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Bismuth ferrite (BiFeO 3) nanorods have been prepared from 2-methoyethanol (2-MOE)-assisted sol–gel technique. Structure, dielectric, and magnetic properties of BiFeO3 nanorods are briefly discussed in this paper. Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) results suggest that the BiFeO3 peaks calcined at 500∘C exhibit a distorted rhombohedral perovskite structure with the absence of other secondary phases like Bi2Fe4O9. Meanwhile, the BiFeO3 showed excellent photoluminescence (PL) behavior due to the transmission of electrons from conduction band to the valence band. Ferroelectric hysteresis loop of BiFeO3 shows an increase of coercivity from 5.5–6 μ C/cm2 in a frequency range of 6–12 kHz. The magnetization measurement resulted in a well-saturated ferromagnetic behavior, and in addition, the temperature-dependent magnetization was discussed for BiFeO3 nanorod using superconducting quantum interference device (SQUID) method. The zero-field-cooled (ZFC) and field-cooled (FC) curves reveal spin-glass effect owing to size effects, spin exchange, and anisotropy of material assembly. [ABSTRACT FROM AUTHOR]

This work reports about annealing time effect on structural and optical properties of pure and Dy 3 + -doped CeO2 nanocrystallites. The nanopowders with an average grain size 13–15 nm are successfully synthesized via a conducive and neoteric Pechini-type sol–gel technique. Surface morphology, composition, band gap and photoluminescence properties of the prepared samples are examined by multifarious characterization techniques like Rietveld refinement, FESEM, HRTEM, FTIR, UV–Vis spectroscopy and PL. The effects of annealing time on structural parameters including lattice parameter, bond distance, bond angle, strain, crystallite size and texture coefficient are computed for all prepared samples which are further ensured by Rietveld refinement. In absorption spectra, blue shift in the band gap of as-prepared samples has been observed due to well-known quantum size effect, however, red shift is noticed in further annealed samples. PL emission peaks are observed in violet, blue and green regions that are devoted to various defect levels and color centers such as F, F + , F + + , etc. It is suggested that defects like oxygen vacancies play vital role in tailoring the band gap of prepared samples and therefore enhance its utility in photonics and oxygen storage appliances. [ABSTRACT FROM AUTHOR]

With the use of sol–gel method BaTiO3–SiO2 multilayer structures were fabricated on glass or fused silica substrates employing dipping or spinning procedure. The photonic stop band was observed in the reflection and transmission spectra of the multilayer structure annealed at 4 5 0 ∘ C. It is redshifted with an increase of the thicknesses of BaTiO3 and SiO2 layers. For structures comprising Eu-doped BaTiO3 layers of different thicknesses photoluminescence with the main band at 614 nm was detected. It is characterized with the double-exponential decay with the lifetimes of about 0.5 ms and 1.1 ms which do not depend significantly on the photonic stop band position. [ABSTRACT FROM AUTHOR]

NiCoxMn2-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 NiCo0.8Mn1.2O4 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. [ABSTRACT FROM AUTHOR]

Pb(Zr1-x, Tix)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. [ABSTRACT FROM AUTHOR]

Zn1-xMnxO (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 Zn0.94Mn0.06O and 135-150 K for Zn0.98Mn0.02O. 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. [ABSTRACT FROM AUTHOR]