Stabilization of the pyrochlore phase of Mn2Sb2O7 by double substitution

Abstract

Polycrystalline samples of (Ce4+Mn2+3)(Ga3+Sb5+3)O14 were synthesized by a high-temperature solid-state reaction. In contrast with the parent Mn2Sb2O7 compound that adopts a rhombohedral or monoclinic structure at T > 600 °C, the pyrochlore structure of CeMn3GaSb3O14 is retained up to at least T = 1070°C. High-resolution synchrotron x-ray diffraction measurements show no sign of a superstructure or distortion from cubic symmetry in the substituted compound. The stabilization of the pyrochlore structure can be attributed to the effect of configurational disorder due to partial substitution of A and B site. Magnetization and heat capacity data suggest a spin-glass transition below T ≈ 2 K. Our results extends the range of available pyrochlore oxides, and demonstrate that entropic stabilization is a viable route to stabilize novel materials with complex structure types.