Sacrificing trap density to achieve short-delay and high-contrast mechanoluminescence for stress imaging. (15th June 2018)

• Record Type: Journal Article
• Authors: Zhang, Jun-Cheng; Fan, Xin-Hua; Yan, Xu; Xia, Feng; Kong, Weijin; Long, Yun-Ze; Wang, Xusheng
• Is Part Of: Acta materialia. Volume 152(2018)
• Page Start: 148
• Page End: 154
• Publication Date: 2018-06-15
• Subjects: Mechanoluminescence -- Structure -- Property -- Trap -- Stress imaging; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.04.011
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Trap-controlled mechanoluminescence (ML) enables the direct observation of stress concentration of load-bearing objects through imaging the ML distribution, showing numerous prospects in stress detection, bio-imaging and optical displays. However, the applications of trap-controlled ML materials universally require long-time delay to fade the noise of symbiotic persistent luminescence (PersL) in order to achieve high-contrast ML images. In view of the difficulty to solve the PersL problem through individually eliminating the PersL traps, herein we propose a novel strategy of sacrificing trap density which decreases PersL and ML traps as a whole. By employing Sr 2+ substitution to decrease the trap density of Ca2 Nb2 O7 :Pr 3+, we identify a novel composition of (Ca0.5 Sr0.5 )2 Nb2 O7 :Pr 3+ displaying short-delay and high-contrast ML images, and evaluate its practicability through a 2-dimensional in-situ imaging experiment of dynamic stress distribution. The underlying mechanism is ascribed to the greater decrease ratio of PersL intensity than ML intensity as a result of the larger detrapping rate of traps due to stress (leading to ML) than that due to thermal energy (PersL). Furthermore, multi-spectral investigations of (Ca, Sr)2 Nb2 O7 :Pr 3+ system reveal a distinctive electron transition process co-regulated by trap levels, charge transfer state and crystal field. The proposed strategy and the associated phosphors are expected to initiate the reconstruction of PersL-type ML materials and bring important implications for real-world stress imaging. Graphical abstract: Image 1