Luminescence of pulsed-laser-deposited SrAl₂O₄:Eu,Dy thin film and its role as a stress indicator

The ultimate goal of the present investigation was to develop an SrAl ₂O₄:Eu,Dy thin-film phosphor on the surface of mechanical test specimens to act as a stress or crack indicator during testing. As a preliminary step, SrAl₂O₄:Eu,Dy thin-film phosphors were deposited on several conventional substrates such as quartz glass, Si(111), Si(001), and corrugated quartz glass using a pulsed laser deposition (PLD) technique. Processing parameters were optimized, in an attempt to enhance the efficiency of luminescence of the SrAl₂O₄:Eu,Dy thin-film phosphor. The optimal PLD processing conditions for the SrAl₂O ₄:Eu,Dy thin-film phosphor were different from that for other conventional oxide thin-film phosphors in that an oxygen supply during the PLD process was not necessary, a postdeposition annealing in an oxidizing atmosphere was ineffective, and the corrugated substrate did not have a significantly enhanced extraction efficiency. By adopting the best PLD processing conditions, based on the preliminary depositions on conventional substrates, the SrAl ₂O₄:Eu,Dy thin-film phosphor was deposited on the surface of a compact tension specimen composed of polycrystalline A1₂O ₃ and the applicability of the SrAl₂O₄:Eu,Dy thin-film phosphor as a stress or crack indicator was verified in an actual mechanical test.