Multiferroic properties of Eu-substituted BiFeO3 fine-grained ceramics

Reference Presenter Authors
08-109 Vasile Adrian Surdu Surdu, V.A.(University POLITEHNICA of Bucharest); Ganea, P.(National Institute of Materials Physics); Kuncser, V.(National Institute of Materials Physics); IANCULESCU, A.C.(University POLITEHNICA of Bucharest, Romania); Bi1-xEuxFeO3 (x = 0 – 0.20) powders were obtained by a sol-precipitation method, using bismuth and iron nitrates as starting materials. After thermal treatment at 600°C/1 h, well-crystallized particles with sizes ranged between 40 and 155 nm, were obtained when the Eu3+ content decreases from x = 0.20 to x = 0. For a substitution degree x ? 0.10 only the rhombohedral form of BiFeO3 was identified by XRD. The increase of europium addition above this value induces the partial conversion of the rhombohedral (R3c) modification into the orthorhombic (Pnma) polymorph. From these powders, fine-grained ceramics were prepared by spark plasma sintering (SPS). FE-SEM investigations indicated that the presence of Eu3+ as solute on Bi sites determines a strong decrease of the grain size from 925 nm for x = 0 to 173-217 nm for x ? 0.05. The ceramics exhibit decreased values of permittivity when increasing the Eu3+ content. The structural transition has a beneficial effect on the dielectric losses which decrease with about one order of magnitude from tan? ~ 0.07 (x = 0) to ~ 0.005 (x = 0.20) at fixed frequency f = 100 kHz. In the temperature range of 400 – 500K, relaxation phenomena occur for x ? 0.15. Magnetic hysteresis loops collected on the ceramics showed an antiferromagnetic behaviour for x = 0 and x = 0.20 and a weak ferromagnetic behaviour for 0.05 ? x ? 0.15.
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