Thermoelectric Efficiency of Reduced <scp> <scp>SrTiO</scp> </scp> ₃ Ceramics Modified with <scp> <scp>La</scp> </scp> and <scp> <scp>Nb</scp> </scp>

Abstract

Ceramics of La x Sr 1− x Nb y Ti 1− y O 3 ( LSNT ) were synthesized under various reducing atmospheres. Covering the specimens with graphite carbon felt under an Ar‐gas flow during sintering drastically enhanced the electrical conductivity, σ. Ti K‐edge absorption spectra indicated the presence of Ti 3+ for heavily reduced specimens. The increase in conductivity was attributed to the 3d band of Ti 3+ . The maximum value for the figure of merit, ZT , was obtained for strontium titanate ceramics modified with both 5 mol% La and 5 mol% Nb, namely 5/5‐LSNT, exhibiting a ZT value of ~0.221 at 473 K. This high ZT value was almost 1.5 × larger than that of the conventional 10 mol% La‐doped sample, 10/0‐LSNT ( ZT ~0.144), and was mainly attributed to the larger Seebeck coefficient of the material.