Two new hydrated oxyhydroxides Sr3Co1.7Ti 0.3O5(OH)2xH2O and Sr 4CO1.6Ti1.4O8(OH) 2,xH2O derived from the RP n = 2 and 3 members: Structural and magnetic behavior versus temperature
Résumé
By varying the cobalt/titanium ratio, two hydrated oxyhydroxides have been prepared in air. The structural study by transmission electron microscopy techniques and thermal analyses shows that these compounds, Sr 3Co1.7Ti0.3O5(OH) 2,xH2O and Sr4Co1.6Ti 1.4O8(OH)2,xH2O are derived from the Ruddlesden-Popper n = 2 and 3 members, respectively. The temperature dependence of the structure shows upon a broad structural transition being warmed from hydrated to anhydrous oxyhydroxides. In the last form, the cobalt/titanium cations adopt a square pyramidal coordination with a long (Co/Ti)-OH apical distance. The phenomenon of water loss during being warmed to 200 °C to obtain these oxyhydroxides is found to be reversible. The magnetic behavior of these phases is governed by the substituted amount of Ti4+ (d 0) for cobalt species: cluster- and spin-glass-like properties are observed for the hydrated oxyhydroxides derived from the RP n = 2 and 3 members, respectively.