Structural Characterizations and Dielectric Properties of Sphere- and Rod-Like PbTiO Powders Synthesized via Molten Salt Synthesis.

By reaction of PbCO and TiO in the eutectic NaCl-KCl salts, both sphere- and rod-like PbTiO (PTO) powders were synthesized via molten salt synthesis (MSS) and template MSS methods, respectively. X-ray diffraction patterns reveal that all the PTO powders crystallize in a tetragonal phase structure. Increasing the molar ratio of PbCO:TiO:NaCl:KCl from 1:1:10:10 to 1:1:60:60 in the MSS process has little effect on the sphere-like morphology of the PTO powders synthesized at 950 °C for 5 h. Large-scale polycrystalline rod-like PTO powders with diameters of 480 nm-1.50 μm and lengths up to 10 μm were synthesized at 800 °C for 5 h by template MSS method, where the rod-like anatase TiO precursors were used as templates and the molar ratio of PbCO:TiO:NaCl:KCl was equal to 1:1:60:60. X-ray energy dispersive spectroscopy spectra reveal that all the PTO powders are composed of Pb, Ti, and O elements, and the measured Pb:Ti atomic ratios are close to 1:1. In the template MSS process, the molten salt content plays an important role in forming the rod-like PTO powders. Under low molten salt content, the rod-like PTO powders cannot be synthesized even if the rod-like TiO templates are used. In addition, prolonging the reaction time suppressed the formation of rod-like PTO powders but promoted the formation of sphere-like PTO nanoparticles. The dielectric properties the sphere- and rod-like PTO powders were comparatively investigated. At room temperature, the dielectric constant and dielectric loss of the spherical PTO powders synthesized by MSS method with the molar ratio of PbCO:TiO:NaCl:KCl equal to 1:1:30:30 were ~ 340 and 0.06 (measured at 10 Hz), respectively. The corresponding values for the rod-like PTO powders synthesized by template MSS method with the molar ratio of PbCO:TiO:NaCl:KCl equal to 1:1:60:60 were 140 and 0.08, respectively. The present results demonstrate the sphere-like PTO powders have better dielectric properties, which have promising applications in the fields of multilayer capacitors and resonators.