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In this study, a series of Gd${}^{3+}$, Ce${}^{3+}$ doped Sr₂P₂O₇ phosphors synthesized by a novel method utilizing stearic acid sol–gel are reported. Structural analysis performed by X-ray diffraction (XRD) pattern revealed that doping of trivalent lanthanide ions did not change the orthorhombic structure possessed by Sr₂P₂O₇ matrix and also confirmed the phase purity and crystallinity of the phosphor. Scanning electron microscopy (SEM) micrograph confirms its surface morphology and particle size in the range of 50nm to $1\mu$m. Photoluminescence (PL) studies revealed that PL emission for Gd${}^{3+}$ and Ce${}^{3+}$-doped Sr₂P₂O₇phosphor gives significant emissions which are suitable for application in UV-LEDs for phototherapy portable devices.

Perovskite solar cells have higher efficiency and low cost as compared to other available commercial solar cells however due to large advantages it is not available commercially because it has very low stability which is nearly equal to one year. So to enhance the stability, different types of Cs-based optimized hybrid nanocomposites are used. Sol–gel and hydrothermal methods were used to prepare the Cs-nanocomposites. The crystallinity, surface morphology, elemental composition, thermal stability and nanocomposites’ absorbance were observed using X-ray diffraction, scanning electron microscope, energy dispersive X-ray, thermo gravimetric analysis, ultraviolet-visible (UV–Vis) and Raman spectroscopy techniques. This research work consents successfully for the synthesis of nanocomposites and enhancement in stability of perovskite substantial-based absorber layer. During analysis of TGA, only 2.5% of the weight of Cs-nanocomposites lost their total weight and J-V properties such as $J_{\mathrm{\text{sc}}}$ and power conversion efficiency of PSCs remarkably increased by nearly 3mAcm${}^{-2}$ and 4%, respectively by using Cs-based NCs.

In this work, M-type hexagonal ferrite nanoparticles having the composition ${\mathrm{\text{Ca}}}_{0.25}{\mathrm{\text{Ba}}}_{0.75}{\mathrm{\text{Cr}}}_x{\mathrm{\text{Fe}}}_{12-2x}{\mathrm{\text{O}}}_{19}$, where $x=(0.0,0.05,0.10,0.15,0.20)$ were fabricated by the sol–gel auto-combustion technique. The influence of chromium doping on structural, dielectric and magnetic characteristics was examined. XRD powder analysis revealed the geometry of single-phase hexaferrite with P63/mmc space group. The magnetoplumbite hexagonal structure was revealed by the X-ray diffraction analysis. Crystallite size, $a$ & $c$ lattice parameters, bulk density, X-ray density, cell volume and porosity were assessed. Crystallite size ranged from 39.54nm to 42.91nm. The X-ray density and bulk density were enhanced while porosity was decreased with the substitution of ${\mathrm{\text{Cr}}}^{3+}$cation. The morphology of the fabricated materials was inspected by the SEM analysis, which displays uniformly scattered particles with hexagonal platelet shape. The value of the dielectric constant is high in the low-frequency regime, and it decreases with increasing frequency. The dielectric constant decreased appreciably with the increase of ${\mathrm{\text{Cr}}}^{3+}$. Such observed dielectric and magnetic features are useful for different technological applications like microwave absorbers, voltage-controlled, dielectric resonators and recording media.

BaTi₅O${}_{11}$ nanocrystals were synthesized by a sol–gel method, and their photocatalytic performance was investigated by degradation of methylene blue (MB) under UV-light irradiation. The single-phase BaTi₅O${}_{11}$ nanocrystals were sintered at 800°C for 180 min, which mainly consisted of nanoparticles and irregular flaky nanocrystals. The BaTi₅O${}_{11}$ nanocrystals showed good photocatalytic degradation efficiency for MB. After 60 min UV-light irradiation, the photodegradation efficiency of MB was 96.5%, and the BaTi₅O${}_{11}$ nanocrystals also exhibited good photocatalytic performance for Rhodamine (89.3%) and tetracycline (TC) (94.2%) degradation. In the process of photocatalytic degradation, the •OH radicals played the most important role, and the radicals of •O₂${}^{-}$ and h${}^{+}$ displayed secondary function.

