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343 results on '"Paraskevopoulos, Konstantinos M."'

3. Understanding the role and interplay of heavy hole and light hole valence bands in the thermoelectric properties of PbSe

Author

Chasapis, Thomas C., Lee, Yeseul, Hatzikraniotis, Euripides, Paraskevopoulos, Konstantinos M., Chi, Hang, Uher, Ctirad, and Kanatzidis, Mercouri G.

Subjects
Condensed Matter - Materials Science
Abstract

The thermoelectric properties of PbSe have significantly improved in recent years reaching figures of merit ZT 1.6. The transport properties of the hole doped high temperature thermoelectric material PbSe are particularly interesting and play a key role in this. Here they were analyzed over a wide temperature and hole concentration ranges. The special features observed in the variation of the experimental Seebeck coefficient, and Hall coefficient can be accounted for within the framework of a two band model. Two valence bands separated by a temperature dependent energy offset are considered. The extremum of the light hole band has a density of states mass 0.27mo at room temperature. It is non-parabolic and anisotropic and can be described by the Kane model. The extremum of the heavy hole band is isotropic and parabolic with a much larger density of states mass 2.5mo. We find that for heavily doped compositions the high mass band contributes the Seebeck coefficient even at room temperature. With rising temperature holes are transferred from the light hole to the heavy hole branch giving rise to the anomalous temperature dependent Hall coefficient which is found peaked near 650 K.

Published
2015
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4. High temperature charge and thermal transport properties of the n-type thermoelectric material PbSe

Author

Androulakis, John, Chung, Duck-Young, Su, Xianli, Zhang, Li, Uher, Ctirad, Hassapis, Thomas C., Hatzikraniotis, Euripides, Paraskevopoulos, Konstantinos M., and Kanatzidis, Mercouri G.

Subjects
Condensed Matter - Materials Science
Abstract

We present a detailed study of the charge transport, optical reflectivity, and thermal transport properties of n-type PbSe crystals. A strong scattering, mobility-limiting mechanism was revealed to be at play at temperatures above 500 K. The mechanism is indicative of complex electron-phonon interactions that cannot be explained by conventional acoustical phonon scattering alone. We applied the first order non-parabolicity approximation to extract the density of states effective mass as a function of doping both at room temperature and at 700 K. The results are compared to those of a parabolic band model and in the light of doping dependent studies of the infrared optical reflectivity. The thermal conductivity behavior as a function of temperature shows strong deviation from the expected Debye-Peierls high temperature behavior (umklapp dominated) indicating an additional heat carrying channel, which we associate with optical phonon excitations. The correlation of the thermal conductivity observations to the high temperature carrier mobility behavior is discussed. The thermoelectric figure of merit exhibits a promising value of ~0.8 at 700K at 1.5 x 10^{19}$ cm^-3., Comment: 14 figures, 2 tables, 12 pages, 53 references

Published
2011
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15. Composite PLGA–Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration

Author

Pouroutzidou, Georgia K., primary, Papadopoulou, Lambrini, additional, Lazaridou, Maria, additional, Tsachouridis, Konstantinos, additional, Papoulia, Chrysanthi, additional, Patsiaoura, Dimitra, additional, Tsamesidis, Ioannis, additional, Chrissafis, Konstantinos, additional, Vourlias, George, additional, Paraskevopoulos, Konstantinos M., additional, Anastasiou, Antonios D., additional, Bikiaris, Dimitrios N., additional, and Kontonasaki, Eleana, additional

Published
2023
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23. Electrospun PLGA Membranes with Incorporated Moxifloxacin-Loaded Silica-Based Mesoporous Nanocarriers for Periodontal Regeneration

Author

Pouroutzidou, Georgia K., primary, Lazaridou, Maria, additional, Papoulia, Chrysanthi, additional, Tsamesidis, Ioannis, additional, Chrissafis, Konstantinos, additional, Vourlias, George, additional, Paraskevopoulos, Konstantinos M., additional, Bikiaris, Dimitrios, additional, and Kontonasaki, Eleana, additional

