This study provides a comprehensive analysis of mechanoluminescence (ML)
and associated phenomena, ultrasonic-induced luminescence (Us-L). The
research begins with the designing of various experimental techniques and
setups to study ML and Us-L under diverse mechanical stimuli. The first
two setups are directly related to ML analysis, namely Impact-induced ML
and Stress-induced ML setups. The third setup focus on the study of Us-L
at 20 kHz, utilizing an ultrasonic probe sonicator and a photomultiplier
to capture Us-L emissions. The results obtained from multiple measurements
of commercially available phosphor materials, includes
Sr0.95Ca0.05(SO4):Mn, CaAl2O4:Eu,Dy,La and SrAl2O4:Eu,Dy validate the
excellent performance of these setups in various categories of ML studies.
In the second part of the study, the mechanoluminescence and
ultrasonic-induced luminescence properties of LiTaO3:Pr materials are
discussed in detail. The LiTaO3 used as a host material have trigonal R3c
structure and praseodymium (Pr) activator ions as a dopant with different
concentration percentages, symbol as S1 (1%), S2 (3%) and S3 (5%),
exhibits emissions at 511 nm, 618 nm, and 892 nm in both photoluminescence
and mechanoluminescence spectra. I-ML measurements demonstrate fast
mechanical impact detection capabilities of the LiTaO3:Pr samples with
excellent ML recoverability and at several impact kinetic energies.
Moreover, S-ML measurement’s results demonstrate a significant
superposition of ML intensity curves extracted in the results of applied
force as a function of time. A notable discovery is that part of the ML
emission from LiTaO3:Pr lies within the infrared biological window,
favorable for medical applications. Additionally, light emission from
LiTaO3:Pr under exposure to low (20 kHz) and high (3.3 MHz) frequency
ultrasonic waves is studied. The different acoustic phenomena at low
(acoustic cavitation) and high (acoustic streaming) frequencies suggest
distinct mechanisms for light emission: ML-driven is prominent at low
frequencies and TL-driven is prominent at high frequencies. By adjusting
the Pr concentration, the activation energy of the traps (i.e., trap
depth) can be modulated, revealing diverse behaviors of Us-L under various
thermal conditions. The findings validate LiTaO3:Pr as a promising
applicant for fast, sensitive, and remote detection of various mechanical
stimuli and ultrasound waves in industrial and biological applications.
The mechanoluminescence and ultrasonic-induced luminescence properties of
additional materials, including SrSi2O2N2:Eu, SrSi2O2N2:Eu,Mn, AlN:Mn and
ZnS:Mn have also been studied. The findings confirm that these materials
possess the ability to detect both stress and ultrasound, converting them
into visible light signals. This makes them promising candidates for
future use in a wide range of mechano-optic sensing applications.