VACANCY ORDERING IN LA1-XSRXCOO3 PREPARED BY CALCINATION OF FREEZE-DRIED POWDERS OF NITRATES

Series of samples of La1 - x Srx CoO3 - y with x = 0.8, 0.5 and 0.2 have been prepared by calcination at temperatures between 550° and 1150° C of fine powders of mixed nitrates obtained by the spray-freeze/freeze-drying technique. Crystallization of the cobaltites at temperatures as low as 570° C was observed. The X-ray diffraction of calcined samples revealed clearly the existence of superstructures apparently due to vacancy ordering. The type of the crystal cell formed was a function of the composition and of the conditions of preparation. The new phases seem to be metastable. © 1990.