Sol-gel synthesis, spark plasma sintering, structural characterization, and thermal conductivity measurement of heavily Nb-doped SrTiO3/TiO2 nanocomposites

Heavily Nb-doped strontium titanate (SrTi1-xNbxO3) nanoparticles and SrTi1-xNbxO3/TiO2 nanocomposite powders were synthesized by a sol-gel method. Structural characterization of the obtained powders was performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. The powders were densified by spark plasma sintering (SPS) method up to 98% of the relative density. Upon composite production, the thermal conductivity of the un-doped samples was effectively decreased for SrTiO3/TiO2 nanocpmposite from 12 to 8 W/m.K. On the other hand, thermal conductivity of the Nb-doped SrTi0.8Nb0.2O3/TiO2 composite was decreased by about 50% down to 3.4 W/m.K in comparison to SrTiO3/TiO2 due to the phonon scattering at the point defects originated from both Nb atoms and TiO2 nanoparticles.