Polymorphism of the iron doped strontium aluminate SrAl1.5Fe0.5O4

摘要: Abstract The partial substitution of Al by Fe atoms in SrAl2O4 allowed to stabilize four stuffed tridymite derivative structures SrAl1.5Fe0.5O4. different phases have been characterized TEM and XRPD techniques. Two are isotypes those observed for the undoped oxides, namely hexagonal phase with 3 A× A×C (with A C being unit cell parameters) space group P63 monoclinic one A×C, β≈93° P21, a synthesis temperature lower than required SrAl2O4. By annealing, two original phases, denoted O1 O2, obtained; they metrically similar (3A× β≈90°) only differ their groups. study showed that transitions between follow topotactic mechanisms, through formation twinning boundaries, antiphase boundaries planar defects. annealed sample exhibits mesomorph state reversible transition from this semi-ordered crystalline phase. This dynamic takes place over very wide range 620 1120 °C. reversibility has studied DSC measurements. crystallization energy orthorhombic is order 10 J/g, at T≈622 °C as T decreases. variation peak height annealing increases explained complex microstructures, which create an ill-defined barrier. Structural models related proposed new forms ferri-aluminate.