Date of Award
Master of Science
Sanjay R. Mishra
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.
dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.
Kunwar, Dom Lal, "Influence of Rare-Earth on Structural, Magnetic and Electrical Properties of Aluminum Doped Strontium Hexaferrite" (2015). Electronic Theses and Dissertations. 1222.