Growth of brownmillerite Ca2Fe2O5 single crystals under air, oxygen and argon atmospheres using optical floating zone technique: a comparative study.

To the best of our knowledge, we report for the first time the growth of brownmillerite Ca₂Fe₂O₅ (CFO) single crystals under Argon (Ar) only ambience by optical floating zone (OFZ) technique and compare its structural and spectroscopic properties with CFO single crystals grown by OFZ method under air and oxygen (O₂) atmospheres. Single-crystal X-ray diffraction confirms growth of Ca₂Fe₂O₅ single crystals in all the atmospheres. Crystals grown in air and oxygen (O₂) atmospheres show both metallic Fe⁰ and Fe³⁺states, whereas in Ar-grown crystals only Fe³⁺ oxidation state is observed. An enhancement in oxygen vacancies is also observed in Ar-grown crystals. Growth ambience is found to have a strong influence on cationic environment and binding energy of constituent elements, as is evident from the X-ray photoelectron spectroscopy of the Ca₂Fe₂O₅ crystals. [ABSTRACT FROM AUTHOR]