REACTION STEPS AND MICROSTRUCTURE FORMATION DURING SHS OF LA0.8SR0.2CRO3

The combustion rate processes involved in the self-propagating high-te mperature synthesis (SHS) of La0.8Sr0.2CrO3 from a mixture of either L a2O3 + SrO2 + Cr + NaClO4 or La2O3 + SrO2 + Cr + CrO3 were studied by quenching the reaction front within a conical combustion-wave arrestin g setup. The intermediate products for both green mixtures included La CrO3, LaCrO4, La2CrO6 and SrCrO4. The final product, La1-xSrxCrO3, sta rts to form in the zone of secondary chemical interactions (post-front zone) and is completed in the final product and cooling zone. The hig h combustion temperature causes partial melting, leading to agglomerat ion of the particles. High temperatures may lead to migration of the C rO3 to the surface. To maintain uniform Cr content in the radial direc tion, it is desirable to operate at the lowest possible combustion tem perature and at high pressure. The combustion temperature may be decre ased by replacing metallic Cr by Cr2O3 in the first reaction mixture a nd by CrO3 in the second mixture.