In this contribution (conference MC2013, Regensburg) we reported on quantitative compositional analyses of Fe-Pd nanorods that were carried out using low-voltage EDS approach by analysing the Fe-La and Pd-La low-energy spectral lines at three SEM accelerating voltages: 8, 6.5 and 5 kV. The atomic Fe/Pd ratios obtained from the quantitative EDS analyses at 10 discrete points along a selected Fe-Pd nanorod reveal consistent results for all the applied voltages. The advantage of low-voltage EDS is the high spatial analytical resolution due to the reduced, submicrometer-sized, X-ray excitation volume at low beam energies. This allowed us to measure the composition and/or compositional variations along the Fe-Pd nanorods on a submicrometer scale with achieved lateral analytical resolution of ≈ 200 nm, which is comparable to the diameter of the nanorods. In selected sample quantitative EDS analysis clearly showed that considerable Fe and Pd concentration gradient along the nanorods is present. In conclusion we found that a high-resolution FEGSEM imaging combined with low-voltage EDS analyses are very appropriate tools for reliable analyses of the morphology and chemical composition of the electrodeposited Fe-Pd nanorods.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 26980903In this contribution, presented at EMAS-2013 (Porto) conference, we reported on the characterization of sintered magnets based on the Nd2Fe14B phase, which were modified by doping with Tb using the grain-boundary diffusion process (GBDP). FEGSEM backscattered-electron images of the microstructure showed that in doped magnets a core-shell-type structure is formed with a thin Tb-rich, (Nd,Tb)-Fe-B reaction phase around the primary Nd2Fe14B matrix grains. These intergranular reaction phases had a thickness from a few tens of nanometers up to a few micrometers. Reliable quantitative compositional analyses of such tiny phases were performed using the EDS analytical set-up that was properly optimized to achieve a high analytical spatial resolution on a nanometer scale. The analyses were undertaken in a JEOL JSM-7600F FEGSEM equipped with an Oxford INCA Energy 350 System and an EDS-SDD X-max-20 silicon drift detector. The “atypical” low-energy Nd-Ma, Tb-Ma and Fe-La spectral lines were measured (instead of the common Nd-La, Tb-La and Fe-Ka) at a primary beam energy of of 5 keV and a beam current of 1 nA. With this dedicated set-up we were able to achieve an improved, ultimate analytical resolution of 150 nm. Since the default EDS analytical system does not support the quantification of the low-energy Tb-M and Nd-M lines, a new standardization and our user-defined quantitative set-up for these spectral lines and also for the Fe-L line was created using dedicated standards Nd2Fe14B and Tb. The results of the quantitative low-voltage EDS analyses verified that after the diffusion of Tb an intergranular reaction phase is formed with a composition described generally by (NdxTb(1–x))2Fe14B. We also found that the diffusion process is completed with an equilibrium Tb concentration that corresponds to x = 0.5, i.e., with an equiatomic Nd/Tb ratio of 1/1. A relatively sharp Tb concentration gradient from the shell to the core occurs within a length of ≈ 0.5 um, while the Fe concentration remains unchanged in both the reaction phase and the matrix grains.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 26740007