Electrical conductivity of magnesium oxide single crystal below 1200 K

Kathrein, H.; Freund, Friedemann

doi:10.1016/0022-3697(83)90052-5

Cited by 63 publications

(52 citation statements)

References 28 publications

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“…This is reminescent of a situation encountered during a study of the model insulator MgO and its electrical conductivity as a function of temperature [Kathrein and Freund, 1983]. MgO had long been considered an excellent insulator up to temperatures above 700øC, the onset of ionic conductivity [Sempolinski and Kingery, 1980;Wuensch et al, 1973].…”

Section: Recapitulationmentioning

confidence: 87%

Time‐resolved study of charge generation and propagation in igneous rocks

Freund¹

2000

J. Geophys. Res.

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Abstract. Electrical resistivity changes, ground potentials, electromagnetic (EM), and luminous signals preceding or accompanying earthquakes have been reported many times, in addition to ground uplift and tilt and other parameters. However, no concept exists that would tie these diverse phenomena together into a physically coherent model. Using low-to medium-velocity impacts to measure electrical signals with microsecond time resolution, it is observed that when gabbro and diorite cores are impacted at relatively low velocities, --100 m/s, highly mobile charge carriers are generated in a small volume near the impact point. They spread through the rocks, causing electric potentials exceeding +400 mV, EM, and light emission. As the charge cloud spreads, the rock becomes momentarily conductive. When a granite block is impacted at higher velocity, --1.5 km/s, the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. After the sound waves have passed, the surface of the granite block becomes positively charged, suggesting the same charge carriers as observed during the lowvelocity impact experiments, expanding from within the bulk. which all nominally anhydrous minerals incorporate when crystallizing in H20-laden environments. The fact that positive holes can be activated by low-energy impacts, and their attendant sound waves, suggests that they can also be activated in the crust by microfractures during the dilatancy phase. Depending on where in the stressed rock volume the charge carriers are activated, they will form rapidly moving or fluctuating charge clouds that can account for earthquake-related electrical signals and EM emission. Wherever such charge clouds intersect the surface, high fields are expected, causing electric discharges and earthquake lights.

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Section: Recapitulationmentioning

confidence: 87%

Time‐resolved study of charge generation and propagation in igneous rocks

Freund¹

2000

J. Geophys. Res.

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189

137

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“…electronic states associated with O À in a matrix of O 2À , also known as positive holes. They had first been identified during an electrical conductivity study of nominally high purity MgO single crystals (Kathrein and Freund, 1983) and later more fully characterized by techniques such as magnetic susceptibility and dielectric polarization (Batllo et al, 1991;Freund et al, 1993).…”

Section: Discussionmentioning

confidence: 99%

“…Fig. 1b shows the electrical conductivity s of nominally high purity MgO single crystals, used to fully characterize h Á charge carriers and their temperature-dependent behavior (Freund et al, 1993;Kathrein and Freund, 1983). The electrical conductivity response was measured during a combined heating-cooling program designed to demonstrate the thermal activation of h Á charge carriers and their characteristic 1 eV activation energy.…”

Section: Solid State Background: Positive Hole Charge Carriersmentioning

confidence: 99%

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Pre-earthquake signals: Underlying physical processes

Freund

2011

Journal of Asian Earth Sciences

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244

148

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“…Consequently, the normalized electrical conductivity reduced as the temperature increased. MgO is widely used as electrical insulators in technical devices such as thermocouples, coaxial heating elements and electrical cables, especially in the temperature region below 1000 K. 56,57 Therefore, the relative electrical conductivity plot in figure 8 depicted an electrically insulating nanofluids as the temperature increases. The graphs of the relative pH against temperature, which is presented in figure 9, show comparable behaviour as noted for electrical conductivity; the values reduced with the increase in the nanofluid temperature.…”

Section: Influence Of Temperature On Ph and Electrical Conductivitymentioning

confidence: 99%

Factors affecting the pH and electrical conductivity of MgO–ethylene glycol nanofluids

2015

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Abstract. The pH and electrical conductivity are important properties of nanofluids that have not been widely studied, especially with regard to temperature and ultrasonication energy. To study the factors that affect the pH and electrical conductivity of magnesium oxide-ethylene glycol (MgO-EG) nanofluid, the effects of temperature, volume fraction, particle size and ultrasonication energy were investigated. Two different sizes of MgO were dispersed in EG base fluid up to the volume fraction of 3%, and the pH and electrical conductivity were monitored between the temperatures of 20 and 70°C. Characterization by transmission electron microscopy and size analyses revealed the morphology and sizes of the nanoparticle samples. The pH values dropped consistently with the increase of temperature, while electrical conductivity value increased with the increase of temperature. The experimental result showed that the increase in the MgO volume fraction increased both the pH and electrical conductivity values of the MgO-EG nanofluid. There was no recognizable influence of ultrasonication energy density on the pH and electrical conductivity of the nanofluid; therefore, it was concluded that temperature, volume fraction and particle size are the predominant factors affecting both the pH and electrical conductivity of MgO-EG nanofluid within the present experimental conditions.

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Electrical conductivity of magnesium oxide single crystal below 1200 K

Cited by 63 publications

References 28 publications

Time‐resolved study of charge generation and propagation in igneous rocks

Time‐resolved study of charge generation and propagation in igneous rocks

Pre-earthquake signals: Underlying physical processes

Factors affecting the pH and electrical conductivity of MgO–ethylene glycol nanofluids

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