  We report about detailed dimensionless figure of merit ($ZT$) calculated by
using Fermi integral method (compared with Bi$_2$Te$_3$, CoSb$_3$, and
SrTiO$_3$) for thermoelectric (TE) materials' design and its module
application. Particularly, TE properties: electrical conductivity (small
polaron: $\sigma$($m$*)), Seebeck coefficient ($S$), thermal conductivity
($\kappa_e$), and $ZT$ were calculated by using reduced energy
($\zeta$=$E$/$k_B T$), as the functions of $T$, and effective mass ($m$*/$m$).
Enhancement of $ZT$ was investigated by contour plots of $T$, and $m$*/$m$
versus $\zeta$.
