ABSTRACT
Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe2O4/SrFe12-2xSmxLaxO19; x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La3+-Sm3+ double substitution on the formation, structure, and magnetic properties of CoFe2O4/SrFe12-2xSmxLaxO19 nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe2O4/SrFe12O19 nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe3+ ion by Sm3-+La3+ions promoted the formation of pure 2CoFe2O4/SrFe12O19 nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm3+-La3+ substitution at ≤1100 °C. In addition, samples with an Sm3+-La3+ ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La3Co3O8; dominant phase) and samarium ferrite (SmFeO3). The crystallite size range at all constituent phases was in the nanocrystalline range, from 39.4 nm to 122.4 nm. The average crystallite size of SrFe12O19 phase increased with the number of Sm3+-La3+ substitutions, whereas that of CoFe2O4 phase decreased with an x of up to 0.5. La-Sm co-doped ion substitution increased the saturation magnetization (Ms) value and the subrogated ratio to 0.2, and the Ms value decreased with the increasing number of double substitutions. A high saturation magnetization value (Ms = 69.6 emu/g) was obtained using a La3+-Sm3+ co-doped ratio of 0.2 at 1200 for 2 h, and a high coercive force value (Hc = 1192.0 Oe) was acquired using the same ratio at 1000 °C.
ABSTRACT
In this report, lanthanum strontium manganite at different Sr2+ ion concentrations, as well as Gd3+ or Sm3+ ion substituted La0.5-YMYSr0.5MnO3 (M = Gd and Sm, y = 0.2), have been purposefully tailored using a sol gel auto-combustion approach. XRD profiles confirmed the formation of a monoclinic perovskite phase. FE-SEM analysis displayed a spherical-like structure of the La0.8Sr0.2MnO3 and La0.3Gd0.2Sr0.2MnO3 samples. The particle size of the LSM samples was found to decrease with increased Sr2+ ion concentration. For the first time, different LSM concentrations were inspected for their cytotoxic activity against CACO-2 (intestinal carcinoma cells) and HepG-2 (human hepatocellular carcinoma cells). The cell viability for CACO-2 and HepG-2 was assayed and seen to decrease depending on the Sr2+ ion concentration. Half maximal inhibitory concentration IC50 of CACO-2 cell and HepG-2 cell inhibition was connected with Sr2+ ion ratio. Low IC50 was noticable at low Sr2+ ion content. Such results were correlated to the particle size and the morphology. Indeed, the IC50 of CACO-2 cell inhibition by LSM at a strontium content of 0.2 was 5.63 ± 0.42 µg/mL, and the value increased with increased Sr2+ ion concentration by up to 0.8 to be = 25 ± 2.7 µg/mL. Meanwhile, the IC50 of HepG-2 cell inhibition by LSM at a strontium content of 0.2 was 6.73 ± 0.4 µg/mL, and the value increased with increased Sr2+ ion concentration by up to 0.8 to be 31± 3.1 µg/mL. All LSM samples at different conditions were tested as antimicrobial agents towards fungi, Gram positive bacteria, and Gram negative bacteria. For instance, all LSM samples were found to be active towards Gram negative bacteria Escherichia coli, whereas some samples have presumed antimicrobial effect towards Gram negative bacteria Proteus vulgaris. Such results confirmed that LSM samples possessed cytotoxicity against CACO-2 and HepG-2 cells, and they could be considered to play a substantial role in pharmaceutical and therapeutic applications.
ABSTRACT
Generally, strontium-doped lanthanum manganites (LSM) are materials connected ordinarily as cathodes in the solid oxide fuel cell (SOFC). In this study, the structural, optical, electrical and magnetic properties of La1-xSrxMnO3 (x = 0.2, 0.5, 0.8) synthesized using an organic acid precursor strategy were investigated, based on using citric acid as a fuel. Evidently, the results disclosed that a pure single monoclinic LSM phase was obtained from the thermally treated precursors annealed at 1000 °C with an annealing time of 2 h. The microstructure of the formed sample relied on the Sr2+ ion content. Moreover, a good optical transparency of 45-60% in a wide range of wavelengths between 800 and 1800 nm for all samples substituted by Sr2+ ions was performed. The optical band gap energy was increased from 2.09 to 2.76 eV by increasing the Sr2+ ion molar ratios. The trend in the calculated refractive index, the high frequency dielectric constant (εα) and the static dielectric constant (ε0) of all the produced samples can be linked to an increase in the Sr2+ ion concentration. Moreover, the magnetic properties were enhanced with increasing Sr2+ ion content.
ABSTRACT
Metal doped barium strontium titanate (BST; Ba0.5Sr0.5TixM1-xO3) nanopowders have been successfully synthesized through the oxalate precursor route based on low cost starting materials. The effect of metal ion substitution, namely Fe(3+), Mn(2+), Co(2+) and Y(3+), on the crystal structure, microstructure and optical, electrical, dielectric and magnetic properties of BST was studied. The results revealed that a crystalline single cubic BST phase was formed for pure and Mn(2+), Co(2+) and Y(3+) ion-substituted BST samples, whereas a tetragonal BST structure was obtained for the Fe(3+) substituted BST sample at an annealing temperature of 1000 °C for 2 h. Furthermore, addition of the metal ions was found to decrease the crystallite size and unit cell volume of the produced BST phase. The microstructure of the produced pure BST phase was metal ion dependent. Most BST particles appeared as a cubic like structure. The transparency of BST was found to increase with metal substitution. Meanwhile, the band gap energy was increased from 3.4 eV for pure BST to 3.8, 4.1, 4.2 and 4.3 eV as the result of substitution by Fe(3+), Mn(2+) and Co(2+) and Y(3+) ions, respectively. The DC resistivity was metal ion dependent. The highest DC resistivity (ρ = 66.60 × 10(5) Ω cm) was accomplished with the Mn(2+) ion. Moreover, the addition of metal ions decreased the dielectric properties of the expected Mn(2+) ion and increased the magnetic properties.