BaTi O3(BTO)与LaAlO3(LAO)组成的BTO/LAO超晶格的介电性能呈现新的变化特点.作者模拟计算了不同弛豫时间对不同层状周期结构的BTO/LAO超晶格介电性能的变化规律;模拟计算表明,BTO/LAO超晶格在厚度为0.8nm/0.8nm～1.6nm/1.6nm时介电常...BaTi O3(BTO)与LaAlO3(LAO)组成的BTO/LAO超晶格的介电性能呈现新的变化特点.作者模拟计算了不同弛豫时间对不同层状周期结构的BTO/LAO超晶格介电性能的变化规律;模拟计算表明,BTO/LAO超晶格在厚度为0.8nm/0.8nm～1.6nm/1.6nm时介电常数出现极大值.认为超晶格的界面电荷的累积对于弛豫时间的作用直接影响了BTO/LAO超晶格的介电性能;BTO/LAO超晶格的介电损耗主要来源于BTO/LAO超晶格的电导率.展开更多
Gadolinium doped Zinc oxide (Zn<sub>1–x</sub>GdxO) nanocrystals with different percentage of Gd content (x = 0, 0.2, 0.4, 0.6, 0.8) have been prepared by the solid state reaction method. The structural, m...Gadolinium doped Zinc oxide (Zn<sub>1–x</sub>GdxO) nanocrystals with different percentage of Gd content (x = 0, 0.2, 0.4, 0.6, 0.8) have been prepared by the solid state reaction method. The structural, mor-phological and chemical studies of the samples were performed by X-ray diffraction (XRD), Scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) analysis. The XRD spectra confirm that all the samples have hexagonal wurtzite structure. Decrease in average crystallite size with an increase in Gd concentration is observed in XRD. SEM images show that the grain size of undoped ZnO is larger than the Gd doped ZnO, specifying the hindrance of grain growth upon Gd doping. The chemical composition of the samples was confirmed using Energy dispersive X-ray (EDX) analysis. The variation of dielectric constant (ε<sub>r</sub>), dielectric loss (tan δ) and AC conductivity as a function of frequency is studied at room temperature in a frequency which ranges from 100 Hz - 4.5 MHz by using LCR Hi TESTER. All the samples exhibit the normal dielectric behavior, i.e. decreases with increase in frequency which has been explained in the light of Maxwell-Wagner model. The dielectric constant and dielectric loss can be varied intensely by tuning Gd concentration in Zn<sub>1–x</sub>Gd<sub>x</sub>O compounds.展开更多
Saturation exponent is an important parameter in Archie’s equations;however,there has been no well-accepted physical interpretation for the saturation exponent.We have theoretically derived Archie’s equations from t...Saturation exponent is an important parameter in Archie’s equations;however,there has been no well-accepted physical interpretation for the saturation exponent.We have theoretically derived Archie’s equations from the Maxwell–Wagner theory on the assumption of homogeneous fluid distribution in the pore space of clay-free porous rocks.Further theoretical derivations showed that the saturation exponent is in essence the cementation exponent for the water–air mixture and is quantitatively and explicitly related to the aspect ratio of the air bubbles in the pores.The results have provided a theoretical backup for the empirically obtained Archie’s equations and have offered a more physical and quantitative understanding of the saturation exponent.展开更多
This paper presents the fabrication and modeling for capacitance-voltage characteristics of multi-layer metal-insulator-metal capacitors. It is observed that, due the applied electric field, the effective dielectric c...This paper presents the fabrication and modeling for capacitance-voltage characteristics of multi-layer metal-insulator-metal capacitors. It is observed that, due the applied electric field, the effective dielectric constant of the stack was increased due to the accumulation of charges at the interface of high-to-low conductance materials. It is observed that the Maxwell-Wagner polarization is dominant at low frequencies （〈10 kHz）. By introducing carrier tunneling probability of the dielectric stack, the model presented in this paper shows a good agreement with experimental results. The presented model indicates that the nonlinearity can be suppressed by choosing the similar permittivity dielectric materials for fabrication of multilayer metal insulator metal capacitors.展开更多
In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-r...In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-ring calamitic LCs,namely(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-octyloxy)benzoate,(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-decyloxy)benzoate and(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-undecyloxy)benzoate.The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds,synthesized as per the known synthetic steps,show not only a ferroelectrically switchable chiral smectic C(SmC*)phase over a wide thermal range,but also other mesophases such as blue phase-I/II(BP-I/II),chiral nematic(N*)and unknown smectic(SmX)phases.Several essential dielectric parameters of the FLC phase have been measured at different temperatures.The relative permittivity has been measured with the variations of temperature and frequency.Besides,the dielectric loss and tanδhave been measured.Different dielectric relaxations have been calculated and explained at the molecular level.The systematic measurements revealed a strong anomaly,and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz.Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.展开更多
