Triboluminescence Properties of Highly Oriented SrAl[sub 2]O[sub 4]:Eu Films on Inconel 600 Substrate

Abstract

We successfully prepared highly oriented SrAl 2 O 4 :Eu ͑SAOE͒ films with different thicknesses on Inconel 600 substrates by radio frequency ͑rf͒ sputtering. The prepared films showed a preferred orientation of ͑0 3 1͒. The uniformity of the growth orientation was not degraded even though the films were more than 10 m thick. At the same time, all the films showed good adhesion on the substrate, as no peeling was observed after each triboluminescence measurement. When friction was applied, a strong green triboluminescence was observed, which suggests that SAOE films can be used as sensors to detect stress in an object.SrAl 2 O 4 :Eu ͑SAOE͒ is a well-known green phosphor with long afterglow characteristics. 1-3 Over the past few years, there has been significant interest in the growth and characterization of SAOE thin films due to their potential applications in display devices, temperature sensors, and other devices. 2-5 Recent research has shown that SAOE exhibits the interesting phenomenon of triboluminescence ͑Tribo-L͒ and/or mechanoluminescence ͑ML͒, which has been extensively investigated by Xu and co-workers. 6-8 Tribo-L is light emission caused by mechanical stimuli such as friction, scratching, cutting, collision, striking, and grinding. 6 This phenomenon can be used to detect mechanical stress by converting mechanical energy into visible light energy and has various widespread applications such as the fabrication of Tribo-L devices, the forecasting of earthquakes, and the predetection of sudden fractures in ceramic construction. 9,10 Currently, yellow Tribo-L films of ZnS deposited on glass substrates have been successfully prepared. 11,12 For developing and improving the Tribo-L sensors, it is necessary to develop other Tribo-L films with high intensity and more colors. Of the ML materials recently developed, including SAOE, 6-10

Trap-controlled mechanoluminescent materials

“…Several methods have been developed to grow ML thin film coatings directly on the surface of a target object, including physical vapour deposition of ion-plating, and radio-frequency magnetron sputtering techniques [15,[17][18][19]105,152,[161][162][163][164][165][166][167][168][169][170][171]. ML thin films offer advantages over powder/polymer composite coatings to image stress distributions in target structures, including thinner films (less than 10 μm), good thermal stability, and a preferred orientation of crystallinity -these features may help to overcome some of the optical and mechanical transmission problems discussed above for composite films (Section 2.3.1).…”

“…While offering advantages over conventional stress sensing devices, the low ML intensity of composite materials could undermine their potential to monitor the structural health of buildings and bridges during daylight hours. To date, efforts to increase the intensity of ML of materials have focused on the crystal structures and trap levels of the ML material, for example by optimizing protocols to synthesize ML particles and coatings [17,19,137,150,152,164,166,208,240,[265][266][267][268][269][270][271][272][273][274][275] that include adjusting the composition deficiency (Section 2.2) [142,150,151,173], exposing the material to SHI irradiation (Section 4.7.1) [247], by substituting host ions in the crystal [94,95,194,[265][266][267] and co-doping crystals with rare earth or transition metal ions [87,88,91,92,123,231,248,249,[268][269][270][...…”

Survey of the literature on mechanoluminescence from 1605 to 2013

“…Only few papers are related to the investigation of EML and PML. The papers related to the studies of EML and PML are: .…”

Ternary-Host and Heterojunction Enabled Eye-Visible Elastic Mechanoluminescence from (Ca0.5Sr0.5)ZnOS/xZnS/Mn2+

“…The elastic-ML materials are being strongly anticipated as a promising alternative to the fluorescent materials for stress sensing, , anticounterfeiting, , onsite infrastructure diagnosis, bioimaging, flexible optoelectronics, and biomimetic multifunctional E-skins , because elastic-ML materials tend to produce even brighter and more reproducible ML than fracto-ML materials . Up to now, a series of elastic ML materials have been proposed by doping transition metal ions (e.g., Mn 2+ , Cu 2+ ) or rare-earth ions (e.g., Eu 2+ , Pr 3+ , Sm 3+ , and Nd 3+ ) into piezoelectric host materials, such as ZnS/Mn 2+ , , ZnS/Cu 2+ , CaZnOS/Mn 2+ , , SrAl 2 O 4 /Eu 2+ , BaSi 2 O 2 N 2 /Eu 2+ , , Ca 2 Al 2 SiO 7 /Eu 3+ , LiNbO 3 /Pr 3+ , CaZr­(PO 4 ) 2 /Mn 2+ , and so on. Unfortunately, there are still several critical bottlenecks need to be solved for the goal of achieving highly efficient ML materials.…”