enhancement of d eff . The nonlinearity has been correlated with the absorption cross sections. [ABSTRACT FROM AUTHOR]

Wolframite type MgZrNb 2 O 8 ceramics were prepared by solid-state method and sol–gel process in this study, and the influence of sol–gel process on the sintering behavior and microwave dielectric properties of MgZrNb 2 O 8 ceramics was investigated. The optimal sintering temperatures of MgZrNb 2 O 8 ceramic for solid-state and sol–gel method were 1225 °C and 1175 °C, respectively. For solid-state method, MZN ceramics sintered at 1225 °C with nearly full density had the microwave dielectric properties of ε r = 27.08, Q· f = 29,070 GHz and τ f = −24.31 ppm/°C. For sol–gel process, MZN ceramics sintered at 1175 °C with nearly full density had excellent microwave dielectric properties of ε r = 22.16, Q· f = 29,490 GHz and τ f = −15.99 ppm/°C. Obviously, sol–gel synthetic route could significantly reduce the sintering temperature and improve the microwave dielectric properties. [ABSTRACT FROM AUTHOR]

The sol–gel spin-coating method is usually used for thin-film deposition rather than to grow one-dimensional nanostructures. In this study, a novel regrowth method for spin-coated ZnO:In 3+ films is demonstrated, using vapor-confined face-to-face annealing (VC-FTFA) in which a mica sheet is inserted between the two films prior to FTFA. ZnO:In 3+ nanorods are regrown when indium chloride is used as the solvent because ZnCl 2 and InCl 3 vapors are generated and confined between the films. The near-band-edge emission intensity of the ZnO:In 3+ nanorods resulting from VC-FTFA at 700 °C is enhanced by a factor of 17 compared with that of ZnO:In 3+ films annealed in open air at the same temperature. Our method offers a simple and low-cost route for the fabrication of ZnO nanorods. [ABSTRACT FROM AUTHOR]

Nanocrystalline powder samples with chemical formula Co x Mg 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized by sol–gel auto combustion method using citric acid as fuel agent. The rietveld refinement study of x-ray diffraction patterns confirmed the spinel single phase formation for all samples. Dielectric constant (ε′), dielectric loss tangent (tan δ ) and AC conductivity of Co x Mg 1−x Fe 2 O 4 ferrite nanoparticles have been measured at room temperature in the frequency range from 1000 Hz to 120 MHz. The dielectric dispersion observed at lower frequency region is attributed to Maxwell–Wagner two layer model, which is in agreement with Koops phenomenological theory. The observed results have been explained by polarization which is attributed to the electron exchange between Fe 2+ and Fe 3+ ions. The temperature variation of ε′ and tanδ for some particular frequencies were studied. The rapid increase in ε′ and tan δ has been explained using thermally activated electron exchange between Fe 2+ ↔ Fe 3+ and Co 2+ ↔ Co 3+ ions at adjacent octahedral sites. The role of interfacial polarization has been focused to explain the high dispersion in ε′ and tanδ with temperature observed at low frequencies. [ABSTRACT FROM AUTHOR]

Effect of incorporation of Ag on the structural, optical, electrical, and fluorescence properties of sol–gel derived Al-rich zinc oxide (ZnO:Al:Ag) nanostructured films was studied. The E g of the film slightly decreased to a minimal value with Ag doping, and was found to be about 3.65 eV for R Ag/Zn = 1% from its initial value of 3.72 eV (R Ag/Zn = 0%). The WF sudden increased to a maximal value of 5.12 eV with Ag doping (for R Ag/Zn = 1%) from its initial value of 4.73 eV for R Ag/Zn = 0% due to substitution of Ag into Zn sites until saturation was achieved (R Ag/Zn = 1%). After more Ag doping, WF started to decrease and finally, reached a value of 4.81 eV for R Ag/Zn = 3% because of the formation of an impurity-defect energy level below the intrinsic Fermi level of ZnO. With Ag-doping, the current increased up to R Ag/Zn = 1% due to the increase in carrier density. For R Ag/Zn = 3% doping, the current density started to increase due to the influence of metallic Ag. The defective peak position was blue shifted, with increased Ag-doping, from 536 nm (R Ag/Zn = 1%) to 527 nm for R Ag/Zn = 2% due to the sizes of the Ag + and Zn 2+ ions. The FL defective peak intensity (I D ) in the green region increased with the concentration of Ag used for doping, up to R Ag/Zn = 2%. The enhancement in the I D may be due to charge difference between the Zn 2+ ions, caused by Ag + ions. [ABSTRACT FROM AUTHOR]

