The effect of in-situ TiB2 segregated network structure on the thermoelectric properties of spark plasma sintered B4C ceramics

Different amounts of TiC particles between 1 and 7.5 vol% were coated on spray-dried B4C granules with a simple dry particle coating method, then spark plasma sintered at 2200 degrees C under vacuum, forming 3D-segregated network structures (SNS) of in-situ TiB2 between 1 and 9 vol%, to improve the thermoelectric (TE) performance of B4C. With the in-situ TiB2-SNS, a maximum ZT of 8.02x10-2 was achieved with 2 vol% TiB2-SNS at 923 K by simultaneous improvement of electrical conductivity due to the electrically conductive network of TiB2 and reduction of thermal conductivity due to the increased phonon scattering, improving the ZT of monolithic B4C by an impressive approximate to 120%. Higher quantities of TiC addition proved inefficient in improving the TE performance; by forming 9 vol% TiB2, approximate to 945% increase in electrical conductivity was achieved; however, the Seebeck coefficient was affected negatively, causing a drastic decrease in the ZT value.