Impedance spectroscopy of grain boundaries in nanophase ZnO

1995 ◽  
Vol 10 (9) ◽  
pp. 2295-2300 ◽  
Author(s):  
J. Lee ◽  
J.-H. Hwang ◽  
J.J. Mashek ◽  
T.O. Mason ◽  
A.E. Miller ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Grain Boundaries ◽  
Defect Characterization ◽  
Impedance Spectra ◽  
Gas Condensation ◽  
Average Grain Size

Sintered compacts of nanophase ZnO (∼60 nm average grain size, presintered at 600 °C) were made from powders (∼13 nm) prepared by the gas-condensation technique. Impedance spectra were taken as a function of temperature over the range 450–600 °C and as a function of oxygen partial pressure over the range 10−3−1 atm (550 and 600 °C only). The activation energy was determined to be 55 kJ/mole (0.57 eV) and was independent of oxygen partial pressure. The oxygen partial pressure exponent was −1/6. Impedance spectra exhibited nonlinear I-V behavior, with a threshold of approximately 6 V. These results indicate that grain boundaries are governing the electrical properties of the compact. Ramifications for oxygen sensing and for grain boundary defect characterization are discussed.

Recrystallization of Oxygen Contaminated Al Films

1986 ◽  
Vol 71 ◽  
Author(s):  
G.J. Van Der Kolk ◽  
M.J. Verkerk
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Substrate Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Relative Increase ◽  
Partial Pressures ◽  
Average Grain Size

AbstractAl was evaporated at oxygen partial pressures, PO2, varying between 10−7 and 10−4 Pa on substrates of silicon nitride. The substrate temperature was varied between 20 °C and 250°C. The films were annealed at temperatures up to 500°C.For Al films deposited at 20°C, it was found that the average grain size decreases with increasing oxygen partial pressure. After annealing recrystallization was observed. The relative increase of grain size was less for higher values of pO2. Annealing gave rise to a broad grain size distribution.For Al films deposited at 250°C, the presence of oxygen caused the growth of rough inhomogeneous films. This inhomogeneous structure remained during annealing.

scholarly journals Acoustic emission study of microcracking in 123-type ceramic superconductors

1990 ◽  
Vol 5 (10) ◽  
pp. 2066-2074 ◽  
Author(s):  
T. J. Richardson ◽  
L. C. De Jonghe
Keyword(s):  
Grain Size ◽  
Acoustic Emission ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Ybco Superconductor ◽  
Sintered Ceramic ◽  
Average Grain Size ◽  
Superconducting Compounds ◽  
Emission Study ◽  
Acoustic Emission Study

Acoustic emission from sintered ceramic YBa2Cu3O7−x (YBCO) superconductor pellets provides a direct measure of microcracking behavior during processing. By detection and statistical analysis of acoustic events, the effects of cooling rates, processing atmosphere, average grain size, additives, and grain alignment on microcracking in YBCO have been studied. The onset temperature and duration of acoustic emission during cooling correlate well with the oxygen partial pressure in the furnace. Rapid changes in oxygen partial pressure at constant temperature produce acoustic emission that is characteristic of microcracking. A reported critical grain size for microcracking in sintered polycrystalline YBCO of about 1 μm has been confirmed. Two superconducting compounds, YSrBaCu3O7−x and LaBaCaCu3O7−x with the 123 structure but with smaller crystallographic anisotropy were also examined. Recommendations are made for minimizing microcracking during processing of superconducting ceramics.

scholarly journals Structural and Electrical Studies on ZnO-Based Thin Films by Laser Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Shanyue Zhao ◽  
Yinqun Hua ◽  
Ruifang Chen ◽  
Jian Zhang ◽  
Ping Ji
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Laser Irradiation ◽  
Nonlinear Coefficient ◽  
Acceptor State ◽  
Xrd Pattern ◽  
Electrical Studies ◽  
Structural And Electrical Properties

The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD pattern shows that the thin films were highly textured along thec-axis and perpendicular to the surface of the substrate. Raman spectra reveal that Bi2O3segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the film was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary were interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the breakdown voltage reduced to 5.34 V.

