COMBUSTION SYNTHESIS AND PROPERTIES OF STRONTIUM SUBSTITUTED LANTHANUM MANGANITES LA1-XSRXMNO3 LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-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 ox idizers and oxalyl dihydrazide as fuel at 300 degrees C in a pre-heate d 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 su rface area and average agglomerated particle size of the as-formed man ganites are in the range 12-19 m(2) g(-1) and 5.4-8.0 mu m, respective ly. Sintering, thermal expansion and de electrical conductivity measur ements of La(Sr)MnO3, have been carried out. Strontium substituted lan thanum manganites achieve > 80% theoretical density after sintering at 1350 degrees C for 4 h and the percentage theoretical density decreas es with increasing strontium content. The thermal expansion coefficien t of La(Sr)MnO, increases with increasing Sr2+ content and La0.84Sr0.1 6MnO3 shows a highest conductivity value of 202 S cm(-1) at 900 degree s C in air.