Space charge limited current conduction in thermoelectric electrospun NaCo2O4 nanofibers

• Published in: Applied physics. A, Materials science & processing Vol. 126; no. 5
• Main Authors: Shah, Yousaf Ali, Iqbal, Muhammad Javid, Rasool, Kamran, Makhdoom, Ata-ur-Rehman, Iqbal, Yaseen, Ullah, Amir, Habib, Muhammad
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2020; Springer Nature B.V
• Subjects: Applied physics; Characterization and Evaluation of Materials; Condensed Matter Physics; Crystal structure; Crystallinity; Current voltage characteristics; Electric potential; Fourier transforms; Gamma phase; Machines; Manufacturing; Materials science; Nanofibers; Nanotechnology; Optical and Electronic Materials; Physics; Physics and Astronomy; Polyvinylpyrrolidone; Porosity; Processes; Roasting; Room temperature; Scanning electron microscopy; Seebeck effect; Space charge; Spectrum analysis; Surfaces and Interfaces; Temperature dependence; Thin Films; Voltage; X-ray diffraction; Seebeck coefficient; Electrospinning; Conduction mechanism; Nanofibers; Thermoelectricity
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-020-03580-9

In this study, NaCo
2
O
4
nanofibers were synthesized via an electrospinning technique. The uniformity and size of these nanofibers were optimized as a function of polyvinylpyrrolidone (PVP) concentration. NaCo
2
O
4
nanofibers were characterized by TG–DTA, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). No crystallinity was observed in the nanofibers when calcined at 100 °C, whereas at 600 °C predominatly γ-phase of NaCo
2
O
4
nanofibers with good crystallinity was achieved. Analysis of XRD and SEM results revealed that PVP concentration and calcination temperature played an important role in the formation of the desired crystalline phase, size, uniformity and porosity of NaCo
2
O
4
nanofibers. Temperature-dependent current voltage (
IV
) characteristics demonstrated the presence of an ohmic region (lower voltage) followed by space charge limited current conduction (SCLC) at intermediate voltage. The presence of surface traps and imperfections can be the possible reason for the SCLC transport. The average value of the Seebeck coefficient “
S
” was 128 μV/K near room temperature.