Phase transitions in CsHSO4 up to 2.5GPa: Impedance spectroscopy under pressure

Bagdassarov, N.

doi:10.1016/j.jpcs.2011.01.008

Cited by 6 publications

(3 citation statements)

References 35 publications

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“…Figure 6 is a Bode diagram that depicts the dependence of modulus ( | Z | ) and phase angle (h) on frequency (f). According to the theory of impedance spectroscopy (Huebner and Dillenburg 1995;Barkmann and Cemič 1996;Bagdassarov 2011), the observed semicircular arcs of complex impedance in the Nyquist diagram are indicative of two different conduction mechanisms. The semicircle in the high-frequency region (*10 3 -10 6 Hz) corresponds to the grain interior conduction mechanism, whereas that in the low-frequency portion (*10 -2 -10 3 Hz) corresponds to polarization between the sample and the electrodes.…”

Section: Resultsmentioning

confidence: 99%

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

Dai

et al. 2011

Contrib Mineral Petrol

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The in situ electrical conductivity of hydrous garnet samples (Py 20 Alm 76 Grs 4 -Py 73 Alm 14 Grs 13 ) was determined at pressures of 1.0-4.0 GPa and temperatures of 873-1273 K in the YJ-3000t apparatus using a Solartron-1260 impedance/gain-phase analyzer for various chemical compositions and oxygen fugacities. The oxygen fugacity was controlled by five solid-state oxygen buffers ). Experimental results indicate that within a frequency range from 10 -2 to 10 6 Hz, electrical conductivity is strongly dependent on signal frequency. Electrical conductivity shows an Arrhenius increase with temperature. At 2.0 GPa, the electrical conductivity of anhydrous garnet single crystals with various chemical compositions (Py 20 Alm 76 Grs 4 , Py 30 Alm 67 Grs 3 , Py 56 Alm 43 Grs 1 , and Py 73 Alm 14 Grs 13 ) decreases with increasing pyrope component (Py). With increasing oxygen fugacity, the electrical conductivity of dry Py 73 Alm 14 Grs 13 garnet single crystal shows an increase, whereas that of a hydrous sample with 465 ppm water shows a decrease, both following a power law (exponents of 0.061 and -0.071, respectively). With increasing pressure, the electrical conductivity of this hydrous garnet increases, along with the pre-exponential factors, and the activation energy and activation volume of hydrous samples are 0.7731 ± 0.0041 eV and -1.4 ± 0.15 cm 3 /mol, respectively. The results show that small hopping polarons Fe Á Mg andprotons (H Á ) are the dominant conduction mechanisms for dry and wet garnet single crystals, respectively. Based on these results and the effective medium theory, we established the electrical conductivity of an eclogite model with different mineral contents at high temperatures and high pressures, thereby providing constraints on the inversion of field magnetotelluric sounding results in future studies.

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Section: Resultsmentioning

confidence: 99%

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

Dai

et al. 2011

Contrib Mineral Petrol

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“…The high-pressure impedance measurement system has been successful in resolving the electronic conductivity of many types of materials along with the physics behind them. [16][17][18][19] However, the study of the ionic conduction behavior of a material under high pressure has scarcely been tackled thus far due to the difficulties of the measurement itself and its subsequent data analysis. Most high-pressure ionic conductivity measurements were conducted with multi-anvils 20,21 or other apparatus, [22][23][24][25] which limited the pressure (<10 GPa).…”

Section: Introductionmentioning

confidence: 99%

The determination of ionic transport properties at high pressures in a diamond anvil cell

Wang

Liu

Han

et al. 2016

Review of Scientific Instruments

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A two-electrode configuration was adopted in an in situ impedance measurement system to determine the ionic conductivity at high pressures in a diamond anvil cell. In the experimental measurements, Mo thin-films were specifically coated on tops of the diamond anvils to serve as a pair of capacitance-like electrodes for impedance spectrum measurements. In the spectrum analysis, a Warburg impedance element was introduced into the equivalent circuit to reveal the ionic transport property among other physical properties of a material at high pressures. Using this method, we were able to determine the ionic transport character including the ionic conductivity and the diffusion coefficient of a sodium azide solid to 40 GPa.

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“…At ambient pressure, the sensitivity of electrical conductivity to water located at grain boundaries has been demonstrated experimentally for a variety of polycrystalline ceramic materials, e.g. LiNiVO4 and LiCoVO4 (Kazakopoulos et al 2008), Li3VO4 (Kazakopoulos and Kalogirou 2009), K+-β-ferrite (Ito et al 1996), CsH2PO4 (Boysen et al 2003), KHSO4 (Bagdassarov and Lentz 2005), CsHSO4 (Bagdassarov 2011). These studies have pointed out that the magnitude of the effect of GB water on grain boundary conductivity depends on water film thickness (Kazakopoulos et al 2008) and composition (Karus et al 2000;Ito et al 1996) as well as on the powder microstructure (Kazakopoulos et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Electrical conductivity of polycrystalline Mg(OH)2 at 2 GPa: effect of grain boundary hydration–dehydration

et al. 2011

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The effect of intergranular water on the conductivity of polycrystalline brucite, Mg(OH)2, was investigated using impedance spectroscopy at 2 GPa, during consecutive heating-cooling cycles in the 298-980 K range. The grain boundary hydration levels tested here span water activities from around unity (wet conditions) down to 10−4 (dry conditions) depending on temperature. Four orders of magnitude in water activity result in electrical conductivity variations for about 6-7 orders of magnitude at 2 GPa and room temperature. Wet brucite samples containing, initially, about 18 wt% of evaporable water (i.e. totally removed at temperatures below 393 K in air), display electrical conductivity values above 10−2-10−3 S/m. A.C. electrical conductivity as a function of temperature follows an Arrhenius behaviour with an activation energy of 0.11 eV. The electrical conductivity of the same polycrystalline brucite material dried beforehand at 393 K (dry conditions) is lower by about 5-6 orders of magnitude at room temperature and possesses an activation energy of 0.8-0.9 eV which is close to that of protonic diffusion in (001) brucitic planes. Above ca. 873 K, a non-reversible conductivity jump is observed which is interpreted as a water transfer from mineral bulk to grain boundaries (i.e. partial dehydration). Cooling of such partially dehydrated sample shows electrical conductivities much higher than those of the initially dry sample by 4 orders of magnitude at 500 K. Furthermore, the corresponding activation energy is decreased by a factor of about four (i.e. 0.21 eV). Buffering of the sample at low water activity has been achieved by adding CaO or MgO, two hygroscopic compounds, to the starting material. Then, sample conductivities reached the lowest values encountered in this study with the activation energy of 1.1 eV. The strong dependency of the electrical conductivity with water activity highlights the importance of the latter parameter as a controlling factor of diffusion rates in natural processes where water availability and activity may vary grandly. Water exchange between mineral bulk and mineral boundary suggests that grain boundary can be treated as an independent phase in dehydroxylation reactions.

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Phase transitions in CsHSO4 up to 2.5GPa: Impedance spectroscopy under pressure

Cited by 6 publications

References 35 publications

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

The effect of chemical composition and oxygen fugacity on the electrical conductivity of dry and hydrous garnet at high temperatures and pressures

The determination of ionic transport properties at high pressures in a diamond anvil cell

Electrical conductivity of polycrystalline Mg(OH)2 at 2 GPa: effect of grain boundary hydration–dehydration

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