The syntheses of phase−pure and stoichiometric iron sillenite (Bi 25 FeO 40) powders by a hydrothermal (at ambient pressure) and a combustion−like process are described. Phase−pure samples were obtained in the hydrothermal reaction at 100 °C (1), whereas the combustion−like process leads to pure Bi 25 FeO 40 after calcination at 750 °C for 2 h (2a). The activation energy of the crystallite growth process of hydrothermally synthesized Bi 25 FeO 40 was calculated as 48(9) kJ mol −1. The peritectic point was determined as 797(1) °C. The optical band gaps of the samples are between 2.70(7) eV and 2.81(6) eV. Temperature and field−depending magnetization measurements (5−300 K) show a paramagnetic behaviour 2 with a Curie constant of 55.66•10 −6 m 3 •K•mol −1 for sample 1 and C = 57.82•10 −6 m 3 •K•mol −1 for sample 2a resulting in magnetic moments of µ mag = 5.95(8) µ B •mol −1 and µ mag = 6.07(4) µ B •mol −1. The influence of amorphous iron−oxide as a result of non-stoichiometric Bi/Fe ratios in hydrothermal syntheses on the magnetic behaviour was additionally investigated.

Magnetoelectric 0‐3 composites consisting of small ferromagnetic Ni particles in the micrometer range embedded in a ferroelectric BaTiO3 matrix are synthesized by reductive sintering in flowing nitrogen with carbon as the oxygen getter. Phase purity of the samples Nix/(BaTiO3)1 − x (x = 0.1–0.7) is verified by powder X‐ray diffraction in combination with scanning electron microscopy/energy‐dispersive X‐ray spectroscopy analyses and magnetization investigations. The magnetoelectric coefficient (αME) is studied for parallel and perpendicular orientations of polarization and magnetic field. For the latter orientation, a reverse sign and a much weaker signal are found. The dependence of αME on the magnetic direct current bias field shows a linear behavior between ≈±2 kOe and a drop to almost zero above ≈4 kOe. Largest values are obtained for x = 0.4. With increasing frequency of the alternating current driving field, αME becomes larger. At low temperatures, two step‐like decreases in the magnetoelectric coefficient occur, reflecting the phase transitions of BaTiO3 (tetragonal→orthorhombic and orthorhombic→rhombohedral). While this finding corroborates the interpretation of αME being a product property of magnetostriction and piezoelectricity, distinct deviations between the field dependence of the integrated ME signal and the magnetostriction of nickel are found.

By high-pressure/high-temperature multianvil synthesis a new high-pressure (HP) phase of Co3TeO6 was obtained. The compound crystallizes in the acentric trigonal crystal system of the Ni3TeO6-type structure with space group R3...

Reduction of Co3O4/BaTiO3 in forming gas followed by sintering in flowing nitrogen with carbon as oxygen getter was applied for the syntheses of magnetoelectric 0-3 Cox/(BaTiO3)1-x composites (x = 0.1...

Investigations on Bi 25FeO40 Powders Synthesized by Hydrothermal and Combustion-LikeProcesses. -Phase-pure iron sillenite (Bi 25FeO40) powders are prepared by hydrothermal reaction of Bi(NO 3)3 and Fe(NO3)3 in aq. HNO3 (1. addition of 10M NaOH at 80 C, 2. reflux, ambient pressure, 6 h) (sample S1) and by combustion processing of the same initial mixture to which soluble starch is given under stirring to form a viscous gel which is then calcined in air (750 C, 2 h) (sample S2). The calculated activation energy of hydrothermal crystallite growth is 48 kJ/mol with a peritectic point at 797 C. The optical band gaps are between 2.70 and 2.81 eV. Temperature and field-depending magnetization measurements (5-300 K) show paramagnetic behavior with a Curie constant of 55.66 x 10 -6 m 3 K/mol for S1 and 57.82 x 10 -6 m 3 K/mol for S2 resulting in magnetic moments of 5.95 and 6.07  B/mol, respectively. The influence of amorphous Fe-O as a result of non-stoichiometric Bi/Fe ratios in hydrothermal syntheses on the magnetic behavior is also investigated. -(KOEFERSTEIN*, R.; BUTTLAR, T.; EBBINGHAUS, S. G.; J. Solid State Chem. 217 (2014) 50-56, http://dx.