Composite electrolytes of La${}_{1.7}$Sm${}_{0.3}$Mo${}_{1.8}$W${}_{0.2}$O${}_{9-}$${}_{\delta }$ (LSMW) and Ce${}_{0.8}$Sm${}_{0.16}$Pr${}_{0.03}$Gd${}_{0.01}$ O${}_{1.9}$ (CSPG) with varying molar ratios of 9:1, 8:2, 7:3, 6:4, and 5:5 were synthesized using the sol–gel method. The characterization and electrochemical performances of the composite electrolyte LSMW–CSPG were studied. The experimental results reveal that when the composite electrolytes are pressed into discs and sintered at 850${}^{\circ }$C for 3 h, they exhibit relative densities above 95% and sintering shrinkage rates below 4%, indicating high sintering activity. The conductivity of the LSMW–CSPG composite electrolyte increases with temperature and CSPG dosage, initially rising and then declining. The maximum conductivity was observed for the LSMW–CSPG composite with a molar ratio of 7:3, which was three times higher than that of the LSMW electrolyte alone, reaching 0.0298 S ⋅ cm${}^{-1}$ at 800${}^{\circ }$C. The activation energy for this composite was determined to be 1.46 eV.

Transparent mesoporous TiO₂ films consisting of uniform anatase particles have been deposited on glass slides by using sol-gel technique. A Europium complex Eu(TTA)₃(bpy), where the TTA ligand is β-diketonate thenoyltrifluoroacetonate and the bpy is 2,2-bipyridine, was formed on TiO₂ surface by physical adsorption of europium ions and successive formation of stable chelate complexes with TTA and bpy ligands. In this way a well dispersion of the complex has been achieved giving significant emission intensity. The excitation of the material in the UV region (374 nm) results in the emission of a nearly monochromatic light at 613 nm (⁵D₀→⁷F₂) via energy transfer from the excited organic ligands to europium emissive state.

Series of the samples with nominal compositions Bi_3.2Pb_0.8Sr₄Ca₅Cu₇O_x and Bi_3.2Pb_0.8Sr₄Ca₅Cu₇O_x/Ag (10 wt%) were prepared by the standard solid state reaction at the same calcination and sintering temperature and time. Three starting mixtures were used, carbonates, oxides and silver i) with nanoparticles, ii) with micrometer size of particles and iii) powder obtained by modified sol-gel process. The main phase in all samples was Bi-2223 and silver formed the separate phase. The sol-gel process was found to be effective way in term of porosity, bulk density and connectivity of the grains. The effect of the microstructure on the transport properties were described by the temperature dependence of resistivity and critical current densities.

Nano-sized mullite was synthesized by mechano-chemical, sol-gel/milling, process. Aluminum nitrate and tetraethyl ortho silicate were used as precursors to prepare the single phase gel. The prepared gel was subjected to intense mechanical activation using a planetary ball mill prior to annealing. DTA/TGA results showed that mullitization temperature significantly decreases due to mechanical activation as mullite starts to form at 1094°C in unmilled sample whereas intermediate milling for 20 hours decreases this temperature to 988°C. Also, mullite formation occurs at 1021 and 1003°C for samples milled for 5 and 10 hours, respectively. SEM results showed that the morphology of the products was altered by the intermediate mechanical activation. Calculation of the mullite crystallite sizes indicated that they were indeed in nano scale and this result was confirmed by TEM investigations which shows the mean crystallite size of 70 nm.

This paper reviews several innovative techniques that have been developed in our labs to overcome the shortages of conventional sol-gel techniques, and discusses the technical details of preparing these ceramic coatings with controllable thickness, microstructure, composition and improved properties.

There are some issues such as tunneling, leakage currents and boron diffusion through the ultra thin SiO₂ which are threatening ultra thin SiO₂ dielectric as a good gate dielectric. A very obvious alternative material is HfO₂, due to its high dielectric constant, wide band gap and good thermal stability on silicon substrate. We have thus demonstrated a number of processes to synthesize La₂O₃/HfO₂ and studied its nano structural properties with using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The obtained results show that La₂O₃/HfO₂ (at 500°C with amorphous structure) can be introduced as a good gate dielectric for the future of complementary metal insulator semiconductor (CMIS) device.

The crystal structure at room temperature (RT), thermal expansion from RT to 1000°C and electrical conductivity, from RT to 600°C, of the perovskite-type oxides in the system Pr_1-xSr_xFeO₃(x = 0, 0.2, 0.4, 0.6) were studied. All the compounds have the orthorhombic perovskite GdFeO₃-type structure with space group Pbnm. The lattice parameters were determined by X-ray powder diffraction. The Pseudo cubic lattice parameter decreases with an increase in x, while the coefficient of linear thermal expansion increases. The thermal expansion is almost linear for x = 0 and 0.2. The electrical conductivity increases with increasing x while the activation energy decreases. The electrical conductivity can be described by the small polaron hopping conductivity model.

