Photo-Induced Thermally Stimulated Depolarization Current (TSDC) in Natural and Synthetic Alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>)

Abstract

The investigation of electrical properties in alexandrite (BeAl 2 O 4 :Cr 3+) in synthetic and natural forms is presented in this paper. Alexandrite is a rare and precious mineral that changes color according to the light incident on it. In the synthetic form, it is used technologically as an active laser medium. The electrical characterization was obtained using the Thermally Stimulated Depolarization Current (TSDC) technique, an interesting tool to study the behavior of impurities in insulators. Alexandrite presented the electric dipole relaxation phenomenon, both in natural and in synthetic samples. It was possible to observe TSDC bands for the synthetic sample at around 170 K, and at around 175 K for the natural sample. Besides, photo-induced TSDC measurements were performed through the excitement of the samples by using a continuous wave argon laser. In addition, photoluminescence measurements were performed to verify in advance whether the laser light would be absorbed by the sample, and in order to complement the photo-induced TSDC measurements analysis. The results of photo-induced TSDC experiments have contributed to the understanding of the TSDC bands behavior: the results obtained with the technique suggest that there is an effective participation of Cr 3+ ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.