Impedance Spectroscopy of Upper Mantle Earth Materials

1995 ◽  
Vol 411 ◽  
Author(s):  
J. A. Tyburczy ◽  
J. J. Roberts
Keyword(s):  
Grain Boundary ◽  
Pressure Dependence ◽  
Upper Mantle ◽  
Boundary Behavior ◽  
Complex Impedance ◽  
Major Constituent ◽  
Boundary Conductivity ◽  
Earth’S Interior ◽  
Earth's Interior ◽  
Grain Boundary Transport

ABSTRACTEarth scientists study electrical properties of Earth materials to understand mechanisms of transport and deformation under conditions existing in the Earth's interior, and for comparison with direct determinations of the conductivity – depth structure of the Earth. We have performed impedance spectroscopic studies of natural and artificial (hot-pressed and sintered) rocks composed of (Mg9Fe1)2SiO4 olivine, a major constituent of the Earth's upper mantle between 40 and 400 km depth. The studies were performed over the frequency range 105 to 10−4 Hz at 1 bar total pressure and temperatures of 800 – 1400 °C under controlled oxygen atmospheres. Complex impedance plane analysis of the results shows depressed impedance arcs corresponding to grain interior and grain boundary transport in series, analogous to the behavior of zirconia and other materials. Distinct grain boundary phases that might cause the resistive grain boundary behavior are not observed. The exponent of the oxygen pressure dependence of the grain boundary conductivity ranges from 0.02 to −0.08, which is very different than the 1/5.5 to 1/7 dependence of the polaronic grain interior mechanism. However, lack of constraints on the composition of the intergranular material limit interpretation of these exponents in terms of mechanism. Key issues for application to the Earth's interior are determination of the mechanism and pressure dependence of the grain boundary transport.

Grain boundary conductivity and microstructure study of 4% Y2O3 doped CeO2 thin films

1996 ◽  
Vol 453 ◽  
Author(s):  
Chunyan Tian ◽  
Siu-Wai Chan
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Complex Impedance ◽  
Preexponential Factor ◽  
X Ray Diffraction ◽  
Ac Impedance Spectroscopy ◽  
Boundary Conductivity ◽  
Transmission Electron ◽  
Brick Layer Model ◽  
Beam Deposition

AbstractThe thin films of 4% Y2O3 doped CeO2 have been deposited on different substrates of Pd film/(001) LaAlO3, Pd film/r-cut sapphire, and Pd film/Quartz using an e-beam deposition technique. The microstructures and electrical properties of the films were investigated by means of x-ray diffraction, transmission electron microscopy, and ac impedance spectroscopy. Both textured and polycrystalline films were produced on different substrates. A brick layer model was adopted to correlate the micro structure and electrical property of the films. Only the grain boundary arc was observed in the film complex impedance plots. The conductivities of the films were similar to the conductivity of 6% Y2O3 doped CeO2 bulk grain boundary because of lower preexponential factor, although the activation energies were smaller than that of bulk grain boundary. The resistive gram boundaries were found to dominate the conductivities of the films.

Origin and significance of seismic discontinuities in the continental upper mantle: An interdisciplinary study

2021 ◽  
Author(s):  
Shun-ichiro Karato ◽  
Lidong Dai ◽  
Gary Egbert ◽  
Jennifer Girard ◽  
Benjamin Murphy ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Grain Boundary ◽  
Pressure Dependence ◽  
Upper Mantle ◽  
Grain Boundary Sliding ◽  
Seismic Attenuation ◽  
Depth Range ◽  
Seismic Discontinuities ◽  
Boundary Sliding ◽  
Interdisciplinary Study

