Influence of Nb substitution and sintering atmosphere on thermoelectric properties of CaTiO₃-based ceramics

Co-substitution of Eu and Nb into insulating CaTiO3 can make it a good n-type potential thermoelectric (TE) material. In the present work, solid solution compounds with the nominal composition Ca0.8Eu0.2Ti1–xNbxO3–δ (x = 0.05, 0.08, 0.1, 0.12) were synthesized and sintered in different atmospheres, including argon (Ar) and forming gas (5 vol% H2 in Ar). Notably, the different reduction effects of these atmospheres resulted in significant differences in phase formation, grain size, oxygen deficiency, and TE properties of the synthesized samples. Introducing additional electrons to the system by donor substitution of Ti with Nb leads to significant changes in the electrical conductivity and Seebeck coefficient. The most favorable TE performance of the prepared samples was found in the sample with x = 0.05, primarily attributed to its proper charge carrier concentration. This work highlights the crucial role of the sintering atmosphere in manipulating the TE performance of n-type CaTiO3-based ceramics, an effect similar to donor doping.