Single-phase polycrystalline samples of stoichiometric RMnO 3+δ (R = Er, Y, and Ho) were achieved in the hexagonal P6 3 cm structure through solid state reaction at ∼1300 °C. Thermogravimetric measurements in oxygen atmospheres demonstrated that samples with the larger Ho and Y show rapid and reversible incorporation of large amounts of excess oxygen (0.3 > δ > 0) at an unusually low temperature range of ∼190− 325 °C, indicating the industrial usefulness of RMnO 3+δ materials for lower cost thermal swing adsorption processes for oxygen separation from air. Further increase of the excess oxygen intake to δ ∼ 0.38 was achieved for all the investigated materials when annealed under high pressures of oxygen. The formation of three oxygen stable phases with δ = 0, 0.28, and 0.38 was confirmed by thermogravimetric measurements, synchrotron X-rays, and neutron diffraction. In situ synchrotron diffraction proved the thermal stability of these single phases and the regions of their creation and coexistence, and demonstrated that the stability of the δ = 0.28 phase increases with the ionic size of the R ion. Structural modeling using neutron powder diffraction for oxygen excess phases describes the formation and details of a large R3c superstructure observed for HoMnO 3.28 by tripling the c-axis of the original parent unit cell. Modeling of the RMnO 3.38 (R = Y and Er) oxygen-loaded phase converged on a structural model consistent with the symmetry of Pca2 1 .

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Using pulsed laser deposition and a unique fast quenching method, we have prepared SrCoO x epitaxial films on SiTiO 3 substrates. As electrochemical oxidation increases the oxygen content from x = 2.75 to 3.0, the films tend to favor the discrete magnetic phases seen in bulk samples for the homologous series SrCoO (3-n/8) (n = 0, 1, 2). Unlike bulk samples, 200nm thick films remain single phase throughout the oxidation cycle. 300 nm films can show two simultaneous phases during deoxidation. These results are attributed to finite thickness effects and imply the formation of ordered regions larger than approximately 300 nm.Many transition metal oxides exhibit a rich phase diagram as electron interactions result in multiple ground states with comparable energy. Of particular interest are doped correlated-insulators, where charge doping, often leads to electronic inhomogeneity and in some cases results in clear electronic phase separation.