<p>              The mid-lithosphere discontinuity (MLD) and the lithosphere-asthenosphere-boundary (LAB) are two well-known seismic discontinuities in the continental upper mantle. Both MLD and LAB are present in most of the continents but at different depths and with different magnitude of velocity change and sharpness. Understanding the causes for these discontinuities including their regional variations is critical in inferring the evolution of the continents from geophysical observations on these discontinuities.</p><p>              Among various models, we focus on the elastically-accommodated grain-boundary sliding (EAGBS) model that provides plausible and unified explanations for the MLD and the LAB (Karato and Park, 2019). This model has a few testable predictions, and the main purpose of this talk is to review the current status of these tests.</p><ul><li>(i) One assumption of the EAGBS model is that EAGBS is enhanced by water. A recent paper by Cline et al. (2018) challenges this hypothesis by showing that water has no effects on attenuation in Ti-doped hydrated olivine. However, the relevance of the results on highly Ti-doped olivine to Ti-poor real upper mantle is unclear.</li> <li>(ii) A clear and unique prediction of the EAGBS is the presence of a peak in seismic attenuation at/near the MLD. However, inferring an attenuation peak in a narrow depth range is challenging and this hypothesis has not been tested.</li> <li>(iii) Another prediction of the “dry” version of the EAGBS model for the MLD is that although seismic wave velocity drops and there is a peak in attenuation, electrical conductivity does not change.</li> <li>(iv) If the MLD is caused by EAGBS, then materials below are in the “relaxed” state. This would explain the lack of large velocity drop at the LAB. However, the validity of this explanation depends on the pressure dependence of grain-boundary sliding. If pressure dependence of EAGBS is large, then the un-relaxed state will re-establish itself at a relatively shallow depth within the lithosphere. In this case, a deeper thermal transition to the relaxed state should produce stronger LAB than reported.  </li> </ul><p>We have conducted an interdisciplinary study to address these issues including mineral physics and seismology. We found that the addition of Ti modifies the defect-related properties of olivine and complicates the application of Cline et al. (2018) to actual upper-mantle conditions. We determined the pressure dependence of olivine grain-growth, from which we infer that the pressure dependence of grain-boundary sliding is small. Regarding the seismological test of attenuation peak, we forward-modeled surface-wave dispersion in a dispersive medium. Calculations show that the over-tones of Love waves are a key to detecting an attenuation peak near the GBS transition. Combined with a comparison of seismological studies (on velocity and attenuation) and MT estimates of electrical conductivity, we will have better constraints on the validity of the EAGBS model for the origin of the MLD.</p>

Impedance Spectroscopy Analysis of p Type Li Doped ZnO Thin Film Effect

2011 ◽  
Vol 415-417 ◽  
pp. 1925-1932 ◽  
Author(s):  
Kuo Chuang Chiu ◽  
Yu Han Wu
Keyword(s):  
Thin Film ◽  
Impedance Spectroscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Complex Impedance ◽  
Spectroscopy Analysis ◽  
Boundary Conductivity ◽  
Impedance Spectroscopy Technique ◽  
P Type ◽  
Li Content

Impedance spectroscopy technique was employed to characterize the LixZn1-xO2 (x=0.001~0.008) polycrystalline thin film. IS is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries resistance to the complex impedance of a compound, accurately estimating its electrical conductivity as well as its corresponding activation energies and conclude on its structural properties. This is demonstrated for the case of lithium segregation in the grain/grain boundary of LixZn1-xO2., we found that the activation energy decrease associated with grain-boundary conductivity reflects the onset of the segregation of excessive Li in the grain boundaries when the Li-content exceeds 0.5 mol%. For Li-content below 0.5mol% is the detection of a transition from p-type conductivity. It might be due to that the Li+ doped mainly in grains and no precipitation observed on the grain boundaries. So we could be process stable p type thin film for Li content below 0.5mol%.

scholarly journals Experimental study on the electrical conductivity of quartz andesite at high temperature and high pressure: evidence of grain boundary transport

Solid Earth ◽  
2015 ◽  
Vol 6 (3) ◽  
pp. 1037-1043 ◽  
Author(s):  
K. S. Hui ◽  
H. Zhang ◽  
H. P. Li ◽  
L. D. Dai ◽  
H. Y. Hu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Grain Boundary ◽  
Conduction Mechanism ◽  
Small Polaron ◽  
Boundary Conductivity ◽  
Boundary Process ◽  
The Relationship ◽  
Grain Boundary Transport ◽  
Ion Conduction Mechanism

Abstract. In this study, the electrical conductivity of quartz andesite was measured in situ under conditions of 0.5–2.0 GPa and 723–973 K using a YJ-3000t multi-anvil press and a Solartron-1260 Impedance/Gain-Phase Analyzer. Experimental results indicate that grain interior transport controls the higher frequencies (102–106 Hz), whereas the grain boundary process dominates the lower frequencies (10−1–102 Hz). For a given pressure and temperature range, the relationship between Log σ and T−1 follows the Arrhenius relation. As temperature increased, both the grain boundary and grain interior conductivities of quartz andesite increased; however, with increasing pressure, both the grain boundary and grain interior conductivities of the sample decreased. By the virtue of the dependence of grain boundary conductivity on pressure, the activation enthalpy and the activation volume were calculated to be 0.87–0.92 eV and 0.56 ± 0.52 cm3 mol−1, respectively. The small polaron conduction mechanism for grain interior process and the ion conduction mechanism for grain boundary process are also discussed.

