A NEW MULTIPLE PEROVSKITE FAMILY SR3(BI1-YSBY)O5.5-DELTA(0-LESS-THAN-OR-EQUAL-TO-Y-LESS-THAN-OR-EQUAL-TO-1)

The solid state reaction of an Sb2O3-SrCO3 mixture (Sr/Sb=3/1 ) gives a mixed valency antinomy compound that can be written Sr3SbO5.5-delta. Several structural modifications have been characterized by high temperature X-ray diffraction, TGA and DSC. The room temperature form is isostructural to (beta)Sr3BiO5.5; a transformation into a cubic 2ap X 2ap X 2ap superstructure is noted between 285 and 350-degrees-C. Over 350-degrees-C, the tetragonal pattern is isostructural to (alpha)Sr3BiO5.5, with a = 8.460(2) angstrom, c = 16..493(6) angstrom - both forms correspond to a maximum Sb(V) content. At 440-degrees-C the beta form is again obtained. When annealed at 950-degrees-C, it yields a multiple perovskite superlattice. We have identified two solid solution domains Sr3(Bi1-ySby)O5.5-delta: for 0 less-than-or-equal-to y less-than-or-equal-to 0.25 the Sr3BiO5.5 structural evolution versus temperature is kept and a cubic perovskite superlattice is stabilized for 0.3 less-than-or-equal-to y < 1.