| Summary: | 碩士 === 輔仁大學 === 物理學系碩士班 === 103 === ABSTRACT
This work studies the temperature-dependent Raman scattering in A-site doped (Bi1-xAEx)FeO3-δ (x=0.0, 0.05, 0.10, and 0.15; AE= Ca, Sr, Ba) multiferroic ceramics in the low temperature range of -150 – 25 oC. Raman spectra and XRD reveal a rhombohedrally distorted perovskite structure with R3c space group in BiFeO3. However, the doped samples of 5 %, 10%, and 15% have a structure transition towards a nonrhombohedral symmetry with increasing Ca, Sr, and Ba concentrations. The Raman spectra of all doped BFO samples reveal a sudden change in the peak position and FWHM, especially for A1(1) and A1(2) modes. This anomaly may be attributed to an additional magnetic phase transition of spin reorientation. Fe atoms are mainly involved in vibration modes between 150 and 270 cm−1 and A1(1) and A1(2) modes are approximately at ~170 and ~220 cm-1, respectively.
Keywords : alkaline-earth (Ca, Sr, Ba) doped BiFeO3, Raman scattering, X-ray diffraction
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