Mechanochemical synthesis of LaMnO3+δ fine powder assisted with water vapor

An alternative mechanical synthesis route for LaMnO3+δ fine powder is presented. Mechanical forces such as compression and shear stress were repeatedly applied on a mixture of La2O3 and Mn3O4, using an attrition type milling apparatus. No media balls were employed in this milling. A proper quantity of water vapor in the milling chamber induced an efficient grinding of the mixture at early stage of the milling. The formation of LaMnO3+δ was observed in the subsequent milling, and its synthesis was completed after only 30 min. The average diameter of the resultant LaMnO3+δ was 110 nm, and the amount of contamination was less than 20 ppm in mass. Influences of the water vapor on phase evolution and changes in particle size are shown, and a possible mechanism of the present mechanochemical reaction is discussed.