Hydrothermal synthesis of La1-xSrxMnO3+δ manganites

The hydrothermal synthesis of lanthanum manganites, La1-xSrxMnO3+delta, was investigated for x = 0 and x = 0.2, under autogenous pressure in the temperature range 140-240degreesC, varying the time (2 - 410 hours) and the nature of the metal precursors and of the base. Several pathways leading to pseudo-cubic polymorphs were established. A calcination of the hydrothermal products, at 650degreesC (x = 0) or 550degreesC (x = 0.2), is always needed to crystallize the manganite; the powders are 2 then formed of interlaced chains and exhibit surface areas close to 35 m(2).g(-1). A further calcination at 1000degreesC leads to the pseudo-cubic to rhomboedric polymorphic transformation and breaks the chains forming grains with sizes in the range 100 - 200 nm (x = 0) and 50 - 100 nm (x = 0.2).