Influence of morphology and thermal processing on the dielectric properties of TiO₂ powders and nanofibers

Titanium dioxide (TiO₂) exhibits dielectric properties that vary significantly with its physical morphology and thermal history. This work evaluates the dielectric responses of calcined nanopowder, electrospun nanofibers before and after heat treatment. Utilizing TEM, SEM, EDX, FTIR, and XRD allows for a detailed assessment of the morphological, and structure differences across the TiO₂ samples. The uncalcined nanofibers exhibit an amorphous structure with significant polyvinylpyrrolidone (PVP) content. Calcination transforms these amorphous precursors into crystalline fibers with a mixed anatase and rutile phase. Dielectric measurements carried out over a frequency range of 1 Hz to 1 MHz demonstrated that the calcined nanofibers feature a dielectric constant (ε′) that is both reduced and mostly stable across the measured frequency range. At higher frequencies, the dielectric constant was found to approach free-space permittivity, with the material additionally exhibiting low dielectric loss (ε″, tan δ), and reduced low AC conductivity (σ). The calcined TiO₂ nanopowders, and uncalcined fibers by contrast revealed higher ε′ values and more substantial losses. The calcined TiO₂ nanofibers thus exhibit superior insulating characteristics, demonstrating that nanostructuring combined with controlled thermal treatment can be effectively employed to alter dielectric performance. These findings carry meaningful implications for designing dielectric materials, particularly in enabling the optimization of low and stable dielectric permittivity alongside low-loss properties across a broad frequency range for electronic circuits applications.