Low　thermal　conductivity　is　the　key　property　dominating　the　heat　insulation　ability　of　thermal　barrier　coatings　(TBC).　Reducing　the　intrinsic　thermal　conductivity　is　the　major　topic　for　developing　advanced　TBCs.　Defect　engineering　has　attracted　much　attention　in　seeking　better　TBC　materials　since　lattice　defects　play　a　crucial　role　in　phonon　scattering　and　thermal　conductivity　reduction.　Oxygen　vacancies　and　substitutions　are　proven　to　be　the　most　effective,　while　the　accompanying　lattice　distortion　is　also　of　great　importance.　In　this　paper,　recent　advances　of　reducing　the　thermal　conductivity　of　potential　thermal　barrier　coating　materials　by　defect　engineering　are　comprehensively　reviewed.　Effects　of　the　mass　and　size　mismatch　between　the　defects　and　the　host　lattice　are　quantitatively　estimated　and　unconventional　thermal　conductivity　reduction　caused　by　the　lattice　distortions　is　also　discussed.　Finally,　challenges　and　potential　opportunities　are　briefly　assessed　to　further　minimize　the　thermal　conductivity　of　TBC　materials　in　the　future.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.