A non-alkoxide sol-gel method for the preparation of homogeneous nanocrystalline powders of la _0.85Sr _0.15MnO ₃

Homogeneous, nanocrystalline Lai _1-xSr _xMnO ₃ (LSM) powders, with x ∼ 0.15, were synthesized with the epoxide addition sol-gel method. Through this simple technique, sol-gel materials were prepared from methanolic solutions of metal chlorides without the need for alkoxides, polymeric gel agents, or elaborate reaction schemes. The gels were dried in ambient conditions, resulting in mesoporous xerogels with networked nanostructures interconnecting particulate regions. Calcination of the dried gels resulted in the crystallization of single-phase LSM by 700 °C, after decomposition of intermediate hydroxide, chloride, and oxychloride compounds. SEM analysis indicated that the calcined powders were nanocrystalline and consisted of discrete particles, free of hard agglomeration. The average crystallite size and equivalent spherical diameter determined from XRD line broadening and BET analysis, respectively, were in good agreement with the SEM results (∼100 nm). The activation energies for the electronic conductivity from 1000 to 400 °C of sintered LSM xerogels were from 0.13 to 0.15 eV, in excellent agreement with previous reported results for LSM with x ∼ 0.15.