Nicolae Drăgan

Properties of Ba1−x Sr x TiO3 Ceramics Prepared by the Modified-Pechini Method

Single phase Ba 1−x Sr x TiO 3 powders (x = 0; 0.20; 0.25; 0.30 and 0.35) were obtained via modified Pechini method after annealing of the polymeric precursors in air at 850°C for 2 hours. When the strontium content, x, increases, the tetragonality degree decreases, so that the unit cell symmetry changes from a tetragonal one, specific to the pure BaTiO 3 powder towards a cubic form, for powders with x ≥ 0.30. Dense and homogeneous microstructures, free of secondary phases were obtained for the related ceramics resulted after sintering in air, at 1350°C for 3 hours. High values of the relative permittivity (of ∼ 1500–12000) and low dielectric losses were obtained at the room temperature for all the compositions.

Preparation, Structural and Magnetic Properties of Mn-Doped La0.1Bi0.9FeO3 Ceramics

Bi 0.9 La 0.1 Fe 1 − x Mn x O 3 ceramics with compositions x = 0. 0.1. 0.2, 0.3, 0.4 and 0.5 were prepared by solid state reaction. Ceramics with lower Mn content (x < 0.4) tend to a single phase composition even after calcination at 650°C for 2 hours. Unlikle the porous Bi 0.9 La 0.1 FeO 3 ceramic sample, homogeneous and dense microstructures were obtained for all the manganese-modified compositions thermally treated in the same conditions. The effect of Mn substitution on the magnetic properties of the Bi 0.9 La 0.1 Fe 1 − x Mn x O 3 ceramics was investigated. While the 10% La addition does not change the antiferromagnetic order typical to the BiFeO 3 system, the presence of Mn has a non-monotonous influence on the magnetic moment values at a given field. A weak ferromagnetism seems to be induced around x = 0.2, while for x = 0.4 and 0.5, the antiferromagnetic order is back recovered. The compositions around x = 0.2 are candidate as multiferroic magnetoelectrics and they will be further investigated in detail.