The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) in synthetic and natural forms is presented in this paper. Alexandrite is a...The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) 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<sup>3+</sup> ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.展开更多
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 tra...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.展开更多
Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defec...Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defects.With Mn doping,a significant increase in the reversible electrostrain from 0.05%to 0.17%could be achieved in potassium niobite lead-free piezoelectric ceramics.The origins of the large electrostrain were analyzed via in situ X-ray diffraction(XRD)under an electric field.The electrostrain and other typical electrical properties of the samples were measured at various temperatures,which enabled the ceramics to perform under a very wide temperature range,such as−80–130℃ for the 0.5 mol%Mn-doped sample with low dielectric loss(≤0.02).More importantly,combined with characterizations of the defect behavior by thermally stimulated depolarization current(TSDC),the failure mechanisms of electrostrain in a hightemperature environment could be revealed,which was associated with synergistic damage to the defects caused by the electric field and high temperature.The results can provide good ideas and a basis for the design of piezoelectric materials with good electrostrain stability over a wide temperature range.展开更多
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(morp...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.展开更多
文摘The investigation of electrical properties in alexandrite (BeAl<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>) 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<sup>3+</sup> ions in the formation of TSDC bands because they were more intense when the sample was exposed to the argon laser beam.
基金Project supported by the National Natural Science Foundation of China(Grant No.20974108)the Natural Science Foundation of Anhui Province,China(Grant No.1308085QB40)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant Nos.2013HGQC0016 and 2011HGBZ1323)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.12135019 and 52202154)the 2115 Talent Development Program of China Agricultural University,the Scientific Research Start-up Fund for Outstanding Talent of China Agricultural University,Chinese Universities Scientific Fund,and High-performance Computing Platform of China Agricultural University。
文摘Piezoelectric ceramics provide high strain and large driving forces in actuators.A large electrostrain can be realized by the introduction of point defects such as vacancies,interstitial defects,and substitution defects.With Mn doping,a significant increase in the reversible electrostrain from 0.05%to 0.17%could be achieved in potassium niobite lead-free piezoelectric ceramics.The origins of the large electrostrain were analyzed via in situ X-ray diffraction(XRD)under an electric field.The electrostrain and other typical electrical properties of the samples were measured at various temperatures,which enabled the ceramics to perform under a very wide temperature range,such as−80–130℃ for the 0.5 mol%Mn-doped sample with low dielectric loss(≤0.02).More importantly,combined with characterizations of the defect behavior by thermally stimulated depolarization current(TSDC),the failure mechanisms of electrostrain in a hightemperature environment could be revealed,which was associated with synergistic damage to the defects caused by the electric field and high temperature.The results can provide good ideas and a basis for the design of piezoelectric materials with good electrostrain stability over a wide temperature range.
文摘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.