To investigate characterization of Zr_xLa_1-xO_y nanocrystallites as a buffer oxide in forming the metal-oxide-semiconductor field effect transistors (MOSFETs) structure, we synthesized Zr_xLa_1-xO_y nanocrystallites by sol–gel method. Moreover, from the solution prepared, thin films on silicon wafer substrates have been realized by "dip-coating" with a pulling out speed of 5 cm min^-1. The structure, morphology, electrical properties of thin film was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) techniques. Electrical property characterization was performed with metal-oxide-semiconductor (MOS) structures through capacitance–voltage (C–V) and current density–voltage (J–V) measurements. The leakage current density was below 1.0 ×10^-6A/cm² at 1 MV/cm.

Styrene-doped ZrLaO_y nanostructures were obtained by sol–gel method low-temperature synthesis. The nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and transmission electron microscopy (TEM) techniques. The observation using SEM and TEM revealed that the ring-shaped nanostructures were very uniform. Further characterization using XRD disclosed that the cohesion of the samples was controllable with annealing temperatures in the range of 800–1500°C. Cohesion property was investigated for the samples. The cohesion increased when increasing the annealing temperature. This was linked to the reinforcement of the oxygen bound on the ZrLaO_y nanostructures The shape of nanostructures showed a transformation from a ring-shaped growth mode to a hole-surfaced growth mode with increasing annealing temperature. The styrene-doped ZrLaO_y nanostructures with controllable crystallinity will have great potential for various applications in fuel, cells, batteries, electronics devices and chemical sensors.

A synthetic process for the formation of Zr_xY_1-xO_y nanostructures is demonstrated by the reaction of yttrium nitrate hexahydrate with zirconium propoxide. The reactions are carried out at temperature 60°C and pressure 0.1 MPa. The energy dispersive X-ray (EDX) spectroscopy measurements confirm formation of Zr_xY_1-xO_y nanostructures and the presence of carbonate and hydroxide species which are removed after high temperature anneals. It was found that the oxygen pressure during synthesis plays a determinant role on the structural properties of the nanostructure. This effect is further studied by atomic force microscopy (AFM) measurements and scanning electron microscope (SEM), which showed the formation of an isotopically organized structure. X-ray diffraction (XRD) measurement reveals that these changes in the nanostructural efficiency are associated with structural and compositional changes among the substrate. The dielectric constant as measured by the capacitance–voltage (C–V) technique is estimated to be around 39.05. C–V measurements taken at 1 MHz show the maximum capacitance for the Zr_0.05Y_0.95O_y film. The leakage current densities were below 10^-5 A/cm² for the Zr_0.05Y_0.95O_y film.

The sol–gel method was developed to synthesize A₅B₅O₁₇-type Na_0.4K_0.6Ca₄Nb₅O₁₇ layered perovskite ceramics, using NaNO₃, KNO₃, CaNO₃⋅4H₂O and NbCl₅ precursors. Samples were calcined at 950°C and sintered at 1200–1350°C. The phase and microstructural analyses of samples were carried out using X-ray diffractometer (XRD) and scanning electron microscope. X-ray diffraction analysis revealed single phase monoclinic symmetry, within the detection limit of in-house XRD facility. Microstructural analysis shows ~ 10 μm elongated rod-like grains. The microwave dielectric properties of the sintered composition at 1300°C were: relative permittivity (ε_r) = 42, quality factor (Q × f₀) = 8270 GHz and temperature coefficient of resonant frequency (τ_f) = -10.1 ppm/°C.

In this work, ZnO and Cu-doped ZnO nanoparticles $({\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Cu}}}_x\mathrm{\text{O}}$, $x=3\%)$, with a calcination temperature of 500${}^{\circ }$C were synthesized using the sol–gel method. The particles were analyzed using atomic absorption spectroscopy (AAS), X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) at X-band, measurement in a temperature range from 90 K to room temperature. AAS confirmed a good correspondence between the experimental doping concentration and the theoretical value. XRD reveals the presence of ZnO phase in hexagonal wurtzite structure and a nanoparticle size for the samples synthesized. EPR spectroscopy shows the presence of point defects in both samples with $g$-values of $g=1.959$ for shallow donors and $g=2.004$ for ionized vacancies. It is important when these materials are required have been used as catalysts, as suggested that it is not necessary prepare them at higher temperature. A simulation of the Cu EPR signal using an anisotropic spin Hamiltonian was performed and showed good coincidence with the experimental spectra. It was shown that Cu${}^{2+}$ ions enter interstitial octahedral sites of orthorhombic symmetry in the wurtzite crystal structure. Temperature dependence of the EPR linewidth and signal intensity shows a paramagnetic behavior of the sample in the measurement range. A Néel temperature $T_N=78\pm 19$ K was determined.

