Journal of Sol-Gel Science and Technology

Zirconium carbide (ZrC) was synthesized from inorganic–organic hybrid precursor’s pyrolysis by solution-based processing. Zirconium-containing complexes, which were obtained by chelation of oxide bidentate ligands to zirconium, were used to combine with phenolic resin to form precursors for ZrC. The precursors using specific ligands including acetylacetone, ethyleneglycol, and salicylic acid transformed into pure ZrC at a relatively low temperature (1,550 °C) in addition to that using lactic acid. As a comparison, synthesis of ZrC only using zirconium oxychloride octahydrate (ZrOCl2·8H2O) and phenolic resin was also conducted. The synthesized powders had a small average crystallite size (~300 nm), and a low oxygen content (~2.5 at.%). The conversions from as-synthesized preceramic precursors to ceramics were studied by means of FTIR, SEM, EDS, XRD, and XPS. The oxidation behavior of the synthesized ZrC in air was studied by DSC-TG analysis.

Lead zirconate titanate is one of the most well-known ferroelectric oxides and has been widely used in nano/micro-electromechanical systems and piezoelectric industries. Doping the lead zirconate titanate thick films by Fe3+ as an acceptor dopant leads to hard lead zirconate titanate piezoelectrics for specific applications including high frequency transducers. In this article, Fe-doped lead zirconate titanate thick films with the thickness of 27 µm are synthesized by using a modified acetic acid/alcoholic based sol–gel method and applying diethanolamine as a complexing agent. Crystallographic measurements are performed considering lattice constants and lattice distortion of the films by means of X-ray diffraction. Pure perovskite phase is obtained by adding the dopant up to 5 at. % Fe. The tetragonal lattice distortion and lattice parameters decrease by adding Fe and reach to its minimum level of c t  = 4.024 Å and a t  = 3.966 Å at 3 at. % Fe. The surface morphology and grain size are surveyed using field emission scanning electron microscopy, which shows the reduction in grain size by adding the dopant. Polarization-voltage loops and dielectric constants of the films are calculated by electrical measurement and illustrate reduction in the polarization by increasing Fe dopant. The highest value of coercive voltage is achieved at 3 at. % Fe. Moreover, the lowest dielectric constant of 318 is obtained at 5 at. % Fe. Nanostructured crack-free Fe-doped PZT thick films are successfully prepared by using modified sol–gel route with different Fe dopant percentages (a) surface morphology of PF(3 %)ZT, (b) cross section of PZT thick film.

Photocurrent responses of sol-gel films of silica/titania doped with oxacarbocyanine dye were investigated with a sandwich-type photocell constructed with polymer electrolyte membrane and indium-tin-oxide glass electrodes. At an equilibrium and positive bias voltages, a typical photocell exhibited negative and positive current peaks when the visible light illumination was on and off, respectively. The wavelength dependence of the photocurrent responses well matched to the absorption band of the doped dye. This differential photocurrent response was attributed to trapping of carriers photoexcited in the dye molecules at the defect states in the matrix film. At negative bias voltages, on the other hand, the cell exhibited constant, negative photoelectrochemical currents under illumination. These differential and linear photocurrent responses were affected by the SiO2/TiO2 matrix structures depending on the Si : Ti ratio.

In the recent years, considerable attention has been paid to strontium (Sr) for its therapeutic effects on bone diseases such as osteoporosis. In this study, a series of sol–gel-derived bioactive glasses based on SiO2–CaO–SrO–P2O5 quaternary system was synthesized, in which 0–100 % of the calcium was substituted by strontium. The influence of strontium on structural and biological behavior of the bioactive glasses was evaluated. The XRD analysis showed Sr-free sample to be amorphous without any significant crystalline phases. As the Sr content increased in the glasses, the tendency toward crystallization enhanced. Results of BET analysis confirmed the mesoporous texture (mean pore diameter: 9.16 nm) with a high specific surface area (39.7 m2 g−1) for the glass powders. Bioactivity of the system was studied by immersing the glass powders in simulated body fluid for 3, 7, and 14 days. The presence of strontium significantly accelerated the formation of hydroxyapatite layer onto the surface of glass particles. Besides hydroxyapatite, strontium apatite (Sr10 (PO4)6OH2) was formed onto the surface of Sr-containing bioactive glasses. The present study also investigated the osteoblast response to the Sr-containing bioactive glasses in vitro. Results indicated increased metabolic activity of osteoblasts in the Sr-containing bioactive glasses.

