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.

掺铒硫化锌ACTFEL中深能级的测定

采用热激电流(TSC)法,在180-430K温度内对三种不同结构的ZnS:Er^(3+)交流薄膜电致发光(ACTFEL)样品,测得三个热激电流峰.经分析认为它们对应于ZnS:Er^(3+)层体内,ZnS:Er^(3+) Y_2O_3和ZnS:Er^(3+)-SnO_2界面处存在的不同深度的陷阱能级.估算其位置和密度,并讨论了实验结果.

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.

Evaluations of dielectric property and drug release profile of 5-FU patches based on plasma charged electrets

In the present study,the electret 5-fluorouracil patch was developed,the effective surface potential,piezoelectric coefficient d33,open-circuit thermally stimulated discharge（TSD） current spectra and shear adhesion of the patch were measured.The drug release profile of the patch was determined by using high performance liquid chromatography method.A stable potential difference which was positively dependent on the surface potential of the electret was generated on two sides of the patch.The measurements of d33 coefficient,TSD current spectra and adhesion performance showed that the electrostatic field of the electret could cause polarization and cohesive strength decreasing of the matrix molecules,change the distribution and interaction of the drug molecules in patch,therefore to increase the release of drug from the transdermal patch.

The effects of deep-level defects on the electrical properties of Cd0.9Zn0.1Te crystals

The deep-level defects of Cd Zn Te（CZT）crystals grown by the modified vertical Bridgman（MVB）method act as trapping centers or recombination centers in the band gap,which have significant effects on its electrical properties.The resistivity and electron mobility–lifetime product of high resistivity Cd（0.9）Zn（0.1）Te wafer marked CZT1 and low resistivity Cd（0.9）Zn（0.1）Te wafer marked CZT2 were tested respectively.Their deep-level defects were identified by thermally stimulated current（TSC）spectroscopy and thermoelectric effect spectroscopy（TEES）respectively.Then the trap-related parameters were characterized by the simultaneous multiple peak analysis（SIMPA）method.The deep donor level（EDD/dominating dark current was calculated by the relationship between dark current and temperature.The Fermi-level was characterized by current–voltage measurements of temperature dependence.The width of the band gap was characterized by ultraviolet-visible-infrared transmittance spectroscopy.The results show the traps concentration and capture cross section of CZT1 are lower than CZT2,so its electron mobility–lifetime product is greater than CZT2.The Fermi-level of CZT1 is closer to the middle gap than CZT2.The degree of Fermi-level pinned by EDDof CZT1 is larger than CZT2.It can be concluded that the resistivity of CZT crystals increases as the degree of Fermi-level pinned near the middle gap by the deep donor level enlarges.

AC ageing characteristics of Co-doped ZnO varistors

As the key protection device in the power system, the ageing characteristics of ZnO varistor can directly affect the safe operation of power system. In order to study the influence of Co2O3 content on the electrical properties of ZnO varistors, thermally stimulated current (TSC) characteristics test, capacitance-voltage (C-V) characteristics test, scanning electron microscope (SEM) test, voltage-current (V-I) test were carried out on ZnO varistors before and after AC ageing tests. The results show that the mean grain size decreases while the varistor voltage increases as the Co2O3 content increases, the barrier height and the defects of ZnO varistors increase with the increase of Co2O3 content, and the barrier height decreases at a certain degree after AC ageing test. As the Co2+ ion radius is close to that of Zn2+ ion, it is easy for Co2+ ions to enter into ZnO lattice during sintering process, which is account for the increase of zinc interstitial of ZnO varistors. When the Co2O3 content exceeds a certain range, the AC degradation degree of ZnO varistors will become much more serious. From the experimental results, ZnO varistors doped with 1.0 mol% Co2 O3 exhibit a better performance.