文摘Gadolinium doped Zinc oxide (Zn<sub>1–x</sub>GdxO) nanocrystals with different percentage of Gd content (x = 0, 0.2, 0.4, 0.6, 0.8) have been prepared by the solid state reaction method. The structural, mor-phological and chemical studies of the samples were performed by X-ray diffraction (XRD), Scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) analysis. The XRD spectra confirm that all the samples have hexagonal wurtzite structure. Decrease in average crystallite size with an increase in Gd concentration is observed in XRD. SEM images show that the grain size of undoped ZnO is larger than the Gd doped ZnO, specifying the hindrance of grain growth upon Gd doping. The chemical composition of the samples was confirmed using Energy dispersive X-ray (EDX) analysis. The variation of dielectric constant (ε<sub>r</sub>), dielectric loss (tan δ) and AC conductivity as a function of frequency is studied at room temperature in a frequency which ranges from 100 Hz - 4.5 MHz by using LCR Hi TESTER. All the samples exhibit the normal dielectric behavior, i.e. decreases with increase in frequency which has been explained in the light of Maxwell-Wagner model. The dielectric constant and dielectric loss can be varied intensely by tuning Gd concentration in Zn<sub>1–x</sub>Gd<sub>x</sub>O compounds.
基金The authors would like to thank the National Natural Science Foundation of China(41874151,41821002)the Fundamental Research Funds for the Central Universities(18CX05008A)for financial support of this work.
文摘Saturation exponent is an important parameter in Archie’s equations;however,there has been no well-accepted physical interpretation for the saturation exponent.We have theoretically derived Archie’s equations from the Maxwell–Wagner theory on the assumption of homogeneous fluid distribution in the pore space of clay-free porous rocks.Further theoretical derivations showed that the saturation exponent is in essence the cementation exponent for the water–air mixture and is quantitatively and explicitly related to the aspect ratio of the air bubbles in the pores.The results have provided a theoretical backup for the empirically obtained Archie’s equations and have offered a more physical and quantitative understanding of the saturation exponent.
基金Project supported by the Science and Engineering Research Board(No.ECR/2016/001156)
文摘This paper presents the fabrication and modeling for capacitance-voltage characteristics of multi-layer metal-insulator-metal capacitors. It is observed that, due the applied electric field, the effective dielectric constant of the stack was increased due to the accumulation of charges at the interface of high-to-low conductance materials. It is observed that the Maxwell-Wagner polarization is dominant at low frequencies （〈10 kHz）. By introducing carrier tunneling probability of the dielectric stack, the model presented in this paper shows a good agreement with experimental results. The presented model indicates that the nonlinearity can be suppressed by choosing the similar permittivity dielectric materials for fabrication of multilayer metal insulator metal capacitors.
文摘In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-ring calamitic LCs,namely(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-octyloxy)benzoate,(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-decyloxy)benzoate and(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-undecyloxy)benzoate.The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds,synthesized as per the known synthetic steps,show not only a ferroelectrically switchable chiral smectic C(SmC*)phase over a wide thermal range,but also other mesophases such as blue phase-I/II(BP-I/II),chiral nematic(N*)and unknown smectic(SmX)phases.Several essential dielectric parameters of the FLC phase have been measured at different temperatures.The relative permittivity has been measured with the variations of temperature and frequency.Besides,the dielectric loss and tanδhave been measured.Different dielectric relaxations have been calculated and explained at the molecular level.The systematic measurements revealed a strong anomaly,and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz.Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.
