Particle size effect on microwave absorbing of La_0.67Ba_0.33Mn_0.94Ti_0.06O₃ powders prepared by mechanical alloying with the assistance of ultrasonic irradiation

Doped manganites have attracted substantial interest due to their unique chemical and physics properties, which makes it possible to be used for microwave absorbing materials. In this paper we report synthesizes and characterization of La_0.67Ba_0.33Mn_0.94Ti_0.06O₃ powders prepared by mechanical alloying with the assistance of a high power ultrasonic treatment. After solid state reaction, the presence of single phase was confirmed by X-ray Diffraction (XRD). Refinement results showed that samples are single phase with monoclinic structure. It was found that powder materials derived from mechanical alloying results in large variation in the particle size. A significant improvement was obtained upon subjecting the mechanically milled powder materials to an ultrasonication treatment for a relatively short period of time. As determined by particle size analyzer (PSA), the mean particle size gradually decreased from the original size of 5.02μm to 0.36μm. Magnetic properties were characterized by VSM, and hysteresis loops results showed that samples are soft magnetic. It was found that when the mean particle size decreases, saturation was increases and coersitivity was decreases. Microwave absorption properties were investigated in the frequency range of 8-12GHz using vector network analyzer. An optimal reflection loss of 24.44dB is reached at 11.4GHz.