Properties of Ultrasound‐Induced Luminescence of LiTaO ₃ : Pr at kHz and MHz Frequencies

Abstract This study presents the light emission from LiTaO ₃ :Pr when exposed to low‐frequency (20 kHz) and high‐frequency (3.3 MHz) ultrasound waves. Upon excitation at 270 nm, LiTaO ₃ :Pr exhibits photoluminescence with three prominent emission peaks at 511, 618, and 892 nm. Additionally, charge carrier trapping occurs in LiTaO ₃ :Pr, leading to persistent luminescence and thermoluminescence. These trapped charge carriers can also be released when exposed to ultrasound waves. By varying the concentration of praseodymium (1% for sample S1, 3% for sample S2, and 5% for sample S3), the activation energy of the traps (i.e., the trap depth) is modulated. For sample S1, the energy difference between the deep and shallow traps is ≈0.1 eV, whereas for samples S2 and S3, this difference increases to ≈0.45 eV. Moreover, S1 has a relatively higher concentration of shallow traps compared to S2 and S3. The variation in trap formation in each sample is also responsible for the distinct behavior under ultrasound exposure in different experimental conditions. The distinct acoustic phenomena observed at low (acoustic cavitation) and high (acoustic streaming) frequencies may lead to different mechanisms of light emission: predominantly mechanoluminescence‐driven at 20 kHz and thermoluminescence‐driven at 3.3 MHz.