This paper focuses on the enhancement of thermal stability of Ag-Al2O3 nanocermet films by means of alloying of Ag nanoparticles with Al element. The optical analysis demonstrated the AgAl embedded Al2O3 cermet films (namely, AgAl-Al2O3) possess excellent thermal tolerance even at 500 degrees C for 260 h under nitrogen ambient. The evolution of microstructural and chemical properties of Al2O3/AgAl-Al2O3/Al2O3 stack layers during the annealing process was comprehensively investigated, in order to grasp the thermal stability mechanism. It is believed that the enhanced thermal stability was ascribed to the formation of fresh alumina as capping layer riveted on the Ag nanoparticles surfaces, which acted as the pinning points to prevent silver element from migrating so as to maintain the expected optical properties. (C) 2015 Elsevier B.V. All rights reserved.