Electronic Theses and Dissertations

Identifier

2444

Date

2015

Document Type

Thesis

Degree Name

Master of Science

Major

Physics

Concentration

Materials Science

Committee Chair

Sanjay R. Mishra

Committee Member

Jingbiao Cui

Committee Member

Prabhakar Pradhan

Abstract

Kunwar, Dom Lal. M.S. The University of Memphis. August 2015. Influence of Rare-earth on Structural, Magnetic and Electrical Properties of Aluminum Doped Strontium Hexaferrite. Major Professor: Sanjay R. Mishra, PhD. Among family of ferrites, M-type hexaferrites find host of industrial applications ranging from simple magnets to microwave devices. Improvement in magnetic and dielectric properties of ferrites is a continuous area of interest. The adapted strategies to bring in aforementioned desired improvements are via exploring various synthesis route and doping strategies including viz. magnetic, non-magnetic, and rare-earth atoms in ferrites. In view of the above, the present work studies in detail the effect of co-doping rare-earth (RE: Pr, Sm, and Gd) and aluminum in Sr0.82RE0.18Fe12-xAlxO19 (x=0.0, 0.5, 1.0, 1.5, 2.0) synthesized via autocombustion technique. Detailed synthesis, structural, magnetic, and electrical measurements of samples were performed towards understanding structural-magnetic-electrical property relationship. The variations in physical properties of as synthesized samples were understood in terms of rare-earth ion charge distribution, site occupancy of RE3+ and Al3+ ions, and grain size. The substitution of RE3+-Al3+ brings in grain refinement due to induced lattice strains upon accommodating doped ions. Gd3+-Al3+ displayed smallest crystallite size among all RE3+-Al3+ samples. The Al3+ substitution for Fe3+ brings in significant enhancement in coercivity but reduces magnetization due to magnetic dilution effect. Additional coercivity enhancement was possible with RE3+ doping without affecting the magnetization of samples. This is an important development towards producing high energy magnets. Among all RE3+ doped samples Pr3+ doped samples showed highest Curie temperature, (Tc~465ºC), while Gd3+ doped samples showed little variation in dielectric properties in GHz frequency range. This makes RE3+ doped samples as ideal candidate for high frequency microwave applications. From above observations Pr3+ with oblate charge distribution (negative Stevens constant) was observed to substitute well into the lattice consequently brining in desired improvements in physical properties of Sr0.82RE0.18Fe12-xAlxO19 ferrite.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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