Alumina-yttria　stabilized　zirconia　(Al2O3-YSZ)　composite　coatings　are　recognized　as　a　potential　alternative　material　for　thermal　barrier　coatings.　In　this　paper,　Al2O3-YSZ　composite　coatings　were　deposited　using　atmosphere　plasma　spraying.　The　effects　of　alumina　addition　and　annealing　treatment　on　the　microstructure　and　mechanical　properties　of　the　plasma　sprayed　Al2O3-YSZ　composite　coatings　were　investigated　by　XRD,　SEM　and　an　instrumented　indentation　testing　system.　Owing　to　the　existence　of　YSZ　in　the　composite　coatings,　the　formation　of　amorphous　alumina　was　suppressed.　The　quenching　stress　is　high　enough　to　trigger　microcracking,　these　microcracks　will　further　propagate　or　close　under　the　post　deposition　thermal　mismatch　stress.　Young＇s　modulus　of　the　coatings　keeps　an　upward　tendency　from　50.56　GPa　to　55.93　GPa　and　hardness　increase　from　536　GPa　to　5.93　GPa　with　alumina　contents　varying　from　10　wt%　to　55　wt%.　After　an　annealing　treatment,　Young＇s　modulus　and　hardness　increase　compared　with　the　as-sprayed　ones.　Fracture　toughness　of　Al2O3-YSZ　composite　coatings　is　higher　than　the　YSZ　one,　and　it　increases　firstly　and　then　decreases　with　alumina　addition　varying　from　10　wt%　to　55　wt%.　The　fracture　toughness　of　coatings　is　related　to　the　amount　of　heterogeneous　specific　interface　between　Al2O3　and　YSZ　splats　and　the　high　microcracks　density　in　the　composite　coatings.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.