Microstructure and densification mechanism of low temperature sintering Bi-Substituted yttrium iron garnet

Abstract

The low temperature sintering and densification mechanism of Bi-substituted yttrium iron garnet (Bi:YIG) polycrystalline samples were studied in this paper. The Bi:YIG polycrystalline samples, with the composition of Y3−x Bi x Fe5O12 (x = 0–1.2), were prepared by the solid-state reaction method. The X-ray diffraction (XRD) patterns show that Bi-substitution can lower the formation temperature of garnet phase from about 1200 to 900 °C and the thermo-mechanical analysis (TMA) indicates that the sintering temperature of ceramics can be decreased from over 1350 °C to below 1000 °C. The microstructure of grains and grain boundaries was observed by high resolution electron microscopy (HREM). The bismuth distribution in grains and grain boundaries was performed by X-ray energy dispersive spectroscopy (EDS). The occurrence of liquid phase with Bi-contained oxide in the sintering process caused the decrease in sintering temperature.