Narrow Results

Pb containing ruthenium-based superconducting cuprates Ru(Sr_1.5Ca_0.5)PbCu₂O₈ (Ru-1212 type) have been successfully synthesized through the sol–gel route. The optimum annealing temperature for the ruthenium-based cuprate superconductor was found to be 890°C. The crystal structure determined by X-ray powder diffraction method showed a single Ru-1212 type phase with tetragonal symmetry with lattice parameters a = b = 3.920 Å, and c = 11.76 Å. The Ru(Sr_1.5Ca_0.5)PbCu₂O₈ material showed onset temperature, T_c-onset at 35 K and zero resistant temperature, T_c-zero at 20 K. Pb together with the partial substitution of Sr with Ca lowered the formation temperature of the Ru-1212 type phase.

A series of (Pb_0.4Sr_0.6)_1-xLa_2x/3TiO₃ (PSLT) thin films were deposited on ITO/glass substrates by sol–gel technique. Their phase status, surface morphology, and dielectric properties were studied by X-ray diffraction, scanning electron microscope, and impedance analyzer, respectively. Results show that the PSLT thin films were consisted of tetragonal perovskite phase PSLT thin films for x < 0.4, and cubic perovskite phase PSLT thin films for x > 0.4. Dielectric properties such as dielectric constants, dielectric tunabilitis, and inharmonic coefficient were characterized as a function of the film composition.

The nano-crystalline iron nitride films with a mixture of γ-Fe₄N, εFe₃N and αFe₂N phases were synthesized on copper substrate by sol–gel technology. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. The films are ferromagnetic at room temperature. Magnetic properties such as coercive forces and saturation magnetization were found to be 398 Oestered and 32.92 emu/cm³, respectively.

Undoped and magnesium-doped zinc oxide thin films were prepared by the sol–gel method. Results from X-ray diffraction indicated that the films exhibited a hexagonal wurtzite structure and were highly oriented along the $c$-axis. The intensity of the (002) diffraction peak increased with increasing the Mg doping concentration. Also, Mg doping inhibited the growth of crystallite size which decreased from 46nm to 38nm with doping concentration. Morphological studies by atomic force microscopy (AFM) indicated the uniform thin film growth and the decreasing of grain size and surface roughness with Mg doping. Optical analysis showed that the average transmittance of all films was above 90% in the visible range and Mg doping has significantly enhanced the bandgap energy of ZnO. Two Raman modes assigned to $E_{2L}$ and $E_{2H}$ for the ZnO wurtzite structure were observed for all films. UV emission peak and three defect emission peaks in the visible region were observed by photoluminescence measurements at room temperature. The intensity ratio of UV emission to the visible emission increased with the Mg concentration. Photocurrent measurements revealed that all films presented the photoresponses with $n$-type semiconducting behavior and their generated photocurrents were reduced by Mg doping. The prepared thin films of high quality with improved properties by Mg doping could be proposed to workers in the field of optoelectronic devices for using them as a strong candidate.

Zn_1-xMn_xO (x = 0, 0.02, 0.06, 0.10, 0.15) nanopowders were synthesized by the sol–gel technique calcinated at low temperatures. By decreasing the grain size in ZnO, the solubility of magnetic impurity has been increased and no detectable secondary phases were observed even in the high Mn-doping samples. The phase formation, size and morphology of nanoparticles were investigated using X-ray diffraction and SEM observations. The samples were ferromagnetic and the Curie point was found in the range 150–170 K for Zn_0.94Mn_0.06O and 135–150 K for Zn_0.98Mn_0.02O. Optical characterization and the effect of doping were carried out by means of Fourier transform infrared (FTIR) spectroscopy. Kramers–Kronig analysis was employed to evaluate the optical constants of pure ZnO and ZnO:Mn nanopowders.

Pb(Zr_1-x, Ti_x)O₃(x = 0.05) with pyroelectric properties have been synthesized by sol–gel technique at low temperatures. XRD results indicate that the powder has perovskite structure without secondary phases and the average of particle size was estimated to be about 40 nm in diameters. The optical constants such as refractive index, n, extinction coefficient, k, and the dielectric function of PZT nanopowders have been investigated by Fourier transmittance infrared (FTIR) spectrum and Kramers–Kronig (KK) analysis program. The use of the KK method to analyze the normal incidence infrared (IR) reflectance spectra with a single resonance has also been described. The results indicated that the optical constant increases slowly as temperature of calcinations increases.

NiCo_xMn_2-xO₄ (x = 0.4, 0.8, 1.2, 1.6) thermistor with nanopowders have been synthesized by the auto-combustion method at low temperatures. The size and morphology of the calcinated powders have been investigated using XRD and TEM techniques. The average particle size was estimated to be about 65 nm in diameter with the cubic and cubic + tetragonal phases for low and high cobalt concentrations, respectively. The grain size of NTC ceramics sintered at 1200°C is verified with scanning electron microscopy (SEM) images. Upon increasing the cobalt concentration, the grain size of NTC samples increases from about 2 μm to a few μm in size.

