Sr11Mo4O23(SMO)　material　has　a　double-layer　perovskite　superstructure,　which　exhibits　unusual　structural　flexibility　and　oxygen　ion　mobility.　However,　the　Sr11Mo4O23　cubic　phase　will　transform　into　SrMoO4　tetragonal　phase　at　400　°C,　which　leads　to　a　sharp　decrease　in　conductivity.　In　order　to　solve　this　problem,　Ta　doped　Sr11Mo4-xTaxO23-δ　(SMTO,　0　≤　x　≤　1.25)　electrolytes　were　synthesized　by　a　route　combining　the　Pechini　method　and　solid-state　reaction.　The　effects　of　acceptor-type　Ta5+　doping　on　the　structural　stability,　micro-scale　structure　and　ionic　conductivity　of　SMO　are　characterized　by　X-ray　diffraction,　thermogravimetric　analysis,　differential　scanning　calorimetry,　scanning　electron　microscopy,　and　electrochemical　impedance　spectroscopy.　All　Sr11Mo4-xTaxO23-δ　powders　are　single-phase　and　no　secondary　phase　is　detected.　Moreover,　the　phase　transition　of　Sr11Mo4O23　to　SrMoO4　is　highly　inhibited　by　partially　replacing　Mo　with　Ta　(x　≥　0.50)　during　the　heat　treatment,　and　the　Sr11Mo4O23　cubic　phase　with　high　conductivity　may　be　maintained　for　a　long　time　at　800　°C.　The　total　ionic　conductivity　of　Sr11Mo4-xTaxO23-δ　samples　increases　with　increasing　the　Ta　concentration,　and　then　declines　at　higher　doping　content　(x　=　1.25).　The　ionic　conductivity　of　Sr11Mo3TaO23-δ　(SMTO100)　pellet　is　the　highest,　reaching　1.44　×　10−2　S/cm　at　800　°C.　More　remarkably,　the　conductivity　of　STMO100　pellet　remains　at　its　peak　during　the　100　h　annealing　test　at　the　temperature　of　800　°C.　©　2022　Elsevier　Ltd　and　Techna　Group　S.r.l.