Crystal growth of NdNiO3 perovskite under high oxygen pressure

Well-shaped single crystals of NdNiO3 perovskite have been grown for the first time under high oxygen pressure conditions, in a belt-type press at 4 GPa. The reaction took place in sealed platinum capsules, in the presence of KClO3 as the oxidizing agent. It seems that the choice of hydroxides of the cations involved as departure reagents is crucial for the success of the crystal growth, via water vapour transport reactions. The perovskite has been characterized by x-ray diffraction, scanning microscopy and differential scanning calorimetry measurements, suitable to identify the metal-insulator transition. The transition temperature of the as-grown crystals, of 191.2 K in the heating run, is significantly lower than that reported for powder NdNiO3 materials. This suggests a better metallicity of the present crystals, probably due to an improved oxygen stoichiometry associated with the much stronger oxidizing conditions utilized for its preparation.