Effect of Bi-substitution on the dielectric properties of polycrystalline yttrium iron garnet

The effect of Bi-substitution on the dielectric properties of yttrium iron garnet (YIG) was studied in this paper. The Bi-substituted YIG (YIG:Bi) polycrystalline samples, having composition of Y3-xBixFe5O12, were prepared by the solid-state reaction method. x varied from 0 to 1.2. The phase formation and microstructure were performed by X-ray diffraction and scanning electron microscopy, respectively. Ions valency was identified by X-ray photoelectron spectroscopy. The impedance analyzers are used to measure the frequency dependence and the temperature dependence of relative dielectric constant (epsilon(r)) and loss tangent (tan delta). The experimental results show that the Bi-substitution lowers the phase formation and sintering temperature. Electronic carrier concentration drops dramatically due to limitation of ferric valency variation. Hence, epsilon(r) and tan delta decrease with addition of Bi. Dispersion characteristic indicates non-Debye-type dispersion. A maximum of epsilon(r) appears as the temperature rises. (C) 2004 Elsevier B.V. All rights reserved.