Sol-gel spin coating has a low ‘thermal budget’, is cheap compared to vacuum-based techniques and is now routinely used to produce dense, pore-free ferroelectric films. PbZrx Ti(1 − x)O3 (PZT) is utilized in most applications because it has a large remanent polarization, high piezo- and pyroelectric coefficients and optimized electromechanical coupling factors, depending on precise composition. This paper will review some of the principles and applications of PZT films and highlight using transmission electron microscopy some of the basic problems and solutions involved in producing device-quality material on Si-substrates.

Synthesis process, structure and luminescent properties of NASICON (Na super ionic conductor) type phosphates doped with europium have been investigated for the Na1-xEu0.33xTi2(PO4)3 series. The samples were synthesized via Pechini technique. Differential thermal analysis of the reaction mixtures was used to choose the optimal scheme for the thermal treatment of the phosphates. The obtained samples were studied by means of X-ray powder diffraction (including Rietveld structure refinement), Infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was shown that the phosphates with 0 ≤ x ≤ 0.1 were crystallized in the space group $$R\overline 3 c$$ , while the phosphates with 0.2 ≤ x ≤ 1.0 characterized by the space group $$R\overline 3$$ . Photoluminescence emission spectra of the phosphates Na1-xEu0.33xTi2(PO4)3 showed typical emission bands of Eu3+ ions, due to 5D0 → 7FJ transitions. The intensity of the emission bands rises with the concentration of europium up to x = 0.7 (Na0.3Eu0.23Ti2(PO4)3), while a further increase of x results into concentration quenching. Na0.5Eu0.167Ti2(PO4)3 structure and Na1-xEu0.33xTi2(PO4)3 photoluminescence emission spectra

“Sol paint” that yields yttrium-based compounds was prepared by mixing four chemical ingredients, yttrium acetate tetrahydrate precursor, diethanolamine, isopropyl alcohol, and hydrochloric acid, and then applied as oxidation/corrosion resistant coatings for Inconel 625 substrates. Annealing the coatings at 500°C developed a coalescent microstructure of coarse particles consisting of amorphous yttrium carbonate as the major component and crystalline yttrium oxide (Y2O3) as the minor one. At 700°C, the yttrium carbonate was transformed into Y2O3 by decarbonation. Increasing the annealing temperature to 900°C led to the formation of the YCrO3 phase yielded by interaction between Y2O3 and the Cr2O3 which had arisen from the oxidation of the underlying Inconel; the YCrO3 phase created a particle coating with a densified microstructure. There were two key factors in mitigating the degree of oxidation of Inconel at 900°C in air: (1) an uptake of oxygen by Y2O3 in the coatings, and (2) a densified coating layer that suppresses the diffusion and permeation of oxygen through it. Furthermore, inhibiting the rate of NaCl-caused corrosion was not only due to the excellent coverage of particle coatings over the entire surfaces of the substrates, but also may be associated with a good adherence of the coatings to the substrates.

Li3V2(PO4)3/C (LVP/C) composite materials have been successfully synthesized via a sol–gel method with oxalic acid as chelating agent and polyethylene glycol (PEG) as the supplementary carbon source, in which oxalic acid and PEG serve as double carbon sources. The X-ray diffraction patterns indicate that all of the samples are well crystallized. Transmission electron microscopy images reveal that the LVP/C sample prepared with 10 wt% PEG is uniformly coated by carbon layer with an appropriate thickness of 10–16 nm, resulting in a high electrical conductivity and a fast kinetics. The Li+ diffusion coefficient in the LVP/C sample prepared with PEG is 3.482 × 10−13 cm2 s−1, which is larger than that of the LVP/C sample prepared without PEG. In the range of 3.0–4.3 V, the LVP/C-10 electrodes exhibit good rate capability and excellent cyclic performance, which discharge capacities are 131.9 mAh g−1 at 0.1 C and 105.3 mAh g−1 at 5 C. The present work provides a valuable route for preparing lithium metal phosphates with double carbon sources to improve the conductivity and hence the electrochemical performance.

The structure of the silica aerogels was studied by Raman spectroscopy. The spectra of the solid network resembles that of bulk silica with additional bands related to organic groups and a large amount of OH groups. The typical bands due to ring breathing also called defect bands D 1 and D 2 located at 490 and 610 cm−1 are present. However, the evolution of the D 2 band compared to that of OH band (980 cm−1) seems apparently, in contradiction with the results previously reported in the literature. During heat treatments between 25 and 300°C the D 2 and the OH bands increase simultaneously. Generally, in silica glass the defect band D 2 grows at the expense of the OH groups. This result is explained by the oxidation of the organic compounds which, in this temperature range, leads to the formation of the both species (OH) and those related to siloxane rings. 29Si MAS NMR results are in agreement with the Raman study.