Microstructural Correlation with Electrical Properties for Y2O3 Doped CeO2 Thin Films

1997 ◽  
Vol 500 ◽  
Author(s):  
Chunyan Tian ◽  
Siu-Wai Chan
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Complex Impedance ◽  
Fused Silica ◽  
X Ray Diffraction ◽  
Spectroscopy Analysis ◽  
Boundary Conductivity ◽  
Bulk Ceramic ◽  
Transmission Electron ◽  
Beam Deposition

ABSTRACTHigh quality textured 0.58% Y2O3 doped CeO2 films with (001), (111)/(001) and (110) were prepared using an e-beam deposition technique on substrates of (001) LaAlO3, r-cut sapphire, and fused silica, respectively. The composition and stoichiometry of the films were verified by Rutherford backscattering spectroscopy analysis. Both x-ray diffraction and transmission electron microscopy analyses gave consistent microstructural information. Complex impedance measurements have been performed to study the electrical properties of these films as a function of temperature. The conductivities of the films were dominated by grain boundaries of high conductivities as compared to that of the bulk ceramic of the same dopant concentration. The activation energies for the film conductivities were only slightly higher than that for the bulk lattice conductivities, but much lower than that for the bulk grain boundary conductivity. These results have been discussed in terms of the differences of the grain size and grain boundary microstructures between the films and the bulk ceramics.

FREQUENCY DEPENDENCE OF THE GRAIN-BOUNDARY CONDUCTIVITY IN (Y2O3, CaO)-STABILIZED ZrO2

2011 ◽  
Vol 25 (01) ◽  
pp. 131-142 ◽  
Author(s):  
TONGWEI LI ◽  
WEIWEI JU ◽  
JINCANG ZHANG
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Frequency Dependence ◽  
Power Law ◽  
Boundary Effect ◽  
Complex Impedance ◽  
Impedance Method ◽  
Boundary Conductivity ◽  
Grain Boundary Effect ◽  
Power Law Parameters

Five samples of mixed Y 2 O 3/ CaO doped ZrO 2 electrolytes, with the same nominal chemical composition of ( ZrO 2)0.90–( Y 2 O 3)0.04-( CaO )0.06, were sintered at 1600°C for 2, 4, 6, 8 and 10 h, respectively. The frequency dependence of the grain-boundary conductivity of each sample was measured using complex impedance method in the temperature range from 773 to 1073 K and experimental results were analyzed according to a power law, which was frequently referred to as the so-called universal dynamic response (UDR). Results indicated the apparent ac grain-boundary conductivity can be well-described by the power law and some useful information about the grain-boundary effect, such as the activation energy of the grain-boundary conduction and the dissociated energy of the charge carrier in the space charge layer, can be obtained by analyzing the temperature dependence of the power law parameters.

scholarly journals Experimental study on the electrical conductivity of quartz andesite at high temperature and high pressure: evidence of grain boundary transport

2015 ◽  
Vol 7 (2) ◽  
pp. 1555-1576
Author(s):  
K. S. Hui ◽  
H. Zhang ◽  
H. P. Li ◽  
L. D. Dai ◽  
H. Y. Hu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Conduction Mechanism ◽  
Activation Volume ◽  
Small Polaron ◽  
Boundary Conductivity ◽  
Arrhenius Relation ◽  
Boundary Process ◽  
The Relationship ◽  
Grain Boundary Transport

Abstract. In this study, the grain boundary conductivity of quartz andesite was in situ measured under conditions of 0.5–2.0 GPa and 723–973 K using a YJ-3000t multi-anvil press and Solartron-1260 Impedance/Gain-phase Analyzer. Experimental results indicate that grain interior transport controls the higher frequencies (102–106 Hz), whereas the grain boundary process dominates the lower frequencies (10−1–102 Hz). At a given pressure and temperature range, the relationship between log σ and 1/T conforms to an Arrhenius relation. As temperature increased, both of the grain boundary and grain interior conductivities of quartz andesite increased. Under increasing pressure, however, both of the grain boundary and grain interior conductivities of the sample decreased. By the virtue of the dependence of grain boundary conductivity on pressure, the activation enthalpy and the activation volume were calculated at 0.77–1.03 eV and 5.29 ± 1.94 cm3 mol−1, respectively. Furthermore, the small polaron conduction mechanism between the ferrous and ferric ion is also discussed.