A group of ABO₃ perovskite-type oxides is currently under intensive studies for their potential as chemical sensing, ferroelectric memories, gas separation and computer devices. This group includes La${}_x$Sr${}_{1-x}$CoO₃ (LSCO). In the present work, we have synthesized LSCO samples by using the sol–gel method and studied their nano structural and electrical properties with using the scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Current density–voltage ($J$–$V$) and Fourier transform infrared spectroscopy (FTIR) techniques. We synthesized nanoparticles with diameters between 50 and 100 nm by calcination of the pulverized gel powders, and then studied its structure. The band gap characteristics of the La${}_{0.5}$Sr${}_{0.5}$CoO₃ structure were also analyzed. The obtained results show that La${}_{0.5}$Sr${}_{0.5}$CoO₃ with favorable carrier mobility ($\sim 1.7\times 10^{-2}$ cm²v${}^{-2}$s${}^{-1}$) and dielectric constant (16) exhibits a variety of interesting physical properties which include ferroelectric, dielectric, pyroelectric and piezoelectric behavior.

Li–Ni–Co ferrite samples with compositional formula Li${}_{0.45-0.5x}$Ni${}_{0.1}$Co${}_x$Fe${}_{2.45-0.5x}$O₄ with $x$ ranging from 0.00 to 0.1 in steps of 0.02 were prepared by sol–gel method. X-ray diffraction (XRD) analysis confirmed the formation of single phase with spinel structure in all the samples. The lattice constant evaluated from XRD data was found to increase with increase of Co${}^{2+}$ substitution and crystallite size was observed in the range of 30–59 nm. The microstructure of the samples was studied by using scanning electron microscopy (SEM). Nanocrystalline nature of ferrites was also confirmed by transmission electron microscopy (TEM). $M$–$H$ measurements were made using a vibrating sample magnetometer and hysteresis parameters such as saturation magnetization and coercivity were obtained for all compositions. The frequency variations of initial permeability and permeability loss showed a dispersive behavior for all compositions and an increase in initial permeability is observed with increase of Co${}^{2+}$ substitution. The results obtained and mechanisms involved are discussed in the paper.

The ${\mathrm{\text{Cu}}}_2{\mathrm{\text{ZnSnS}}}_4$ (CZTS) thin film is a photovoltaics material with excellent photoelectric properties and has good potential applications. The CZTS thin films with different spin-coated layers and sulfurized temperatures were successfully prepared by a sol–gel spin-coating technique. The relationships of microstructure, surface morphology and processing parameters were studied using XRD, SEM and EDS. The results indicate that the grain size of the sample sulfurized at $600^{\circ }$C was larger than that of the sample sulfurized at $550^{\circ }$C. With increasing layers of spin, coatings, the films showed better crystalline structure. The sulfureted CZTS thin films prepared by six spin-coating possess uniform elemental distribution.

Multiferroic nanocrystalline Bi${}_{1-x}$Sr${}_x$FeO₃ ($x=0$, 0.05, 0.1) samples were synthesized using the sol–gel method and characterized by powder X-ray diffraction, Mössbauer spectroscopy and SQUID system. The small-angle X-ray diffraction analysis showed that the sample underwent phase transition from rhombohedral to pseudo-cubic structure with the enhancement of Sr content. In addition, impurity peaks gradually diminished, indicating that content of impurities of samples reduced. Furthermore, it can be determined that there is only Fe${}^{3+}$ in all the samples and impurity phase that existed in the samples was Bi${}_{25}$FeO${}_{40}$ by fitting Mössbauer spectra. It is further confirmed that Bi${}_{1-x}$ Sr${}_x$FeO₃ samples were generated by oxygen vacancy equilibrium valence state when Sr${}^{2+}$ ions replaced Bi${}^{3+}$ ions. The change of quadrupole splitting indicated that a low concentration of Sr${}^{2+}$ ions diffused homogeneously in the sample. Magnetization measurement showed that the magnetization of the sample increased gradually with the substitution of Bi${}^{3+}$ by nonequivalent Sr${}^{2+}$ ions, which can be ascribed to the decrease of grain size and the increase of oxygen vacancy and specific surface in the samples.