Photo-Induced Thermally Stimulated Depolarization Current (TSDC) in Natural and Synthetic Alexandrite (BeAl2O4:Cr3+)

The investigation of electrical properties in alexandrite (BeAl2O4:Cr3+) 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 Cr3+ ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.

Effect of heating treatment on trap level distribution in polyamide 66 film electrets

The effect of heating treatment on the trap level distribution in polyamide 66 film electret is studied by thermally stimulated depolarization current （TSDC） technique. For annealed polyamide 66, there are three trap levels that respectively originate from space charge trapped in amorphous phase, interphase and crystalline phase. There is one peak that originates from space charge trapped in amorphous phase for quenched one. Using multi-point method to fit the experimental curves, the detrapping current peaks can be separated and the trap depth is obtained. The shallower trap levels trapped in amorphous phase and interphase are obviously close to the deeper trap level trapped in crystalline phase for annealed polyamide 66 as the polarization temperature increases, while the trap level distribution remains unaffected by polarization temperature for quenched one.

Ultralow frequency dielectric dispersion in PZT+PFS ferroelectric ceramic

The depolarization decaying currents were measured for the PZT compound with morphotropic composition modified by the Fe 1=3 Sb 2=3 cations,i.e.,Pb[Fe_(1/3)Sb_(2/3)_(x)Ti_(y)Zr_(z)]o_(3) with x+y+z=1,x=0.1,y=0.44(morphotropic boundary)and y=0.47.The measurements were performed at room temperature and a few temperatures above(up to 473K),as well as at a few lower temperatures(down to 77K).The samples were poling at fields 0.02kV/cm and 0.2kV/cm at higher and lower temperatures,respectively.In the high temperature range,the time dependence depolarization current follows the fractional power law with two different exponents(n<1 and m>1),while in the low temperature range with a single exponent(n).The appropriate procedure has been used to transform the results obtained in the time domain into the frequency domain in order to calculate real and imaginary parts of the dielectric permittivity in the frequency range 5×10^(-5)-0.1Hz.The possible dielectric relaxation mechanisms have been discussed.