Published
2022
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28. Effect of Artemisinin-Loaded Mesoporous Cerium-Doped Calcium Silicate Nanopowder on Cell Proliferation of Human Periodontal Ligament Fibroblasts

Author

Tsamesidis, Ioannis, primary, Gkiliopoulos, Dimitrios, additional, Pouroutzidou, Georgia K., additional, Lymperaki, Evgenia, additional, Papoulia, Chrysanthi, additional, Reybier, Karine, additional, Perio, Pierre, additional, Paraskevopoulos, Konstantinos M., additional, Kontonasaki, Eleana, additional, and Theocharidou, Anna, additional

Published
2021
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48. Investigation of the Influence of Gastric Acid on the Surface Roughness of Ceramic Materials of Metal-Ceramic Restorations. An In Vitro Study.

Author

Matsou, Eirini, Vouroutzis, Nikolaos, Kontonasaki, Eleana, Paraskevopoulos, Konstantinos M., and Koidis, Petros

Subjects
TOOTH erosion, GASTRIC acid, SURFACE roughness, DENTAL ceramics, DENTAL ceramic metals, BULIMIA, ATOMIC force microscopy, SAMPLE size (Statistics)
Abstract

The rehabilitation of eroded teeth in patients suffering from bulimia nervosa generally includes ceramics. This study compared the roughness of three ceramics before and after exposure to simulated vomit solution (SVS) with a pH of 3.8. Surface roughness parameters Ra, RMS, and AH were calculated using atomic force microscopy before and after exposure to SVS (novel peristaltic pump for 24 hours at 37°C) and were analyzed statistically. Apart from the initial high AH values of the glass-ceramic, none of the parameters evaluated were statistically significantly different after acid exposure. Under the limitations of this in vitro study, the investigated ceramics seem suitable for use in bulimia nervosa patients. [ABSTRACT FROM AUTHOR]

Published
2011

49. Structure inhomogeneities, shallow defects, and charge transport in the series of thermoelectric materials K2Bi8-xSbxSe13.

Author

Kyratsi, Theodora, Hatzikraniotis, Euripides, Paraskevopoulos, Konstantinos M., Malliakas, Christos D., Dyck, Jeff S., Uher, Ctirad, and Kanatzidis, Mercouri G.

Subjects
THERMOELECTRIC materials, BISMUTH-antimony alloys, CHARGE transfer, THERMAL properties of semiconductors, ELECTRIC conductivity, ELECTRONIC structure, ELECTRON diffraction
Abstract

The charge transport properties of the low-dimensional thermoelectric materials K2Bi8-xSbxSe13 (02Bi8-xSbxSe13 was analyzed on the basis of the classical semiconductor theory and discussed in the context of recent band calculations. The results suggest that the K2Bi8-xSbxSe13 materials possess coexisting domains with semimetallic and semiconducting characters whose ratio is influenced by the value of x and by local defects. The extent and relative distribution of these domains control the charge transport properties. Electron diffraction experiments performed on samples of K2Bi8-xSbxSe13 with x=1.6 show evidence for such domains by indicating regions with long range ordering of K+/Bi3+ atoms and regions with increased disorder. The semiconducting behavior is enhanced with increasing x (i.e., Sb/Bi ratio) in the composition through a decrease of the semimetallic fraction. [ABSTRACT FROM AUTHOR]

Published
2006
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50. Highly anisotropic crystal growth and thermoelectric properties of K[sub 2]Bi[sub 8-x]Sb[sub x]Se[sub 13] solid solutions: Band gap anomaly at low x.

Author

Kyratsi, Theodora, Dyck, Jeffrey S., Chen, Wei, Chung, Duck-Young, Uher, Ctirad, Paraskevopoulos, Konstantinos M., and Kanatzidis, Mercouri G.

Subjects
SOLID solutions, ANISOTROPY, THERMOELECTRICITY
Abstract

The thermoelectric properties of solid solutions of the type β-K[sub 2]Bi[sub 8-x]Sb[sub x]Se[sub 13] (0

Published
2002
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