Structure, dielectric and magnetic properties of Ba6FeNb9O30 tungsten bronze ceramics
ABSTRACT Ba6FeNb9O30 ceramics were synthesized by a standard solid-state sintering process. X-ray powder diffraction (XRD) refinements were carried
out to analyze the crystal structure, and the dielectric, ferroelectric and magnetic properties were investigated and discussed.
The tetragonal tungsten bronze structure in space group P4bm was determined with the lattice parameters: a=12.597(6) Å, b=12.597(6) Å, c=3.989(1) Å. An extremely high dielectric constant was indicated at higher temperatures, and it dropped quickly when the
sample was cooled down through a critical temperature, and this critical temperature showed strong frequency dependence. This
dielectric relaxation was more obviously observed in the dielectric loss curve. The nonlinear magnetic hysteresis curve was
observed in the present ceramics at 5K, which was related to the magnetic ions (Fe3+) in tungsten bronze structure.
- SourceAvailable from: Martin C. Stennett[show abstract] [hide abstract]
ABSTRACT: Strong coupling between local polar displacements and a commensurate octahedral tilting is proposed to explain the onset of classic ferroelectric behavior in tetragonal tungsten bronzelike dielectrics Ba <sub>2</sub> La <sub>x</sub> Nd <sub>1-x</sub> Nb <sub>3</sub> Ti <sub>2</sub> O <sub>15</sub> . The ferroelectric phase transition is associated with a discontinuous non-lock-in transformation of an incommensurate tilted structure to a commensurate superstructure. In a manner reminiscent of perovskitelike oxides, the driving force for commensurate tilting increases as the average ionic radius of the rare-earth ion decreases; no classical ferroelectric transition is observed for compositions with x≫0.75 , which remain incommensurate and exhibit only relaxor behavior below room temperature.Applied Physics Letters 10/2006; · 3.79 Impact Factor
- Recent developments of the program FULLPROF in commission on powder diffraction (IUCr)..