The formation of spinel structure of powders has been studied by Fourier transform infrared (FTIR) spectroscopy. An ab initio calculation of electronic properties of NiCo_0.8Mn_1.2O₄ using full potential of the linear augmented plane wave (FP-LAPW) method has been performed. The results indicate that only the 3d-Mn orbitals play an important role in the conduction mechanism. The dependency of material resistivity constant (B) and temperature coefficient (α) have been measured.

Mn-doped 0.92(K_0.5Na_0.5)NbO₃–0.08LiNbO₃ (0.92KNN–0.08LN) lead-free piezoelectric ceramics have been prepared by a developed sol–gel routes using Nb₂O₅ as Nb source. Due to the high quality of gel precursor, Mn-doped 0.92KNN–0.08LN nanopowders with the mean particle size about 20 nm were obtained at 500°C. The addition of Mn can promote the densification of nanopowders effectively at 950°C, and also influences in a pronounced way both the crystal structure and microstructure of the materials. With the increase of the amount of Mn addition, 0.92KNN–0.08LN ceramics are transformed from dominant orthorhombic to coexistence of the orthorhombic and tetragonal phases, and the grain sizes are enhanced simultaneously. Optimized parameters, such as d₃₃ = 212 pC/N and k_p = 0.46, were achieved in 0.2 Mn-doped 0.92KNN–0.08LN systems, which are good candidate material for lead-free piezoelectric devices.

Yttrium oxide–magnesium oxide (Y₂O₃–MgO) composite nanopowders were synthesized via three distinct methods: sol–gel, co-precipitation and glycine–nitrate process. The synthesized powders were calcined at various temperatures, and their microstructure, specific surface area and particle size were characterized. A comparative study was conducted to assess the impact of the synthesis method on the microstructure and transparency of the resulting ceramic sintering. Notably, the powder synthesized by the sol–gel technique exhibited the highest specific surface area and superior light transmittance, reaching a maximum of 85.33% at a wavelength of 5.31$\mu$m.

In spite of attractive bioactivity of bioactive ceramics i.e. hydroxyapatite and bioactive glasses, their poor mechanical properties have restricted their clinical applications. To overcome these limitations, an alternative approach suggested is preparation a composite including these bioactive ceramics with others. It is expected that a ceramic reinforcement with reduced grain size below 100 nm promotes theirs. The aim of this work was fabrication and characterization of hydroxyapatite-forsterite-bioglass composite nanopowder. Novel hydroxyapatite-forsterite-bioglass composite nanopowder was synthesized by incorporation of the forsterite and bioactive glass in hydroxyapatite matrix via a sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy techniques were utilized in order to evaluate the phase composition, agglomerates size distribution, morphology and particle size and functional groups of synthesized. The effects of sintering temperature and time were also investigated. Results showed that the appropriate temperature for calcination was 600°C and the particle size of composite nanopowder was about 60-70nm. The decomposition of hydroxyapatite was increased with the increase of the sintering temperature and sintering time. Obtained results indicate that prepared composite nanopowder could be a good candidate for medical applications.

Amorphous alumina films are isotropic and have no grain boundaries, which make them have smooth surfaces, excellent properties, and wide applications in protective coatings, catalysis, and microelectronics. However, high-quality alumina films were usually prepared by vapor-phase approaches which need expensive equipment and long production time. Additionally, amorphous films are long-range disordered, which makes the study of structure–property relationships challenging. Here, a simple sol–gel method is employed to obtain high-quality amorphous Al₂O₃ thin films. The microstructure, morphology, and mechanical properties of amorphous Al₂O₃ thin films were systematically investigated. All the Al₂O₃ thin films heat-treated at 600–800^∘C are in amorphous state with ultrasmooth surface (Ra values about 0.29–0.43 nm) and high mechanical properties (elastic modulus ∼170GPa, hardness ∼20GPa). The mechanical properties (E and H) of Al₂O₃ films gradually increase with the increase of heat-treating temperature. Additionally, the Al coordination of the amorphous alumina films are analyzed by solid-state NMR and correlated with the mechanical properties. The results show that in amorphous alumina, the presence of tetrahedral Al ([4]Al) and octahedral Al ([6]Al) is helpful to improve the mechanical properties, while the five-coordinated Al ([5]Al) is not conducive to improve the mechanical properties. The results demonstrate that sol–gel method is an attractive alternative to time-consuming and expensive vapor-phase approaches and are useful for scale-up to applications and research of amorphous alumina films.