Substitutional　point　defects　of　aliovalent　enable　a　significant　manipulation　in　carrier　concentration　thus　optimize　the　charge　transport　for　an　enhanced　thermoelectric　power　factor,　while　dislocations　induce　strong　lattice　strain　fluctuations　for　scattering　phonons　thus　a　reduced　lattice　thermal　conductivity.　With　decades　of　development,　both　types　of　defects　can　be　well　controlled　in　conventional　PbTe　thermo-electrics,　motivating　the　current　work　to　focus　on　Gd-doping　for　increasing　the　electron　concentration　at　a　high　mobility　and　on　Cu2Te-alloying　for　creating　dense　in-grain　dislocations　for　scattering　phonons.　Such　a　two-wheel　driven　approach,　namely　Gd-doping　for　a　high　power　factor　and　Cu2Te-alloying　for　a　low　lattice　thermal　conductivity,　eventually　enables　an　extraordinary　thermoelectric　figure　of　merit,　zT　of　similar　to　1.7　in　n-type　PbTe　thermoelectrics.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.