One-step molten-salt synthesis of BaTi4O9nanowires with oxygen deficiency-enhanced dielectric performance

Abstract

One-dimensional nanostructures of BaO-xTiO₂ binary oxides with a high oxygen deficiency and a good dielectric performance are of great interest but seldom studied. In the present study, single-crystalline BaTi₄O₉ (stoichiometric BaO–4TiO₂) nanowires were synthesized using a simple, one-step molten-salt method by co-heating the powder mixtures of NaCl, TiO₂ and BaCl₂ nanoparticles at 750 °C. A series of spontaneous processes in the molten NaCl/BaCl₂ salt mixture with the dispersed TiO₂ nanoparticles, including ion diffusion, chemical reaction, particle agglomeration and ion exchange, yielded the BaTi₄O₉ nanowires. Photoelectron spectroscopic and dielectric analyses indicated that a high fraction of oxygen deficiency for 10.4% provided the as-synthesized BaTi₄O₉ nanowires with a high capacitance density of 13 F/m². Thermal annealing lowered the oxygen deficiency to 6.6% and the capacitance density to 9 F/m². The increase in wire length increased the oxygen deficiency and dielectric constant of the nanowires.