Raman vibrations, domain structures, and photovoltaic effects in A-site La-modified BiFeO 3 multiferroic ceramics
Schmidt, V. Hugo
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Micro‐Raman spectroscopy, X‐ray diffraction, high‐resolution transmission electron microscopy (TEM), oxygen vacancies, synchrotron X‐ray absorption spectroscopy, magnetizations, optical band gaps, and photovoltaic (PV) effects have been studied in (Bi1−xLax)FeO3 (BFO100xL) ceramics for x = 0.0, 0.05, 0.10, and 0.15. XRD, Raman spectra, and TEM confirm a rhombohedral R3c symmetry with the tilted FeO6 oxygen octahedra in all compounds. The low‐frequency Raman vibrations become broader and shift toward higher frequency as La3+ increases. Fe K‐edge synchrotron X‐ray absorptions reveal that Fe3+ valence and Fe–O–Fe bond angle are not modified by the La3+ substitution. All compounds exhibit a linear antiferromagnetic feature. Optical transmission reveals band gaps in the range of 2.22–2.24 eV. The heterostructures of indium tin oxide (ITO) film/(Bi1−xLax)FeO3 ceramics/Au film show a p–n junction‐like I–V characteristic behavior. The maximal PV power conversion efficiency can reach 0.19% in ITO/BFO15L/Au under illumination of λ = 405 nm. A junction‐like theoretical model can reasonably describe open‐circuit voltage and short‐circuit current as a function of illumination intensity.
C.-S. Tu, C.-S. Chen, P.-Y. Chen, Z.-R. Xu, Y.U. Idzerda, V.H. Schmidt, M.-Q. Lyu, T.-S. Chan, and C.Y. Liu, “Raman vibrations, domain structures, and photovoltaic effects in A-site La-modified BiFeO 3 multiferroic ceramics,” to appear in Journal of the American Ceramic Society (2015). doi: 10.1111/jace.13983.