Drastic Change In Conductivity Research Articles

Studies on properties of NiO-GDC nano-composite and Ni-GDC cermet

Abstract In the present research, NiO-GDC nano-composite and Ni-GDC cermet are studied comparatively. The change in microstructure and conductivity before and after reduction has been reported. NiO-GDC nano-composite samples are prepared by solution combustion synthesis. As-synthesized powders are reduced in H2 atmosphere at 500 °C for 5 hr. These samples are characterized by XRD and FE-SEM to confirm phase purity and microstructure respectively. The conductivity measurement of both NiO-GDC and Ni-GDC samples is measured by two probe and four probe method respectively. Drastic change in conductivity is observed after reduction of NiO-GDC to Ni-GDC.

Structural, morphological, electrical and electrochemical study on plasticized PVdF-HFP/PEMA blended polymer electrolyte for lithium polymer battery application

The compositional effect of blending plasticized poly (vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) with different wt% of poly(ethyl methaacrylate) (PEMA) on its electrical properties was studied through AC impedance analysis. The maximum ionic conductivity of 2.14 × 10−2 S/cm at 303 K was found for 5 wt% of PEMA blended film which almost one order higher than the plasticized PVdF-HFP film with no blending (3.15 × 10−3 S/cm). However, blending of 10 wt% of PEMA dropped the conductivity to (5.12 × 10−4 S/cm). This drastic change in conductivity was explained in detail by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) analysis. The dielectric studies showed increase in side chain movements of the host polymer PVdF-HFP for 5 wt% of PEMA blending. However, this segmental motion was found hindered for 10 wt% of PEMA due to steric effect. TG-DTA shows the thermal stability of the plasticized polymer membrane to be increased for the addition of 5 wt% PEMA. Lithium metal polymer cell was made using the optimized blend membrane as an electrolyte with LiV3O8 as cathode and Li metal as anode. The lithium metal polymer cell was found to deliver the specific discharge capacity of 223 mAh/g at the second cycle.

Switching mechanism in resistive random access memory by first-principles calculation using practical model based on experimental results

For the practical use of resistive random access memory (ReRAM), many formation/rupture models of conductive paths are proposed. In this paper, we report both the probability of conductive path formation on grain surfaces and the marked drastic change in conductivity caused by a small number of atoms migrating on grain surfaces, determined by using experimental and calculation results complementarily. Experimental results of resistive switching operating modes suggest that resistance changes at grain boundaries, to which our calculation results can give an explanation. The energy for the conductive change from a low-resistance state to a high-resistance state is estimated to be about 0.05 eV per surface atom, which is much smaller than the formation and migration energies of vacancies (1.44–4.42 eV) and is comparable to the estimated temperature of the conductive path in the reset process.

Study Of Structural And Electrical Properties Of Pure And Zn-Cu Doped SnO2

Numerous metal oxide semiconductor materials were reported to be usable as semiconductor gas sensor, such as ZnO, SnO2, and TiO2 and so on. The samples of Zn and Cu doped SnO2 (SnZnO3 and SnCuO3) have been synthesized by solid-state reaction method. Some aspect of crystal structure of the compound at room temperature was studied using X-ray diffraction technique. The XRD study of the compound shows that there is a change in the basic crystal structure of SnO2 on substitutions of ZnO and CuO. The patterns of the SnO2 sample are indexed as tetragonal perovskite type with a = 7.3928 Å, c = 5.2879 Å but on substitution of ZnO and CuO the structure becomes orthorhombic with lattice constant a = 23.5237Å, b = 8.2183 Å and c =5.8017 Å or a = 21.8594 Å, b = 5.3200 Å, and c = 5.1803 Å, respectively. The temperature variation of resistance shows that compounds have negative temperature coefficient of resistance. The gas sensitivity for LPG (liquefied petroleum gas) showed a drastic change in conductivity.

Study of Candidate Insulating Materials for Use in Shock Wave Switches

One challenge in high power switching is to have a compact switch, which can hold off high voltages and close rapidly at the proper time. Most high power switches are large or complicated, such as triggered spark gaps. Typical opening switches are also not compact and often have too long switching time. It has been shown previously that certain insulating materials undergo a drastic change in conductivity under shock loading. Using such a material could greatly reduce the size of a switch. We will report on our continuing studies of different candidate materials for shock wave switches.

Conduction properties of non-stoichiometric hydroxyapatite whiskers for biomedical use

Hydroxyapatite (HA) whiskers were synthesized by a hydrothermal method and ion conductive property was investigated in order to develop HA whisker electrets for biomedical utilization. Based on infrared (IR) spectroscopy and inductively coupled plasma optical emission spectrometry (ICP-OES), the obtained whiskers were assumed to be Ca deficient HA with a composition of Ca9.18[HPO4]0.82[PO4]5.18[OH]1.18·n H2O. The results of complex impedance measurements proved that the conduction properties of whiskers and powders showed almost the same temperature dependence as those of sintered HA above 600°C. The mechanism is understood by the migration of protons originating in OH- ions. In the temperature range below 600°C, however, the non-linear Arrhenius relationship of conductivity (σ vs. 1/T) was only observed in the whiskers and powders. In particular, a drastic change in conductivity with temperature appeared in the whiskers within 250-600°C; the conductivity increased to 5.0 × 10-9 S/cm at 500°C, then decreased to 1.7 × 10-9 S/cm with the temperature elevated to 600°C. Since HPO42- ions are reportedly supposed to convert into P2O74- in almost the same temperature range where the drastic change in conductivity appeared, the increase in whisker conductivity up to 500°C is presumably the result of an increase in the number of mobile protons generated from HPO42-. The subsequent decrease in conductivity seemed to be caused by a decrease in the number of protons achieved by water elimination, causing the conversion of HPO42- to P2O74-.

Applications of an all-polymer solution-processed high-performance, transistor

Low cost production and a simple manufacturing process are desired for organic field effect transistors, OFETs, even though this usually significantly lowers device performance. We report on applications and characterization of a high performance polymer field effect transistor that utilizes a hygroscopic insulator. The latter enables the device to be used as a sensor element to detect the presence of various solvents. We show a drastic change in conductivity and current modulation for some organic solvents. Furthermore, the use of the device in electric circuits is demonstrated by combining hygroscopic insulator field effect transistor (HIFET) devices in an inverter/amplifier circuit.

Electrical conductivities of the superionic composites composed of frozen α-AgI and AgI-based glasses

New composite materials in which α-AgI was frozen in the superionic conducting glasses in the systems AgI-Ag 2O-M x O y (M x O y =B 2O 3, GeO 2, P 2O 5, MoO 3) exhibited extremely high ion conductivities of about 10 −2−10 −1S cm −1 at room temperature. In such superionic composites, it was found that fine particles of α-AgI were dispersed in AgI-based glass matrices. During heating of the composites a large drop of conductivities due to the crystallization of the matrix glasses was observed in the case of the composites with P 2O 5 and MoO 3, whereas no drastic change in conductivity was observed in the composites with B 2O 3 and GeO 2. On cooling process, a conductivity drop due to the α-β phase transformation of AgI was observed in all the composites. However, the temperature at which the conductivity started to drop was lower in the case of the latter composites than in the case of the former composites.