SrAl2O4:Eu,Dy mechanoluminescent flexible film for impact sensors

The present work is devoted to make a mechanoluminescent film for making an impact sensor that is flexible, durable and non-destructive. For this, a flexible film of SrAl2O4:Eu,Dy phosphor is prepared by mixing SrAl2O4: Eu,Dy with polydimethylsiloxane (PDMS). The XRD patterns indicate the formation of a monoclinic phase of SrAl2O4: Eu,Dy phosphor. The SEM images reveal the surface morphology of the reported samples (powder and film). In order to measure the mechanoluminescence (ML) intensity, the flexible film is excited impulsively with a steel ball. Snapshots of ML patterns taken with cathode ray oscilloscope are presented to visualize the activity exactly. Variations in peak ML intensity and total ML intensity with time are discussed. The photoluminescence (PL) spectra are found to peak at 520 nm when excited with 365 nm wavelength. The broad green emission obtained from flexible film is attributed to 4f65 d1→4f7 transitions. The time corresponding to peak ML intensity (tm) does not change much with increasing impact velocity of the steel ball. The ML behaviour under cyclic loading is also recorded and analyzed. When SrAl2O4:Eu,Dy flexible ML film is rubbed with smooth glass rod, it produces the ML pulses of different intensities. These characteristics are useful for the development of the pressure and impact sensors.