Synthesis and Rapid Densification of Nanoparticles of Barium Praseodymium Hafnium Oxide: A New Complex Perovskite

Nanoparticles (25–100 nm) of barium praseodymium hafnate (Ba₂PrHfO_5.5), a new substrate material for high temperature superconducting YBa₂Cu₃O_7- and Bi-cuprate films has been synthesized through an exothermic chemical reaction for the first time. The Ba, Hf and Pr ions required for the formation of Ba₂PrHfO_5.5 were obtained in solution by dissolving a stoichiometric mixture of BaCO₃, Pr₆O₁₁ and HfO₂ heated at 1200°C for 4 h in boiling nitric acid. By complexing the ions with citric acid and adjusting the oxidant/fuel ratio, it was possible to obtain Ba₂PrHfO_5.5 as nanoparticles in a single step chemical process. The nanoparticles thus obtained were characterized by powder X-ray diffraction, thermogravimetric analysis, differential thermal analysis, infrared spectroscopy, and surface area analysis. The Ba₂PrHfO_5.5 synthesized through the present exothermic chemical process, because of its nanoparticulate nature, could be sintered to a density of 98% in a period of just 9 min at a temperature of 1435°C in air. Scanning electron microscopic studies on the sintered Ba₂PrHfO_5.5 samples showed that densification has occurred without significant microstructural coarsening up to a sintered density of 98% of its theoretical value in a short duration.