Mechanically Activated Low Temperature Synthesis of Sr Doped Lanthanum Manganite

Alkaline earth doped lanthanum manganites (La(1-x) M(x)Mn O(3+delta), with M = Ca, Sr, Ba ...) are attractive materials because of their special properties manifested in giant magnetoresistance and electrocatalytic activity. A mechanosynthesis technique is attempted on a mixture of La2O3, MnO2, and SrCO3 in order to verify the possibility of obtaining La(0.7)Sr(0.3)MnO3 with high specific area and small grain size. LaMnO3 is also synthesized in the same way for comparison. The behavior of the mixtures is monitored by XRD. Thermogravimetry (TG) and differential thermal analysis (DTA) are used to follow the thermal behavior compared to that of a simply blended mixture. TG and DTA thermograms indicate that the synthesis of manganite, already present in the milled samples, is completed at temperatures much lower (650 to 700 C) than those of conventional routes. Preliminary measurements of specific surface area confirm that mechanically activated synthesis of lanthanum manganite is able to produce powders having higher surface area and smaller particle size than those obtained by conventional solid state reactions. (Author)