| Summary: | 碩士 === 國立中正大學 === 物理系 === 99 === BiFeO3 is currently a hot research topic for multiferroic materials, because it exhibits a magnetoelectric effect at the room temperature. Rare-earth elements substitution for A-site and B-site in the ABO3 structure for the BiFeO3 has been known as an important step to improve its electrical and magnetic properties. However, rare publications reported their effects at the high frequencies, especially on microwave range. This thesis focuses on analyzing the high-frequency properties of BiFeO3 materials partially substituted by Sm、Gd、 Nd and La ions.
The investigation can be divided into three parts. The first part is to synthesize and analysis the BiFe0.9X0.1O3 (X = Sm、Gd、Nd、La) samples. The Sm、Gd、Nd、La substitute ratio 10% is selected for the samples by the solid-state reaction method. After 850 ℃ sintering temperature, the X-Ray diffraction (XRD) and SEM are used to identified the structure and calculate the lattice constant and average particle size for the different sintering time. The second part is to identify their electric and magnetic properties by the VSM, impedance analyzer and TF analyzer, respectively. The third part is to measure their dielectric properties at the x-band microwave frequency. A resonance frequency of the x-Band cavity is designed to make the measurement in this study. Their dielectric constant and dielectric loss are then extracted by the perturbation method and their high-frequency responses. Compared with the XRD structures and high-frequency results, in this study we conclude that the 10% rare-element substitution changes the ABO3 structure of the BiFeO3 and directly affects their dielectric properties at the high frequencies.
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