Petrological and geochemical evidence for convection in the Earth’s mantle

1965 ◽  
Vol 258 (1088) ◽  
pp. 168-179 ◽  
Keyword(s):  
Upper Mantle ◽  
Mantle Convection ◽  
Tholeiitic Basalt ◽  
High Alumina ◽  
Convective System ◽  
General Terms ◽  
Serpentinized Peridotite ◽  
Earth’S Interior ◽  
Earth's Interior ◽  
Lines Of Evidence

Various lines of evidence suggest that layer 3 of the oceanic material is partially serpentinized peridotite. Hess (1962) suggested that this layer originated by serpentinization of the upper part of the mantle, the necessary water being derived from the degassing of rising columns of mantle convection cells beneath the mid-ocean ridges. In this paper it is shown that support for this hypothesis can be derived from two entirely different lines of evidence. The first concerns the characters of volcanic lavas extruded in oceanic areas. Although these are, in general terms, basaltic, significant minor differences exist between basalts dredged from different parts of the ocean floor and between many dredged basalts and the lavas of oceanic islands. In particular high-alumina tholeiitic basalt of Warner type has been obtained from the more deeply submerged parts of the Mid-Atlantic Ridge. Experimental work has shown that, although alkali basalts and normal tholeiitic basalt could be derived by partial fusion of a dry mantle, the presence of water in the upper mantle is probably necessary for the genesis of Warner type basalts. The apparent restriction of Warner type basalts to the mid-ocean ridge areas suggests a similar restriction of the presence of water in the upper mantle and thus the restriction of the serpentinization process to these localized areas as suggested by Hess. The wide distribution of layer 3 in the oceanic crust must then imply some mechanism such as mantle convection currents for its dispersal from the areas of origin. The second concerns the contrast in composition between the total volatiles that have emerged from the Earth’s interior throughout geological time and the gases emerging from oceanic volcanoes at the present time. The state of oxidation of modern oceanic volcanic gases is very close to that predicted for gases in equilibrium with a Mg-Fe-silicate upper mantle, which suggests they have suffered no appreciable contamination on their way to the surface. They are, however, on a percentage basis, much richer in compounds of G, S and N and poorer in those of Cl and H20 than the total emergent volatiles. The amount of water which must have emerged from some other source than oceanic volcanoes in order to explain the total volatiles composition can be calculated to be 8500 to 12600 x 1020 g. On the basis of the Hess hypothesis the amount of water liberated by dehydration of serpentinized peridotite in convective down currents can also be calculated. It is 13 000 x 1020 g for a convective system moving at a rate of 1 cm/y. Two-channel escape of volatiles from the Earth’s interior should result in minor changes in the partial pressure of carbon dioxide in the atmosphere. These should be reflected in the geochemistry of sedimentary rocks. The agreement between deduced and observed effects is surprisingly good in view of the uncertainties in the data and supports the hypothesis of transfer of the serpentinized perioditite layer from areas of convective up-current in the ocean basins to those of down-currents under the continents or continental margins.

scholarly journals Effect of Reduced Atmosphere Sintering on Blocking Grain Boundaries in Rare-Earth Doped Ceria

Inorganics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 63
Author(s):  
Soumitra Sulekar ◽  
Mehrad Mehr ◽  
Ji Hyun Kim ◽  
Juan Claudio Nino
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Ionic Conductivity ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Complex Impedance ◽  
Doped Ceria ◽  
Composite Electrodes ◽  
Boundary Conductivity ◽  
Rare Earth Doped

Rare-earth doped ceria materials are amongst the top choices for use in electrolytes and composite electrodes in intermediate temperature solid oxide fuel cells. Trivalent acceptor dopants such as gadolinium, which mediate the ionic conductivity in ceria by creating oxygen vacancies, have a tendency to segregate at grain boundaries and triple points. This leads to formation of ionically resistive blocking grain boundaries and necessitates high operating temperatures to overcome this barrier. In an effort to improve the grain boundary conductivity, we studied the effect of a modified sintering cycle, where 10 mol% gadolinia doped ceria was sintered under a reducing atmosphere and subsequently reoxidized. A detailed analysis of the complex impedance, conductivity, and activation energy values was performed. The analysis shows that for samples processed thus, the ionic conductivity improves when compared with conventionally processed samples sintered in air. Equivalent circuit fitting shows that this improvement in conductivity is mainly due to a drop in the grain boundary resistance. Based on comparison of activation energy values for the conventionally processed vs. reduced-reoxidized samples, this drop can be attributed to a diminished blocking effect of defect-associates at the grain boundaries

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