(Bi 13 Co 12 )CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5 )CoO 40 (BCFO) nanoparticles are prepared by sol–gel auto combustion method. The X-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100 nm to 75 nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30 K, which seems to be competing paramagnetic and antiferromagnetic behavior. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, through-out the temperature range for BCO. For BCFO, the behavior may be divided under two regions viz., intrinsic (<260 K) and extrinsic (>260 K). Relaxation in both the regions is described by Arrhenius behavior with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak–Negami equation is found to better describe the observed relaxation data. [ABSTRACT FROM AUTHOR]

The aim of the work is to study the effects of oxygen vacancy and surface hydroxyl group density on the photocatalytic activity of Fe 3+ -doped TiO 2 , and to investigate how the titanium dioxide doped with different levels of the Fe 3+ influenced their physical and chemical characterizations. The photocatalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), electron spin resonance (ESR), X-ray photoelectron spectroscope (XPS) and Fourier transform infrared (FTIR) spectra. The results revealed that adsorbed hydroxyl group density significantly influenced the photocatalytic activity, and a small amount of Fe 3+ can act as a photo-generated hole and a photo-generated electron trap and inhibit the electron–hole recombination. The 0.10%-Fe 3 + -TiO 2 with the highest surface hydroxyl group density revealed the maximum rate constant of 0.716 and the optimal photocatalytic degradation of MB. As Fe 3+ doping levels are larger than 0.10%, the cluster of Fe Ti ′ – V ¨ O – Fe Ti ′ generated gradually. This implied that an excessive amount of Fe 3+ doped into TiO 2 is detrimental to the photocatalytic activity due to the formation of Fe Ti ′ – V ¨ O – Fe Ti ′ clusters and enhances the recombination of photogenerated electrons and holes. [ABSTRACT FROM AUTHOR]

Room temperature magnetoelectric (ME) measurements are carried out on phase pure BiFeO 3 and BiFe 0.98 Co 0.02 O 3 , prepared via sol–gel technique. At zero magnetic field, the longitudinal ME coupling coefficient ( α ) for BiFeO 3 is found to be α = 20.935, which decreases on application of magnetic field and displays hysteresis in magnetic field ( H ) for the increasing and decreasing cycle of H . This hysteresis disappears for BiFe 0.98 Co 0.02 O 3 and α becomes linear in H along with 17% drop in the magnitude compared to parent BiFeO 3 . In spite of 17% drop, magnitude of α = 17.375 is good enough for device applications especially where α must follow the applied magnetic field linearly, e.g., transistors, transducers, etc. Neutron diffraction studies show lattice stiffening due to cobalt substitution in BiFeO 3 and likely to be the cause of disappearance of hysteresis in α . Calculated value of polarization P (using the parameters derived from neutron diffraction) shows 19% drop in magnitude of P for cobalt substituted sample. Surprisingly, dielectric measurements also showed 18% decrease in dielectric constant ɛ ′ due to cobalt doping. Such a one to one correspondence in the three parameters viz., α , P and ɛ ′, reflects a strong interdependence so that variation in any one of them is reciprocated in the other. Room temperature magnetodielectricity of 5% and 3.2% is observed for BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively. Interestingly similar to α , ɛ ′ also shows hysteresis in magnetic field for BiFeO 3 and the hysteresis disappears for BiFe 0.08 Co 0.02 O 3 . The dc electrical resistivity measurements, suggests variable range hopping (VRH) with average hopping range 50.038/ T 0.25 and 40.058/ T 0.25 in BiFeO 3 and BiFe 0.98 Co 0.02 O 3 respectively, as the conduction mechanism. [ABSTRACT FROM AUTHOR]

The nanofabrication, characterization, microstructural and magnetic properties of pure and Mg 2+ doped cadmium ferrite (CdFe 2 − x Mg 1.5 x O 4 ; x = 0.0–0.7) have been carried out. Morphology and the microstructure of the nanostructured oxide materials obtained through sol–gel process using hydrated metal-citrate precursor were studied by powder X-ray diffraction (XRD), electron microscopy (SEM, TEM) and N 2 -physisorption (BET) showing an ordered cubic arrangement of 11–23 nm diameter pores with single-phase spinel grains averaging 13–38 nm in diameter. Room temperature magnetic measurements using magnetometer (VSM) demonstrate that the nature and concentration of dopant both control the site preference in the crystal lattices, suggesting the partial inverted spinel structure of soft Cd ferrites, which differs from bulk CdFe 2 O 4 showing practically no inversion in structure. An increase in Mg 2+ substitution leads to a decrease in the lattice parameter, an increase in saturation magnetization as well as BET surface area of the as-synthesized ferrites. [ABSTRACT FROM AUTHOR]

