Electronic Structures and Electrical Properties of Cr-, Cu-, Ni-, and Zn-Doped Sodium Titanate Nanotubes.

Sodium titanate nanotubes (Na-TNTs) and their metal-doped derivatives were prepared using simple hydrothermal and metal ion-exchange methods, respectively. The as-prepared doped materials were characterized by X-ray powder diffraction, thermal gravimetric analysis, high-resolution transmission electron microscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The dielectric constant, the loss tangent, and the AC electrical conductivity of NaM-TNTs (where M = Cr, Cu, Ni, or Zn) were measured at selected frequencies (400 kHz and 2 MHz) as a function of temperature.