Structure, dielectric and magnetic properties of Ba_6FeNb_9O_(30) tungsten bronze ceramics

摘要

Ba_6FeNb_9O_(30) 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) A, b = 12.597(6) A, c = 3.989(1) A. 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 5 K, which was related to the magnetic ions (Fe~(3+)) in tungsten bronze structure.