Oxygen deficient perovskites LaTiO 3− δ and La 0.8 A 0.2 TiO 3− δ (A = Ba, Sr, Ca) were synthesized by sol–gel method. The effect of divalent dopants on microstructure is investigated in detail using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The oxidation states of La 3+ and Ti 3+ ions have been deduced using X-ray Photoelectron Spectroscopy (XPS). Impedance spectroscopy was used to analyze the total conductivity, an increase in conductivity was observed after doping in the A-site with divalent cations Ba, Ca and Sr. Among the investigated perovskites La 0.8 Ca 0.2 TiO 3− δ exhibited the maximum conductivity of 1.22 × 10 −2 S/cm in air atmosphere at 650 °C. [ABSTRACT FROM AUTHOR]

Iodine doped tin oxide (SnO 2 :I) nanoparticles were prepared by sol–gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO 2 :I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO 2 nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO 2 nanoparticles under similar illumination conditions. [ABSTRACT FROM AUTHOR]

We report an isothermal formation kinetics of nanocrystals in LiNb 0.5 Ta 0.5 O 3 (LNT) glass prepared by the polymerized complex sol–gel process with no addition of glass former. It is observed that the LNT glass transforms into rhombohedral LNT crystal at an elevated temperature and most crystal grains are confined within the size of ∼30 nm. We have determined that the formation mechanism of nanocrystals is the diffusion-controlled growth with a constant nucleation rate, based on the Avrami exponent n ∼2.5 in Johnson–Mehl–Avrami equation. [ABSTRACT FROM AUTHOR]

The AgLa(PO3)4 phosphors activated with trivalent rare-earth (Eu3+, Tb3+) ions were prepared by a sol-gel synthesis method. The crystal structure of the compound was studied by X-ray diffraction patterns and found to be crystallized in the monoclinic system with a space group P21/c, indicating the calculated lattice parameters of a = 10.08 Å, b = 13.12 Å, and c = 7.314 Å. The Fourier-transform infrared spectrum, photoluminescence excitation/emission spectra, and decay curves were examined to study the optical properties. The analysis of the Eu3+ ions related emission spectrum revealed the presence of highly symmetric sites for the activator ions. The Tb3+ ions related emission spectrum exhibited a 5D3 emission due to the prolonged calcination at high temperatures, which reduces the residual hydroxyl ions. The optical properties show that this host material is suitable for phosphor materials and laser crystals. [ABSTRACT FROM AUTHOR]

Amorphous powders of iron doped 3:2 mullite (3Al2O3⋅2SiO2) were prepared by sol-gel combustion process using ethanol-water solutions of Al(III) nitrate, Fe(III) nitrate, TEOS and urea. Compositions up to 15wt% of Fe2O3 were investigated. After combustion and heat treatment at 800°C for 4h, XRD analysis confirmed that the powders were amorphous. This is in agreement with the thermodynamic predictions that direct formation of mullite has not occurred during the aluminum nitrate - urea combustion reaction. XRD patterns of uniaxially pressed and sintered pellets at 1550°C for 4h revealed the crystal structure of orthorhombic mullite. The lattice parameters and unit cell volume increases as the mullite solid solutions were enriched by iron. The TGA/DSC analysis showed the reducing of crystallization temperature of iron doped mullites with increasing of iron content in reaction mixtures. The mullitization reaction is two-step process including formation of transient spinel phase below 1000°C and mullite crystallization at temperatures about 1200°C. The SEM micrographs of the sintered samples reveal elongated mullite grains with grain length up to 40μm. Increasing of the iron content in the reaction mixture enhances the grain size and the grains become elongated and better packed increasing the density of sintered samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] CoFe2O4 behaves as n–type semiconductor in the temperature range of 320–800 K. [•] All CoCrxFe2-xO4 behave as p-type up to 360K and above 360K as n-type semiconductor [•] ‘α’ value increases with increase in Cr content at lower temperature. [•] The value of thermoelectric power shows maximum at Curie temperature Tc (K). [•] The conduction up to Tc is due to polarons and above Tc due to magnetic transition. [Copyright &y& Elsevier]

Abstract: In this paper, transparent resistive switching cells using Al/SnO2:Mn/F:SnO2 capacitor were fabricated, which exhibited an optical transmittance of approximately 75% in the visible region (550nm). We also studied interface modified bulk like space charge limited conduction and observed bipolar resistive switching in the Al/SnO2:Mn/F:SnO2 structure. The results showed that the ON/OFF ratio between high resistance state and low resistance state exceeds 103 at +1V and −1V. And the devices also showed a fast reset speeding (100ns). Due to the creation of a hole in the surrounding oxygen ion, the Mn3+ located at Sn4+ site reduced the electron density, thus increasing the resistance of high resistance state and enlarging memory window of the sample. [Copyright &y& Elsevier]

