Entropy stabilization was attempted through the addition of 5 different rare earth cations, 5 different transition metal cations and all these 10 cations in the form of three compounds based on NiFe2O4. Equiatomic ratios of these cations were used to maximize the entropy stabilization effect. The compounds attempted and investigated were NiFe1.9(Dy0.02Er0.02Gd0.02Ho0.02Tb0.02)O4, (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)Fe2O4 and (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)Fe1.9(Dy0.02Er0.02Gd0.02Ho0.02Tb0.02)O4. Synthesis of these compounds were carried out by sol–gel technique and all the compounds were found to crystallize in [Formula presented] spinel structure indicating the entropy stabilization. An appropriate calculation of configurational entropy of mixing employing the sublattice model is demonstrated for such entropy stabilized oxides. © 2019

Budaraju Srinivasa Murty

Department of Metallurgical and Materials Engineering

G. Markandeyulu

Department Of Physics

Tripta Parida

Anirudha Karati

K. Guruvidyathri

Chromium compounds

Cobalt compounds

Dysprosium compounds

Erbium compounds

ferrite

Gadolinium compounds

Holmium compounds

Iron compounds

Manganese compounds

Nanocrystalline materials

Nanocrystals

Nickel compounds

Positive ions

Rare earths

Soft magnetic materials

Sols

Stabilization

Terbium compounds

Transition metals

CONFIGURATIONAL ENTROPY

GEL TECHNIQUE

NANOCRYSTALLINE SOFT MAGNETIC MATERIALS

RARE EARTH CATIONS

Spinel structure

STABILIZATION EFFECTS

SUB-LATTICE MODEL

TRANSITION METAL CATIONS

entropy

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It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Scripta Materialia

Structural, Mössbauer studies and improved electrical characteristics of Sm, Gd and Dy doped Ni ferrite materials in comparison to that of pure NiFe2O4 are reported. Pure NiFe2O4 crystallizes in inverse spinel phase without any impurity phase. NiFe 1.925Sm0.075O4, NiFe1.925Gd 0.075O4 and NiFe1.925Dy0.075O 4 compounds crystallize in the cubic inverse spinel phase with a very small amount of RFeO3 as additional phase. The back scattered electron imaging analysis indicates the primary and secondary phase formation in NiFe1.925Sm0.075O4, NiFe 1.925Gd0.075O4 and NiFe1.925Dy 0.075O4 compounds. The room temperature DC resistivity values of NiFe2O4, NiFe1.925Sm 0.075O4, NiFe1.925Gd0.075O 4 and NiFe1.925Dy0.075O4 compounds are found to be 17×107 Ω cm, 162×107 Ω cm, 171×107 Ω cm and 305×107 Ω cm respectively. The AC resistivity values (at 1 KHz) of NiFe 2O4, NiFe1.925Sm0.075O4, NiFe1.925Gd0.075O4 and NiFe 1.925Dy0.075O4 materials are 10×10 5 Ω cm, 77×105 Ω cm, 147×10 5 Ω cm and 251×105 Ω cm, respectively. Temperature dependent electrical resistivity curves reveal two different types of conduction mechanisms. The hyperfine parameters viz., the hyperfine magnetic field, the isomer shift and the quadrupole splitting confirms the substitutions of R3+ ions at B site and their effects on superexchange interactions and structural distortion. The enhanced electrical resistivity of rare earth doped Ni ferrite suggest that tuning properties for desired high frequency applications can be achieved by controlling the doping element and their amount.© 2013 Elsevier B.V. All rights reserved.

Journal of Magnetism and Magnetic Materials

Mössbauer studies and enhanced electrical properties of R (R=Sm, Gd and Dy) doped Ni ferrite

Journal of Molecular Structure

Facile synthesis and ferrimagnetic property of spinel (CoCrFeMnNi)3O4 high-entropy oxide nanocrystalline powder

Evidence of surface spin-glass behavior in NiFe2O4 nanoparticles determined using magnetic resonance technique

Journal of the European Ceramic Society

Rare earth and transition metal based entropy stabilised perovskite type oxides

Materials Letters

Synthesis and microstructure of the (Co,Cr,Fe,Mn,Ni) 3 O 4 high entropy oxide characterized by spinel structure

Novel rare-earth and transition metal-based entropy stabilized oxides with spinel structure

Journal	Scripta Materialia
Publisher	Acta Materialia Inc
ISSN	13596462
Open Access	No