The effect of synthesis technique on thermoelectric properties of nanocrystalline NaCo2O4 ceramics


Erdal M. O. , Koyuncu M., USLU İ.

JOURNAL OF NANOPARTICLE RESEARCH, vol.16, no.11, 2014 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 16 Issue: 11
  • Publication Date: 2014
  • Doi Number: 10.1007/s11051-014-2715-5
  • Title of Journal : JOURNAL OF NANOPARTICLE RESEARCH
  • Keywords: Thermoelectric properties, Sodium cobaltine, Nanocomposite, Electrospinning, Sol-gel, Energy conversion, FABRICATION, SYSTEM, POWER

Abstract

Sodium cobalt oxide (NaCo2O4) nanocrystalline thermoelectric ceramic powders were synthesized using conventional polymerized complex sol-gel and electrospinning techniques and then consolidated into bulk ceramics. We have investigated the differences in the microstructure and thermoelectric properties of the samples prepared using electrospinning and sol-gel methods. The crystal structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy before and after calcination at different temperatures. Nanofibers prepared by electrospinning have a diameter of approximately 300 nm, while the diameter of the grains of sol-gel powders ranges from 1 to 5 mu m. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system in the temperature range of 15-300 K. The calculated values of dimensionless figure of merit at 300 K are 6 x 10(-7) and 4 x 10(-5) for sintered powders from sol-gel and nanofibers, respectively. While electrospinning production technique increase thermoelectric power approximately 15 % and it fold electrical conductivity average 20 times, it decreased thermal conductivity by 90 %.