High pO 2 Flux Growth and Characterization of NdNiO 3 Crystals.

Single crystals of the perovskite nickelate NdNiO₃ with dimensions of up to 50 μm on edge have been successfully grown using the flux method at a temperature of 400 °C and oxygen pressure of 200 bar. The crystals were investigated by a combination of techniques, including high-resolution synchrotron X-ray single-crystal and powder diffraction and physical property measurements such as magnetic susceptibility and resistivity. Resistivity measurements revealed a metal-insulator transition (MIT) at T_MIT~180 K with apparent thermal hysteresis; however, no superlattice peaks or peak splitting below T_MIT, which corresponds to a structural transition from Pbnm to P2₁/n, was observed. The successful growth of NdNiO₃ crystals at relatively low temperatures and oxygen pressure provides an alternative approach for preparing single crystals of interesting perovskites such as RNiO₃ (R = Sm-Lu) and parent phases of superconducting square planar nickelates. [ABSTRACT FROM AUTHOR]