Synthesis and characterization of Sr-doped lanthanum manganite nanoparticles

Polycrystalline, nanometer-sized powders of La1-xSrxMnO3 with x = 0.25 and 0.45 were prepared by a citrate gel technique and annealed at 600, 700,and 800 degrees C in air for a period of 3 or 10 h. This synthesis technique resulted in the characteristics of the nanoparticles being highly reproducible from different, but identically prepared starting solutions. The average particle sizes as determined from the width of the (024) X-ray diffraction peak were found to be in the 11-15 nm range for the x = 0.45 Sr concentration materials and in the 12-17 nm range for x = 0.25 materials. For both concentrations, the average particle size increases roughly linear with annealing temperature while the effect of increasing annealing time (3 h versus 10 h) appeared to increase with the particle size, but not in a uniform way. Likewise, the saturated magnetizations at 300 K (7-26 emu/g) and transition temperatures (275-350 K) were found to increase linearly with the average particle diameter for each Sr concentration of nanoparticles.