Ferromagnetism and optical properties of La1???x Al x FeO3 nanopowders

La_{1 − x} Al _x FeO₃ (x = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) nanopowders were prepared by polymerization complex method. All prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and UV-vis spectrophotometry (UV-vis). The magnetic properties were investigated using a vibrating sample magnetometer (VSM). The X-ray results of all samples show the formation of an orthorhombic phase with the second phase of α-Fe₂O₃ in doped samples. The crystallite sizes of nanoparticles decreased with increasing Al content, and they are found to be in the range of 58.45 ± 5.90 to 15.58 ± 4.64 nm. SEM and TEM images show the agglomeration of nanoparticles with average particle size in the range of 60 to 75 nm. The FT-IR spectra confirm the presence of metal oxygen bonds of O-Fe-O and Fe-O in the FeO₆ octahedra. The UV-vis spectra show strong absorption peaks at approximately 285 nm, and the calculated optical band gaps are found to be in the range of 2.05 to 2.09 eV with increasing Al content. The M-H loop of the pure sample is antiferromagnetic, whereas those of the doped samples tend to be ferromagnetic with increasing Al content. The magnetization, remanent magnetization, and coercive field of the Al-doped sample with x = 0.5 are enhanced to 1.665 emu/g, 0.623 emu/g, and 4,087.0 Oe, respectively.     

Synthesis and structure analysis of La0.5SR0.5TiO3 nanoparticles prepared by thermal decomposition method

La0.5Sr0.5TiO3 (LSTO) nanoparticles were synthesized by thermal decomposition method using Cl3La, CI2Sr x 6H2O and C16H28O6Ti as starting materials. The obtained precursor in a powder form was calcined at 700, 900, 1100 and 1300 degrees C for 3, 6 and 9 h in air. The structures of all samples were analyzed by XRD and some of them were taken for SEM, TEM and VSM measurements. The results from SEM showed the parallelpipe like shape of the particles with sizes distributed between 80 and 180 nm and the sizes of these particles were increased with the increasing of calcination temperature and time. The XRD's results showed the perovskite structure with the lattice type of orthorhombic at the calcination temperature of 900, 1100 and 1300 degrees C for 3, 6 and 9 h. The TiO and others unknown phase were found at low calcination temperature and they were disappeared as the calcination temperature and time were increased. The results of TEM support the orthorhombic structure of LSTO nanoparticles with crystallite size less than 200 nm as revealed by SEM and XRD. The magnetic property of all samples was measured by VSM and revealed that those prepared at 700, 900, and 1100 degrees C exhibit diamagnetic behavior, whereas one at 1300 shows ferromagnetism at room temperature. In this work, it is found that the nano-LSTO of high crystalline phase and purity can be prepared by thermal decomposition method at calcination temperature of 900 to 1300 degrees C in air for 6-9 h.     

La0.5Sr0.5TiO3 nanopowders prepared by the hydrothermal method

La_0.5Sr_0.5TiO₃ nanopowders were prepared by the hydrothermal method. The influence of processing parameters, including KOH concentration, reaction temperature and reaction time on the obtained products were studied. The structure and morphology of the obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that pure phase La_0.5Sr_0.5TiO₃ nanopowders can be successfully synthesized with 2 M KOH concentration at a low temperature of 220 °C for 24 h. In addition, the product has a plate-like shape with particle sizes in the range of 25–100 nm as estimated by TEM.     

Effects of Mn Doping on the Dielectric Relaxations and Dielectric Response in Multiferroic BiFeO3 Ceramics

We report the influences of Mn doping on the dielectric relaxation properties of multiferroic BiFeO₃ ceramics. The dielectric permittivity of the BiFeO₃ ceramic is suppressed by doping with Mn ions, which are suitably associated with the increase of the resistance and conduction activation energy of the bulk ceramic. Three sets of dielectric relaxations observed in the BiFeO₃ ceramic are concealed to a single set of dielectric relaxation in the BiFe_0.95Mn_0.05O₃ ceramic. The dielectric relaxation behavior of these ceramics might be ascribed based on the charge carriers hopping and/or the present of oxygen vacancies inside the grains.     

Improved cure characteristics and mechanical properties of an epoxidized natural rubber filled with cerium oxide nanoparticles: Influence of epoxide levels and filler loading

In this study, cerium oxide nanoparticles (nanoceria, CeNP) were used as a nanofiller in epoxidized natural rubber with varying epoxide levels, including 25% epoxidation (ENR-25) and 50% epoxidation (ENR-50). Co-precipitation methods were employed to synthesize a pure phase of CeNP with an average particle size of 11.4 ± 2.0 nm. CeNP was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The effect of CeNP loading with 0–3 parts per hundreds of rubber (phr) on the properties of rubber nanocomposites was explored. ENR-25 nanocomposites with 1 phr of CeNP exhibited higher tensile strength and elongation at break compared to ENR-50 nanocomposites. These findings correspond to a lower Payne effect, improved scorch safety, and better processability. The strongest and most effective CeO₂–ENR interactions via silane linkages are expected to outperform sulfur crosslinking in ENR-25 having 1 phr of CeNP. Microstructural evaluation of an ENR-25 sample containing 1 phr of CeNP indicated well-distributed nanofillers in the ENR-25 matrix, indicating that CeNP and ENR-25 appeared to be well-matched. Hardness of all ENR nanocomposites increased with CeNP loading. The cracking resistance, creep properties, and thermal stability of rubber nanocomposites were unaffected by addition of CeNP in the ENR-25 and ENR-50 samples.