Electrical Properties of Donor and Acceptor Doped Gd2Ti2O7

1994 ◽  
Vol 369 ◽  
Author(s):  
Igor Kosacki ◽  
Harry L. Tuller
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Conductivity Measurements ◽  
Donor And Acceptor ◽  
Mn Doped

The results of electrical conductivity measurements on Nb, W, and Mn-doped Gd2Ti2O7 are presented. A correlation between electrical conductivity, the oxygen partial pressure and type of dopants has been obtained. The source of the different PO2 dependence for Mn-doped material is discussed.

Characterization of YBa2Cu4O8 high temperature electrical properties and thermodynamic stability

1991 ◽  
Vol 6 (10) ◽  
pp. 2054-2058 ◽  
Author(s):  
B-S. Hong ◽  
T.O. Mason
Keyword(s):  
High Temperature ◽  
Electrical Property ◽  
Electrical Properties ◽  
Seebeck Coefficient ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Pressure Range ◽  
Stability Range

Via in situ electrical property measurements (conductivity, Seebeck coefficient) over the temperature range 500–800 °C and oxygen partial pressure range 10−4-1 atm, the equilibrium transport properties and stability range of YBa2Cu4O8 were determined. YBa2Cu4O8 behaves like the intrinsically mixed-valent compound, magnetite (Fe3O4), with small variations in electrical properties with changes in oxygen partial pressure. The decomposition boundary to YBa2Cu3O6+y (or YBa2Cu3.5O7.5±z) and CuO occurs at log(po2, atm) = −1.24 × 104/T(K) + 11.01(773 ⋚ T(K) ⋚ 1073).

Thermal Stability of Ultrafine-Grained Pure Titanium Processed by High-Pressure Torsion

2021 ◽  
Vol 1016 ◽  
pp. 338-344
Author(s):  
Wan Ji Chen ◽  
Jie Xu ◽  
De Tong Liu ◽  
De Bin Shan ◽  
Bin Guo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Annealing Temperature ◽  
High Pressure Torsion ◽  
Stored Energy ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Thermal Stability Of

High-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 °C, and the size of the grains increases significantly for samples at the annealing temperature of 600 °C.

Influence of sand grain size and nest microenvironment on incubation success, hatchling morphology and locomotion performance of green turtles (Chelonia mydas) at the Chagar Hutang Turtle Sanctuary, Redang Island, Malaysia

2018 ◽  
Vol 66 (6) ◽  
pp. 356 ◽  
Author(s):  
Taylor A. Stewart ◽  
David T. Booth ◽  
Mohd Uzair Rusli
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Swimming Speed ◽  
Green Turtle ◽  
Chelonia Mydas ◽  
Sand Particle ◽  
Emergence Success ◽  
Sand Grain Size

The nest microenvironment affects hatching and emergence success, sex ratios, morphology, and locomotion performance of hatchling sea turtles. Sand grain size is hypothesised to influence the nest microenvironment, but the influence of sand grain size on incubation of sea turtle eggs has rarely been experimentally tested. At the Chagar Hutang Turtle Sanctuary, Redang Island, Malaysia, green turtle (Chelonia mydas) nests were relocated to sands with different sand grain sizes on a natural beach to assess whether grain size affects nest temperature, oxygen partial pressure inside the nest, incubation success, hatchling morphology and hatchling locomotion performance. Green turtle nests in coarse sand were cooler; however, hatching success, nest emergence success, oxygen partial pressure, incubation length and hatchling size were not influenced by sand particle size. Nests in medium-grained sands were warmest, and hatchlings from these nests were better self-righters but poorer crawlers and swimmers. Hatchling self-righting ability was not correlated with crawling speed or swimming speed, but crawling speed was correlated with swimming speed, with hatchlings typically swimming 1.5–2 times faster than they crawled. Hence, we found that sand particle size had minimal influence on the nest microenvironment and hatchling outcomes.

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