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Piezoelectric Materials and Their Applications
Published in Song Sun, Wei Tan, Su-Huai Wei, Emergent Micro- and Nanomaterials for Optical, Infrared, and Terahertz Applications, 2023
Mechanoluminescence (ML) is a kind of light emission phenomenon induced by external mechanical excitation (e.g., grinding, stretching, compressing, or shaking) on a solid, and is also called piezoluminescence for piezoelectric materials. Metal ions as activators in ML are responsible for photoexcitation and illustrate the piezophotonic effect. Specifically, lanthanide ions and transition-metal ions, whose luminescence covering a broad optical spectrum from UV to infrared regions, are the two primary metal ions used as activators for piezophotonics [23]. To date, metal ion-doped ZnS, CaZnOS, SrAl2O4, or LiNbO3 have drawn much attention for developing high-performance mechanoluminescent devices in stress sensing, energy harvesting, displaying, and other flexible/stretchable optoelectronics [11].
Borate Phosphor
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
The behaviour of a system under pressure can be studied by luminescence measurements of solids at high hydrostatic pressures. The pressure can gradually be increased so that the surrounding molecular environment can be changed in a controlled manner. This way, the effect of pressure on energy levels can be studied [91]. Mechanoluminescence is an interesting phenomenon, which is a light emission caused by friction, rubbing, striking, grinding, cutting, etc. The emission of light intensity depends on how the material is deformed. The apparatus used to measure ML should have a device for a deforming sample and another for the spectral measurements [1]. The deformation of a sample can be done by various techniques such as compression, loading, piston impact, needle impact, bending, stretching, scratching, air blast, rubbing, grinding, etc. Figure 9.2 shows the device used for this purpose by Chandra [1]. Figure 9.2(a) is a desktop model Instron testing machine. In this technique, ML intensity is measured with a load cell and strain with a linear variable differential transducer. Figure 9.2(b) is a schematic diagram of a piston impact technique used by Chandra [1]. The ML is excited by the impact of a moving piston on the crystal with the velocity of the moving piston being measured by a transducer.
Visualization of crack propagation for assisting double cantilever beam test through mechanoluminescence
Published in The Journal of Adhesion, 2018
Nao Terasaki, Yuki Fujio, Yoshitaro Sakata, Shin Horiuchi, Haruhisa Akiyama
From the ML images in Figure 4, an enlarged ML image was extracted, as shown in Figure 5(a), and the ML behavior during the DCB test was explained based on 3 observations. First, at the initial stage of fracture generation, strong mechanoluminescence was observed at the tip of the initial crack (mark i) owing to intense stress concentration. Then, as described above, moving of the ML point (mark ii) was observed along the adhesive layer during crack propagation and delamination in the DCB test. In addition to the ML point, an ML distribution was observed on the upper and lower adherends, slightly ahead of the ML point, due to stress concentration at the crack tip accompanied with crack opening and bending, as shown at mark iii. From the sequence of ML images, the region of interest (denoted as ROI) was set for each ML point, and then, the ML points were automatically tracked by image processing software, as shown in Figure 5(b).