Combustion synthesis and properties of strontium substituted lanthanum manganites La1-xSrxMnO3 (0<=x<=0.3)

Strontium substituted lanthanum manganites La1-xSrxMnO3 (x = 0, 0.1, 0.16, 0.2 and 0.3) have been prepared by a solution combustion process using lanthanum nitrate, strontium nitrate and manganese nitrate as oxidizers and oxalyl dihydrazide as fuel at 300 degrees C in a pre-heated muffle furnace. As-formed lanthanum manganites are X-ray crystalline showing cubic symmetry. The cubic LaMnO3, with 36% Mn4+ changes to a rhombohedral phase (Mn4+=28%) on calcination at 1000 degrees C. The surface area and average agglomerated particle size of the as-formed manganites are in the range 12-19 m(2) g(-1) and 5.4-8.0 mu m, respectively. Sintering, thermal expansion and de electrical conductivity measurements of La(Sr)MnO3, have been carried out. Strontium substituted lanthanum manganites achieve > 80% theoretical density after sintering at 1350 degrees C for 4 h and the percentage theoretical density decreases with increasing strontium content. The thermal expansion coefficient of La(Sr)MnO, increases with increasing Sr2+ content and La0.84Sr0.16MnO3 shows a highest conductivity value of 202 S cm(-1) at 900 degrees C in air.