The Effects of Sintering Temperature on the Dielectric Behavior and Magnetic Property of Ferrimagnetic ${\hbox {Tb}}_{3}{\hbox {Fe}}_{5}{\hbox {O}}_{12}$

Abstract

High-purity Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> samples were prepared by the solid-state reaction method at 1300-1390 $,,^{circ} $C and their magnetic and dielectric properties were studied. The results showed that although the magnetic properties did not change notably with the processing conditions used, the dielectric behaviors of the polycrystalline Tb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> were affected significantly. The increase of sintering temperature from 1300 to 1390°C resulted in a dramatic increase in bulk density, dielectric constant and loss-peak frequency, but a decrease in the $alpha$ parameter of the Cole-Cole equation. The Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> -Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> hopping process was proposed for the observed dielectric behaviors. The hopping activation energy, calculated by the Arrhenius plots, decreased from 0.438 to 0.289 eV as the sintering temperature increased from 1300 to 1390°C . The Cole-Cole equation could be used to describe the relaxation behaviors of these samples and the calculated α parameter decreased from 0.305 to 0.059. High sintering temperature had both the effects of improving crystallinity and enhancing the Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> → Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> reduction. The former lowered the hopping activation energy and narrowed the distribution of the relaxation time (as indicated by α → 0), while the later increased the dielectric constant and loss, as well as the DC conduction in the low frequency region.