Stabilization Of FeCo Alloy Phase In FeCo-SiO2 nanocomposites

Abstract

A series of FeCo-SiO 2 granular films of different FeCo atomic concentration (33-54%) have been prepared by fast atom beam sputtering technique and post-annealed in inert (Ar) and reducing (H 2 ) gas environments. Fe and Co K-edge XANES analysis of as-deposited films indicate that both Fe and Co are present mainly in their elemental (Fe 0 , Co 0 ) state. A partial oxidation of Fe and Co is observed, as the FeCo alloy content decreases (54 to 33%) due to reduced particle size. XANES/XAFS analysis shows the formation of FeCo alloy with bcc Fe structure in H 2 environment annealed films. The XRD and Raman analysis of Ar environment annealed films suggest the formation of Co 3 O 4 and CoFe 2 O 4 phases. The Ar environment is found not to be effective reducing medium to stabilize the FeCo alloy phase, while H 2 environment annealing (450-700 o C) leads to formation of bcc FeCo alloy.

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

“…This latter fact supports the assumption of the complete oxidation of FeCoZr metallic granules in the films during deposition in an oxygen-containing atmosphere at Р O = 3.7 • 10 -3 Pa. Taking this conclusion into account one should note the good coincidence between the positions of the lines for completely oxidized FeCoZr nanoparticles in the X-ray diffraction patterns of the (FeCoZr) 81 (PZT) 19 , films deposited at two different oxygen pressures Р O = 2.4 • 10 -3 and 3.7 • 10 -3 Pa.…”

“…The films with х ≥ 67 at.% also exhibit the formation of a-FeCo(Zr,О) ferromagnetic nanoparticles or their ferromagnetically interacting agglomerations whose contribution increases with x. With an increase in the oxygen pressure (Р О = (3.7÷5.0) • 10 -3 Pa) during the synthesis, only superparamagnetic particles of the Fe 3+ (Co,Zr)O complex oxide form over the whole range of experimental compositions [10,[17][18][19].…”

Unraveling The Origin of Enhanced Field Emission from Irradiated FeCo-SiO2Nanocomposites: A Combined Experimental and First-Principles Based Study

“…More technical details of experimental FAB set up can be found in ref . The stabilization of FeCo phase in the nanocomposite was further achieved by 2 h of annealing in H 2 atmosphere in a tubular furnace at 600 °C. , The as-deposited and annealed samples were then subjected to 5.0 × 10 13 (5e13) and 1.0 × 10 14 (1e14) ions/cm 2 fluences of 120 MeV Au 9+ (SHI) irradiation at the 15UD Palletron accelerator of IUAC, New Delhi, India. Following this, FE current was recorded with a Keithley multimeter (196 system DMM, resolution 1 nA) using the film as cathode in simple diode geometry kept in a high vacuum chamber.…”

Spectral weight shift in the valence band density of states and concurrent increase in field emission by hydrogenation of FeCo–SiO2 nanocomposites

“…Fe and Co foils were co-sputtered using neutral Ar atoms with SiO 2 for the synthesis of FeCo-SiO 2 nanocomposite lms using a fast atom beam (FAB) sputtering technique as described in our earlier work. 15 The content of metallic nanoparticles in the composite was kept at $20% as per the calculation based on the area fraction and sputtering yield. 23 A set of the as prepared samples (AD) was then subjected to tubular furnace annealing in a hydrogen gas environment for 2 hours at 200 C and 350 C and named as 200AN and 350AN.…”

“…13,14 The FeCo alloy has a lower work function and lesser possibility of getting oxidized in comparison to individual Fe/Co. Thus, stable FeCo nanoparticles 15,16 embedded in a SiO 2 matrix can act as promising eld emitters.…”