ChemInform Abstract: Investigations on Bi 25 FeO 40 Powders Synthesized by Hydrothermal and Combustion-Like Processes (original) (raw)

Investigations on Bi 25FeO40 Powders Synthesized by Hydrothermal and Combustion-Like Processes.-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.;