144 research outputs found
Influence of electric field on the Eu+3 photolumiscence in lead-free ferroelectric Na1/2Bi1/2TiO3
Eu modified Na1/2Bi1/2TiO3 (NBT) was investigated for electric-field induced
Eu+3 photoluminescence (PL) and structural changes. Detailed analysis revealed
that below a critical Eu composition electric field irreversibly suppresses the
structural heterogeneity inherent of the host matrix NBT and brings about a
long range ferroelectric state with rhombohedral (R3c) distortion. PL study
revealed that structural disorder on the nano-scale opens new channels of
radiative transitions which can be suppressed by electric field. This study
suggests that Eu+3 luminescence can be used to probe the relative degree of
field induced structural ordering in relaxor ferroelectrics and also in high
performance piezoelectric alloys where electric field couples very strongly
with the lattice and structural degrees of freedom.Comment: 19 pages, 9 figure
Size Control and Magnetic Property Trends in Cobalt Ferrite Nanoparticles Synthesized Using an Aqueous Chemical Route
Cobalt ferrite (CoFe2O4) is an engineering material which is used for applications such as magnetic cores, magnetic switches, hyperthermia based tumor treatment, and as contrast agents for magnetic resonance imaging. Utility of ferrites nanoparticles hinges on its size, dispersibility in solutions, and synthetic control over its coercivity. In this work, we establish correlations between room temperature co-precipitation conditions, and these crucial materials parameters. Furthermore, post-synthesis annealing conditions are correlated with morphology, changes in crystal structure and magnetic properties. We disclose the synthesis and process conditions helpful in obtaining easily sinterable CoFe2O4 nanoparticles with coercive magnetic flux density (H-c) in the range 5.5-31.9 kA/m and M-s in the range 47.9-84.9 A.m(2)Kg(-1). At a grain size of similar to 54 +/- 2 nm (corresponding to 1073 K sintering temperature), multi-domain behavior sets in, which is indicated by a decrease in H-c. In addition, we observe an increase in lattice constant with respect to grain size, which is the inverse of what is expected of in ferrites. Our results suggest that oxygen deficiency plays a crucial role in explaining this inverse trend. We expect the method disclosed here to be a viable and scalable alternative to thermal decomposition based CoFe2O4 synthesis. The magnetic trends reported will aid in the optimization of functional CoFe2O4 nanoparticle
Surface oxidation for enhancing the hydrogen evolution reaction of metal nitrides: a theoretical study on vanadium nitride
A single oxide layer acts as a surface oxide activation layer (SOAL) on top of the VN surface toward the HER. VN is a simple model nitride, and this picture can be used for designing enhanced nitride-based catalysts with controlled oxidation of surfaces
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