Highlights: [•] Lanthanum-alumino-silicate gels with high fluorine content are synthesized. [•] Trifluoroacetic acid (TFA) is used as the fluorine source in a sol–gel process. [•] Thermal decomposition of TFA prevents the conversion of gels to monolithic glasses. [•] The Ce-doped gels show photoluminescence in the blue spectral region. [Copyright &y& Elsevier]

Highlights: [•] Ultrafine Ni3Fe nanoalloy nanoparticles were synthesized via a modified novel sol–gel process. [•] The prepared Ni3Fe nanoalloy nanoparticles have a narrow size distribution. [•] The Ni3Fe nanoparticles exhibit superparamagnetic behaviors at room temperature. [ABSTRACT FROM AUTHOR]

• (100), (110) and (111)-oriented (Na 0.5 K 0.5)NbO 3 based lead-free films are fabricated by a sol-gel method. • The maximal dielectric constant and remnant polarization are observed in the (110)-oriented film. • The maximum piezoelectric response is obtained in the (100)-oriented films, resulting from the extrinsic contribution. [Display omitted] The intrinsic and extrinsic contributions to the piezoelectric response are deeply dependent on the crystallographic orientation in the thin films. Herein, (100), (110) and (111)-oriented (Na 0.5 K 0.5)NbO 3 (KNN) based lead-free piezoelectric films are synthesized by a sol-gel method. The dielectric, ferroelectric and piezoelectric properties of the KNN-based films at the rhombohedral-orthorhombic (R-O) phase boundary are investigated with the focus on the influence of the film orientation. The maximum piezoelectric response is obtained in the (100)-oriented film, resulting from the extrinsic contribution stimulated by the external electric field, although the (110) and (111)-oriented films have the higher dielectric constant and remnant polarization. There are more varied ways of domain switching and domain configuration under the external electric field in (100)-oriented film, leading to the higher extrinsic contribution to the piezoelectric response. The study of the orientation effect on the piezoelectric response can shed light on the exploration of optimal piezoelectricity by tailoring the preferred orientation in KNN-based lead-free films. [ABSTRACT FROM AUTHOR]

Highlights: [•] Optimal parameters for preparation by sol–gel of core–shell (BT-Nb0.005)/SiO2 are presented in this paper. [•] Single crystalline BT-Nb0.005/SiO2 core–shell composite with ∼34nm shell thick was prepared. [•] The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. [ABSTRACT FROM AUTHOR]

Highlights: [•] LiCrNiO is a giant dielectric material for microelectronic applications. [•] Sol–gel process was used for the LiCrNiO preparation using ethylene glycol as chelating agent. [•] The products had the single phase of cubic rock-salt structure and large dielectric constants. [•] The lattice parameter decreased as calcining temperature increased. [ABSTRACT FROM AUTHOR]

Highlights: [•] The new, facile methodology for synthesis of silica covered SPIONs is proposed. [•] The SPIONs was modified with cationic chitosan and coated with silica shell. [•] Negatively charged, rounded in shape particles of ca. 330nm were obtained. [•] The product exhibits the superparamagnetic properties. [•] The product properties imply its potential applications in biomedicine areas. [ABSTRACT FROM AUTHOR]

Highlights: [•] The optical band gap of the Ag–AZO film is tuned with Ag doping. [•] The PL intensity of the Ag–AZO film in visible region is increased with Ag doping. [•] The PL positions of these peaks were blue shifted with increased Ag content. [•] The increase in I B and I G is due to the charge difference between Ag+ and Zn2+. [•] The shifting of the PL positions is due to the size of Ag+ and Zn2+ ions. [ABSTRACT FROM AUTHOR]

Bismuth silicate (Bi4Si3O12, BSO) thin films have been fabricated by sol–gel process. The stable sol was synthesized by using Bi(NO3)3·5H2O and Si(OC2H5)4 (TEOS) as the precursors, acetic acid and 2-ethoxyethanol as the solvents. The thin film precursor was deposited onto SiO2 substrates by spin-coating at 3000rpm and was dried at 110°C. X-ray diffraction showed that BSO phase starts to form at 700°C and single-phase BSO polycrystalline thin films were obtained at 800°C. The micromorphology and luminescent properties of coated films were characterized by means of scanning electron microscopy and fluorophotometer respectively. [ABSTRACT FROM AUTHOR]