Thermal Conductivity Anomaly in (Fe 0.78 Mg 0.22 )CO 3 Siderite Across Spin Transition of Iron

2019 ◽  
Vol 124 (2) ◽  
pp. 1388-1396 ◽  
Author(s):  
Keng‐Hsien Chao ◽  
Wen‐Pin Hsieh
Keyword(s):  
Thermal Conductivity ◽  
Spin Transition ◽  
Conductivity Anomaly

Effect of spin transition of iron on the thermal conductivity of (Fe, Al)-bearing bridgmanite

2019 ◽  
Vol 520 ◽  
pp. 188-198 ◽  
Author(s):  
Yoshiyuki Okuda ◽  
Kenji Ohta ◽  
Ryosuke Sinmyo ◽  
Kei Hirose ◽  
Takashi Yagi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Spin Transition

Thermal Conductivity, Anomaly in Temperature-dependence for Liquids

1971 ◽  
Vol 49 (14) ◽  
pp. 2468-2469 ◽  
Author(s):  
J. E. S. Venart ◽  
N. Mani
Keyword(s):  
Thermal Conductivity ◽  
Temperature Dependence ◽  
Freezing Point ◽  
Cluster Formation ◽  
Linear Functions ◽  
Empirical Equations ◽  
Conductivity Anomaly ◽  
Simple Liquids

Most empirical equations express the thermal conductivity of normal simple liquids as linear functions of temperature. The majority of measurements to date, except water, support such a description. Very precise new measurements on toluene over the complete liquid range at 1 atm (0.299 < Tr < 0.645) show a substantial pre-freezing anomaly. At the freezing point (tf) there is a depression of the expected conductivity of 7.9 × 10−3 W/m °K. This tf behavior is attributed to cluster formation.

scholarly journals Effects of composition and pressure on electronic states of iron in bridgmanite

2020 ◽  
Vol 105 (7) ◽  
pp. 1030-1039 ◽  
Author(s):  
Susannah M. Dorfman ◽  
Vasily Potapkin ◽  
Mingda Lv ◽  
Eran Greenberg ◽  
Ilya Kupenko ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Mössbauer Spectroscopy ◽  
Quadrupole Splitting ◽  
Mossbauer Spectroscopy ◽  
Spin Transition ◽  
Site Occupancy ◽  
Electronic States ◽  
Center Shift ◽  
Mößbauer Spectroscopy ◽  
Wide Range

Abstract Electronic states of iron in the lower mantle's dominant mineral, (Mg,Fe,Al)(Fe,Al,Si)O3 bridgmanite, control physical properties of the mantle including density, elasticity, and electrical and thermal conductivity. However, the determination of electronic states of iron has been controversial, in part due to different interpretations of Mössbauer spectroscopy results used to identify spin state, valence state, and site occupancy of iron. We applied energy-domain Mössbauer spectroscopy to a set of four bridgmanite samples spanning a wide range of compositions: 10–50% Fe/total cations, 0–25% Al/total cations, 12–100% Fe3+/total Fe. Measurements performed in the diamond-anvil cell at pressures up to 76 GPa below and above the high to low spin transition in Fe3+ provide a Mössbauer reference library for bridgmanite and demonstrate the effects of pressure and composition on electronic states of iron. Results indicate that although the spin transition in Fe3+ in the bridgmanite B-site occurs as predicted, it does not strongly affect the observed quadrupole splitting of 1.4 mm/s, and only decreases center shift for this site to 0 mm/s at ~70 GPa. Thus center shift can easily distinguish Fe3+ from Fe2+ at high pressure, which exhibits two distinct Mössbauer sites with center shift ~1 mm/s and quadrupole splitting 2.4–3.1 and 3.9 mm/s at ~70 GPa. Correct quantification of Fe3+/total Fe in bridgmanite is required to constrain the effects of composition and redox states in experimental measurements of seismic properties of bridgmanite. In Fe-rich, mixed-valence bridgmanite at deep-mantle-relevant pressures, up to ~20% of the Fe may be a Fe2.5+ charge transfer component, which should enhance electrical and thermal conductivity in Fe-rich heterogeneities at the base of Earth's mantle.

scholarly journals Effects of iron on the lattice thermal conductivity of Earth’s deep mantle and implications for mantle dynamics

2018 ◽  
Vol 115 (16) ◽  
pp. 4099-4104 ◽  
Author(s):  
Wen-Pin Hsieh ◽  
Frédéric Deschamps ◽  
Takuo Okuchi ◽  
Jung-Fu Lin
Keyword(s):  
Thermal Conductivity ◽  
Lower Mantle ◽  
Lattice Thermal Conductivity ◽  
Spin Transition ◽  
Radial Profile ◽  
Substitution Effect ◽  
Optical Pump ◽  
Mantle Dynamics ◽  
Ultrafast Optical ◽  
Diamond Anvil

Iron may critically influence the physical properties and thermochemical structures of Earth’s lower mantle. Its effects on thermal conductivity, with possible consequences on heat transfer and mantle dynamics, however, remain largely unknown. We measured the lattice thermal conductivity of lower-mantle ferropericlase to 120 GPa using the ultrafast optical pump-probe technique in a diamond anvil cell. The thermal conductivity of ferropericlase with 56% iron significantly drops by a factor of 1.8 across the spin transition around 53 GPa, while that with 8–10% iron increases monotonically with pressure, causing an enhanced iron substitution effect in the low-spin state. Combined with bridgmanite data, modeling of our results provides a self-consistent radial profile of lower-mantle thermal conductivity, which is dominated by pressure, temperature, and iron effects, and shows a twofold increase from top to bottom of the lower mantle. Such increase in thermal conductivity may delay the cooling of the core, while its decrease with iron content may enhance the dynamics of large low shear-wave velocity provinces. Our findings further show that, if hot and strongly enriched in iron, the seismic ultralow velocity zones have exceptionally low conductivity, thus delaying their cooling.

Evidence for high-spin-to-low-spin transition under pressure in Fe 72 Pt 28 Invar alloy

2000 ◽  
Vol 80 (2) ◽  
pp. 155-163 ◽  
Author(s):  
S. Odin, F. Baudelet, E. Dartyge, J. P
Keyword(s):  
High Spin ◽  
Spin Transition ◽  
Invar Alloy
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