In this article we report on the advanced microstructural characterization and compositional analyses of submicrometer-sized reaction phases in modified Nd-Fe-B sintered magnets doped with terbium. Using a grain-boundary diffusion process (GBDP) the Tb reacts with matrix Nd2Fe14B grains and consequently core-shell structures are formed at the surface of original matrix grains with shell thickness from a few tens of nanometers up to a few micrometers. Such structures were investigated using a high-resolution FEGSEM scanning electron microscopy and energy-dispersive (EDS) and wavelength-dispersive (WDS) X-ray spectroscopies. In order to achieve submicrometer analytical resolution two methods were applied: (i) WDS with measurements of the common Nd-L, Fe-K and Tb-L spectral lines and (ii) low-voltage EDS, analyzing the “atypical” low-energy Nd-M, Tb-M and Fe-L lines with dedicated standardization procedure. The Monte Carlo calculations confirmed that in both cases an enhanced, submicrometer lateral analytical resolution was achieved, i.e. 0.4 m with the WDS and only 0.15 m with the EDS. The quantification of spectroscopic measurements was performed using modern matrix correction XPP and with standards specially prepared for those analyses. Quantitative analyses confirmed that the reaction phase (NdxTb1–x)2Fe14B is formed after the diffusion of Tb with the equilibrium concentration of Tb being equal to x=0.5, i.e., with the atomic ratio of Nd/Tb equal to 1/1. We also found that a relatively sharp Tb concentration gradient from the shell to the core occurs within a length of ≈ 0.5 m, while the Fe concentration remains unchanged. In terms of magnetic properties, the Tb-doping significantly increased coercivity by ≈ 30 % while the remanence remained at the same value as in the undoped Nd-Fe-B.
COBISS.SI-ID: 25799207
In the present work we report on the synthesis of dense, highly transparent and conductive polycrystalline ZnO films on amorphous glass substrates using low temperature hydrothermal route. Among other characterization methods we have applied the FEGSEM/EBSD analyses in order to determine the texture of the obtained oriented ZnO films. Because of small size of the ZnO crystals the EBSD technique was modified and optimized for achieving the analytical resolution in submicrometer range, which allowed us to confidently determine the orientation of ZnO grains smaller than 1 m. From the recorded EBSD crystal orientation image maps we have defined the orientations of the individual ZnO crystals. From corresponding pole figures we found that ZnO films have prominent texture in crystallographic c-axis direction, i.e. that the ZnO crystals have their basal {0001}-planes oriented within ± 3o with respect to the substrate surface.
COBISS.SI-ID: 25764903
Fe-Pd thin films with various compositions and thicknesses were produced by electrodeposition using constant potentials from -1.0 to -1.3 V. FEGSEM and AFM analyses revealed a smooth, nanostructured surface morphology of the films, with more granular features appearing at more negative potentials. High-resolution FEGSEM images of the films’ cross-sections and complementary calculations using data from the EDS thin-film analyses were used to determine the film thicknesses, showing that 50-nm to 120-nm ultrathin films were obtained. The chemical compositions of the films were measured by quantitative EDS electron-probe microanalysis using two independent approaches: (i) low-voltage analysis (LVEDS) and (ii) variable-voltage analysis with a dedicated thin-film analysis (TFA) method. Both approaches were properly modified and optimized on the basis of Monte Carlo simulation data. The results showed that the composition of the Fe-Pd films was close to the preferred equiatomic Fe50Pd50 stoichiometry (which is important for achieving good magnetic properties) and was obtained at -1.3 V and -1.2 V. At more positive potentials the Fe-Pd films became Pd-rich. The best agreement between the LVEDS and TFA quantitative results was achieved for Fe-Pd films that were thicker than 80 nm, and a slight discrepancy within the ± 10 % relative between the LVEDS and TFA values was observed for films thinner than 70 nm. The faster LVEDS approach is suitable for the routine analyses of numerous Fe-Pd samples, i.e., to obtain information about the film’s composition in a short time. The more demanding TFA approach was found to be very appropriate for accurate compositional analyses of Fe-Pd ultrathin films and for determining the film thickness.
COBISS.SI-ID: 27199783
Fe–Pd nanowires were synthesised in anodic alumina templates by applying potentiostatic and pulsed electrodeposition regimes. When using potentiostatic deposition, only fragmented nanowires were obtained; however, the use of pulse deposition was shown to be effective for producing solid, homogeneous nanowires. The morphology and the composition of these nanowires were studied by high-resolution FEGSEM and low-voltage EDS quantitative elemental analysis that was optimized for submicrometer spatial analytical resolution. Using the pulse deposition the nanowires with the composition Fe55Pd45, length of 2.5 um and diameter of 200 nm were synthesised. The soft-magnetic as-deposited nanowires with a fcc crystal structure were subsequently annealed at 600 oC for 5 h in order to promote the ordering into the hard-magnetic L10 phase, with achieved highest coercivity of 122 kA/m.
COBISS.SI-ID: 27644199
The size, morphology, crystal structure and crystallinity of synthesized rutile (TiO2) nanoparticles were analyzed using X-ray powder diffraction (XRD), high-resolution scanning electron microscopy (FEGSEM) and transmission electron microscopy (TEM). The results show that the gel-sol process allows control over the final nanoparticle characteristics with the proper choice of reaction parameters. The gel-sol synthesis resulted in anisotropic rutile nanoparticles that are 60–160 nm long, depending on the reaction parameters, and have an aspect ratio of about 5. A reaction mechanism was proposed, explaining the influence of various reaction parameters on the characteristics of the TiO2 nanoparticles.
COBISS.SI-ID: 18903605