Tomasz Pikula

Structure and Mössbauer spectroscopy studies of mechanically activated (BiFeO3)1-x-(BaTiO3)x solid solutions

Abstract (BiFeO3)1-x-(BaTiO3)x solid solutions with x = 0.1–0.4 and 0.7 were investigated. The ceramics were prepared by mechanical activation technology and subsequent heat treatment. As was proved by X-ray diffraction, increase of BaTiO3 concentration causes a change in the crystalline structure from the rhombohedral structure characteristic of BiFeO3 to a cubic one. 57Fe Mössbauer spectroscopy allowed observation of a gradual transformation from an ordered spin structure of Fe3+ ions to the paramagnetic state with an increase of x.

Mössbauer Spectroscopy and Magnetoelectric Effect Studies of Multiferroic Ceramics Based on BiFeO3

In this work the results of investigations for (BiFeO3)x(BaTiO3)1-x and Bi1-xNdxFeO3 solid solutions are described. Samples were prepared by the conventional solid-state sintering method. X-ray diffraction, 57Fe Mössbauer spectroscopy, and magnetoelectric effect measurements were applied as complementary methods to determine the structure and magnetic properties of materials. For (BiFeO3)x(BaTiO3)1-x solid solutions Mössbauer spectroscopy revealed the relationship between the content of BiFeO3 and the magnetic properties of the samples. Moreover, the presence of magnetoelectric coupling in (BiFeO3)x(BaTiO3)1-x solid solutions was registered at room temperature for the materials sintered at various temperatures. The maximum value of magnetoelectric voltage coefficient was achieved for 0.7(BiFeO3)0.3(BaTiO3) sintered at 1153K. Structure of Bi1-xNdxFeO3 solid solutions was investigated in the whole range of concentration. Hyperfine interactions parameters were determined for the first time for these solid solutions.

Synthesis and characterization of AgFeO2 delafossite with non-stoichiometric silver concentration

Abstract The simple co-precipitation method was used to prepare AgxFeO2 delafossite with non-stoichiometric silver concentration in the range of x = 0.05-1. The obtained material was investigated using X-ray powder diffraction and 57Fe Mössbauer spectroscopy at room temperature. The structural and hyperfi ne interaction parameters were recognized in relation with decreasing silver concentration. The study revealed that the delafossite structure of AgxFeO2 was maintained up to x = 0.9; as the range of silver concentration was decreased to 0.05 ≤ x ≤ 0.8, a mixture of AgFeO2, Fe2O3 or/and FeOOH was formed.

Effect of BaTiO3 concentration on structural and magnetic properties of mechanically activated BiFeO3-BaTiO3 system

Abstract In this research, the mechanical activation method is proposed as an alternative process of preparation of the (BiFeO3)1-x-(BaTiO3)x solid solutions with various concentrations of barium titanate (x = 0.1÷0.9). However, mechanical milling itself does not allow obtaining the desired products and additional thermal treatment is needed to complete the solid-state reaction. In the present studies, X-ray diffraction and 57Fe Mössbauer spectroscopy were applied as complementary methods in order to study the structural and magnetic properties of materials. The investigations revealed that an increase of BaTiO3 concentration causes changes in the crystalline and hyperfine magnetic structure of the studied (BiFeO3)1-x-(BaTiO3)x system.