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Elastic, electronic and thermoelectric properties of Sr3MN (M?= Sb, Bi) under pressure
摘要： We have performed first-principles calculations to study the structural, elastic, electronic and thermoelectric properties of Sr3MN (M = Sb, Bi) under pressure. The optimized lattice parameters are in good agreement with the available experimental and theoretical measurements. Brittle to ductile transition occurs at 15 GPa and the hardness of both compounds decreases with the increase of pressure. The band gap slightly reduces with pressure and both compounds exhibit semiconducting nature for TB-mBJ potential. The density of states increases slightly at the Fermi level. The inclusion of the spin-orbit coupling effect reduces the band gap of Sr3BiN. The calculated Seebeck coefficient for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 257 and 142 μV/K, respectively. The calculated lattice thermal conductivity of both compounds decreases with the increase of pressure, as phonon scattering increased. The predicted thermoelectric figure of merit (ZT) for Sr3SbN and Sr3BiN at 15 GPa and 600 K are 0.71 and 0.63, respectively. The obtained thermoelectric properties at high pressure making them suitable for thermoelectric device applications.
关键词： Lattice thermal conductivity,Pressure effect,Thermoelectric properties,Electronic properties,Elastic properties
更新于2025-09-23 15:23:52
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Pressure effect on phosphor thermometry using Mg <sub/>4</sub> FGeO <sub/>6</sub> :Mn
摘要： This study examined the effect of ambient pressure on the luminescent lifetime of Mg4FGeO6:Mn phosphors in different morphologies. To evaluate the pressure sensitivity of phosphor in the form of particle, agglomerated particle and chemically bonded coating, samples including phosphor powder, pressed phosphor disc, and chemically bonded phosphor coating were fabricated and calibrated using a PMT-based measurement system for a pressure range of 20-200 kPa and a temperature range of 298-873 K. The results showed no obvious pressure effect on the lifetime of the chemically bonded Mg4FGeO6:Mn coating. However, the lifetime of the phosphor powder and pressed phosphor disc decreased as pressure increased. This pressure effect was most obvious for the pressed phosphor disc, which was further aggravated at higher temperatures. The atomic distance between manganese ion and other atomics reduced as pressure increased, which induced the movement of excited state in the configuration coordinate. Considering this dependency of pressure sensitivity on phosphor morphology, it is important to adopt the same fabrication procedure for calibration and temperature measurement using Mg4FGeO6:Mn. In addition, for in-flow measurement using Mg4FGeO6:Mn tracer particles, the influence of environmental pressure must be considered.
关键词： Phosphor thermometry,Lifetime,Mg4FGeO6:Mn,Pressure effect
更新于2025-09-23 15:23:52
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Spectral characteristics of underwater laser-induced breakdown spectroscopy at high pressure conditions
摘要： Laser-induced breakdown spectroscopy (LIBS) has been proven to be an attractive technique for the in-situ oceanic applications. However, when applying LIBS into deep-sea, the pressure effect caused by different ocean depth is inescapable and could have great influence on the LIBS signals. In this work, spectral characteristics of underwater LIBS were investigated as a function of pressure in the range of 0.1–45 MPa. A high-pressure chamber built in the laboratory was used to simulate the high-pressure environment of deep-sea. Optimal laser energy and detection delay were first determined under different pressure conditions and were shown to be independent on the external pressure. The increase in pressure has a significant impact both on the peak intensity and line broadening of the observed spectra. The peak intensity of Na, Li and K lines increases with the increasing pressure until a maximum intensity reached at 12.5 MPa. Above this value, the peak intensity decreases gradually up to 45 MPa. For Ca line, the maximum intensity was observed at 30 MPa. The line broadening keeps constant at low pressures from 0.1 to 10 MPa while it increases linearly at higher pressures, indicating a higher electron density caused by the compression effect of the high external pressure. We also compared the spectral data obtained from the high-pressure chamber and from the field sea trials, and the good consistency between the laboratory data and sea-trial data suggested the key role of pressure effect on underwater LIBS signals for the practical deep-sea applications.
关键词： high-pressure chamber,underwater laser-induced breakdown spectroscopy,deep-sea application,pressure effect,spectral characteristics
更新于2025-09-16 10:30:52