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Phase control, especially for amorphous phase, is challenging with pulsed laser ablation in liquid (LAL), where ablated materials experience crystallization even at extreme cooling rate during particle solidification processes. Here, metallic glass nanoparticles (MG-NPs) were prepared by picosecond-laser ablation of a Fe 78 Si 9 B 13 metallic glass (MG) in several organic solvents (i.e. ethanol, acetone, acetonitrile). The employment of ternary MG precursor effectively avoids elemental segregation of plasma-induced matters; meanwhile, in-situ carbonization by decomposition of solvents further complexes the alloy system to successfully achieve amorphous phase in the NPs. The carbon-rich molecules in solvents enhance the relative fraction of MG-NPs, while parasitic Fe oxide phases are formed due to the competition kinetics of oxygen (e.g. dissolved oxygen and miscible water). Further magnetic measurements and Mössbauer spectra confirm the contribution of MG and Fe oxide NPs to the magnetism. This work provides a new route to produce magnetic MG-NPs for further multifunctional applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead iron niobate, Pb(Fe 0.5 Nb 0.5)O 3 (PFN), belongs to the family of multiferroic materials combining ferroelectric and antiferromagnetic ordering. Its properties to a large extent depend on the synthesis conditions. For applications it is important to obtain materials with large polarization and low electric leakage. In this paper we investigate the effect of processing parameters on the structural, electrical and magnetic behaviour of PFN ceramics prepared by the solid state method. The optimal calcination and sintering temperatures are found, which enable us to obtain ceramics with a large polarization P max = 28 μC/cm2 and dielectric permittivity ε Max ≈ 55 000. We also find that increasing the calcination and sintering temperatures decreases diffuseness of the ferroelectric phase transition and shifts the Néel temperature to lower values, which might be due to a change of the distribution of Fe3+ and Nb5+ across the B-sites of the perovskite towards a more ordered structure. [ABSTRACT FROM AUTHOR]

In this article we report on the synthesis and multiferroic properties of cobalt ferrite (CoFe 2 O 4 )–barium titanate (BaTiO 3 ) biphasic composites. The initial composite nanopowder was synthesized by a combination of co-precipitation and organosol methods. A ceramic sample with (3–0) connectivity, i.e. BaTiO 3 grains in a CoFe 2 O 4 matrix was obtained by a combination of spark plasma sintering and annealing. In order to understand the correlations between morphology, electric properties, and magnetization, we present a detailed study at different preparation steps and compare it to the properties of a conventionally sintered sample with the traditional (0–3) connectivity, i.e. CoFe 2 O 4 grains in a BaTiO 3 matrix. We observe that the (3–0) sample shows improved magnetic properties in comparison to the conventionally sintered composite of the same composition. In spite of relatively large leakage current for the (3–0) sample compared to the traditional (0–3) one, it exhibits a converse magnetoelectric effect that follows the H dc dependence of the piezomagnetic coefficient. The magnetic field-dependence of electric polarization at the surface was investigated utilizing X-ray absorption spectroscopy and its associated linear and circular dichroisms. [ABSTRACT FROM AUTHOR]

The conversion of biomass-derived char is substantially influenced by its metal content. One of the main catalytically active metallic elements in biomass is Fe, which occurs in various mineral forms. For the implementation of catalytic effects into char conversion models, investigations on the role of mineral type and loading are required. In this work, the catalytic effect of an Fe sulfate loading series on the oxidation and gasification of an inherently mineral-free cellulose-derived char was analysed. Characterisation focused on the Fe phases present in the char identifying the transformation from FeSO 4 to γ-Fe 2 O 3 during doping, and further to ε-Fe 2 O 3 and α-Fe 2 O 3 upon char oxidation as well as to FeO and γ-Fe upon char gasification. Very high loading-dependent activities of ε-Fe 2 O 3 and FeO were quantified by kinetic modelling. These iron oxides strongly catalyse char conversion, lowering the activation energy by up to 14% and 18%, respectively, relative to the mineral-free char. • Catalytic effect of Fe on biomass-derived model char conversion in O 2 - and CO 2. • γ-Fe 2 O 3 transformation to ε-Fe 2 O 3 during char oxidation with high catalytic activity. • Additional transformation to α-Fe 2 O 3 during oxidation without catalytic activity. • γ-Fe 2 O 3 transformation to FeO and to γ-Fe during char gasification. • Partially re-oxidation of γ-Fe in CO 2 resulting in Fe 3 O 4 remaining in the ash. [ABSTRACT FROM AUTHOR]

Studying multiferroic magnetoelectrics has been a focus field for the last decade and a half, and the exploration of new materials is one of the several aspects of this quest. Here we report on the synthesis and characterization of NiFe 2 O 4 -based multiferroic composites which employ (Ba,Ca)(Zr,Ti)O 3 as the ferroelectric/piezoelectric component and NiFe 2 O 4 as the magnetostrictive phase. We find that these composites show excellent magnetoelectric properties. Especially the composite with 30 vol% of NiFe 2 O 4 has a converse ME coefficient approximately two times larger than the previously reported one for BaTiO 3 -CoFe 2 O 4 composites. A relationship between the phase connectivity within these composites and the ME properties was explored by the time of flight secondary ion mass microscopy. We believe that our investigation will be helpful for the design of magnetoelectric materials as components of sensors and memory devices. [ABSTRACT FROM AUTHOR]